fuel efficiency changing from small blocks to big blocks?

[Tim.M]

A 6,000 lb boat currently has twin small block GM 350 cubic inch 5.7 liter engines / 260 hp each. It cruises at 3,500 rpm around 35 knots.

If this boat were repowered with twin GM 454 cubic inch 7.4 liter engines / 330 hp each what would you expect to happen to the fuel economy cruising at the same 35 knots?

[CDK]

I hate to use the word 'economy' in connection with these dinosaur engines, but assuming that both sets of engines have the same peripherals, there won't be much difference in fuel consumption. If the small blocks have Rochester carbs and the large ones have injection, the gas consumption will be noticeably lower.

[Tim.M]

Thanks CDK. What's the difference in fuel economy between these dinosaur 5.7 L GM engines and a current model ~300 hp IO engine?

[Frosty]

HP is made by burning fuels. 10GPh per 100Hp for 2 stroke. 7GPH per 100HP for 4 stroke. 5 GPH per 100 HP for diesel.

Please note that is per 100 HP used.

[CDK]

Thanks CDK. What's the difference in fuel economy between these dinosaur 5.7 L GM engines and a current model ~300 hp IO engine?

When Mecruiser adopted the EFI-system they claimed 15-20 % better fuel economy. The figures Frosty gives are rule-of-thumb, actual figures for a specific engine depend on how closely the optimal air/fuel ratio can be maintained.
With carburetors the mixture is generally on the rich side because the engine responds better, but the amount of fuel for which there is no air to burn it, is wasted. EFI offers more precise control so wastes less.

[speedboats]

A correctly tuned carb will offer the same burn rate as that of its injected brother. That is because to make 260hp you need to burn 260hp worth of fuel. Any difference will come in the way of transfer of the energy to the crank, so unless you can find an engine that wastes less energy making heat and noise when combusting fuel then they'll all be much of a muchness.

[CDK]

A correctly tuned carb will offer the same burn rate as that of its injected brother. That is because to make 260hp you need to burn 260hp worth of fuel. Any difference will come in the way of transfer of the energy to the crank, so unless you can find an engine that wastes less energy making heat and noise when combusting fuel then they'll all be much of a muchness.

True, but only for the "correctly tuned carb". That is not what you get when you buy an engine.
What you do get is a 4-barrel Rochester that offers only a mixture adjustment screw for the idle range. At 3500 rpm it provides a rich mixture which you cannot adjust, only at full throttle the air/fuel ratio is correct. Carbs have always suffered from the same problem, even the ones with 3 jets for each barrel. The best design ever was the SU constant vacuum carb with a plunger and a tapered needle, but that also had its weaknesses.
If you look at the 3D injection diagram of a modern EFI unit, it becomes clear that you can never achieve the same precision with a mechanical device.

[TeddyDiver]

A correctly tuned carb will offer the same burn rate as that of its injected brother.
Nope.. injected "brothers" have higher compression ratios and accordingly higher effiency.. like diesel engines..

[Frosty]

SU is constant velocity not constant vacuum.

carbs are adjustable all they way through rev ranges ,its just that it is done by Tapered needles on the carbs your talking about and are set by the factory.

Fuel injected engines IMHO dont offer economy over carbs in the marine engine as a constant RPM or there abouts is required. When you drive a car and release throttle to change gear for instance the fuel in injected engines is Off unlike a carb where the slow running jet is still operative.

Todays modern carbs do give almost perfect 14.7:1 and the emission control guys see to that.

Injected engines have high compression? Prove it!!

[pkoken]

Nope.. injected "brothers" have higher compression ratios and accordingly higher effiency.. like diesel engines..

Higher compression gasoline engines do not have diesel efficiency.*

*Unless you use specific combinations of Marvel Mystery Oil and fuel line magnets properly aligned with the cosmic flux.

[Boston]

I made this exact conversion in my 2 1/2 ton duely cause I got a bigger horse trailer and didnt want to have to buy a bigger truck
thing sucked fuel like a prom date

didnt mater if I was hauling anything or not
it ate gas
I ended up putting a 150 gallon tank in it so I could drive past a gas station

[pkoken]

Comparing car (or truck) fuel efficiency to a boat is not a good comparison.

Car engines spend most of their time loafing along at a light partial load. Closed loop fuel injection systems can then lean the mixture WAY out, beyond stoic and back again in a process called dithering. The average fuel mixture ends up being VERY lean.

Boat engines seldom loaf along at light loading. The vast majority (almost all!) of fuel injected boat engines cannot operate in closed loop.

A perfectly tuned carburetor could equal a perfectly tuned injection system in efficiency. However the average carb is much worse than the average fuel injection system.

[Boston]

thing was a custom built 2 1/2 ton duely
the total cab weight was about 10,000 lbs and it only came out to play when I had something to haul
it was carborated because unless you get the million dollar computer to run the fuel injection perfectly your going to lean out at high altitude and burn the valves rather than end up running rich and loose some efficiency
but keeping your engine in one piece
the big trailer weighed in at about 20,000 lbs half loaded with horses and we typically were aiming for either Yellowstone or Rocky Mountain National park
so I knew the altitude change and could tune accordingly
thing never loafed along was built to the gills and you could watch the gas gauge go down when it was working up a hill
at least untill I put the big tank in it

you shouldn't use fuel injection to haul anything at the passenger level cause it leans out according to oxygen levels and not according to load
cuts the engine life in half or there about

load is a load whether its a boat hull or a trailer
just my two cents
B

[speedboats]

higher compression means more effiency? ah-huh

Higher compression means that the chemical reaction between the gas and air will happen at a faster rate (perhaps this is why we have to retard the timing... I don't know... it's just a guess). With fuel burning at a faster rate we can burn more fuel per cycle, more fuel = more power. Period.

Alot of the ECU stuff we've been doing for injected motors is open loop, this is due to the complexities of getting an O2 sensor in a water jacketed exhaust mainfold to run correctly. Not that it matters much, at throttle positions above around 30% the ECU will generally ignore the O2 sensor anyway and provide fuel according to a pre-programmed map. That map is generally conservativly rich to look after internal parts (like the piston crown and exhaust valve)

Injection has taken favour to help comply with environment standards, it messes around with the fuel ratios under certain perameters to acheive the applicable standards.

Your carb fuel mileage sucks compared to injection? Clean the carb and get it tuned, easier than grabbing your ankles to pay for an injection swap, unless you really want to make more power (more than just an extra 50hp) to make it worth it.

The effiency differences between carb and injection are negligable.

You must remember, a boat engine is always under load, to turn a prop / impellor through water will require a constant amount of power, unlike your truck that will burn power to 60, then back right off to about 8% throttle to maintan speed and overcome wind drag and rolling friction. When was the last time you 'cruised' your boat at less than 30% throttle?

CDK... you keep refering to GM product as dinosaur engines with no economy... what's your choice of engine???

[Boston]

looks like we agreed on most of it there Sr Speedy and your right about most over the road engines running at some fraction of there potential most of the time
course I was at highway most of the time and generally going up hill both ways so I think I got a handle on the fuel efficiency of the proposed swap out cause basically I did exactly what this fuel eating fiend is about to
spend more money

oh and if your carb millage is all that bad check to see if its jetted correctly during that cleaning mentioned above
there are very specific jets for very specific altitudes also there are differences between marine and otr carbs
go with a otr carb even on a marine application
its more tunable and has better filters
B

[Frosty]

I don't think altitude compensation really affects boats.

It a long time since I drove it up a hill.

[Boston]

well said but you never know what carb some fool put on that thing so its worth checking
I think they have specific jets just for marine applications and its entirely possible thats not what is on those engines
Ill throw you a few points on humor value though
I got a good laugh out of that Mr Frosty

rrrrrg
wont let me points you mate

[Fanie]

Hi Tim,

All the chevy spares are available to make that big block a state of the art modern as you can get motor, fuel injection the works.

As Frosty said, big machines suck fuel. No matter how nice you make those big blocks they will be heavy on fuel. You could maybe tow a tanker with it it is that strong, but heavy on fuel.

Small blocks are on the verge of being heavy on fuel, depending what the motor is made out of and how efficient it is. Marine motors use a bit different setup from cars. Any of the chevy component sellers will happily assist you as to what is needed to get them a bit more lively.

Imo it would benefit you more to give the small blocks a bit of a facelift.

A nice 5.7L chevy motor should kick at average around 400hp. Don't just swap the old broomstick with a hot cam, it won't work. There is a combination of spares that characterise a motor. If you do the right things you will get better fuel efficiency as well as better performance.

Of course an outboard still is the best power to weight ratio and fuel efficiency...

[CDK]

""CDK... you keep refering to GM product as dinosaur engines with no economy... what's your choice of engine??? ""

I use the word dinosaur for grey cast engines, developed shortly after 1945, pushrod operated valves, specific power 50 HP/liter or less, raw water cooled so they never reach optimal temp. Now facelifted with EFI, but for decades sold with carbs only.

My boat engines are old-fashioned VW 1,9 turbocharged diesels, liquid cooled, my cars also have diesels, but the CRDI type, except the vintage Porsche in my garage, which has a light alloy V-8 gasoline engine with Bosch mechanical injection. Not quite a dinosaur yet, but hi-tech from the early 80's.

[TeddyDiver]

Higher compression gasoline engines do not have diesel efficiency.*
Nobody said so.. They just have better effiency compared to lower compression gasoline engines ;)

[mydauphin]

A 6,000 lb boat currently has twin small block GM 350 cubic inch 5.7 liter engines / 260 hp each. It cruises at 3,500 rpm around 35 knots.

If this boat were repowered with twin GM 454 cubic inch 7.4 liter engines / 330 hp each what would you expect to happen to the fuel economy cruising at the same 35 knots?

I had 1979 27' Glastron Carlson CVX27 6000lb empty... Originally had 260hp Mercruiser as above, replaced with 330 hp bigblocks. Boat went from doing 60 knots to 75knots... Fuel economy was so bad, I ran out of fuel almost every time I went out. It ate 120 gallons in 30 minutes... It was fast in between tows .... Sank - water got into engine compartment docked behind my house - it was too low in the stern...

Never want a boat like that again.

[mudman]

If you want to move anything any ammount of distance you will need a certain ammount of power. Power = force X distance / Time. A 350 chevy should burn the same ammount of fuel as a 454 big block for a given weight and speed.

A gallon of gasoline has 1.3X10 to the 8th Joules of energy. You can not change that. You will use a certain ammount of energy to go a certain speed on any given boat. You can have an inefficient engine, poor carb, so on. Simply put, if you want to go faster, you will use more power.

This is true in cars trucks etc. too. Go look at the stats for a full size truck with different engines. A full size F150 with a V6 gets the same fuel economy as the ones with the V8's. The V8 has more power, towing capacity and better accelleration. Same MPG on the highway though.

Many other factors come into play on a repower including hull design and prop selection. This changes the Force part of the equation. With 454's you will probably run less rpm to get to 35 knots, but you will burn the same ammount of fuel in theory. If you want to go over 35 knots, I don't know. Depends on the hull.

I know that I upgraded from 115 hp to 150 hp on a Sabre hull and saw very little change in speed, but drastic change in fuel consumption at WOT. Seems that the hull that I had was designed to run at 40 mph. When I tried to get over that, I gained about 3 mph. The boat did 40 mph wide open with a 115. It also did 40 at about 4800 rpm with the 150. Push the 150 to 5500 and gain 3 mph. Not worth it for that hull. The faster you want to push through the water the harder it gets.

[mydauphin]

Sorry MUD but your wrong and here is why.
The 350's had 600 cfm carbs, the 454 had 780 cfm. So at idle the 454 consume more directly proportional to additional air. volume and fuel. Also 454 were many hundreds of pounds heavier. So that added to fuel consumption. Then then lets rev then to 3500 rpm .. 350 ... 40 gals of fuel per hour per engine. 454 ..60 gallons of fuel per hour per engine.

With fuel injection and lean burn technologies, these numbers go down... But most people that have these boat want to run at fuel throttle and there the numbers are really amazing....

[Boston]

as I said
I made this conversion and it ended up costing me a fortune in both swap costs and in fuel
I'd have to say Mr Douphin is got it down to an art as to why
I did however get the additional power I needed out of the deal

[Jimbo1490]

A correctly tuned carb will offer the same burn rate as that of its injected brother. That is because to make 260hp you need to burn 260hp worth of fuel. Any difference will come in the way of transfer of the energy to the crank, so unless you can find an engine that wastes less energy making heat and noise when combusting fuel then they'll all be much of a muchness.

There's a lot of truth in this statement, but the complete truth is actually a bit more complex.

The chief advantage to EFI is not really that it meters the fuel better. As you've pointed out, a carburetor that is set up properly will meter the fuel just as well.

But this does not address the very important subject of intake manifold design. Intake manifolds intended to mount a carburetor look a certain way (the '180 degree' (http://images.search.yahoo.com/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3D180%2Bdegree%2Bintake%2Bmanifold%26fr%3Dyfp-t-501-s%26ei%3Dutf-8%26x%3Dwrt%26y%3DSearch&w=256&h=256&imgurl=www.dougherbert.com%2Fimages%2FWEI-8021.jpg&rurl=http%3A%2F%2Fwww.dougherbert.com%2Fstealth-intake-p-8128.html&size=9.4kB&name=WEI-8021.jpg&p=180+degree+intake+manifold&oid=f224cc0dd2b81630&no=12&tt=14&sigr=11l42rct9&sigi=1177bo1fg&sigb=13g3khmah) type is the most common) because of design limitations due to the location in the air stream where the fuel is introduced, namely at the beginning of the intake tract. The manifold has to be designed to provide just the right amount of turbulence to keep the fuel suspended in the air charge at low and moderate engine speeds (part throttle). This need ultimately limits not only peak power, but adversly affects cylinder filling (volumetric efficiency) at ALL engine speeds and power settings.

Take a look at this (http://images.search.yahoo.com/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3D180%2Bdegree%2Bintake%2Bmanifold%26fr%3Dyfp-t-501-s%26ei%3Dutf-8%26x%3Dwrt%26y%3DSearch&w=256&h=256&imgurl=www.dougherbert.com%2Fimages%2FWEI-8021.jpg&rurl=http%3A%2F%2Fwww.dougherbert.com%2Fstealth-intake-p-8128.html&size=9.4kB&name=WEI-8021.jpg&p=180+degree+intake+manifold&oid=f224cc0dd2b81630&no=12&tt=14&sigr=11l42rct9&sigi=1177bo1fg&sigb=13g3khmah) typical EFI intake (for a 'dinosaur' V8) for comparison to the 180 degree style in the first link. Now what do you think would happen to the fuel/air mixture if you mounted a side draft carburetor to the EFI style manifold in the picture? Would the engine run? Would it run well? The answer is "NO!" it would not run well, if you could manage to start it, at any throttle setting except wide open.

A properly designed EFI manifold is actually a lot like an old-school tunnel ram (http://images.search.yahoo.com/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Dtunnel%2Bram%2Bintake%2Bmanifold%26ei%3Dutf-8%26y%3DSearch%26fr%3Dyfp-t-501-s%26xargs%3D0%26pstart%3D1%26b%3D21%26ni%3D20&w=181&h=165&imgurl=www.alloypolishing.com%2Fgallery%2Fauto%2Ftunlram.jpg&rurl=http%3A%2F%2Fwww.alloypolishing.com%2Fmain%2Fgalleries%2Fautomotive.html&size=12.1kB&name=tunlram.jpg&p=tunnel+ram+intake+manifold&oid=0834eba84e0d7904&no=28&tt=32&b=21&ni=20&sigr=11s2celmp&sigi=11fb185jt&sigb=146k4vl0o) type intake which is used mostly for drag racing. These intakes could make the most peak power (using a carburetor) but had dismal part throttle performance and were VERY hard starting. Without turbulence, the fuel will simply precipitate out of the air stream and puddle on the floor of the manifold. Not Good:(

The EFI manifold can have long, straight, tuned length pipes of large cross-section, rather than smaller cross-section pipes with deliberate bends. And all the pipes can feed from a significant plenum volume to greatly reduce inter-cylinder negative interactions. Carburetors are incompatible with large plenums (the plenum in a carburetor manifold is minuscule by comparison) because large plenums reduce 'signal'(velocity) at the carburetor, another big no-no in carburetor intake manifold design.

All this is possible with EFI simply because the fuel is squirted right into the cylinders at the end if the manifold rather than and the beginning of the manifold.

And we have not even touched on the cam design changes that this permits!

Jimbo

[TollyWally]

Quite interesting Jimbo, please go on. :)

[CDK]

I had 1979 27' Glastron Carlson CVX27 6000lb empty... Originally had 260hp Mercruiser as above, replaced with 330 hp bigblocks. Boat went from doing 60 knots to 75knots... Fuel economy was so bad, I ran out of fuel almost every time I went out. It ate 120 gallons in 30 minutes... It was fast in between tows .... Sank - water got into engine compartment docked behind my house - it was too low in the stern...

Never want a boat like that again.

Good to know I wasn't the only one. My Glastron Carlson came with 260hp, the engine exploded after one year and was also replaced by a big block. It was not just the financial side that bothered me: circling around a crowded fuel station and the tedious process of filling a large tank that 'burped' twice a minute made me hate this thing. Sold it after a few years to someone who crashed it midships into another boat.

[Boston]

ah you plumbed your tank without a feed back hose on the fill tube
thats why it burped gas at you

[speedboats]

Jimbo... While your argument is concise and compelling, and for the most part I agree with you, however we are talking fuel efficiency rather than volumetric efficiency. That is gallons of fuel burnt to produce a given horsepower rather than horsepower per cubic inch of displacement.

Herein lies my statement, the far majority of engines will burn about the same amount of fuel to produce the same amount of hp.

Everything else aside...
what is the burn rate on the carb sbc @ 260hp?
What is the burn rate in the inj bbc @ 260hp?

I'd hazzard a guess +/- the same?

[Frosty]

120 gallons in 30 minutes is 240 gall per hour!! is that imperial or Us gallon? it does'nt matter.

1 ton per hour. Sigh--- makes a Lancaster bomber look economical.

[mudman]

According to Mercruisers website a Crownline 260 LS with a 350 MAG will run at 45.2 mph and burn 20.2 mpg (5000 rpm). The same boat with a 496 MAG and of course proped different will run at 45.5 mph and burn 19 mpg (4000 rpm). Top speed of this boat is 48 mph with a 350 (22.6 gph) or 53.2 mph with the 496 (31 mpg). More speed = more fuel consumption. I agree that at idle you will burn more fuel with a larger engine, but for normal running, I still think that If you want to go 30 mph, you will burn 30 mph worth of fuel.

RPM __mph 350__gph 350__mph 496__gph 496
1000__5.4 ______1.4 ______6.5______2.2
2000__9.1 ______4.1 ______13.4_____6.8
3000__23.7______8.0______31.0_____9.8
4000__35.5______12.8_____45.5 _____19
4700____________________53.2______31
5000__45.2 _____20.2
5250__48.0 _____22.6

I am not sure about the reduction on the drive units on these 2 boats, but hey, GPH is GPH and HP is HP. Prop selections and reduction on the drive units will have more impact on fuel consumption if you want to go 40 knots, more so than the engine displacement IMO.

Carbs are a primitive form of fuel delivery, and I think that fuel injection will offer better fuel/air mixtures. Especially when you start getting into HPDI. I still like a Holley though. Mainly because I can adjust and fix them if need be.

[Jimbo1490]

Jimbo... While your argument is concise and compelling, and for the most part I agree with you, however we are talking fuel efficiency rather than volumetric efficiency. That is gallons of fuel burnt to produce a given horsepower rather than horsepower per cubic inch of displacement.

Herein lies my statement, the far majority of engines will burn about the same amount of fuel to produce the same amount of hp.

Everything else aside...
what is the burn rate on the carb sbc @ 260hp?
What is the burn rate in the inj bbc @ 260hp?

I'd hazzard a guess +/- the same?

While making 260 Hp (the peak power at or near WOT) they will be about the same, assuming they are running the same cam. If these are OEM setups, they probably are running the same cams.

This is one reason that racer's are not all starry eyed over EFI; they know that it may not help them much, if at all, since they are usually at WOT all the time. And when an EFI screws up, you have to figure out what's wrong, then fix it. When a carb screws up, you just remove it and install a spare. Takes 5 minutes.

But with both engines running part throttle, the situation changes. The EFI, due to it's superior manifold design, will have a decided advantage due to reduced pumping losses and better cylinder filling.

The very nearly 'stratified' charge of the EFI engine introduces another wrinkle, namely cam design. Because the fuel and air are not mixed until the last possible moment, and the fuel injection even can be timed to an exact moment in the valve cycle (this is sequential EFI, another thin we have not mentioned yet) a cam profile can be selected that would be a disaster if a typical carb and intake were installed.

So in your example, both engines are running at WOT, and presumably running the same cam. In such a case, the EFI just looks like an overly complex way to get the job done, kinda like a computerized can opener.

You'd probably be amazed that many OEM's were very lazy about changing cams when the EFI revolution hit. They often kept using the same 'holdover' cams from the carb era. (inititally they even used the same intake manifolds; that is why there's such a thing as 'TBI)

But if you take advantage of what EFI permits you to do with the intake and cam, there are power and efficiency advantages over a carburetor.

Then there's a whole other conversation about combustion chamber design for EFI. Finally in the 1990's all the big three US auto makers redesigned their cylinder heads to take advantage of EFI's capabilities. As with cams, they had lazily re-used the old heads which are for homogenized charge, not stratified. The shape and size of the combustion chamber is radically different.

This is the stuff that made these engines 'dinosaurs', NOT their large displacement or even that they 'only' have 2 valve heads and pushrods. But if you need 300HP, and your old design cams, intake and combustion chambers will only let you make ~50 HP per liter, then 6 liters makes sense. When you add EFI with all that comes with it, and now you can quite easily make 80 Hp per liter with reliability and fuel economy (ask any owner of a 5.0 Mustang hot rod) then 6 liters makes no sense at all, as you only need 300 Hp, not 500. And why carry all that extra weight for power you don't need?

Jimbo

[CDK]

ah you plumbed your tank without a feed back hose on the fill tube
thats why it burped gas at you

Nope, I didn't plumb anything, the boat was new.The filler hose was very long with a couple of short curves. The ventilating hose and non-return valve were toy size. Glastron Carlson was always more concerned with good looks....

[Boston]

thats bad
someone can get seriously hurt by splashing fuel
not to mention the fire hazard
and ya You need a hose about half the size of the filler tube so froth doesn't get in the way of return air

sucks mate Ild have been pissed off if my new boat spit gas all the time and I had to go fix it myself

[mydauphin]

CDK, I never understood it, but come to think about it my Baby spit gas also. One time at marina, I almost got ticket for it.

[speedboats]

Jimbo... again, I agree with you and can't fault your statement.

However, you are talking about volumteric efficiency. How much hp / litre of engine displacement.

My statement is about how much litre of consumption / hp.

Changing a cam, or the way the fuel/ air mix gets atop of the piston will not change how much fuel is required to make the said 260hp.

Changing cam, intake runners, head design, compression, fuel distribution affects how much air you can get into the chamber. More air means MORE FUEL can be added, resulting in more bang per cycle and MORE POWER MADE. I agree that the changes mentioned above mean you can easily get more power out of the same displacement engine, but 260hp will +/- always consume the same amount of fuel no matter the type of engine or configuration used.

[Fanie]

The fastest cheapest way to improve fuel economy and performance is to increase the compression ratio. The chevy motors used to run at 7.8:1 in the old days. If you up this to to 10.4:1 there is a difference already. Now you can replace the cam with one that has a bit more cam in it, but not much. You can buy std pop up pistons the original flat ones gets replaced with.

Smaller motors give better fuel per kw performance. Unfortunately there is not a cheap as in cheap solution, and no happy ending in sight either.

In the meantime think about sails and the trade winds :D

Eh, and what about a nice kite. If you can overcome the current and wind drag on the boat you can actually go somewhere.

[Jimbo1490]

All the newer EFI heads allow higher C.R.'s for sure. We ran 10.25-10.5 real measured CR all the time in our street Mustangs with Dart and Edelbrock heads with little or no detonation. Those new 'heart shaped' chambers made a huge difference over the old Ford heads. We had the same experience with the newer Vortec heads for Chevy after '96. They were simply superior to any head we had run, regardless of how much money we had poured into them at the machine shop. More CR with less detonation.

Jimbo

[Boston]

in a diesel the higher compression is what makes it so efficient
or at least one reason

but in gas engines you get into preignition problems with the fuel being a joke of mismanagement
the petroleum distillers are even allowed to put up to 100,000 tons of toxic waste into the fuel annually each, annually.
Thanks Reorge for the great legacy ( and nice job with the economy as well ).

The octane rating of fuel is highly dubious as its not checked all that often and when it is, its always lower than whats reported
Friend of mine was a formula one driver and he was always going off on passenger fuel and its lack of quality control. as apposed to all the controls the industry puts into the fuel he uses, same stuff but extremely clean

higher compression engines gas means you need higher octane levels and more expensive gas
trade offs no mater which direction you turn

[speedboats]

Again... up-ing the compression ratio doesn't mean that you get more energy (power) out of the same amount of fuel. As posted above, it forces the chemical reaction to go faster (ask any high school chemistry student).

A faster reaction means you can put MORE FUEL on top of the piston, creating a bigger bang means MORE POWER...

[Fanie]

Again... up-ing the compression ratio doesn't mean

It does too... You get better fuel consumption as well as more power.

The higher compression gives a bigger explosion than the low compression. You are limited in petrol engines by the compression ratio tho. A higher than 10 point something comp ration can result in spontanious combustion, which means if your engine doesn't stop running when you kill the ignition you may have to get out and shoot the darn thing :D Yes, arnour piercing works best :rolleyes:

What chemical reaction ??? The gas ignites by the spark and explodes. The smaller chaimber and higher compression burns more complete and faster than a low compression ratio. You can check all the new cars have higher comp ratio's.

That said, the higher the octane fuel the lower the compression ratio, the lower the octane the higher the comp ratio can be.

[Boston]

I think he should get a steam engine

:P

[Fanie]

Neuclear driven steam engines. VERY efficient, and you can go day and night non stop,,,

[Jimbo1490]

in a diesel the higher compression is what makes it so efficient
or at least one reason

but in gas engines you get into preignition problems with the fuel being a joke of mismanagement
the petroleum distillers are even allowed to put up to 100,000 tons of toxic waste into the fuel annually each, annually.
Thanks Reorge for the great legacy ( and nice job with the economy as well ).

The octane rating of fuel is highly dubious as its not checked all that often and when it is, its always lower than whats reported
Friend of mine was a formula one driver and he was always going off on passenger fuel and its lack of quality control. as apposed to all the controls the industry puts into the fuel he uses, same stuff but extremely clean

higher compression engines gas means you need higher octane levels and more expensive gas
trade offs no mater which direction you turn

Diesels are NOT more efficient because of their higher compression ratio, rather they are more efficient despite their higher compression ratio. See if you can dig up some info on the Continental Motors AVDS1100 to see what a variable compression ratio diesel can do.

The higher compression ratio is only needed for cold starting and is absolutely worthless at all other times, robbing the engine of power and efficiency by uselessly over-compressing the air charge. The optimum compression ratio for best power in a diesel engine is surprisingly similar to that of a spark ignited engine, about 12.5:1. Trouble is, the engine will not start at this CR.

Various schemes have been worked out over the years to address this including dual fuel engines and variable compression ratio, but most are deemed too costly or complex for widespread use.

This problem declines with increasing engine size due to the greater heat loss per unit displacement and some other factors like engine design speed which all work against the smaller engines in this regard.

Many large diesels have surprisingly low CR's and still start just fine. The GM EMD engines (http://www.tugboatenthusiastsociety.org/Pages/tugmach-diesel-modern-EMD.htm) use 14.5:1 without any starting aids like glow plugs but then they are 567, 645 and 710 cubic inches (9.3, 10.6 and 11.6 liters) per cylinder, so these are big engines

Jimbo

[mydauphin]

Back in the old days.... About 20+ years ago. When my friends and I would buy old muscle cars with 10 to 1 compression for $500. We would port the heads, manifolds, shave heads, install dome pistons . We made sure combustion chambers were smooth no sharp edges. We raised compression to 10.5 or even 11. We used avgas mixtures and water injection. Sometimes we retarded ignition timing or even cams. Anyway, we would get an extra 20% for all the trouble. Nitrous would also help cool intake and reduce detonation. This was all without EFI, or anything fancy just timing work and trial and error. Imagine if you did all this work on a big diesel or efi modern engine.

[Boston]

I think the computer in a modern engine would fight with whatever you tried to do and you would end up with a mess

[speedboats]

What chemical reaction ??? The gas ignites by the spark and explodes. The smaller chaimber and higher compression burns more complete and faster than a low compression ratio. You can check all the new cars have higher comp ratio's.

That said, the higher the octane fuel the lower the compression ratio, the lower the octane the higher the comp ratio can be.


2 things...

Firstly, to combust fuel with oxygen is a chemical reaction. 2 CH4+3 O2=2 CO2+ 2 H2O. Although this is a way over-simplification of what happens in your internal combustion engine (there is alot of other crap in the fuel as well, and this example is methane), it will hopefully help explain things for those whos IQ didn't quite make double digits...:rolleyes:

Secondly, the higher the octane rating the slower the fuel will burn, this is where a higher compression helps as then the burn can be better controlled throughout the power stroke. Therefore your second statement in the quote above is all on the piss

[TeddyDiver]

it will hopefully help explain things for those whos IQ didn't quite make double digits...:rolleyes:
Allthough you have your facts allmost :rolleyes: right in the last message there's no reason to IQing before you understand that the energy content of the fuel and the effiency of a combustion engine are two different things.. ;)
To explain it simply, higher combustion ratio turns a higher percentage of the energy of the burning fuel to mechanical energy..=> higher effiency
A conventional carburator combustion engine can't handle too high combustion ratios. EFI's and other injection engines like diesels can.. :)

[Jimbo1490]

2 things...

Secondly, the higher the octane rating the slower the fuel will burn, this is where a higher compression helps as then the burn can be better controlled throughout the power stroke. Therefore your second statement in the quote above is all on the piss


This is not exactly right. I used to think this was true, but someone kicked my ass proving my understanding was wrong about this. I will be much kinder ;)

Some VERY high octane rated fuels are extremely fast burning rather than slow burning. But they are also extremely resistant to pre-ignition. The thing is, pre-ignition is 'abnormal' combustion. It results from the fuel molecules suffering a certain type of chemical breakdown before the spark event, which causes them to rapidly(explosively) oxidize. This breakdown is the result of being subject to heat and pressure. Think of it as a kind of 'spontaneous combustion', just as you might get from a huge pile of oily rags left to sit a long time, but happening in an instant rather than over many days. This type of combustion takes a different chemical 'pathway', and produces a different set of combustion by-products and slightly different BTU output.

So octane rating is an index of resistance to abnormal combustion, rather than an index of burn speed. It might seem a fine point, but it is actually an important distinction.

Jimbo

[Fanie]

Higher octane rating means fuel burn faster and is more explodable. A 10 octane fuel you'd have to keep a flame on it to keep it burning, a 200 octane would ignite if you rub on it.

A higher octane like 103 will run like a diesel, even if the ignition is off you will get spontanious ignition on a high compression engine like 11:1 or higher.

A low octane on a low compression engine won't get you up the hill.


A chemmical reaction is when two matters are mixed to produce a different matter. When you mix fuel and air you don't get a chemical reaction, you just have a fuel and air mix. Neither the fuel, athough atomised (spray or mist), or the air undergoes any kind of change or 'reaction'.

As for the IQ, sorry to hear you're stuck in the double digits...

[Jimbo1490]

A conventional carburator combustion engine can't handle too high combustion ratios. EFI's and other injection engines like diesels can.. :)

Diesel (compression ignited) is really a totally different deal. You are mixing apples and oranges. Please read my previous post about diesels WRT their high compression ratio.

Diesel engines are by their nature stratified charge. They have to be because they burn fuel by compression ignition. This is a condition that (hopefully) never happens in a spark-ignited engine. If the diesel were to intake it's entire intended (by throttle setting) fuel charge at once, the entire charge would ignite at once, probably causing engine damage at any condition other than idle. In a running diesel under load, the charge ignites as soon as injection begins. But injection continues even as the fuel charge burns until the full fuel charge is delivered. This sequence of events keeps the engine from destroying itself because the entire fuel charge is never sitting in the cylinder un-ignited. The only time it does not work this way is at idle, where the entire charge (small as it is) gets injected before combustion begins. Then the whole charge burns at once, causing the characteristic diesel knock. Note that diesels knock most at idle and under light loading. Many do not knock at all once under a heavy load.

Spark ignited engines can take some advantage from have their fuel/air charge more nearly stratified, but this is for fairly different reasons. Many carbureted engines successfully run 12.5:1 compression ratios and even higher. Yes, fast burn chambers and EFI can get you a small incremental improvement here, but most OEM engines are not running anywhere near the edges of their performance envelope so this won't be a factor.

Jimbo

[Jimbo1490]

Higher octane rating means fuel burn faster and is more explodable. A 10 octane fuel you'd have to keep a flame on it to keep it burning, a 200 octane would ignite if you rub on it.

A higher octane like 103 will run like a diesel, even if the ignition is off you will get spontanious ignition on a high compression engine like 11:1 or higher.

A low octane on a low compression engine won't get you up the hill.


A chemmical reaction is when two matters are mixed to produce a different matter. When you mix fuel and air you don't get a chemical reaction, you just have a fuel and air mix. Neither the fuel, athough atomised (spray or mist), or the air undergoes any kind of change or 'reaction'.

As for the IQ, sorry to hear you're stuck in the double digits...

This is wrong. Higher octane rating fuels are very resistant to pre-ignition, spontaneous ignition, 'dieseling' or whatever you want to call it. This is a kind of chemical 'breakdown'. It's the lower octane fuels that are more susceptible to this problem.

Under some conditions of high heat and high pressure (sounds like an engine, huh?) a fuel air mixture can indeed undergo a chemical reaction (rapid oxidation) that causes it to burn, though in a different (inferior) way than if it were ignited by spark.

This is all very well-documented phenomena. I can dig up the book titles for you to read and learn about fuels and combustion. It's all very fascinating stuff.

Jimbo

[TeddyDiver]

You are right Jimbo about the octanes..
About the EFI and diesel comparison.. it's just like I said. It got to be remembered thou that if you build EFI engine with diesel engines CR you have actually a diesel engine. The fact that such engine is more demanding to manufacture and accordingly more costly to produce, and the second fact that if one produces such engine there's no more any point to burn gasoline when diesel can be used.
It's also just irrelevant how you light up a candle so the argument of ignition method is dead. EFI's you normally see are in the "mid" section what comes to CR due cost effectivines considering the fact they burn gasoline.

Chears Teddy

[CDK]

Octane is the "straight" molecule hydrocarbon with 8 Carbon atoms. Similar to propane, pentane etc. but longer.
The oil industry uses pure octane as the standard of fuel quality as far as pre-ignition is concerned. Gasoline 92 means that it behaves like a fuel containing 92 % octane, but the actual hydrocarbon mixture may be completely different and in theory contain no octane at all.
How fast a fuel/air mixture burns depends on other factors like pressure, moisture, temperature, equal distribution, shape of the cavity and the place of ignition.

All this bears no relation of course with the title of this thread, as is often the case as soon as the number of pages exceeds 1.

[mydauphin]

I think the computer in a modern engine would fight with whatever you tried to do and you would end up with a mess

Yes regular computers would fight. You would need to design system from scratch or use something like race cars used that fuel-ignition curve is fully programmable.

The point of my last email is that preignition is preventable in a gasoline engine. Removing hot spots in cylinder heads, improving flow, direct fuel injection, cooling fuel, intake, increasing octane, retarding ignition under load. All these things could be done a Internal combustions engine to increase efficiency.
260hp would almost always need same amount of gasoline, but torque curve could be enhance thus allowing to achieve same performance with less gas.

Same things can be used to enhance performance in a diesel.

[powerabout]

Higher octane has no relation to burn time.

Your avgas is designed to run in engines that do 3500rpm max and has pretty much been the same spec since WWII.
Thats why people who make race fuel have an industry, they make fuel that burns fast.

One more..F1 engines do 19500 rpm and use EU spec pump gas!!!!!

[Jimbo1490]

Higher octane has no relation to burn time.

Your avgas is designed to run in engines that do 3500rpm max and has pretty much been the same spec since WWII.
Thats why people who make race fuel have an industry, they make fuel that burns fast.

One more..F1 engines do 19500 rpm and use EU spec pump gas!!!!!


Avgas changed COMPLETELY during the late 1970's. The three grades (80, 100 & 115 octane) were replaced by a single grade called "100LL', the 'LL' an abbreviation for 'low lead'. 100LL is a low leaded formulation only in the world of aircraft, where the older 100 grade had several times as much lead as auto premium. 100LL has about twice the lead that auto premium ever had, so it's not really 'low lead' in the strictest sense.

The statement about F1 fuel being similar to street gas is accurate to a point; they have the same ingredients, but not anything close to the same formulations. The intent of the F1 fuel regs is to keep the exotic substances (like nitropropane, for example) out, but it's perfectly OK to use aromatic hydrocarbons like toluene. Please keep in mind that gasoline is a blend of various hydrocarbons, not a 'monolithic' substance. Two completely different formulations that have wildly different octane ratings can have exactly the same ingredients but in different proportions. Think of city tap water, swimming pool water and bleach. All have the same ingredients.

The F1 cars uses a formula or 'spec fuel' that is standardized among all the competitors. It is mostly toluene (about 85%) with the rest 'neutral' hydrocarbons. All these substances can be found in EU gasoline. Toluene has an octane rating of about 114, R+M/2.

Note that US fuels are no longer allowed to have much toluene or other 'aromatics' in them. These were 'outlawed' in the early '90's with the latest amendments to the Clean Air Act. These were removed because they contribute excessively to the 'unburned hydrocarbon' portion of auto emissions. Fuel refiners responded with newer formulations that maintained the octane ratings despite the absence of toluene.

This turns out to be a blessing in disguise for those that need a high octane rated fuel. Now simply adding a small fraction of toluene (~10%) will boost octane rating several points at low cost, with no harmful side effects whatsoever, as all the fuel system components are 100% compatible with toluene.

The unburned HC is only an issue in a very small group of geographical locations, such as the the California valleys, where it forms photochemical smog. It presents no problem anywhere else.


Jimbo

[Boston]

got a question folks
its a little off base but you guys might be able to help
no telling till I ask

that F 250 diesel 7.3 1990
I loaned it to a friend who put gas in it
brilliant eh
then drove it till it died hoping I wouldn't notice
I noticed

purging the fuel system isnt any big deal
and replacing the separator
priming it with wd40
checking the primary fuel pump
all those fun things are no big deal
Ive always turned my own wrenches
but
this thing has shut down its electrical system
dead
Ive talked to several "specialists" and they seem to know nothing about this issue
any ideas

yes the batteries are new and properly hooked up
and yes I already tried disconnecting em to see if a lack of elec would reset the offending sensor

no go
nor can I find any inertial shut off switch
thing appears to be scrap metal again
bites to cause it was free and I had it running like a top

I just dragged my first load of wood back from Missouri with it the other day and now this

Im stumped
B

[powerabout]

Jimbo1490
Can you translate this for me from the 2009 FIA F1 spec on fuel
( each fuel manufacturer can make his own formula for each car. Shell stated on TV before the singapore GP they formulate on the day to a pre tested spec but very close to V power pump gas. When asked will the Ferrari run on V Power pump gas he said yes.)

19.2 Definitions :
Paraffins - straight chain and branched alkanes.
Olefins - straight chain and branched mono-olefins and di-olefins.
- monocyclic mono-olefins (with five or more carbon atoms in the ring) with or without
paraffinic side chains.
Di-olefins - straight chain or branched or monocyclic or bicyclic or tricyclic hydrocarbons (with five
or more carbon atoms in any ring) with or without paraffinic side chains, containing
two double bonds per molecule.
Naphthenes - monocyclic alkanes (with five or more carbon atoms in the ring) with or without
paraffinic side chains.
Aromatics - monocyclic and bicyclic aromatic rings with or without paraffinic or olefinic side chains
and/or fused naphthenic rings. Only one double bond may be present outside the
aromatic ring. Fused naphthenic rings must meet the naphthene definition above.
Oxygenates - organic compounds containing oxygen.
19.3 Properties :
The only fuel permitted is petrol having the following characteristics :
Property Units Min Max Test Method
RON 95.0 102.0 ASTM D 2699-86
MON 85.0 ASTM D 2700-86
Oxygen %m/m 3.7 Elemental Analysis
Nitrogen mg/kg 500 ASTM D 4629
Benzene %v/v 1.0 EN 238
RVP hPa 450 600(1) ASTM D 323
Lead g/l 0.005 ASTM D 3237
Density at 15°C kg/m³ 720.0 775.0 ASTM D 4052
Oxidation Stability minutes 360 ASTM D 525
Existent gum mg/100ml 5.0 EN 26246
Sulphur mg/kg 10 ASTM D 5453
Copper corrosion rating C1 ISO 2160
Electrical conductivity pS/m 200 ASTM D 2624
(1) The maximum RVP may rise to 680hPa if a minimum of 2% bio-methanol and/or bio-ethanol are included
in the fuel.
2009 F1 Technical Regulations 53 of 67 12th December 2008
Distillation characteristics:
At E70°C %v/v 20.0 50.0 ISO 3405
At E100°C %v/v 46.0 72.5 ISO 3405
At E150°C %v/v 75.0 ISO 3405
Final Boiling Point °C 210 ISO 3405
Residue %v/v 2.0 ISO 3405
The fuel will be accepted or rejected according to ASTM D 3244 with a confidence limit of 95%.
19.4 Composition of the fuel :
19.4.1 The composition of the petrol must comply with the specifications detailed below :
Component Units Min Max Test Method
Aromatics %v/v 35* GCMS
Olefins %v/v 18* GCMS
Total di-olefins %m/m 1 GCMS
Total styrene and alkyl derivatives %m/m 1 GCMS
* Values corrected for fuel oxygen content.
In addition, the fuel must contain no substance which is capable of exothermic reaction in the absence of
external oxygen.
19.4.2 The total of individual hydrocarbon components present at concentrations of less than 5% m/m of the total
fuel must be at least 30% m/m of the hydrocarbon component of the fuel.
19.4.3 The total concentration of each hydrocarbon group in the total fuel sample (defined by carbon number and
hydrocarbon type), must not exceed the limits given in the table below :
% m/m C4 C5 C6 C7 C8 C9+ Non PONA* Unassigned
Paraffins 10 30 25 25 55 20 - -
Naphthenes - 5 10 10 10 10 - -
Olefins 5 20 20 15 10 10 - -
Aromatics - - 1.2 35 35 30 - -
Maximum 15 40 45 50 60 45 1 5
* Non-PONA are components not meeting definitions in 19.2 and 19.4.4.
For the purposes of this table, a gas chromatographic technique must be employed which can classify
hydrocarbons in the total fuel sample such that all those identified are allocated to the appropriate cell of
the table. Compounds present at concentrations below 0.1% by mass may be deemed unassigned, except
that it is the responsibility of the fuel approval laboratory to ensure that components representing at least
95% by mass of the total fuel are assigned. The sum of the non-PONA and unassigned hydrocarbons must
not exceed 5% by mass of the total fuel sample.
19.4.4 The only oxygenates permitted are paraffinic mono-alcohols and paraffinic mono-ethers with a final boiling
point below 210°C.
19.4.5 A minimum of 5.75% (m/m) of the fuel must comprise oxygenates derived from biological sources. The
percentage that each component is considered to originate from a biological source is calculated from the
relative proportion of the molecular weight contributed by the biological starting material.
2009 F1 Technical Regulations 54 of 67 12th December 2008
19.4.6 Synthetic hydrocarbons or mixtures of synthetic hydrocarbons, which have been produced from biomass,
will be considered for future inclusion into Formula One fuel, provided that a suitable analytical procedure
is available to verify their biological origin.
19.4.7 Manganese based additives are not permitted.
19.5 Air :
Only ambient air may be mixed with the fuel as an oxidant.

What can you make form these rules
Cheers

[powerabout]

Tim M
Sorry for the hijack
I have done some work on 260's and 330's and on the dyno in the 80's same size carb on both.
The 260 probably has port volumes a bit to large for the 260 engine and hence the small block fords 888, 233, 255's produced way more torque and probably better fuel consumption ( but I never did any technical testing other than drive them..yes more torque then a stock marine chev.)
The 330's peanut ports are about right and with a good port job are very good for the engine, low volume high velocity can make 500hp with a bit more cam, compression and a new inlet manifold with the same quadrajet ( although jetted richer especially the secondarys)
Great BSFC numbers.

The carb v fuel inj story as I see it.
Stock carb on a 260 ( quadrajet era) has a spring under the power valve that is too strong for many installations and as you open up it gets very rich till the revs get to about 4000 then ok (rich on heavier boats,under 50mph.)
Now being vacuum controlled this is dependant on the load so each set up will have a different fuel curve.
The poorly cast iron manifold also makes 4 cylinders rich and 4 lean as does the 330 ( which is worse).
Straight away if your engine has port injection it is in front and not having a spring ( which follows the hookes law rule) and can make a complex curve from the fuel delivery even reading the same MAP as the carb did, no comparison.
Modern carbs and manifolds can produce very good even distribution especially at WOT as much moola has been spent on racing them.
Part throttle is a different story.

So you see in a boat load is everthing as it will determine where the carb is going to do what and if your lucky it suits your load you have the optimal.

The other major issue with a boat is drag,( load) not really an issue on a vehicle.
Raising your drives could produce a boat that goes faster than the same boat with big blocks sunk low.
Your carb will see more vacuum at the same revs as the sunk drives and meter a leaner mixture.
Raise your drives then you can ( will need to) start playing with props as you will need to maintain your bow lift etc and if using Bravos you can get stand off boxes, short lowers etc.
There is also a ton of cast iron you can take off the 260 and replace with ally further reducing the load/drag
Would your project be 260 Bravo and 330 Bravo? dont do 330trs as they perform the same as a 260 Alpha 1 in the same boat
Cheers
PS If you drive at WOT put oil coolers on them as a stock 260/330 can send the sump oil temp to 300f without one.

[wardd]

mercedes did tests some years ago with different size engines moving the same car technology being the same its the weight that mostly determins fuel burn and not cubes

[powerabout]

weight and aero drag in a car
weight and water drag in a boat which are linked together.
water being more of a drag than air by large factor.

[Jimbo1490]

Jimbo1490
Can you translate this for me from the 2009 FIA F1 spec on fuel
( each fuel manufacturer can make his own formula for each car. Shell stated on TV before the singapore GP they formulate on the day to a pre tested spec but very close to V power pump gas. When asked will the Ferrari run on V Power pump gas he said yes.)

19.2 Definitions :
Paraffins - straight chain and branched alkanes.
Olefins - straight chain and branched mono-olefins and di-olefins.
- monocyclic mono-olefins (with five or more carbon atoms in the ring) with or without
paraffinic side chains.
Di-olefins - straight chain or branched or monocyclic or bicyclic or tricyclic hydrocarbons (with five
or more carbon atoms in any ring) with or without paraffinic side chains, containing
two double bonds per molecule.
Naphthenes - monocyclic alkanes (with five or more carbon atoms in the ring) with or without
paraffinic side chains.
Aromatics - monocyclic and bicyclic aromatic rings with or without paraffinic or olefinic side chains
and/or fused naphthenic rings. Only one double bond may be present outside the
aromatic ring. Fused naphthenic rings must meet the naphthene definition above.
Oxygenates - organic compounds containing oxygen.
19.3 Properties :
The only fuel permitted is petrol having the following characteristics :
Property Units Min Max Test Method
RON 95.0 102.0 ASTM D 2699-86
MON 85.0 ASTM D 2700-86
Oxygen %m/m 3.7 Elemental Analysis
Nitrogen mg/kg 500 ASTM D 4629
Benzene %v/v 1.0 EN 238
RVP hPa 450 600(1) ASTM D 323
Lead g/l 0.005 ASTM D 3237
Density at 15°C kg/m³ 720.0 775.0 ASTM D 4052
Oxidation Stability minutes 360 ASTM D 525
Existent gum mg/100ml 5.0 EN 26246
Sulphur mg/kg 10 ASTM D 5453
Copper corrosion rating C1 ISO 2160
Electrical conductivity pS/m 200 ASTM D 2624
(1) The maximum RVP may rise to 680hPa if a minimum of 2% bio-methanol and/or bio-ethanol are included
in the fuel.
2009 F1 Technical Regulations 53 of 67 12th December 2008
Distillation characteristics:
At E70°C %v/v 20.0 50.0 ISO 3405
At E100°C %v/v 46.0 72.5 ISO 3405
At E150°C %v/v 75.0 ISO 3405
Final Boiling Point °C 210 ISO 3405
Residue %v/v 2.0 ISO 3405
The fuel will be accepted or rejected according to ASTM D 3244 with a confidence limit of 95%.
19.4 Composition of the fuel :
19.4.1 The composition of the petrol must comply with the specifications detailed below :
Component Units Min Max Test Method
Aromatics %v/v 35* GCMS
Olefins %v/v 18* GCMS
Total di-olefins %m/m 1 GCMS
Total styrene and alkyl derivatives %m/m 1 GCMS
* Values corrected for fuel oxygen content.
In addition, the fuel must contain no substance which is capable of exothermic reaction in the absence of
external oxygen.
19.4.2 The total of individual hydrocarbon components present at concentrations of less than 5% m/m of the total
fuel must be at least 30% m/m of the hydrocarbon component of the fuel.
19.4.3 The total concentration of each hydrocarbon group in the total fuel sample (defined by carbon number and
hydrocarbon type), must not exceed the limits given in the table below :
% m/m C4 C5 C6 C7 C8 C9+ Non PONA* Unassigned
Paraffins 10 30 25 25 55 20 - -
Naphthenes - 5 10 10 10 10 - -
Olefins 5 20 20 15 10 10 - -
Aromatics - - 1.2 35 35 30 - -
Maximum 15 40 45 50 60 45 1 5
* Non-PONA are components not meeting definitions in 19.2 and 19.4.4.
For the purposes of this table, a gas chromatographic technique must be employed which can classify
hydrocarbons in the total fuel sample such that all those identified are allocated to the appropriate cell of
the table. Compounds present at concentrations below 0.1% by mass may be deemed unassigned, except
that it is the responsibility of the fuel approval laboratory to ensure that components representing at least
95% by mass of the total fuel are assigned. The sum of the non-PONA and unassigned hydrocarbons must
not exceed 5% by mass of the total fuel sample.
19.4.4 The only oxygenates permitted are paraffinic mono-alcohols and paraffinic mono-ethers with a final boiling
point below 210°C.
19.4.5 A minimum of 5.75% (m/m) of the fuel must comprise oxygenates derived from biological sources. The
percentage that each component is considered to originate from a biological source is calculated from the
relative proportion of the molecular weight contributed by the biological starting material.
2009 F1 Technical Regulations 54 of 67 12th December 2008
19.4.6 Synthetic hydrocarbons or mixtures of synthetic hydrocarbons, which have been produced from biomass,
will be considered for future inclusion into Formula One fuel, provided that a suitable analytical procedure
is available to verify their biological origin.
19.4.7 Manganese based additives are not permitted.
19.5 Air :
Only ambient air may be mixed with the fuel as an oxidant.

What can you make form these rules
Cheers

Translation:

The alkanes, parrafinics, olefins, and others are the 'neutral hydrocarbons' I mentioned. That leaves the 'aromatics' (mostly toluene and to a lesser extent, xylene) and the 'napthenics' to do the heavy lifting. These give you most of the basic octane and energy density you need while the others are blended to reduce the octane of toluene to bring it into spec without increasing the 'octane sensitivity' too much. This is especially a big problem with turbo/supercharged engines where you wind up with a big split between 'research' (R) compared to 'motor' (M) octane ratings. Nobody wants to use 'oxygenates' other than the 'exotics' (like nitropropane) because they kill energy density. The mention of manganese near the bottom is there to prohibit MMT(Methylcyclopentadienyl manganese tricarbonyl) which, like TEL(Tetra-ethyl lead), boosts octane and provides scavenging of free radicals that both attack engine components and promote detonation.

The numbers with the percentages are all about concentration limitations on specific 'species' or 'isomers' of various hydrocarbons. This part gets very technical, but keep in mind that even a substance like toluene is not a 'monolithic' substance as there are several different molecular configurations (isomers) that all qualify to be called 'toluene', and those numbers are calling out the mix of the different isomers that is allowed under F1 rules for a given hydrocarbon group.

Jimbo

[powerabout]

Many thanks,
So with the above restrictions how different can they formulate this compared to EU pump gas considering they hold you at EU RON/MON numbers.
Cheers
Powerabout

[Jimbo1490]

The race day formulation will have the lowest 'octane sensitivity' and the fastest burn possible, and highest octane rating allowed under the rules, without concern about either cost or longevity of the basic parameters, since a new batch can presumably be mixed before each race. Some of these compounds can be WAY more expensive to fraction or synthesize than others, so they don't appear in any great quantity in street gas, even if they are the cat's meow as a fuel component.

Jimbo

[powerabout]

Jimbo1490

My mate tells me you can stilll get 110-130 in OZ from Shell, BP and Mobil
Thats what he sticks in his Lancair.

Elf make most of the race fuel in OZ and have a very informative web site
http://www.racefuels.com.au/

Cheers

Cheers

[Boston]

interesting read Jim
have I ever mentioned I suspected you worked for the oil and gas industry at some point

anyway
dam impressive answer
B

[TollyWally]

LOL Jimbo,
I wish I knew what you have forgotten. :)

[powerabout]

heres a bit from Shell.com It explains what happened to 130..just the name
http://www.shell.com/home/content/aviation/products_and_services/products/fuels/avg

History of AVGAS Grades

Avgas is gasoline fuel for reciprocating piston engined aircraft. As with all gasolines, avgas is very volatile and is extremely flammable at normal operating temperatures. Procedures and equipment for safe handling of this product must therefore be of the highest order.

Avgas grades are defined primarily by their octane rating. Two ratings are applied to aviation gasolines (the lean mixture rating and the rich mixture rating) which results in a multiple numbering system e.g. Avgas 100/130 (in this case the lean mixture performance rating is 100 and the rich mixture rating is 130).

In the past, there were many different grades of aviation gasoline in general use e.g. 80/87, 91/96, 100/130,108/135 and 115/145. However, with decreasing demand these have been rationalised down to one principle grade, Avgas 100/130. (To avoid confusion and to minimise errors in handling aviation gasoline, it is common practice to designate the grade by just the lean mixture performance, i.e. Avgas 100/130 becomes Avgas 100).

Some years ago, an additional grade was introduced to allow one fuel to be used in engines originally designed for grades with lower lead contents: this grade is called Avgas 100LL, the LL standing for 'low lead'.

All equipment and facilities handling avgas are colour coded and display prominently the API markings denoting the actual grade carried. Currently the two major grades in use internationally are Avgas 100LL and Avgas 100. To ease identification the fuels are dyed i.e. Avgas 100LL is coloured blue, while Avgas 100 is coloured green.

Very recently a new Avgas grade 82 UL (UL standing for unleaded) has been introduced. This is a low octane grade suitable for low compression engines. It has a higher vapour pressure and can be manufactured from motor gasoline components. It is particularly applicable to those aircraft which have STCs to use automotive gasoline.

******************************************************
so 100LL is new and 100/130 is now called 100
just checked the ozzie site and it says as above and the data sheets says about 100;

The combustion performance is equivalent to Avgas 100 LL. Avgas 100
has a maximum lead content of less than 0.85 gm/ litre. Avgas 100 is also known as
Avgas 100/130.

Is .85 high or low compared with the old pump gas?

[FAST FRED]

" They just have better effiency compared to lower compression gasoline engines."

Unless the low CR was intentional to use dual turbos with waste gates to create loads of power as required or great economy..

FF

[powerabout]

FF
what was the question you just answered?

[MattZ]

All else being equal, you will lose fuel efficiency going to a larger displacement engine. The boat same torque will still be required at 3500 RPM, but the larger engine will operate at lower effective pressure (torque/volume), which implies a lower manifold absolute pressure, which means a higher manifold vacuum. The manifold vacuum is a significant source of loss in an internal combustion engine, particularly at light loads. Now since you have a larger engine you can use a higher compression ratio, and maybe make back some of your fuel efficiency loss.

[TollyWally]

Matt,
Would you mind explaining in more detail the relationships between vacuum, effective pressure, absolute pressure, etc. I feel like I am on the verge of an aha moment but I am not quite getting it.

[Yellowjacket]

All else being equal, you will lose fuel efficiency going to a larger displacement engine. The boat same torque will still be required at 3500 RPM, but the larger engine will operate at lower effective pressure (torque/volume), which implies a lower manifold absolute pressure, which means a higher manifold vacuum. The manifold vacuum is a significant source of loss in an internal combustion engine, particularly at light loads. Now since you have a larger engine you can use a higher compression ratio, and maybe make back some of your fuel efficiency loss.

Matt,

You are correct in noting that the pumping losses are higher for the larger engine if you run it at the same speed. But you are assuming that you wouldn't change the props at the same time, which directly effects the pumping losses.

If you have more torque you can (and should) also increase the prop pitch and slow down the engine. While it won't make up for all of the effects of the displacement increase (the displacement increase is linear and the speed increase is a square root function, so you can't change the gearing as much as you would if the speed increase was linear, so don't get it all back) a taller prop pitch will reduce the pumping losses and help with the part power fuel economy.

You are left with two effects, the higher weight effect on speed and drag, and somewhat higher pumping losses (approximately 1/2 of what they would be if you didn't change the props). Both are real, but they aren't a huge impact on fuel economy, you are probalby going to be within 10%, or maybe even less.

The difference is that you have a pair of engines that aren't being loaded as highly, so there are payoffs in terms of engine life, and if you want higher speed you have that too if you want to bend the throttles.

[Yellowjacket]

Matt,
Would you mind explaining in more detail the relationships between vacuum, effective pressure, absolute pressure, etc. I feel like I am on the verge of an aha moment but I am not quite getting it.

What Matt is describing are called pumping losses. With a gasoline engine you control the power output with a throttle plate. That means before the air gets to the cylinders it gets sucked past a throttle plate that (at part power) isn't open all the way. So the engine is really getting it's air from a low pressure intake manifold. To exhaust the air, you have to pump it from the lower pressure intake manifold out to the atmosphere. At idle the pumping losses are 100% of the load. As the engine speed increases the engine wants to pump more air, but if you don't want much power you have to pump the air that you do need back up to atmospheric pressure to get it out of the engine.

This is why many cars have a really tall gear ratio so that they are barely turning over on the highway. My Corvette for example is only turning over at 1700 rpm at 70 mph. This tall gear ratio allows a wider throttle opening at lower speed, and the net effect is better efficiency. A Corvette six speed typically gets about 30 mpg at 70 mph, which is, for a car of that capability is most impressive.

[Jimbo1490]

All else being equal, you will lose fuel efficiency going to a larger displacement engine.

A bigger factor is if the engine is running at or near it's peak torque output, which indicates best cylinder filling and peak efficiency. A well-optimized large displacement engine can operate at or near it's peak torque over a very broad range of engine speeds. This can be especially helpful for an application where you change engine speeds often and don't have the benefit of a gearbox to re-match the engine to the load at the different engine speeds. This is a good description of a powerboat doing, say ski tug duty where you are frequently accelerating and decelerating. In these applications, the large displacement engine can have an efficiency advantage because of being tuned for a very wide torque peak. The larger displacement allows some peak power to be traded away in this fashion. The faster the boat comes up on plane, the better for efficiency as the drag penalty for a planing hull that is not yet planing is very high.

The 26-28 MPG Chevy Corvette is a good example of a vehicle with a large displacement engine that because of it's wide torque peak can be surprisingly efficient when in high gear. A small displacement engine would not have the torque at 1500 rpm to pull this little hat trick off.

Jimbo

[MattZ]

In response to the OP, my explanation is correct. Unless the gear ratio in the drive is changed, or the prop is changed, the engine efficiency will decrease.

[TollyWally]

YellowJacket,
Thanks for the explanation I believe I'm getting it. Correct me if I'm wrong. In the example of the vette running the motor in overdrive at lower RPMs but opening the throttle more allows the motor to run more efficiently. The example of the propeller, by increasing the pitch and slowing down the motor and prop, one is "harvesting" the excess torque of the motor.

[MattZ]

The point is that by minimizing the intake manifold vacuum you are reducing the intake pumping loss.

(Intake pumping loss) = (RPM)*(engine displacement)*(manifold vacuum)

The equality should really be a proportionality.

By going to a bigger displacement without changing prop or reduction ratio, you end up increasing both engine displacement and manifold vacuum.