fuel efficiency changing from small blocks to big blocks?

[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]

Originally Posted by Fanie

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...

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]

Originally Posted by speedboats

it will hopefully help explain things for those whos IQ didn't quite make double digits...

Allthough you have your facts allmost 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]

Originally Posted by speedboats

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]

Originally Posted by TeddyDiver

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]

Originally Posted by 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...

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]

Originally Posted by 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

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]

Originally Posted by 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!!!!!

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.