Diesel VS 4 stroke outboard fuel consumption

The larger engine has much larger area of the cylinder wall, head and piston crown. Much greater heat loss on a heat engine = less efficiency.

I like your post FAST FRED

Easy Rider

 

That's a factor, but other factors are more significant. Check a bsfc map.

 

back home.......

Well to compare apples to apples....everyone wants to compare a new outboard (aluminum,DOHC,multivalve,new injection etc) to old school heavy diesels.

I only used a VW once as it,other than maybe Steyr, is the highest tech (turbo,direct injection,aluminum etc) small diesel engine out there.
U may notice I used Yan and outboards from the same year.

I have shown weights,I have shown fuel charts and diesel kicks a$$ on the outboard.

Now it's gone to underloading....no one has yet to explain why my 350 hp (peak) and I think around 220 continuous/700tq Cummins can loaf down the freeway for hundreds of thousands of km using 9-10 litres an hour.
So maybe 40(?) hp to run down the freeway which means it's running at ~20% load.

Which,according to popular ideals,means it should be glazing and blowing blue and be a wreck after a very short time.
But after 425,000 km all that has been needed is regular maintenance and it still burns very little oil (shows 3 mm on the stick) between changes.

Now on Detroits and loading....thats another story.

 

West Van,
Where'd you find trucking land w/o hills, grades, stop lights on hills ect. I drove an 18 wheel flat bed w a 335 Cummins and only a 10 speed gear and I recall loading it regularly more that my boat engine and I run the boat engine harder than most. I don't know if under loading's worth talking about as everyone's doing it and no one seems ready to stop.

Easy

 

Been East of the Rockies? In case not: it's pretty much flat.

One business I have is specialized manufacture of light yet bulky items for the oil industry.
My driver makes the deliveries,drives around Alberta....and it's flat.

 

"Much better to install the 20-30 hp engine in the first place."

No question , and most sailboat folks DO install a far better choice in choosing engines.

The hassle is the power cruisers , biggest oxymoron is "fast trawlers", where the boat has 400hp and cruises at 7K on 30hp.

"My driver makes the deliveries,drives around Alberta....and it's flat."


Sure but every stoplight , every bit of traffic will have the vehicle accelerate , usually with mucho throttle.

The changing loads , changes in RPM and esp the blasts of throttle on acceleration help clean the carbon out and the engine functioning.

"down the freeway for hundreds of thousands of km using 9-10 litres an hour.
So maybe 40(?) hp to run down the freeway which means it's running at ~20% load."

10L per hour would to me be 2 1/2 gph .

AT a cruise of 60mph that would be about 23 miles per gallon , this is a far cry from the 5 to 7 mpg most class 8 trucks get here.

What is your secret for 300% to 400% better fuel mileage?



FF

 

What don't you get?? IT IS FLAT and he drives on freeways and back roads for hours on end.

"With mucho throttle" WTF? Well you've never driven one.

Plz don't try to tell me how my truck runs or it's mileage,I don't tell you how to run your Detroits.

I never said it was a semi truck- why do you assume so?



"""Fuel capacity: 34 gals.

""""Observed fuel economy: 17 city / 21 highway

http://www.gulfcoastnews.com/autoweb/GCNRT2006DodgeRamDiesel.htm

 

I never said it was a semi truck- why do you assume so?

my 350 hp (peak)

This is not what is common in a delivery van, a 350 hp engine is usually far to expensive for this service , more common would be a throw away like a CAT 3208 , maybe 200 hp on a really GREAT day.

FF

 

Fred:

You need to check out the diesels that are being offered in the 3500 and 4500 class of pickup trucks by Ford/GM/Dodge.

350 hp puts the engine at the bottom of the class - 2011 GM's are rated at 397hp, and 765 lb-ft of torque.

My '07 Ram only has 325 hp, and it normally exceeds 20 mpg (US), in the mountains. And btw, using full throttle when empty is not a good idea. Tires and speeding tickets get expensive very quickly.
Truly remarkable performance for a 7000lb vehicle.

Jim

 

Now it's a delivery van???

 

Automotive (or tiny truck) engines are nor rated the same way as industrial diesels or engines usually selected as boat motors.

A look at any site of boat motors will usually show 4 or 5 HP graphs.

One is for 15 -30 seconds , getting a hulk up on plane.

The other graphs will show lower and lower power till you get to the 24/7 workboat rating.

IT is the work boat rating that should be used to assure engine longevity.

Not only for the load for days on end , but using at least 60 % of the 24/7 loading for cruising will usually stop the slobber hassles.

Sometimes a 24/7 rated engine at cruise will be only a tiny percentage of the advertised Flash rating, so it fools folks into thinking their 475hp is doing fine at 60 hp.

When actually its a 100Hp engine (24/7) and 60 hp cruising is fine.

FF