The BSFC chart thread (post 'em if you got 'em)

[Old Tele man]

...while it "...ain't gonna happen..." during MY lifetime, but I'd like to see the car companies required to provide BSFC and ALL technical aspects of the vehicle in the Owners Manual that goes with each car--mandated!

...on CD or DVD!

[some_other_dave]

Some used to provide a subset of that, 30+ years ago. I have an owner's manual that shows nominal HP and torque curves (not just the max ratings!) and a nominal BSFC curve. The values shown in that curve are almost certainly at WOT only, so they aren't super useful for our purposes, but they are more than I've seen in most newer cars.

There was also a chart of speed vs. RPM in all gears, hill-climbing ability (which assumed a lot of things of course!) and other info that I haven't seen in newer owner's manuals.

-soD

[kubark42]

(Sort of cross-posting, but I hope it's forgiven because of general interest to this thread)

If you don't have a BSFC curve/efficiency map, why not make your own?

Announcing a complete solution to mapping engine efficiency

[PowerHaus930]

Does anyone have or know where to get a BFSC chart for the SOHC 1.9 in the Saturn S-series?

[The Toecutter]

The following topic has a BSFC map for the Mercedes Benz OM617 5 cylinder turbodiesel engine used in the 300 SD, along with a lot of other relavent graphs:

OM617 SAE Paper

I saved a copy and am posting it here:

om617a-bsfc.jpg

I do believe the OM617 is the 2nd sturdiest engine ever put in a passenger car sold in the U.S. The OM617 can repeatedly and regularly last 500,000+ miles before a rebuild, provided you do regular maintenance. Some examples had been run with no oil(not low oil, no oil) and have lasted 20,000+ miles operating in those conditions. The show LeMons once had a segment where a crowd gathered around a clunking 617 and tried to get it to sieze up while running; they poured liquid sement, rocks, milk, and other things into the engine to try to seize it, and it kept on clunking... The #1 place goes to the 4 cyl used in the 240D, which can reliably rack up more than 1 million miles before a rebuild. The engine used in my 300 SDL is very well built, but its reliability just doesn't compare with the 5 cyl.

That said, for such a tank-like engine, the efficiency is not that bad, either. The C111-III streamliner used this engine, but with a larger turbo. The stock internals of the 617 engine can reliably handle 400 horsepower, although the C111-III was a bit conservative with the upgrades.

[cfg83]

Hello -

I was looking at this Wiki :

Brake specific fuel consumption - Wikipedia, the free encyclopedia

Some examples of lower heating values for vehicle fuels are:

Certification gasoline = 18640 BTU/lb = 0.01204 kW·h/g
Regular gasoline = 18917 BTU/lb = 0.0122225 kW·h/g
Diesel fuel = 18500 BTU/lb = 0.0119531 kW·h/g

Thus a diesel engine's efficiency = 1/(BSFC*0.0119531)

and a gasoline engine's efficiency = 1/(BSFC*0.0122225)

Can someone state whether or not the above fuel efficiency statements are dimensionless or not? When I add units to the calculation I see the units in the divisor cancel out. For example :

Gasoline with 250 g/kW·h BSFC :
1 / ( 250 * 0.0122225)
= 1 / ( 250 in g/kW·h * 0.0122225 in kW·h/g )
= 1 / 3.055625
= 0.32725 "efficiency"

Is this the way it's supposed to be? Are there units for this?

Thanks,

CarloSW2

[thorpie]

the result is 0.32725 joules out as work for each joule input - joules/joule cancels out so it is unitless

[bwilson4web]

Originally Posted by cfg83

. . .
Is this the way it's supposed to be? Are there units for this?
. . .

"Efficiency" is the ratio of mechanical energy output divided by the chemical energy input. At best, it can approach 100% but heat engine efficiency is limited by the ratio of peak and exhaust temperatures. The Wiki article about heat engines would be a good introduction.

Bob Wilson

[MechEngVT]

Originally Posted by cfg83

Gasoline with 250 g/kW·h BSFC :
1 / ( 250 * 0.0122225)
= 1 / ( 250 in g/kW·h * 0.0122225 in kW·h/g )
= 1 / 3.055625
= 0.32725 "efficiency"

Is this the way it's supposed to be? Are there units for this?

That's correct; your end result is the percentage. In your calculation the engine is 32.725% efficient, with percentages being unitless ratios.

Note that diesel has lower heat energy per pound than gasoline. Diesel fuel is 7.1 lb/gal density whereas gasoline is just over 6 lb/gal. Diesel has more energy per gallon as a result, yet less energy per pound. Diesel engines with comparable BSFC ratings as a gasoline counterpart are therefore more "fuel efficient" in a L/100km or MPG aspect despite requiring equal energy per power output.

[cfg83]

thorpie and Bob and MechEngVT -

Ok, that helps. Thanks for the feedback.

CarloSW2