BSFC 50 to 250HP?

[FAST FRED]

Just wondering if any folks have had any success in finding a "Fuel Map" or BSFC for the common marinizations .

Say 50 to 250Hp .

Any brand any mfg .Please supply a link , or if you can post them.

TIA

FF

[sbmar.com]

Using #2 Diesel based on 7.001 lbs/US gallon at 60F you be somewhere like below..


All the diesels in marine service ( and other service too) that I have come in contact with over the past 25+ years fall in to a BSFC ranges of .450 to .325 (lbs/bhp/hr.) With a little math, one can derive the "magic number" of 20 hp/gallon/hr (.355) as this is a BSFC that matches (a high average) the amount of hp that is produced by a modern 4-stroke, direct injected, turbo charged/after cooled high speed diesel of modern design. At the far end of this scale (lousy BSFC) you will find normally aspirated 2-stroke diesels ( whose design characteristics date back to pre-WWII w/ many being mechanically supercharged although called NA's) and a few NA, indirect injection, 4-stroke diesels (which are not nearly as old).

Hope that helps..


Tony

[Submarine Tom]

That's about what I get out of my 20hp, 4-stroke Merc OB, WOT: 20hp/gallon/hr

-Tom

[FAST FRED]

".450 to .325 (lbs/bhp/hr."

The range here is considerable , to optomize fuel use only a BMEP map will do.

They seem to be impossible to shake loose.

FF

[Yellowjacket]

Originally Posted by Submarine Tom

That's about what I get out of my 20hp, 4-stroke Merc OB, WOT: 20hp/gallon/hr

-Tom

But you are burning gasoline, which weighs less than diesel. Your BSFC is more like .42 lb/hp hour and that's only when you are at WOT, at lower power levels it's worse than that due to throttling losses.

[Yellowjacket]

Caterpillar has a lot of BSFC curves in its engine data sheets, you have to register to get into that area of their site, but there is a huge amount of information in there. I think most of those are in the 250hp and up to 1200 hp range, but that's the best place to start. Cummins also has data for their engines. I haven't seen curves on the web for MTU's or some others.

Remmber that the "best" BSFC point is usually at high power and you need to look at the prop demand curve to find the BSFC that has any meaning for your application.

Most diesel BSFC curves are pretty flat in the middle and crank upward at low power levels because there is a lot of excess air in the cycle, and at high speed and power because of higher frictional losses and aerodynamic losses.