Specific Fuel Flow - LS Series

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TXFlyGuy

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Based on reading various forums, Corvette, boating, etc., it would appear that we should plan on .38 to .50 pounds per hour per horsepower with our LS376-480.

That is a wide range, for sure. With an ECU fuel injected engine, it is said we would be very efficient. Perhaps close to that .38 figure.

What is your experience? I honestly don't know as this is all new to me!
 

rv7charlie

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Don't forget to tell them what MP & rpm you expect to operate at in cruise. Otherwise you may just get the 'corrected' max HP numbers.

.38 sounds very optimistic; .50 sounds a bit pessimistic, at least for cruise power.
 

TXFlyGuy

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Don't forget to tell them what MP & rpm you expect to operate at in cruise. Otherwise you may just get the 'corrected' max HP numbers.

.38 sounds very optimistic; .50 sounds a bit pessimistic, at least for cruise power.
Another figure provided by an operator of the LC9 327 Chevy is 4 gallons per hour, per 100 hp. In our case, that would be WOT and 3750 rpm (10,000' MSL). This would equate to 10 GPH fuel flow. Yes, that sounds extremely optimistic. At .45 it would be 18 GPH. There is no way that LS3 will burn that much in cruise. At least...I hope it won't suck fuel at that rate!
 

rv7charlie

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Also remember that very few (and I mean *very* few) pilots have any of the tools required to actually compute HP levels correctly in any situation except on takeoff from a runway next to the beach, with a constant speed prop equipped a/c. All other conditions are wild speculation for almost everyone flying. Ask a Cessna 172 pilot about his fuel burn, & he's likely to give you a '75%' number running at 7500' & 2400 rpm. It ain't, and it can't be. I recently had an alternative engine supplier try to convince me that the GPH at 75% on that particular engine was a number that worked out to around .23 BSFC; better than the most efficient internal combustion engine on record (a giant marine engine that has cylinders big enough for 4 or 5 guys to stand on top of each piston, comfortably). No doubt he's a good machinist, but he's absolutely clueless about mother nature & physics.

Reality is, your motor is going to burn about the same amount of fuel as any other engine that's flying in that plane, at the same climb rates and the same cruise speeds. You can compute the extra fuel it will use at increased climb rates using the flying weight of the plane & the rate of climb, and you can compute the extra fuel for faster cruise at a given altitude by the cube function of the speed ratio. All internal combustion engines are roughly the same, with noticeable but not huge improvements in BSFC in low power cruise when using computerized engine controls.

BTW, which engine controller are y'all using? Hopefully it's not the automotive unit...
 

TXFlyGuy

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We are using the Link G4+ Xtreme ECU. It is currently flying with the V6 Honda, and the V8 Chevy with excellent reliability and programming capabilities.
We will have the answer to fuel burn rates soon enough...July, 2017.
 

TXFlyGuy

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It's gph vs hp that determines bsfc. Dyno shops are renowned for fudging hp figures...
That is real time, real world consumption. The hp figure was taken straight from GMPP. Every dyno shop in the world will tell you that GM is way conservative in their numbers. The hot rod guys will tell you the same thing.
 

tspear

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That is real time, real world consumption. The hp figure was taken straight from GMPP. Every dyno shop in the world will tell you that GM is way conservative in their numbers. The hot rod guys will tell you the same thing.
I was told GM and Ford were both sued years ago for inaccurate HP numbers. It cost them a small fortune at the time. Since then, the company culture has been to be conservative on power numbers. No idea if true.

Tim
 

pictsidhe

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That is real time, real world consumption. The hp figure was taken straight from GMPP. Every dyno shop in the world will tell you that GM is way conservative in their numbers. The hot rod guys will tell you the same thing.
If the power figure you are using to calculate BSFC is 'way conservative' then your actual BSFC is less than 0.4, which is getting very hard to swallow for a mostly stock engine with a hot cam.
 
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