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Horse power to fuel ratio

Bob Burnside

Bob Burnside

Well-known member
My question is what will use more fuel a small block or big block, giving they both put out 500 HP and 500 foot pound of torque. what will last the longest if they are both taken cars of the same? Is there a formula for fuel burn and HP?
 
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both engines would burn the same amount of fuel on paper .How long a small block would last generating 500 hp is debatable.

A formula that can be used is .5 lbs fuel per hp per hour.It realy depends on how efficient yor engine is. Example A 500 hp engine stuck in the mud using all of its available power would be burning 250 lbs of fuel per hour +or - close to 40 gallons per hour depending on how much your gas weights.The Same boat cruising burning 8 gallons per hour generates about 100 hp to cruise around.
 
Stan is rite on. There is only so much "Power" in each gallon of gas. An efficient engine can get more HP out of the same gallon of gas but there is a narrow range limit. To use less fuel you must use less HP. The single most important factor in boat fuel economy at a given speed is weight. Less weight= less HP to get the same speed. Less HP= less gas burned per hour. Air boats are flat bottom so there is very little advantage to one hull over another (For fuel use only) beyond weight.

A quick way to guess fuel use is 1/10 of the HP in gallons used per hour. This is not the true formula as it comes out showing more gas burned than actually will be but it gets you close and you can do it in your head fast. 1/10 of 500 is 50 so a 500 hp engine will use LESS than 50 gallons per hour wide open.

Diesel engines are more efficient because the engines are built better and more importantly each gallon of diesel fuel contains more BTU (Energy) per gallon than gas.

JIM
 
Smaller things are always more efficient! Smaller motors are more efficient! A 500HP motor is now a walk in the park and very reliable the metallurgy and quality of parts has shot thru the roof. Ten years ago when you bought a set of pistons you bored each cylinder to a piston, well now if you buy a set of pistons there is no need to even number them because they are all with in a ten of one thousands of an inch. The old forged pistons were with in 3 thousands of an inch if you were lucky! Anyway a 500HP motor today is about as reliable as a 300HP motor was in 1970. Think about it few 400HP 454's in 1970 never made it to 50,000 miles now probably 90% of all the 405HP LS2's in Corvettes will make it well over a 100,000 miles! Germany, Japan, Asia none of them have anything that can run with the GEN III Chevy Small block! Diesels are more efficient because they burn fuel and they have a more complete burn, gasoline engines explode the fuel and do not have a complete burn! This is because gasoline is a more volatile fuel!
 
P.S. the smaller engine would burn slightly less fuel because there is far less parasitic drag in the engine! If you took a 500HP Big block and a 500HP small block and turned them booth with a 20 HP electric motor the small block would turn more RPM's and require less amps to do so!
 
For what it is worth I have run both big and small blocks and I found that the small blocks will burn a little less fuel at cruise but they do not last as long. The more power you squeeze out of a smaller box the quicker it will wear out or let go. The other side to this coin is that it cost much less to blow a small block motor into a thousand pieces then it does a big block.
 
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