Compression Ratio vs MPH

bill dedman · 04-28-2009, 10:48 PM

If they both made the exact same maximum horsepower, you'd have to look at the areas under the curve to determine which engine would build more speed, because the MPH is going to be a reflection of the total amount of horsepower expended during the entire run, not just the maximum an engine makes at its power peak. They could be both putting out 500 HP max, but one might have a torque advantage at lower rpms that would affect acceleration, but wouldn't affect the maximum horsepower at its power-peak rpm.

Maximum horsepower shows what an engine can do at its power peak, but drop the rpms down 1500 and see which engine is pulling harder; that's the engine that will haul the weight up to a higher speed, given equal maximum horsepowers for the two. The total horsepower expended over the course of the run will be greater, and so will the speed in spite of the max HP being the same.

Now, as to which engine, the low-compression or the high compression engine would have more area under the curve, I am afraid there are too many variables for me to even attempt to answer that one. It would depend on a multitude of factors. That's my 2-cents...

Bill

04-28-2009, 10:48 PM	#8
bill dedman VIP Member Join Date: Feb 2002 Location: Conway, AR Posts: 1,739 Likes: 0 Liked 6 Times in 4 Posts	Re: Compression Ratio vs MPH If they both made the exact same maximum horsepower, you'd have to look at the areas under the curve to determine which engine would build more speed, because the MPH is going to be a reflection of the total amount of horsepower expended during the entire run, not just the maximum an engine makes at its power peak. They could be both putting out 500 HP max, but one might have a torque advantage at lower rpms that would affect acceleration, but wouldn't affect the maximum horsepower at its power-peak rpm. Maximum horsepower shows what an engine can do at its power peak, but drop the rpms down 1500 and see which engine is pulling harder; that's the engine that will haul the weight up to a higher speed, given equal maximum horsepowers for the two. The total horsepower expended over the course of the run will be greater, and so will the speed in spite of the max HP being the same. Now, as to which engine, the low-compression or the high compression engine would have more area under the curve, I am afraid there are too many variables for me to even attempt to answer that one. It would depend on a multitude of factors. That's my 2-cents... Bill __________________ Bill