Quote:
Originally Posted by Kodak
I read a post the other day (can't seem to locate it) that confused me a bit. Maybe I misread it.
Here is what I know: Aero improvements cannot change engine rpm for a set gear and speed because gear ratios are fixed. Aero improvements can only decrease the required throttle position to maintain that speed, by putting more engine power towards forward motion (versus overcoming wind resistance). One could opt for a taller final drive ratio, but that's a whole different story.
But here's the part that tripped me up: In some situations, the lighter throttle position invites more pumping losses? I can't wrap my head around a situation in which better Cd, which means lighter cruising throttle pos., could have a negative result.
Perhaps pumping losses are increased, but it's still always a net gain - right?
I'll try to see if I can come across the post, but I think I explained it correctly.
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I believe it was Gino Sovran that published that unless gear-matching was accomplished along with drag reduction,up to 60% of the streamlining benefit could be lost,as the engine BSFC is moved into a less efficient operating regime.Hucho covers this in his book.Chrysler discovered this firsthand in 1934 when they aero-modded the DeSoto Airflow test mule.
I may have just experienced this with the trailer project.Only further,higher speed testing will tell.