Increased RPM's ??

[Excaliber]

I've often noticed in cars with an overdrive that top speed is still "limited" to the max engine rpm in the 1:1 gear. 5400 rpm, top loader 1:1 4th gear being 128 mph.

OK, so lets say you have a 5 speed. At 128 you shift because engine rpm is at it highest. RPM falls to say 4800 rpm (estimated), but top speed REMAINS about 128 or even FALLS to 126.

Like SCOBRAC pointed out: At some point "aero drag", tire friction, rotational forces in the drivetain, these all "eat up the horse power" and you can't "get there from here".

I recall the LeMans Porsche 908 series cars (I think it was 908) had about 350 hp (not "that much" for a race car) but it could do 200 mph! The 917 had about 1000 hp? Their top speed was very close to the same. So there is a lot more going on here than just rpm! No doubt the 917 had a lot more "down force" at that speed and was more stable. I bet the 908 was "on the edge" and cleared for takeoff at that speed.

I guarentee you will NOT do anywhere near 200 in a Cobra with only 350 hp. But you might "approach" that number with, say, 600-700 hp? 600 hp being enough to let your engine turn up to max rpm. Or does it make 600 hp BECAUSE it turns high rpm? Both!

But 350 hp aint enough with a Cobra "brick" body to do 200! I don't care WHAT gears your running or how much RPM your engine is "capable" of! 350 hp at 5000 rpm or 8000 rpm is STILL 350 hp. But I bet the 8000 rpm motor is way smaller than the 5000 rpm motor and there both making the same hp!

Now Racer "X" would prefer the smaller, lighter, higher reving motor for his race car! Others may prefer the "torque" (pulling power like a "truck") at lower rpm the big motor would have.

If your "pulling stumps", go for torque! If you want to get there "in a hurry" go for high rpm (horse power).

Ernie