View Single Post
      12-09-2007, 01:16 AM   #194
Lieutenant Colonel

Drives: Legacy GT - 13.704@99.39
Join Date: Jul 2007
Location: Manheim, PA

iTrader: (0)

It's in the numbers

Originally Posted by lucid View Post
Hi Bruce, thanks for the response. So I questioned two things in you PS.

1. How come redline does not matter? In the sense that it will allow you to apply Tq at even a greater rate and result in more power. You are saying the same thing above, and as far as I can see, contradicting what you said in your PS unless I am missing something here.
Of course you have the potential for making more power when you can run the engine faster, but it's only the power that matters, and what the rpm range is where the power is made is immaterial.

Originally Posted by lucid View Post
2. I looked at the M3 example with the different final drive ratios. Of course it will be a seesaw battle, and that the more aggressively geared car will win although that depends on when the race ends since it will take a hit on top speed, but for most practical purposes, that’s not an issue. What you are claiming is that the aggressively geared car is winning because it has some kind of an acceleration advantage early on ONLY, which forms the basis for the rest of the race. That part seems inaccurate to me. The aggressive gearing will give it an acceleration advantage throughout the race overall—ignoring the details around shit points—and not just at the start. That’s just physics. I don’t see how the aggressive final drive ratio all of a sudden will cease to be an advantage just because you are past a certain distance in the race since it is a static factor.
I had hoped that my pointer in note 184 to the site where the geared vs stock E46 M3 simulation was made would make the point, but perhaps another look at that data would help. Let's call the "distance units" referred to in that illustration as each representing a car length. It doesn't particularly matter, but it's probably not way far off. In that note, the geared E46 M3 had a .2752 distance unit advantage at 36 mph, which was the first shift event in the race, obviously in the geared car. If I call a car length 15 feet (about right), then the geared car had an approximate four foot advantage at that point and would be about a fender up on the stocker. That equates to about a .075 second advantage.

Now, let's flash forward to 182 mph, the last data point shown in that note. At 182 mph, the geared car has a .8489 car length advantage, call it about 13 feet. At 182 mph, that's about .05 seconds.

You see the point, I think. In the first couple of seconds into the race, the geared car gets a four foot advantage at 36 mph, and then in the next 146 mph and what, maybe a minute? it gets another nine feet, and actually loses some time (from a .075 second advantage to a .05 second advantage) against the stocker.

Yeah, once you get up into the power range, gearing kind of disappears in the noise. Edit: Furthermore, if you get into a race from a rolling start, either car may in fact be able to win, based on who got the early advantage. That early advantage will be determined by the starting speed, and whether the stocker can be in a lower gear at the onset.