View Single Post
      12-07-2007, 12:07 PM   #189
lucid
Major General
lucid's Avatar
United_States
116
Rep
8,034
Posts

 
Drives: E30 M3; Expedition
Join Date: Apr 2007
Location: USA

iTrader: (0)

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
First let's dispose of the redline issue: It's immaterial except as a potential method for making more horsepower, so it's power that directly matters, no matter the rpm.

As for gearing, perhaps the best way to illustrate my point is to visualize identical vehicles except for gearing. One is stock, and the other has been treated to a more aggressive final drive ratio.
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.

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.

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
In a drag race, the geared car, given reasonable traction, will launch harder than the stock vehicle, and begin to pull away - and the reason for this is that it's making more power because it's operating higher in the rev range. Sure, you can do the mechanical advantage/torque at the drive wheels thing if you so desire, but you'll find that horsepower is a great shorthand in this environment. Enigma may be impolite, but he's exactly correct.
Enigma is carrying on a virtual debate in his mind with other people on the internet he must have encountered before, who claim high max Tq at shaft matters more than anything else. I did not say anything even remotely closely to that line of argument in my response to your post. Conversely, I've argued for the opposite on this forum several times, that you don't need high shaft Tq to win a drag race and all that, and that a higher redline allowing you to apply less Tq at a much higher rate, which means higher Hp, will win you races. I even used the example of why an F1 engine with less peak shaft Tq, but with higher Hp, will pounce on the E92 M3 with significantly more peak shat Tq, but less Hp, given equal vehicle weights.

That said, Hp is indeed, as you put it, a shorthand. It is how the capability of the engine to do work per unit time is measured, which is a very useful number to have because it incorporates a “rate”, or a delta t, whereas a Tq number does not. Technically speaking, Hp does not cause acceleration.

Cheers,