Wind force figures

[Paul Workman]

I ran across a tech artical that I'm decyphering, but there is a missing piece to the puzzle that I need. Anyone have wind resistance in ft# corrected for sealevel at say 100 mph for the ZR-1 (C4)?

TIA,

P.

[Kevin]

i need my maths to have less letters and more numbers. the only post i understand in this thread is curtis'

[Paul Workman]

Well, you're very intuitive, my friend. And, although that isn't the particular question I'm pondering, there is some tidbits in the treatments I can use.

Putting a little more light on the subject, my questions have to do with differential gearing choices vs. different engine performance characteristics.

In a nutshell, it stands to reason that a 400 RWHP (LT5) and a 580 RWHP LT5) would benefit from efforts to optimize the differential ratio for drag racing, for a given set of (ZF-40) gear ratios. Other scenarios come to mind as well.

My Cd question relates to wind resistance which, along with rolling resistance, etc, which needs to be considered - especially since some impediments change in a linear fashion and others (line air resistance) change exponentially with speed...is the reason for my OP.

After assembling a workable model, I hope to run several "what ifs" so I may edify myself a bit more w/ regard to selecting the optimum differential gear ratio for a set of given circumstances (i.e, engine characteristics). Not trying to do anything but learn a bit more about gearing, and have fun in the process.

I'm a sick bastard, I know. But, I love this chit - as you know!

P.

[A26B]

Is this of any interest?

[Paul Workman]

Originally Posted by A26B

Is this of any interest?

That'll do!

P.

[USAFPILOT]

I would have never expected the C5 to have more drag than the C4...is that what those charts are showing?

[cward]

Removing the mirrors will also help. Dynomite's figures look pretty good to me. I had about 370 rwhp when I ran BBORR in 2001. Stock suspension w/mirrors. Ran a sustained 181 mph. 2002 #364 ran a little faster with coilovers, no mirrors, and about 390 rwhp.

[Paul Workman]

Originally Posted by Dynomite

Starting from scratch............Coefficient of drag (Cd) depends somewhat on the Rynolds Number (for this discussion we shall consider Cd constant or 0.34). Reynolds Number Calculator (just to show what is involved as there is no chart showing Cd vrs Reynolds Number for ZR1 vehicles) http://www.efunda.com/formulae/fluids/calc_reynolds.cfm

Question: Where did you pull the .34 Cd from? It is becoming a critical component to graduating from achedamia to reality... Some empirical wind tunnel data would be ever so helpful. I seem to recall reading that the C4 was the first Vette to take considerable advantage in wind tunnel data in the design of the body. Must be some data somewhere, methinks. I suppose the Cd could be reverse engineered, but that has pitfalls too. Googling...

P.

P.

[cward]

Been following this thread with some interest. I can even understand the math most of the time. However, it mainly interests me in the academic sense. There are so many variables in actually trying to go fast that common sense seems to apply in the real world. Yes, all the math is there but when out on the road course with the pedal to the metal on a very long straight, math is just math. You are trying to go very fast without flying. C4 is not an airplane. However, at 200+ mph, the fact that is might try to become one is there in the back of your mind. Really do not want to try a back flip. And there are dips and bumps in the road. It is a rush when all four wheels leave the ground at high speed but not one that you are trying for. I realize the topic started as a drag race question but it also (perhaps even more so) a top speed problem. The LT5 is a great engine for top end as it has a very broad power band. Still you have to be in that power band to achieve your goal. Which is why 6th gear is no good for most Z's because when you shift from 5th to 6th, even with 4.10 gears you drop too many rpms and are not producing enough hp to continue to accelerate. So even if the math shows 185 @ 4200 rpm, forget it, it ain't happening unless you are producing about 400+ rwhp at that rpm and I don't know of many lt5's doing that. I tried shifting out of 5th at about 7400 rpm and dropped out of my power band. This was with 4.10 gears. I achieved about the same speed (181) in both 5th and 6th. I shifted a few times just to test and later in race to cool the engine oil.

So I take this thread as informational just like dyno info. It gives you some idea of what is going on but when you take it to the track you get to do actual testing under the existing conditions and that works. Just my opinion. I did like the thread. Most of the time, the more information you have, the better.