Kenji,
As I'm sure you're aware, I have driven in a lot of track events (well over one hundred). One thing I've found is that appropriate shifting can make a significant difference in lap times. And gearing can affect shifting dramatically. We have a track near here called GingerMan. It has ten turns and is 1.8 miles long. It has relatively short straights. When I drive it in my stock geared '91 NSX, I upshift and downshift between second and third five times each lap. When I drive it in my ITR, I leave it in third all the way around, because I run out of revs in second gear before track-out at every turn, so there's not much benefit. I point this out, not to compare the ITR with the NSX, but only to note that shifting can provide a significant benefit, but only when deliberately chosen for the places where it provides the most benefit.
However, I am not sure whether you are better off with a gearset that requires more shifting or less shifting. Let's make up an example of a track where your speed is varying from 60 to 80 mph all the way around the track, and assume you have a stock five-speed. If you have a stock R&P, you will leave the transmission in second gear all the way around the track. If you have a 4.55 R&P, you will be doing a lot of shifting, to keep it in second gear from 60 to 72 mph, and upshift to third where you will be from 72 to 80 mph. In this situation, is one "better" than the other, i.e. will produce quicker lap times? I'm not sure. One will accelerate faster in the slower portions, and the other faster in the faster portions. I think that overall, the differences will be relatively minor.
The differences between the various gearsets are very easily quantified. You can check the numbers and see for yourself which ones do better at the speeds you're most interested in. You can take your slowest and fastest speeds as you do a lap of Thunderhill and see which gearset has the advantage within that range. (If you let me know these speeds, I'll be happy to give you Bob Butler's calculated acceleration numbers for the gearsets you're considering.)
I think your best bet would be to see if you can catch rides with other NSXers around that track, particularly the experienced instructors, hopefully driving different NSXs with the gearsets you're considering. Watch where they shift, and see if you think it might work for you. If you have the opportunity, see if you can drive their cars for a few laps, and see how you like it. Do the same for driving around the street.
Also keep in mind that perception thing. You may find that you like to reach redline sooner by lowering the shift points, regardless of how much actual difference in performance that represents. If you do, then go for the shorter gearing.
My personal opinion is that, if money were no object, I would probably choose the following gearsets, in order of preference starting with the most preferred:
1. Six speed, 4.55 R&P
2. Six speed, 4.235 R&P (I'm not sure this is even feasible)
3. Six speed, 4.062 R&P
4. Short gears five speed, 4.235 R&P
5. Short gears five speed, 4.062 R&P
6. Stock gears five speed, 4.235 R&P
7. Stock gears five speed, 4.062 R&P
8. Short gears five speed, 4.55 R&P
9. Stock gears five speed, 4.55 R&P
However, the actual performance differences among any of these options are too minor to be worth the cost to do so, so for that reason, I wouldn't bother. Just my personal O.
[This message has been edited by nsxtasy (edited 24 September 2002).]
