I am wondering why it doesn't make MORE of a difference.
Now, THAT’S an interesting question. Here’s my guess as to why the NSX might be different from your Vette in this respect.
There are a couple of general design principles that differentiate the NSX from other sports cars, and result from its use of the VTEC system to have that extra lobe kick in above the VTEC crossover point. One is that the torque curve is relatively flat from idle to just short of redline (as you can see from the diagram
http://www.nsxprime.com/FAQ/Technical/images/97/97NSXPowerCurve.gif ). The other is that the NSX redline is much higher than non-VTEC cars.
Next thing to note is a concept that applies to all cars: what makes the car accelerate is TORQUE AT THE WHEELS. This is equal to torque at the crank, multiplied by gearing. For maximum acceleration, you want to maximize torque at the wheels. For example, when you’re determining your shift points when accelerating, with some other cars you need to pick the point when the torque curve falls off enough that torque at the wheels in the lower gear is equal to that at the higher gear (IOW, even after multiplying torque at the crank for the gearing effect). Not so with the NSX. With our cars, you can keep them in gear almost up to redline, so that the optimal shift points are in the 7500-8000 rpm range in every gear. IOW as a general rule, your NSX acceleration is maximized by keeping the transmission in the lowest gear you can. And within a given gear, your torque at the wheels doesn’t vary all that much. All of this explains why the NSX is as quick as it is, despite relatively low torque numbers: because its torque is maintained up to higher rev points than other cars, so that the NSX can stay in a lower gear while other cars would need to upshift, lowering their torque to the wheels. This also explains why horsepower (torque times revs) is a more accurate reflection of the NSX’s capabilities than torque: because it reflects the NSX’s ability to maintain torque as the revs rise higher and higher, so that it can be used as a measure of power and as a proxy for torque at the wheels.
I think that the THEORY behind the short gears is slightly different from the ACTUAL TRUTH. What do I mean by that? The theory is that the short gears provide greater acceleration because the stock gears have too wide a gap between first and second, dropping you out of the VTEC range (because after the upshift, your revs are 4433 rpm, whereas the short gears have revs at 5013 rpm after upshifting). However, as you can see from the torque curve graph, the torque at these revs isn’t drastically different from the torque at higher revs. As for the actual truth, I suspect that there is a bit better acceleration in the short second gear than the stock second gear, but that this is primarily due to the gearing multiplier (the conversion from torque at the crank to torque at the wheels) rather than the size of the gap between the gears - IOW the same thing that makes a higher-numerical-ratio ring and pinion gear accelerate quicker in a given gear. Furthermore, with the shorter gears, the PERCEPTION of the additional acceleration is exaggerated, because your revs are higher (therefore louder) and you are reaching redline quicker (although at a lower road speed). Regardless of the additional impact of your perceptions, your acceleration will indeed actually be better in the short second than in the stock second...
...UNTIL YOU UPSHIFT. With the short gears (or R&P), you have to upshift at a lower road speed. And immediately after the upshift, you start losing the benefits, because your acceleration will be faster with the stock second gear than with the short third gear. Again, for the exact same reason - at those road speeds, you have "shorter gearing" (the conversion of the relatively constant torque at the crank into torque at the wheels) with the stock gears.
Let’s look again at the chart, "What are the numbers" (in
http://www.nsxprime.com/FAQ/Performance/gears.htm ) and see how this comes into play. Compare the numbers between the stock five-speed ("baseline") and the short gears with stock R&P (Japanese 5-speed). You can see that acceleration from 0-40 is the same (2.92 seconds) with both gearsets - no surprise, since first gear is identical between the two, and the first upshift is around 40 mph. Accelerating from 40 to 70 mph, the short gears are significantly quicker (3.68 vs 4.07 seconds, after you subtract the 0-40 time from the numbers in the table). But accelerating from 70 to 80 mph, the stock gears are significantly quicker (1.47 vs 1.92 seconds) even after accounting for the .3 seconds that it takes to complete the shift. The reason for this is that the stock gears are in second gear while the short gears shift up to third. Bottom line is that there ARE advantages of one set of gears, but only at certain road speeds, and those advantages are negated at other road speeds. Overall it winds up being close to a wash.
I am not familiar with the Vette, so I really can’t speculate on the improvements due to gearing in that car. It could be that the torque curve drops off and the gearing helps keep the car within the power band. It could be that the gearing improvements are only at certain road speeds, just like with the NSX. It could be that the differences are exaggerated by perceptions rather than what would be reflected in actual measurements. I just don’t know.
Hope this makes sense and is helpful. Sorry for the long-winded reply.
