Best shift points for optimal acceleration ?

[MvM]

Was doing some acceleration runs with the AP-22 last night on a quite piece of road. Not enough room to go really fast but there was enough space to do some 0-100 runs (that's kph, not miles).

Quickest run so far is only 5.61 sec. That was with about a quarter of fuel left. Spare and bracket are removed, Odyssey 680 mounted. Also, Taitec GTC exhaust and Dali-chip.

What I do is, start at around 4K rpm, then run the car up to its limiter (which is now higher due to the Dali-chip) and shift to 2nd.
I wonder, given the highes torque is a lower rpm than the rev-limiter, should I shift then and not at redline?
Although torque at the max. torque revs may be higher than at redline, being in second gear would lower by torque at the wheels. Or am I overlooking something.

 

[ChopsJazz]

Is this the info you need?

 

[nsxtasy]

I wonder, given the highes torque is a lower rpm than the rev-limiter, should I shift then and not at redline?
Although torque at the max. torque revs may be higher than at redline, being in second gear would lower by torque at the wheels. Or am I overlooking something.

You are not overlooking anything. You should shift at the point at which torque at the wheels (torque times gearing) is equal both before, and after, the shift; if there is no such point, shift at redline. This is mathematically equivalent to the point at which horsepower at the wheels is equal both before, and after, the shift.

As a practical matter, that occurs with the stock six-speed NSX somewhere between 7690 and 8000 RPM in each gear. I haven't done the calculations for the stock five-speed NSX but I would suspect that the optimal shift points would again be up in that range. Your mods may, or may not, change the points that result. (The calculations would remain the same, but the torque and hp values for each RPM would be different.)

The discussion in the link is quite comprehensive.

 

[Eric5273]

I'm still learning how to upshift in the NSX. I've never had a car that had such a high redline and what I'm learning is the most important thing about upshifting is where you end up in the rev range after the shift.

In most cars I have owned, after the shift you fall out of the "power band" and then have to accelerate a bit to get back into the power band again. In the NSX, when you finish a shift, it seems that you end up right in the middle of the power band and the car actually lunges forward a bit. I guess this is due to such a wide power band, i.e. VTEC. This definately makes the NSX lots of fun to drive.

 

[Number9]

One pragmatic tip to keep in mind - the tach in most of the NSXs I've seen run at dynos read slightly optimistic, so that an indicated 8K RPM is typically a few hundred RPM less. So shifting at an indicated 8K RPM should work pretty well if your tach reads a bit higher than the actuals. If you bump the rev limiter, you're shifting too late...

 

[MvM]

I have the Dali-chip installed, which raises the redline to, I believe, 8300 rpm. That's an indicated 8500 on the tachometer.
I did some additional runs tonight on the same strech of road but keep hitting around 5.6-5.8 to get to a 100 kph. It doesn't seem to matter much if I switch of TCS or not, both on or off, I keep running in the same figures.
Actually found enough space to do exactly one run 0-190 kph run, of which the results are listed below.

Start Speed 0.0kph
kph s g km kW
10.0 0.52 0.66 0.000 25
20.0 0.93 0.67 0.002 53
30.0 1.32 0.76 0.005 91
40.0 1.87 0.55 0.010 88
50.0 2.37 0.57 0.016 115
60.0 2.87 0.57 0.024 137
70.0 3.41 0.49 0.034 140
80.0 4.25 0.41 0.051 135
90.0 4.96 0.38 0.068 145
100.0 5.66 0.39 0.087 164
110.0 6.44 0.34 0.110 162
120.0 7.60 0.23 0.147 130
130.0 8.61 0.28 0.183 165
140.0 9.66 0.26 0.222 170
150.0 10.81 0.23 0.269 171
160.0 12.14 0.19 0.326 163
170.0 13.96 0.17 0.410 159
180.0 15.74 0.16 0.497 165
190.0 17.70 0.13 0.599 162

All this in kph of course. Would translate to 0-60 mph in 5.46, 0-100 mph in 12.14.
This was with TCS on with the road curving very slightly upwards and with my tank almost empty. Shifting just below my (new) redline, so a little in the red on the tacho

Maybe it is not me, maybe I've just got me a slow car

 

[j14nsx]

Maarten,

Maybe it is you car. You do have big wheels. I have used a AP22 as well, and did some 0-100kph runs. I don't think I drove as hard as I could but still got 5.5 secs. This was with me car as standard.

 

[MvM]

j14nsx,

You might have a very good point there. My BBS-II rims with new tires weigh 25.1 lbs each. Now the tires are practically worn out, so I can shave off a good 2.2 lbs for each tires in rubber lost, but still these wheels are very heavy indeed.
I've been looking for new wheels but haven't made up my mind yet. And neither have supplemented my cash-flow enough after all the other stuff I've bought

 

[NCC-1701D]

i don't think that is slow ..if you can get to 160 km/h in 12.14

(me from Canada) which is almost 100 mph..is that close to the trap speed of a car doing the 1/4 mile....

your 1/4 miles times would be somewhere in the high 12's to low 13's.....

 

[MvM]

NCC-1701D

(You would be a Star Trek fan now would you )

Well, I could do some 1/4 mile runs as well. The AP-22 gives you the possibility to use either metric or US-system settings. Since I live in Europe the metric system is more obvious of course.
Maybe I will give it a try somewhere this week. Might be interesting...

 

[96-EJ6]

Maybe try it with the trac off...most cars bennefit from the removal of trac from the acceleration equation.

 

[peiserg]

redline, always shift at redline, or the revlimiter, whichever comes second.