Andi Baritchi
andi@airmail.net
www.Boostaholic.com
4/2/2000
Optimal shift point calculation
for my '98 Supra TT, at BPU++.
This is according to my 424.4rwhp dyno
chart from 3/31/2000.
Note: The theory behind these
calculations is that you always want to be
in the gear with the highest horsepower, as at any given speed that will
provide the most rear wheel torque. Hence, I've calculated what RPMs you
end up at after each shift, and found the RPMs at which the HP curves in
the "before shift gear" and the "after shift gear" intersect.
Note that my tachometer reads
high by 200 RPM at redline. Thus, I've
calculated the shift points in terms of both actual RPMs and Toyota
Tachometer RPMs. For reference, my tachometer says 7000 RPM at the
rev limiter, and according to the dyno machine it is only at 6800 RPM
at fuel cut.
Summary:
** 1-2 SHIFT AT ACTUAL 6800 RPM (7000 Tach) **
** 2-3 SHIFT AT ACTUAL 6500 RPM (6700 Tach) **
** 3-4 SHIFT AT ACTUAL 6200 RPM (6400 Tach) **
** 4-5 SHIFT AT ACTUAL 6300 RPM (6500 Tach) **
** 5-6 SHIFT AT ACTUAL 6100 RPM (6300 tach) **
Calculations:
gear ratios:
3.83 first gear
2.36 second gear
1.69 third gear
1.31 fourth gear
1.00 fifth gear
0.79 sixth gear
thus the RPM shift ratios
are:
0.62 1-2 shift
0.72 2-3 shift
0.77 3-4 shift
0.76 4-5 shift
0.79 5-6 shift
Note:
bRPM = before shift RPM
aRPM = after shift RPM
bHP = before shift HP
aHP = after shift HP
1-2 shift
bRPM aRPM bHP aHP
6400 3968 380 220
6500 4030 380 225
6600 4092 375 245
6700 4154 370 260
6800 4216 365 280 ** 1-2 SHIFT AT ACTUAL 6800 RPM (7000 Tach) **
2-3 shift
bRPM aRPM bHP aHP
6300 4536 380 375
6400 4608 380 380
6500 4680 380 385 ** 2-3 SHIFT AT ACTUAL 6500 RPM (6700 Tach) **
6600 4752 375 390
6700 4824 370 400
6800 4896 365 405
3-4 shift
bRPM aRPM bHP aHP
6100 4697 395 390
6200 4774 390 395 ** 3-4 SHIFT AT ACTUAL 6200 RPM (6400 Tach) **
6300 4851 380 400
6400 4928 380 405
6500 5005 380 410
6600 5082 375 410
6700 5159 370 410
6800 5236 365 415
4-5 shift
bRPM aRPM bHP aHP
6100 4636 395 385
6200 4712 390 390
6300 4788 380 395 ** 4-5 SHIFT AT ACTUAL 6300 RPM (6500 Tach) **
6400 4864 380 400
6500 4940 380 405
6600 5016 375 410
6700 5092 370 410
6800 5168 365 410
5-6 shift
bRPM aRPM bHP aHP
6000 4740 400 390
6100 4819 395 400 ** 5-6 SHIFT AT ACTUAL 6100 RPM (6300 tach) **
6200 4898 390 405
6300 4977 380 410
6400 5056 380 410
6500 5135 380 410
6600 5214 380 415
6700 5293 370 415
6800 5372 365 420
