Re: Transaxel Comparision
Just wanted to jump into this thread because this is an interesting topic. Any of my input will of course be IMHO.
first what my GT40 replica is utilizing as far as drive train
1989 G50-05 LSD (used) 135lbs. $3500
KEP flywheel $250
KEP 600 ft lb alum PP and disc $600
TO brg and TO fork $200
Mark Williams custom CV axles $1700
Audi clutch slave $30
Toyota shifter (used) $45
HiPerf shifter cables $180
Gear reduction starter $150
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Total $6655
Also spent a lot of time machining cases to shorten and to fit earlier flywheel so starter would fit, est $500 of machining. The pre '89 G50's don't have these problems. Machined my own adapter which incorporates mounts. 60 hrs labor ($200 from KEP) Also scratch built trans end of shifter linkage and modded Toyota shifter. And scratch built the rear mount. About another 120 hrs total labor (but I'm slow).
The Porsche factory rating on this trans is 325 ft.lbs. torque which is very conservative. The general consensus is it's worth about 400 ft.lbs. But no dumping the clutch at that power.
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Now I want to discuss 6 speed transmissions/transaxles, because I think they can be 90 percent hype unless the application is carefully custom tailored.
Here's some ratio comparisons
Borg Warner T5 (typical AC Cobra kit trans)
1 - 2.95
1 - 1.94
3 - 1.34
4 - 1.00
5 - 0.63
Final - 3.36 (for the sake of argument, my Cobra actually was 3.30)
9.91 combined 1st gear ratio
2.12 combined top gear ratio
7.79 spread from bottom to top
Ford GT. (Ricardo) 300 lbs.
1 - 2.61
2 - 1.71
3 - 1.23
4 - 0.94
5 - 0.77
6 - 0.63
Final - 3.36
8.77 combined 1st gear ratio
2.12 combined top gear ratio
6.65 spread from bottom to top
With the same power plant and final ratio the BW is going to have more low end accel and one less (time consuming) shift with the same top speed. The only way the GT is going to gain from the extra shift is to concentrate and shorten the power band. (which I'm sure they did) In other words more power over a shorter rpm range. Probably with induction, exhaust, cam and computer tweaks. So if your just throwing a 6 speed at your normally 4 or 5 speeded V8 setup you're not going to realize much or any perf gain. Maybe even loss with the extra shift. Basically this comparison shows the 6 speed as just adding another ratio in between the bottom and top and in fact less of a spread between bottom and top.
Here's another comparison
'07 Honda Civic 5 spd.
1st: 2.666,
2nd: 1.534,
3rd: 1.022,
4th: 0.721,
5th: 0.525,
Final Drive: 4.437
11.83 combined 1st gear ratio
2.33 combined top gear ratio
9.5 spread
'07 Honda Civic 6 spd.
1st: 3.267,
2nd: 2.130,
3rd: 1.517,
4th: 1.147,
5th: 0.921,
6th: 0.659,
Final Drive: 4.765
15.56 combined 1st gear ratio,
3,14 combined top gear ratio
12.42 spread
And the Honda 6 speed is behind a higher revving engine and/or taller tire/wheel combo so the top end is probably the same or greater. So we can see Honda has gone the other direction (that IMHO I prefer), instead of adding another ratio in between they've added the ratio outside the normal bottom/top thereby increasing the spread. Way more low end and about the same top end. This would also give you more capability at the track etc. without having to change final ratios.