QUOTE(Steve @ May 29 2017, 07:43 PM)
QUOTE(Montreal914 @ May 29 2017, 01:07 PM)
QUOTE(Steve @ May 29 2017, 12:35 PM)
Wouldn't you want a higher ring & pinion to raise the gears? With the 915 Porsche went from 7:31 to 8:31 to raise / lengthen the gears. That sportomatic ring and pinion would lower the gears.
I thought the OP was looking for options for a taller ring and pinion since he has a bigger output engine. Stock is 7:31, and Sporto is taller 7:27.
Easiest is what Mark Henri suggested with different ratios. I always think that A-F (first, second) are low for torquey engines, hence taller R&P, but I don't have experience with these types of engine.
The goal with a bigger engine (more HP) is lower RPM's for the same MPH.
Example a 29:21 5th gear in a 7:31 Ring and Pinion 915 gear box is 70mph at 3k RPM's. The same 29:21 5th gear in a 8:31 Ring and Pinion 915 gear box is 80mph at 3k RPM's.
If we could increase the ring and pinion from 7:31 to 8:31 in a 914 gear box, we could lower the RPM's in each gear and make all 5 gears taller.
A 3.0 six with webers produces enough HP and Torque to make 1st gear pretty much worthless. It winds out way to quick.
Starting out in second, makes for a tall 1st gear.
Play with the gear calculator link. Change the ring and pinion from 7:31 to 8:31 and watch 5th gear increase by 10mph in 5th at 3k rpms.
Yep, exactly what I was trying to express while replying to the OP. He was asking about a taller ring and pinion option.
The Sporto ring and pinion that I'm hoping to fit into a 901-914 box is 7:27 (0.259) vs 7:31 stock (0.225)
. I have heard it has been done before
Your 8:31 option on the 915 happens to be 0.258, pretty dam close to the Sporto 0.259!
This could render both first and second on the 901-914 box better suited for torquey engines, the rest of the gears are open as usual.
Other option, redo the whole 901 box box with a 904 shaft, as previously mentioned, and select 1-5.
No matter how, all fun projects