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Gear Ratios, 20b PP.

Old 05-26-12, 09:57 PM
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Gear Ratios, 20b PP.

I've not run a PP before (in fact never run a rotary before) however due to class regulations in offroad racing there is a distinct advantage to running a 3 rotor. I've got a 6 speed sequential Fortin and wondered what gear ratios or RPM drop I should plan for with a 20b PP. I know I'm pushing it here but I had hoped that someone was seriously running a 20b hard and would be willing to share their experiences.


Current ratios designed around a modified 13brew and with an adjusted 8,800 RPM redline puts my 6th gear beyond what the tin can of an offroader will ever gain in speed. It effectlively turns the box into a 5 speed.


Gearbox Ratios Engine Parameters
1st 3.46
2nd 2.50 Redline 8,800
3rd 1.93
4th 1.61 Revs at what speed? 240
5th 1.37
6th 1.19
Final Drive Ratio
Reverse 3.51 3.88

Results
KPH between gears Redline km/h RPM Drop RPM in new gear
1st 104 0 0
2nd 40 144 2444 6356
3rd 43 187 2006 6794
4th 37 224 1459 7341
5th 40 264 1320 7480
6th 40 303 1147 7653

Reverse 103

Revs at 240 km/h in top gear 6961


Adjusting the CWP gives me a more realistic top speed but may put the gears too close together.

Gearbox Ratios Engine Parameters
1st 3.46
2nd 2.50 Redline 8,800
3rd 1.93
4th 1.61 Revs at what speed? 240
5th 1.37
6th 1.19
Final Drive Ratio
Reverse 3.51 4.86

Results
KPH between gears Redline km/h RPM Drop RPM in new gear
1st 83 0 0
2nd 32 115 2444 6356
3rd 34 149 2006 6794
4th 30 179 1459 7341
5th 32 211 1320 7480
6th 32 242 1147 7653

Reverse 82

Revs at 240 km/h in top gear 8720

Last edited by redmist336; 05-26-12 at 10:04 PM.
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Old 05-26-12, 10:04 PM
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Sorry the tables are in an excel spreadsheet and for some reason aren't formatting well.
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