Hi everybody,

I currently have a 192ps 5MT RX-8. I intend to turbocharge it in the future with Access Port ECU management and by installing the G2871 I will have about 300hp@0.6bar (crank). Just for everyday use and sometimes a trackday or even a dragster race.

My dilemma is to replace the 5MT or not? I have a 6MT already in my Garaze but I hesitate to install it in a 300hp set up car because I am feeling that the turbo set up needs to have longer gears.

Hear is the gear rations for 5MT vs 6MT

Transmission Gear Rations
Type 5-speed manual ---------------------6-speed manual
1st 3.483-------------------------------------- -3.760
2nd 2.015- -------------------------------------2.269
3rd 1.484 --------------------------------------1.645
4th 1.000 --------------------------------------1.187
5th 0.762 --------------------------------------1.000
6th – ---------------------------------------0.843
Final 4.444 ------------------------------------4.444

192ps 5MT RX-8 has rev limiter at 7500rpm

What do you think. ?

Thanks

 

I think try it with the 5 spd and see how that works out . Looks like the 5 spd has a taller top gear anyway , no doubt due to the lower rpm limit .

 

The rev limit on the 192ps MT5 is 7500rpm. So a 6MT on the 192ps 5MT and also 300hp may be proved to be too short?

 

6MT
Tyre Diameter = 2071.46 mm
1st Gear = 55.84 km/h
2nd Gear = 92.53 km/h
3rd Gear = 127.63 km/h
4th Gear = 176.87 km/h
5th Gear = 209.95 km/h
6th Gear = 249.05 km/h


5MT
Tyre Diameter = 2071.46 mm
1st Gear = 60.28 km/h
2nd Gear = 104.19 km/h
3rd Gear = 141.47 km/h
4th Gear = 209.95 km/h
5th Gear = 275.52 km/h
6th Gear = -

 

It looks like the 6 gear transmission is better geared for your application.

 

^ ok but my car is rev limited at 7500rpm as a result the 6MT will have the following speeds

6MT
Tyre Diameter = 2071.46 mm
1st Gear = 55.84 km/h
2nd Gear = 92.53 km/h
3rd Gear = 127.63 km/h
4th Gear = 176.87 km/h
5th Gear = 209.95 km/h
6th Gear = 249.05 km/h

1st and 2nd gear are very short how can a 300hp RX-8 make use of those gears???

 

Yes, they are very short. In the 5 gear gearbox however you have gears that are too long up top.
How many times do you start when driving? (ie, using 1st gear) and how many times do you use the other gears?
Both transmissions aren't perfectly geared but it seems that the 6 speed ends up being a better compromise!

 

Yes this is true and you are right. In 5MT I would benefit from 1st-2nd-3rd gear whereas in the 6MT I would benefit from 4th-5th-6th

5MT it is not bad at all. The biggest problem I think is the 4th gear which is 1.1 and takes too long to rev.

Furthermore, I guess that I can gain some advantage with the 6speed in a track day.

 

With the AP I believe you could raise that limit up a bit, no?