130 RWKW, 4.1 diff; should I go 6 speed?

rhysk · Postby **rhysk** » Wed Feb 14, 2007 10:32 pm

My mechanic has my car in pieces. This afternoon he put the clutch in and asked me if I wanted to put the original five speed, or the six speed that is on his garage floor.

I instinctively said five speed, as I figured first gear on the six would be useless, but the more I think about it, the more it might make sense.

Does anyone have a 6 speed with a 4.1, and is it annoying changing gears more often? While I do have more power than stock, it still feels slow, so any gains in acceleration are welcome.

Fra66L · Postby **Fra66L** » Thu Feb 15, 2007 6:16 am

Go the five... with a roots blower, just ride the torque....
:mrgreen:

Casey · Postby **Casey** » Thu Feb 15, 2007 6:45 am

Unless you are also changing the diff keep the 5 speed - you'll be doing 4000rpm (possible exaggeration :mrgreen:

) on the freeway otherwise.

I find in the SP the final drive (3.6) is too short for my liking, and I would like to try a taller ratio.

Techno · Postby **Techno** » Thu Feb 15, 2007 7:00 am

With a 12.5% difference between the 4.1 and 3.6 you should stay with the 5 speed. The 5 and 6 have a remarkably similar kph per rpm over the first 4 gears and this is because of the 3.6 in the 6 speed.

If you like faster accelleration and can put up with changeing gears earlier that otherwise and using more fuel then go the 6.

pcmx5 · Postby **pcmx5** » Thu Feb 15, 2007 8:28 am

Techno wrote:With a 12.5% difference between the 4.1 and 3.6 you should stay with the 5 speed. The 5 and 6 have a remarkably similar kph per rpm over the first 4 gears and this is because of the 3.6 in the 6 speed.

If you like faster accelleration and can put up with changeing gears earlier that otherwise and using more fuel then go the 6.

Rob,(edit) I looked up your chart(Miatanet) and quite obviously the 6 speed with the same diff as the 5 speed is going to be doing more revs at the same speed in sixth than the 5 sp would in 5th.So i think I have answered my own question?

(previous post)
Are you saying that you would only use more petrol because you are extending it through gears? I thought that 6th in 6 speed and 5th in 5 speed were the same so cruising should be the same but with a better spread of ratios up to top gear.( you know,would allow someone who has more topend power to be there more often, if you get my drift!) Any info you have would be great.

My biggest concern has been the pretty lousy shift quality in the 6 speed which (in the ones I have dríven) seems to have a bit of uncertainty between the 3/4 plane and the 5/6 one.

Peter.

Postby **Boyracer** » Thu Feb 15, 2007 8:37 am

I had a 6 speed with 4.1 diff,like you said,1st gear is pretty much useless,especially with a Turbo car...as Casey says a turbo MX5 can easily handle a 3.6 or taller diff.

The shift on a 6 speed is much nicer than any 5 speed box I have dríven...it's just a case of getting used to it.

The Pupat · Postby **The Pupat** » Thu Feb 15, 2007 11:23 am

If it's at kraschie's just swap the drivetrain from his old race car into it (if he's got one). That'll make the car faster.

Otherwise anything to make it faster do it.

Abyss · Postby **Abyss** » Thu Feb 15, 2007 11:30 am

rhysk wrote:While I do have more power than stock, it still feels slow, so any gains in acceleration are welcome.

You are never happy

The Pupat · Postby **The Pupat** » Thu Feb 15, 2007 11:33 am

Abyss wrote:
rhysk wrote:While I do have more power than stock, it still feels slow, so any gains in acceleration are welcome.

You are never happy

Nah it's the truth still needs more hump.

Though if his needs more hump mine's just rediculous how much more it needs.

Abyss · Postby **Abyss** » Thu Feb 15, 2007 11:46 am

The Pupat wrote:Though if his needs more hump mine's just rediculous how much more it needs.

I was thinking the same thing about mine!

CT · Postby CT » Thu Feb 15, 2007 1:01 pm

I have an NB8B with a 4.1 and 6 speed and it's fine. Top speed is reduced but acceleration through the gears is obviously greater that with the 3.6. First gear is nowhere near useless and is fine. A 3.9 would be ideal and was my first choice but we've done 60000klms with a 4.1 and it's been a good thing.

Sheck · Postby **Sheck** » Thu Feb 15, 2007 1:21 pm

I'm running a 4.3 rear end and a six speed, it's fine. The only reason i want to change the diff is to get a better speed to gear ratio for drifting at QR. But i'm going for more power instead so i guess i'll just be drifting in the next gear up (right now i dont have enough torque to pull through 4th gear at 4k rpm while drifting - i need to keep clutch popping).

If you really dont want to change that many gears then just skip from 2nd to 4th then to 6th or something.
The only same ratio's between a 5 speed and a 6 speed is; 4th=5th at 1:1 the rest of the gears on the six speed are shorter.

Dave

rhysk · Postby **rhysk** » Fri Feb 16, 2007 12:30 pm

Thanks. I decided to stay with the 5 speed.

I did the math and it didn't appear too annoying. Still two shifts to 100 km/h, and only a hundred RPM more at 110.

Fra66L, you are a bad influence.
Pupat, that would be sweet, although top gear in his is 1:1. I'll grab a photo of the engine later today. Hopefully you can still see it under the layer of dust.