Diff ratio for SR20DET Conv?

[Ant_e30]

Hi all,

I am close to pushing the button on an SR20DET conversion into my E30. I won't be going crazy initially, just putting in a stock blacktop with FMIC, intake, exhaust, EBC.

I am wondering what diff ratio to go for? I have read on E30 based forums a lot of people like 3.25 or other similarly long ratios. However my mechanic has recommended 4.1, i assume because this the 'middle of the road' stock ratio for S-series cars that the SR20DET came in.

I've owned 2x SR20 powered S13's so i know how they go. i quite like the short and sharp 1st - 2nd. Plus i would rather low down power than long top end just as i see it being more useable. However seeing so many turbo powered E30 owners saying to go for lower ratios has me unsure.

i would be interested to hear people's thoughts, especially from those who have SR powered E30s.

cheers,
Ant

[FrozenSolid]

i think it would be helpfull if you posted what trans your going to use as well as the gear ratios.. but an e30 with a g260 and a 4.10 diff with boost is overkill imo. i found 3.25s to be a perfect median in my car.

[Tron]

What are you using the car for? Daily? Track? Also what trans your going to slap on it helps too.

[Ant_e30]

Thanks for speaking up guys, appreciated.

Unless i am being ignorant here, I was assuming i would be using the S13 transmission as speaking to my mechanic he was looking at sourcing a complete engine/loom/gbox etc package. So my thought is some mounts will be fabbed up and in it will go with either custom linkage or something like AKG.

The car will be 95% daily driver. I enjoy it even now with the 1.8L Auto and stock shocks and springs, so with an SR20DET and coilovers i may well do a little track stuff but to be honest that'd be only a few times a year. Nothing serious.

[The Humjet]

I've seen guys run 4.10 diff ratios on their m42 turbo e30's

[Tron]

If you run the SR trans than use the 4.10. If you use the KA trans use a 3.73.

[ill roller]

I run a 4.10 and I wish I had shorter gearing.

[derrty 30]

If you run the SR trans than use the 4.10. If you use the KA trans use a 3.73.

the sr and ka trans are the same, just different bell housings, if i remember correctly the 240 ran a 4.10 diff. so you should be good with the 4.10 in the e30.

[E30RedtopSR]

Minimum 4.10. I run 4.27 and 255/40/17 now. Its perfect.

Tried 3.73 at first with 215/40/17 and i could do 55mph in FIRST gear at 7700 rpm.
Way to high a gear. My 2 cents.
I have an e30 with an sr20det. I can speak from experience.

[E30RedtopSR]

If you run the SR trans than use the 4.10. If you use the KA trans use a 3.73.

And no to the 3.73. see previous post