3.7:1 diff with turbo
Turbo Mini Forums

What's the general opinion of running a 3.7:1 diff with a turbo set up.... and valid reasons for and against

You really want a taller diff 2.9:1 or 3.1:1
This is all dependant on personal prefferance, you probably find you will run out of each gear too quick with the 3.7, thats if you can stop it spinning the wheels.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

There's no way anyone can advise you unless you tell us what you intend on doing with the car.

A 3.7:1 would be great if you're hill climbing/sprinting, but not so great if you want to travel any sort of distance.

In the 13's at last!.. Just

i'm going to attempt to run a 4.5:1 diff in my turbo... Albeit not a road car, but i'll report back how usable / unusable its going to be once its up and running properly!

I agree with Gary, it's personal and depending on what the car is going to be used for.

I'm going to be running a 3.4 but I have been running a 2.9 for the last 3 years

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

I've been thinking about this over the past day or so re the diff I'm going to put into the metro. I've currently got a 3.6 to go in however, having watched the sprinting at Kames yesterday, I'm considering the 3.7 as well.

having said all that, my road car has a 2.9 in it

Edited by Rob Gavin on 14th Apr, 2014.

Not bothered about top speed , off the line and back road driving ....acceleration ....

I've gone for a 3.2:1 in the turbo on 10's.

The mini will be used for spirted driving and of course MITP and trackdays.

Had a 3.44:1 in the n/a and found it a little to high for motorways.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

also depends on size of tyres and wheels. 13inch slicks add a fair bit to the rolling radius. low profile 10inch tyres are going to shorten gearing considerably.

You don't have to rev the nuts off turbos to get the power, so I'd go with a 3.1, or a 3.44 if you really want. Acceleration will be quick enough without going with a 3.7 imo

now this is helpful as all my thoughts were on yesterdays viewing!

Car is the metro challenge car running a conservative 150-160bhp on 12's with 175 tyres (although I could consider 13's as well. The car originally ran a regulation 3.9 diff for track stuff. Unfortunately I've never driven it yet or driven a sprint of hill climb before so all my thoughts are just that

sorry for the thread hijack!

Rob

What is the bottom end spec of the engine, turbo choice etc? If the power band would suit the gearing then go for it.

this calculator may help you decide.

http://www.guess-works.com/Tech/ratio.htm

I'm using a 3.44:1 which is great for my car which is only used for the strip and short journeys ( other than driving to the strip ). I'm considering other motorsport too.

If it was only to be used on the road, I'd go for a 2.9:1.

In the 13's at last!.. Just

I'm using a 3.44:1 which is great for my car which is only used for the strip and short journeys ( other than driving to the strip ). I'm considering other motorsport too.

If it was only to be used on the road, I'd go for a 2.9:1.

In the 13's at last!.. Just

For sale.... 3.7:1 straight cut (properly straight cut) crownwheel and pinion for standard/ cross pin/ ATB diff ... £100 plus £7.50 post

gearkit makes a big difference too,

IMO a 3.7 with a std helical box would have a completly pointless first gear.

I would think it has more to do with first gear ratio rather than top speed. I know from experience that with 100lbft torque, first gear on a standard A+ gearset was pretty much a waste of space.

A taller first is definately order of the day with the 3.7:1 FD

O.T Gary what's your top speed at what rpm do you get?

I think yours is a similar spec to me.

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

Not been flat out in top yet Eden. If it was in one piece, I'd give it a try now.

In the 13's at last!.. Just

Should be around 100 at 6k rpm, which isn't too silly really.

Edited by minimole23 on 14th Apr, 2014.

That's kool I'm expecting 8k out this engine

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

Similar spec... ? 8k?

In the 13's at last!.. Just

Fair point Gary.. It was. We both got into the 13's anyway

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!