Diff Ratio question?
Turbo Mini Forums

Hi All,

Just a quick question, Has anyone used a 2.95:1 Final drive on a turbo box with 10" wheels? If so what sort of revs are you getting in top Gear at 60mph?

Im currently building a supercharged motor for my mini and want it set up for road and cruising and have been pointed in the direction of the 2.95:1 ratio as a good all rounder, but the chap that suggested it didnt give me any figures for revs and speed.

Any help would be appreciated.

Rob

what profile are your tires???

someone on here has a really good speed/rev/gear/wheel/fd/tyre calculator that they can email you, cant recall who though?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

I'm using a 2.95 diff and 10" wheels.

On the basis that the 10" tyres are 165/70/10, then you get approx 20mph per 1000 rpm.

I think it's a good choice for a forced induction road car where you do a lot of motorway style driving.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Isnt that what Matt Woods runs?

i got the gear calculator and youll be doing aproximatly 3100rpm at 60mph in forth gear!!

Schrödinger's cat - so which one am I ???

look for 'gearcalc' on google

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

http://www.guess-works.com/Gearbox/Technical/ratio.htm

Thanks for all the info chaps, I'm using 165 70 10's and from what you tell me it sounds like the perfect diff for me to go for as Im looking to be putting some serious mileage in over the next little while. and many thanks for the diff calculatlor, Ive not seen that before and should be a great help.

Rob

A lot of it comes down to personal preference and what you want from the engine.

I personally will not be going lower then a 3.1 again. The 2.9 was fine in the daily drive but not a lot else, I never got close to maximum engine rpm as it couln't pull it (that was a 998 though) it was good on the motorway though.

The 3.44 I have now is ok for the 4000 miles or so my car does a year but it would be nice not the be doing a little more then 90 mph at 6000 rpm

The 3.1 I found to be a good compromise. 60 is at about 3500rpm and had no problem up the motorway sat at 80 at about 4500rpm.

what is the spec of engine it is going on? and what sort of milage are you looking to cover?

Edit: having read the thread again a 2.95 would probably be a good option.

Edited by minimole23 on 11th Jan, 2009.

Cheers Mininole23,

between my brother (Mr GRS of GRS motorsport) and I we are building our own supercharger conversion, I want to aim for the ultimate road mini, and thought a supercharger would be something a bit interesting to have a go at and give plenty of low down and mid range torque. Ive got a share in a turbo mini as well so didnt see the point in having 2 turbo's. The engine spec is a metro turbo block with standard bore and pistons, running an 8.2:1 compression ratio, Kent 266cam, thought it was a good cam for mid range grunt and had one kicking around in the shed, but im open to suggestions if anyone thinks different? Also Ive got a flowed and ported head that I'm thinking of using, but it doesnt have the sodium filled exhaust valves, is this an important thing to have? if anyone has any thoughts on this I'd be pleased to here them? Not sure how many miles I will be doing, it tends to vary year on year, but will be getting in a fair few and plenty will be long journeys so dont want her screaming her lungs out on the motorway, so reckon I prob will go for a 2.95:1 diff, once Ive found one that is? So if anyone has one kicking around let me know!

http://www.csgnetwork.com/multirpmcalc.html

The king of auto-calc sites.

Bugger off, I'm getting there.