10 replies to this topic

[automalt]

Good morning to all.

 

I am planning my engine build for group 2 hill climb Mini 1275GT.

 

I had planned to do a 4.7:1 diff ratio on 10 inch wheels/slicks but I was given the advice by a friend that I should

go lower on the diff - lower as 5'1:1.

 

Anyone has an experienced idea as to which should be better, please???

 

Your input will be greatly appreciated.

 

Thanks alot and good day.

[Ethel]

http://www.guess-wor.../Tech/ratio.htm will help you see where the ratios will fall. You need to know your engine's torque & rev profile and the maximum speed your likely to want.

[whistler]

A friend of mine does Hill Climbs and he uses a 4.6:1.

[mikal]

My God, what speed would 7000 rpm say give you with a 5.1:1 ratio diff?!

Asking out of ignorance but very curious!

 

Cheers

Michael

[Ethel]

a tad under 80mph.

[mikal]

That'd be enough I guess for most hillclimbs?! Thanks Ethyl!

[nicklouse]

What is group 2?
Please provide specs of the engine? What cam etc. What box ratios?

Then what size tyres (of make) as diameter is important.

Then it is also good to look at the hills and what gear changes you will be making. Going cross gate to often is best reduced 2-3 while most changes should be in the up or down the gate.

And then there is the car. Pure hill climb or a bit of road use?

FYI I run 4.1-4.3 normally

Your cam has the biggest effect on the FD as you need to be on the power.

Any other people with minis doing the same hills? Ask them what they use.

[nicklouse]

I did ask someone on your rock a while ago as to what he used.

4.2 plus 1.044 drop gears equals 4.38 final ratio with 170/510 - 13 slicks

But I guess that is not a Group 2 build.

And he is a bit quick.

[Cooperman]

As above, Group 2 does not define the engine spec. With Gp 2 the camshaft is free and the carburation is free so long as the carbs can be mounted on the inlet manifold without the need for an intermediary device (ie an adaptor).
So the characteristics of a Gp 2 engine can be different one from another.

[automalt]

Thank you all for your help!!

 

I think I m gonna go for the 4.38 with standard ratio drop gears on 10 inch wheels on slicks which are much smaller than the standard diameter wheels. So in reality - on the road - I m gonna be lower than 4.38. Then I will adjust  with the drop gear ratios.

 

Good day to you all and thanks again..

[nicklouse]

what size tyres then? 18" or 19"

 

I am guessing 18"?