1 reply to this topic

[robminibcy]

Hi, im doing research into the engine options for my mini. My plan ultimately is a specialist component twin cam supercharged engine with around 160bhp (not sure on torque figure). It'll be a road car and won't be at all stripped out. I'm trying to find out about what gearboxes can be used. I really don't want straight cuts as it will be covering a lot of long distance trips and be doing high milege. I don't mind straight cut drops though. I have seen a few of 5 speed boxes and this sounds ideal for my needs but I don't know what they can take and how reliable they would be. I know kad is a dog leg and this wouldn't bother me if it meant the gearbox would be quiet and reliable. Alternatively can these 5 speeds be upgraded to take additional power and torque?
I know its not the clearest question but any help would be appreciated.at this stage im not looking at any budget but mire at whats technically possible as this is my dream and won't be happening for a few years yet!

[Ethel]

5 speeds have the potential to be weaker as you are either adding bits & running indirect drive in the highest gear or you're squeezing an extra gear in the original space that makes 'em thinner.  I've no practical experience to say whether that's more than compensated for by higher grade materials. If you're using forced induction, then you'll be making much of the extra power by increasing the torque that will negate some of the reason to have closer ratios. I think there's a fair few on Turbo Minis running stock gearboxes. Upgrading the diff & not pointlessly dumping the clutch to shred your tyres seems to do enough. There are a few enhancements possible, like a higher grade layshaft and KAD's extra bearing housing from their 5 speed.

 

You can think of a Turbo as a sort of overdrive - it increases the amount air going through the engine, which is what changing down a gear  also does.