Turbo-ing a 1071 A-series?
Turbo Mini Forums

Hello listers

I have read with considerable interest your thoughts about turbocharging a 998 cc engine in the Help section. As some people pointed out, a 998 has a stronger block and they can rev higher with less danger for the crankshaft. I am not talking about sacrificing a pukka 1071 cc S engine, of course!

See, many years ago Mark Forster, a Mk1 Mini guru, pointed out that it is quite simple (i.e. cheapish) to build a 1071 cc A-series from a 1275 cc by fitting the crankshaft used in the South African 1098 A-series, which was actually a 1275 cc engine with much taller pistons. If I remember correctly, you needed

a) SA 1098cc crankshaft

b) a non-porous 1275 cc block (maybe from a 1300 GT or a 1275 GT), milled down to size (3/4 inch, I think, but I would check it first, I speak from memory)

c) Metro or Innocenti 1275 conrods

d) 1071 Cooper S pushrods

What do you think? It would obviously have less grunt low-down, (although I suppose it woud be nicer than a turbo 998 cc) but with a really small turbo it would make a very nice engine indeed. And there certainly would be less block flexure, being shorter and that.

From what I gather, torque response from boost is directly proportional to stroke. It's almost like a multiplication. Certainly, it would be impressive and would rev its nuts off.

Madmat in OZ was talking about blowing a 1071 with a supercharger.

I reckon that there is enough evidence to say that a supercharger with a 1380 works well as the unit produces more welly for a given boost. Since high revs are not a good idea with Rootes Blowers, it might be an idea to start looking at stroked, big bore engines. I reckon that is the next worthwhile development.

A SA Crank would cost a few quid to get over here, allthough I have a mate in SA.

Back to the blower point of view, off the top of my head, a lot of positive displacement blowers have relatively small rev bands, larger ones lose efficiency at low revs, so blowing a 1071 with anything but a screw blower may cause it to not perform to its potential. You could probably utilise a longer cam and sod the low range though. I'll ask my mate, I think they had a 1071 with a blower on. (Then again, his 850 with a cabin blower used to completely eat 1275 S's)

Bugger off, I'm getting there.

I seem to remember Rich a Minispares North trying to sell me a crank (someone was making them somewhere) to make the 1275 a 1071. It was about ?100 at the time.

It was no use to me, but it might be an easy way to make a 1071.

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Rich's cranks come from SA as a matter of fact :) I've talked to him about them.