29 replies to this topic

[Carlzilla]

currently have a standard 998, and looking forward to getting my hands on a bigger engine, and having it as a project to work on while my 998 is still in the car


using a 1275 engine, what would be the most cost effective and reliable way of getting 120hp out of an a-series engine?

really looking towards t2 turbo-ing using a mirage manifold, although thats not technically cheap, but neither is trying to get the same amount of power from an n/a with reliability

[Guess-Works.com]

Quickest and probably the easiest and most reliable, whack a supercharger on a standard 1275 with a little bit of mods to the head to decrease the compression ratio...

[mini_mad69]

120hp won't have the best driveability N/A, unless you move away from the 5 port head.


A turbo will give the engine the power you want, but as you mentioned is not cheap. Will retain drivability though.


Either way, with 120hp your going to have to invest in drivetrain aswell as the engine.

Not going to be cheap.

[Carlzilla]

not much of a fan of the charger due to the effiency of them, would i be able to get away with head work, or a stage head when going turbo?

plus, would a t2 or t3 be the better option, as ive heard t2s are quite hard to get hold of...


forgot to mention, my car isnt as such a daily driver, i dont really have the need for a car with the job i have at the minute, but id be bored without my mini
i know id have to strengthen the diff from reading other things, anything needing to be done to drivetrain?

Edited by Carlzilla, 13 May 2010 - 06:13 PM.

[James182]

7/8 port head? ive heard of the 8 port med heads going to 140?

[Guess-Works.com]

Well my 1330 was pushing 85 at the wheels, which must be 100 and something at the fly, and apart from high compression and a 296 scatter cam, it's pretty much a standard 1300 GT A series engine engine, if I could be arsed to strap a weber to it and a better flowing head and mappable ignition I could probably get it nearer 100 at the wheels, but it's more a matter of diminishing returns for money spent, plenty of grin factor available as it was...

[rick.spi]

i would get a cross pin diff and some straigh cut drops for that amount of power, better to be safe than sorry.

[Cooperman]

It's a bit more complicated than that really. If you go forced-induction you need the right bits to make it as reliable as possible. the weak link is and will always be the transmission. With, say, 120 bhp you do need the improved drive shafts, a cross-pin diff and a gearbox in really good condition. I would not go to SC drops as they are simply too noisy for the road and helicals are OK anyway. It's normally the diff, shafts and CV joints which fail with ultra-high power output.
If you go normally aspirated, to get 120 bhp you will have, effectively, a full race engine. This will need a lower final drive to keep it 'on-the-cam' as you'll be using a 296 or equivalent cam with nothing much below 3000 rpm. This will mean a loss of top speed as the diff ratio will also need to be lower and a close-ratio box to ensure that when you change up you'll still be in the muh narrower power band. My Cooper 'S' is NA with twin H4's and it gives 115 bhp at 6400 rpm. It is very 'cammy' and I run a 3.9 FD ratio with a SC box, but it's a rally car with 0 - 60 in 7.4 ses. However, at 6000 rpm it only pulling about 85 mph in top. To pull the sort of revs where the engine will give the power will mean serious engine preparation such as centre main strap, full balance, lightened components, top quality pistons, etc.

[Pauly]

You can build a nice turbo engine for probably the same price as a n/a engine making the same power, if you dont want loads of hp then 120hp is quite a nice figure for turbo power, you wont need much boost pressure and will be just as relaible as n/a.

[Puddings]

BUY MY CAR!!!!!!!!!!!!!!!!!

[rick.spi]

drive shafts shouldnt be a problem?

alot of the very high power turbo minis have normal driveshafts, so a 120bhp engine whould be fine. my engine will be tuned to 140bhp with boost for now and ive still got the standard driveshafts.

[Pauly]

Standard shafts are more than up to the job.

[rick.spi]

exactly what i thought.

a good condition standard box, some sc drops and a cross pin diff will be good at 120 bhp, thats not too far off what ive got with 140, but the amount of torque your engine has will affect how long a transmission will last.

Edited by rick.spi, 13 May 2010 - 09:30 PM.

[Carlzilla]

sounds good to me, i want something proper nippy, but nothing ott so 120hp was nice round figure in my head, so im glad thats achieveable without going silly

[rick.spi]

120 should be more than nippy. i would class a well setup standard 1275 as "nippy" lol

Edited by rick.spi, 14 May 2010 - 03:33 PM.