Is this engine spec good enough for a turbo?
Turbo Mini Forums

Hi all,

I've recently brought my mini off the road to do a few odd jobs like the bodywork and interior, and while its off the road I have decided to go down the turbo route as a few parts were available from work and friends.

My main concern is whether the engine spec will be able to take the extra power. I have bought a turbo which is believed to be a t2, which i will confirm when I collect it. I will be using the mirage manifolds and a smart car intercooler which i got through work. I also bought a metro inlet plenum which has been modified for a dump valve.

The engine spec is currently as follows,

1293 A+ block
Standard conrods (balanced)
AE 21253 pistons (10cc)
Standard crank (balanced)
Kent 276 cam
Duplex timing gear
H/C oil pump
Stage 4 trackday head 36in 31ex (22.5cc chambers)
HIF44 carb, alloy inlet and 3into1 ex manifold.
Rebuilt gearbox with straight cut drops
Standard diff (3.1 fd)
Lightened and balanced flywheel
Turbo clutch

I'm not going for massive power output, just to increase the power from the 88.8hp and 82ftlb it is currently running.

My main concern is whether the pistons, crank and box will last?

I will take the head off and take it to MED on monday when i'm in Leicester for him to increase the chambers to lower the CR. Any thoughts as to what cc?

What are peoples thoughts please??
Any help or advice would be greatly appreciated

Thanks,

James.

I think you would want a tamer cam than the 276. A good standard cam for turbo use is the Metro NA cam. Also, is your HIF44 a turbo carb or are you planning to convert an NA carb?

Chamber volume will depend on alot of factors. Decide what boost you want and then choose a CR to suite. Then use a CR calculator to see what you will need in the head

EDIT: oh yeah, and a standard diff isn't worth a wank. Get a minispares cross pin

Edited by GaryOS on 6th Mar, 2009.

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

the carb is a n/a carb, i didnt realise there was any difference between the two. What will I need to do to convert? Hoping to run around 10-12p.s.i?? Oh ok thanks. I may see how the standard diff holds up as I dont want to remove and strip the engine, but i will have to if it fails lol

the carb is a n/a carb, i didnt realise there was any difference between the two. What will I need to do to convert? Hoping to run around 10-12p.s.i?? Oh ok thanks. I may see how the standard diff holds up as I dont want to remove and strip the engine, but i will have to if it fails lol

The 21253 pistons aren't really suited for turbo applications.

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

oh ok, thanks.
how much are the minispares x pin diffs please?

If i strip the engine from the box, would it be worthwhile changing the pistons?

I am trying to do this on a small budget as I am only on apprentice wages.

The X-pin diffs aren't cheap, around £160 from memory, plus all the gaskets, tabwashers etc. you will need to do the swap.

A "budget" solution might be the uprated single pin if you're not going overboard on power.

TBH, as you've already been running at higher than standard, I would strip the whole gearbox and diff (and the drop gears as they are the next weak link) and look at what's worn already.

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

It already has the uprated straight cut drop gears which are only about 6k miles old, so they should be fine, its just the diff thats the problem

If going the uprated diff route, you'll also need new planet gearsm new bushes etc. There is really no excuse for not fitting a twin pin. Do it. Don't be cheap on this item. Remember to buy the Minispares one as the Minisport one is shite in comparison.

Pistons.. Get some MEGA cast ones. You might get away with the 21253s but low boost and spot on timing is needed. If you change the diff and pistons everything would be suited ans strong enough for some proper boost. And ignition timing issues.

as above, but the pistons will peal their tops off at that boost, i would go for omegar 11 cc dish pistons £280 deliverd from med, that togeater with 28cc in the head chambers will give you 8.5:1 CR just right for a saftey margin for detonation, if you want the chambers sorting please give me a PM

As your head is for a NA engine you may find it's been skimmed to give a desired compression ratio. Whether it will be possible to increase the chamber volume to something suitable, will depend how much has been removed.

WWW.TURBO-MINI.COM

thanks for the help. What would you class as low boost? £280 isn't bad for a set of cast pistons really, they would be about that much just for one piston in my brothers car lol. I will probably go that way with it, rather than skimp on important parts and risk failure. It will be a little longer term than i first planned, because of poor apprentice wages. I can probably save a little money at MED by collecting the pistons and paying cash, as he is only about a 20 minute drive from my house.

i've been running 21253's for the last 3 years @ 15psi and they're spot on, they've seen 20psi a few times aswell. mine are dished out to 11cc. i'm running 8.7:1cr and it was making around 160 banana's at 15psi.

iirc nic used to run them aswell before he got all fancy.

Edited by Nick on 7th Mar, 2009.

oh right thanks. If yours are 11cc and mine are 10cc, there isn't much difference, that extra 1cc could be taken from the chambers?? 8.7:1, 15 p.s.i of boost and 160 bannanas?? That is more power than i would be hopefully runnung, but if the pistons will take that then thats reassuring. I would hopefully be running about 10-12 psi, for about 130-140hp? What CR would i need for that please?

My AE pistons saw about 16-17PSI and I had them in there for about 20k and on strip down couldn't see any problems.

Just make sure the fueling is set up on a decent RR and get a decent IC setup and you should be fine.

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1/4mile in 13.2sec @ 111 terminal on 15psi

Oh thanks. I had my engine set up at northampton motorsport before, so will probably go back there. I have a smart car intercooler which i have just had a play trying to mount it, but I'm struggling to find somewhere to mount it. The engine seems to sit quite far foreward and wont go between the dizzy and the front panel. I also have a servo on there which is also in the way. Any ideas on that one?
Thanks.

I'd be tempted to ditch the dizzy and go megajolt.

yeah, thats what i'm thinking. Is it expensive? I can get hold of ford coil packs through work cheap.

I'm in the process of going through it now, got all the bits I need from a scrappy for £25 and the megajolt is about £150. I really need to hurry up and order it.

The trigger wheel and sensor could be free if you can sort it yourself, or up to £100 if your after a machined pully and fancy bracket.

Someone please corret me if i'm wrong here.

yeah, I think i will do that, but i'll probably have to buy a bottom pulley already machined.