Compression ratios
Turbo Mini Forums

Helloo, was just wandering, could anyone tell me the standard compression ratio of a metro turbo engine?

Im gradually stripping down my engine at the mo and have been thinknig about possible setups. I hope to run about 10psi with a 1293 block, all the pistons, 276 cam, fly etc. Does this sound like a nice setup to you guys? I dont want to go overboard as i use my car alot and dont have alot of cash but im looking for somethin with a punch!

What compression ratio should i aim for on this setup? Whats the max psi a standard metty turbo can manage without an intercooler? Im planning to fit and rs turbo one when the lump goes in but am just looking about for feedback from the experts!

Cheers, rich

Standard compression ratio is 9.4:1

I personally wouldn't use a 276 cam in a turbo engine but if you really want to then try and and let us know if its any good.

Any ideas of CR i should aim for on that setup?

What cam would you use?

Rich

the avonbar phase 2 is tried and tested on here and comes back as a good cam, i have been in benrosses car with this cam and it seems verry good, not a bad idle and it pulls like a train.
most boost i have seen on a compleetley standard metro turbo engine is 9psi no other mods, just setup on a roaling road and made 111bhp. sort the intercooler and you looking at much more potential, so get the work done, you will be rewarded
i have a lower Cr tho the cars not running yet and i havent worked out what the CR will be yet.. but had the work done.

Dan

It is a bit of a balancing match, if you want to run big boost pressure e.g. up to 20psi, then you want to aiming around the 8.0:1 mark. However, it is only worth going down this low on compression if your pistons will withstand that kind of boost pressure.............

Ritey, thanks for the info! Well im palnning to re-bore so will be getting bigger pistons and they will be able to handle the job i should think. Cheers for the tip on the cam!

Another thing i was going to ask, when i bought the engine the guy said its got an uprated actuator, i looked at it and its a 12psi avonbar one. Can these be adjusted to lower pressures or is it fixed at 12?

12 minium but csan be increased with a bleed valve

although my 10psi seems to be about 8, avonbar may be able to supply you with a lower rated spring

You may be able to lower the 12psi by lengthening the actuator rod to decrease the preload.

Alternatively I am looking for a higher pressure actuator for my car when it is run in, and will do you a p/x (with some 壣) for a standard actuator, let me know if you are interested.........

the 276 does work on a 1380 turbo but cant coment on a 1293, but does come with the lumpy tickover as per usal, the phase 2 seems to be the top cam on most peoples choice.

just slackern off the preload on the acuator and you can have what ever wastegate setting you like.

ive got a 10 psi and got it to run on 4 psi no probs for a whilst. but the 12 psi one will be more efficient when you starting to want more stage one boost than a standard one.

always looking for them bigger bunches of bannanas

Thanks for the info guys, much appreciated! Ive realised actuators are quite expensive! So may be wanting to stick to the 12 i have now, ill keep what you said in mind tom :).

Whats the best advice for a setup on 12psi? I may aswell get an intercooler fitted when i put the engine in, a decent head and a cam. Im getting the gbox recon'd and as stated before, possibly a re bore and new pistons. Would anyone reccomend anything else? Would it be adviseable to get new rod bolts and head studs etc, is this a must have?

rich

Straight cut drops

Cross pin diff

The standard items will not put up with 12psi for long!

ARP rod bolts are always a good idea on any engine build in my opinion.

A friend of mine {Mike} ran a 1275 Turbo motor with a 276 cam, T2, intercooler and 10psi boost. The engine made 132 bananas {hp} and was a great little motor. Idle was slightly lumpy but it pulled well enough, drivability may not have been as good had a T3 been fitted .....
On the other hand the Phase 2 is a proven item.

Phil.

WWW.TURBO-MINI.COM

Edited by Richie on 21st Dec, 2005.

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MikeRace, Mini13

If I were building an engine and wanting to do it on a budget, I would get the gearbox and bottom end done first as a priority. Cross pin diff and straight cut drops make a good strong gearbox, straight cut gears as well if you can afford them. Then moving upwards, centre main strap, ARP rod bolts, good quality pistons, Avonbar Phase 2 camshaft.

If you do all that, then the difficult bit is done, you will not need to pull the engine to do further upgrades as you will have a strong bottom end. You can then do the turbo conversion, and run about for a bit on standard boost and cylinder head etc. Then, once you have ironed out any installation quibbles and got it all working OK, then is the time to start upping the ante, with a better cylinder head, more boost, intercooler, etc etc.

Remember that Leyland kept boost down to 4psi in the mid range to help the transmission survive, if you put 12 or 10psi for that matter through a standard gearbox, it does not take a genius to work out the life expectancy of it............

I thought ARP rod bolts/nuts were only required if you are planning on revving the engine hard (7500rpm+)!!! Or is this just for piece of mind?

-MINI CLUBMAN 1380 TURBO-

For me, piece of mind, and also as an "insurance" policy, we all know the damage a failed rod bolt can do to a normal engine, let alone a mini with its gearbox is close proximity! Having spent a considerable amount of time money and effort on building a straight cut gearbox, an extra £60-odd for a set of ARP rod bolts does not seem too bad!

i shoud know about the weakness of a standard box with starship miles on !

up the boost and it will all go pearshaped

Yes fair point

-MINI CLUBMAN 1380 TURBO-

Wiked! Thanks for that! I think its a good idea actually, getting the box and bottom end up together and just ipgradeing the rest once its bedded in!

I was thinking about putting the engine in and then taking it somewhere to get it tuned/setup because i dont know loads about this sort of thing yet. Can anyone reccomend a decent place to get it running properly? Does avonbar set up? I live by Slark racing Minispeed and Janspeed which is cool, who would you lot reccomend?

Once again, thanks

Rich

Edited by richminiturbo. on 22nd Dec, 2005.

AlexF