27 replies to this topic

[connorwmc]

I've just got my hands on a metro turbo set up.. Turbo, carb, manifolds, fuel reg.... 

long story short I've come into the possession  of a 1293cc NA engine in which has got one nasty melted piston... thats the only bad thing about the engine.. I've got receipts to say...

full gearbox rebuild with 4 pinion diff

turbo clutch,

lighten flywheel,

high compression rods

fast rod cam

new crank

new oil pump

skimmed head

double value springs

 

My thoughts were to get a rebore resulting in a 1275+40 and get new pistons in... and the turbo on add and intercooler

 

My First question is with new pistons will this set up cope or will i just end up with more melted pistons?

 

Secondly I've been doing my homework on turboing, and I'm finding it hard to familiarise myself with the ignition system... from what i can work out when the turbo is running the timing will be no good using a standard dizzy... and result in the engine going bang... i could really do with someone spelling this part out to me as I'm at bit of a loose end 

 all help appreciated 

 

thanks in advance 

[wile e coyote]

You didn't score those bits of fleabay yesterday by chance - if so - sorry it was me bidding you up! More knowledgeable views to follow as am none too familiar with turbo'ed engines but - sounds like you've got the basic engine as is build for normally aspirated high compression and that's , as is no good for turbo'ed use which I think needs a CR of approx. 8:1......but as you need new pistons and a rebore anyway then should be ok there...

 

I'm not sure what high compression rods are......

 

But your head will probably be no good - by virtue of the fact it's been skimmed (I have a gen. never run on UL turbo head in perfect condition  - if you need one PM me and we'll chat)...

 

The cam may need taming too - depends what it is - by factory MG metro turbos ran the standard 1275 cam from memory....

[Turbo Phil]

Basically if you can get the compression ratio down to a suitable level there's no reason you can't Turbocharge it. As you require new pistons anyway you need to get some with a suitable dish to drop the compression to something suitable.
You need to measure the chambers in your current head, if you're planning on using it, as if it's been skimmed a huge amount, even with very large dished pistons your compression may not be low enough.
You need to decide how much boost your planning on running and what Turbo as this ultimately dictates how low you need to go with the compression.

Phil.,

[connorwmc]

You didn't score those bits of fleabay yesterday by chance - if so - sorry it was me bidding you up! More knowledgeable views to follow as am none too familiar with turbo'ed engines but - sounds like you've got the basic engine as is build for normally aspirated high compression and that's , as is no good for turbo'ed use which I think needs a CR of approx. 8:1......but as you need new pistons and a rebore anyway then should be ok there...
 
I'm not sure what high compression rods are......
 
But your head will probably be no good - by virtue of the fact it's been skimmed (I have a gen. never run on UL turbo head in perfect condition  - if you need one PM me and we'll chat)...
 
The cam may need taming too - depends what it is - by factory MG metro turbos ran the standard 1275 cam from memory....

Haha no worries, yeah that was me, I brought them on a impulse been thinking of a turbo for a while and these were the closest ones I'd seen to home. I might need to take you up on heading if this one is no good...

[connorwmc]

Basically if you can get the compression ratio down to a suitable level there's no reason you can't Turbocharge it. As you require new pistons anyway you need to get some with a suitable dish to drop the compression to something suitable.
You need to measure the chambers in your current head, if you're planning on using it, as if it's been skimmed a huge amount, even with very large dished pistons your compression may not be low enough.
You need to decide how much boost your planning on running and what Turbo as this ultimately dictates how low you need to go with the compression.
Phil.,

thanks for the reply

How would I go about measuring it? And working out the ratios from it.
The turbo I have I believe to be the t3. And from my research I would be planning on running the boost at 4-7psi which I believe to be quite safe? Correct me if wrong haha..
Can you suggest what the compression should be based on that please?

[Turbo Phil]

The standard Metro Turbo is 9.4-1 compression ratio and runs 7psi max boost. There's some info on my site regarding compression ratios that may help.

Phil.

[Carlos W]

I've got some astra turbo diesel intercoolers which could be ideal for a mini set up

[connorwmc]

The standard Metro Turbo is 9.4-1 compression ratio and runs 7psi max boost. There's some info on my site regarding compression ratios that may help.

Phil.

Hi phil,

 

Your website has been a huge help to clear some other things up and I've been soaking in a much as i can off it for the past few weeks.. 

i look back at the compression section this morning and got this

 

v- 328 (1312/4)

using your values for the cylinder head (21.4cc) and turbo gasket (3.8cc) and without the pistons in the block i don't know how they will sit? ( unless theres away someone could explain) ill assume they sit flush. the deepest dished pistons i could find off the shelf were (minispares p21251-40) and they come out at (8.4cc)

this being said 

c-33.6

 

v+c/c = 10.8 ?

 

the description next to the pistons on mini spares says typical installation would get a CR of 8.8 ?  

and lets face it I'm way out  if this is the case and I've work everything out right then I'm not sure where to go from here :/

and any help or comments would be appreciated as I'm at bit of a loose end ....

[Turbo Phil]

The pistons you mention will not sit flush with the block as standard, so there will be some volume here, dropping the compression. For a boosted engine I'd be looking at something more suitable.
If you're on a budget the 21253 pistons are good and can be dished to about 13cc. Otherwise the 10cc cast Omega pistons are excellent.

Phil.

[connorwmc]

The pistons you mention will not sit flush with the block as standard, so there will be some volume here, dropping the compression. For a boosted engine I'd be looking at something more suitable.
If you're on a budget the 21253 pistons are good and can be dished to about 13cc. Otherwise the 10cc cast Omega pistons are excellent.

Phil.

Great thanks for you help, i really do appreciate this...

the pistons i have in the block at the moment sitting flush with the block is this because the block as been modified? ( the pistons are high compression pistons if that helps)

i think ill go with the piston i can dish to 13cc to lower the compression ratio unless the omega pistons can also me dished out to a greater depth?

 

using the 21253 pistons dished out to 13cc i would get a compression ratio of 9.35.... would this be low enough to run a turbo without the risk of anything meting or combusting when it shouldn't be...?

 

 

Also i don't know if you can tell how much this head as been skimmed i don't know if there is any away you can tell.. as id like to keep the head if i can get the compression low enough using it?

Attached Files

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[Turbo Phil]

You could measure the thickness of the head, this will tell you if the heads been skimmed, but it won't tell you the chamber volume, you need to measure that by filling the chambers accurately with liquid through a flat piece of Perspex with a hole in, sealed to the head face with some grease, using, preferably, a burette, though a large syringe would do to get a rough measurement.
9.35-1 will be fine for your proposed 7psi.

Phil.

[connorwmc]

You could measure the thickness of the head, this will tell you if the heads been skimmed, but it won't tell you the chamber volume, you need to measure that by filling the chambers accurately with liquid through a flat piece of Perspex with a hole in, sealed to the head face with some grease, using, preferably, a burette, though a large syringe would do to get a rough measurement.
9.35-1 will be fine for your proposed 7psi.
Phil.

5

Great ill try that at some point this week if it'll save me some money instead of forking out for another one... I'm sorry to keep bothing you, but I found this this morning http://audisrs.com/a...t__t_46497.html he's running the same bore and the 10cc omega pistons but I can't get my head around how he manage to get the compression that low... would you be able to shed any light

[Turbo Phil]

The Omegas sit about 0.040" down the bore at TDC on an unskimmed block. This gives another 4cc plus the 10cc dish. Looking at the picture of the head he posted I'd guess the chambers were at least about 27cc to.

Phil.

[69k1100]

did you get your answer regarding ignition?

[connorwmc]

did you get your answer regarding ignition?

if you could shed some light on that area that would be great and appreciated