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Need Help....mg Metro Turbo Engine Compression Rates With No Turbo


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#1 doughbot

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Posted 18 March 2008 - 02:01 PM

hi guys

I bought a 2nd hand engine and was told it was a mg engine (no engine number) have connected everything and set the dizzy up like you guys helped me to yesterday but...

still nothing, so i called in a local mini guy and he has done a compression test on the engin and it is running on approx 75 PSI or 6 BAR, he has suggested that it maybe a turbo engine and so i'm asking you guys if you know what the compression ratio for a turbo engine is without the turbo

i have done as much resaerch on the net as i could find but i couldn't find this so any hepl would be appretiated lots

the engine is firing right, all gaps (points and plugs are set right but all i'm getting is a few little puts, i know a mini should run at about 150 PSI so please help out if you can

cheers

#2 mini_turbo_pete

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Posted 18 March 2008 - 02:08 PM

If it's running 75psi i think it might have a slight problem, my turbo challenge engine thats running 8.5:1 is running about 120psi compression.

Check your tappets as they could be incorrectly set, it could also need the valves lapping in or it could be broken rings

#3 Jammy

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Posted 18 March 2008 - 02:47 PM

Not quite so helpful, but if its that low on compression then your at least going to have to take the head off to see what the problem is, at which point you'll be able to see whether it has dished pistons or not, and any other clues which might point to it being a turbo.

The other option is to find a garage that can perform a leak down test which will tell you if any compression is being lost anywhere.

#4 doughbot

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Posted 18 March 2008 - 03:11 PM

the engine was split and claened up, tappets are set to correct gap, piston rings are fine (got the mini mechanic aout to look at it once the engine was split, the pisons say +.020 which i know means the engine has been bored.

the head was machined and new valve seats put in but i'm at a loss now,

could it be the the turbo head needs lapping down for a smaller combustion chamber????

any advice welcome

cheers

#5 mini_turbo_pete

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Posted 18 March 2008 - 04:01 PM

Did you mini mechanic pull the pistons out and check them? as pistons can be damaged around the side but it's not visable unless they are taken out.

One of my engines was down on compression on 2 cylinders when i took the pistons out i found this damage to them, from the top they looked perfect...

There was no signs or scoring on the bores that anything had gone.

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Edited by mini_turbo_pete, 18 March 2008 - 04:03 PM.


#6 doughbot

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Posted 18 March 2008 - 04:31 PM

yeah i see that, but i'm getting the same reading across all 4 bores, so for 1 or 2 pistons OK but 4, the engine would show somw signs of being well and truely ragged and it doesn't?

#7 mini_turbo_pete

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Posted 18 March 2008 - 05:10 PM

yeah i see that, but i'm getting the same reading across all 4 bores, so for 1 or 2 pistons OK but 4, the engine would show somw signs of being well and truely ragged and it doesn't?


My engine i pulled those pistons out of had done 45K from new had full service history and had honing marks present in the cylinder walls, there was no signs of ragging, the only problem was that the boost was wound up but the timing and fueling hadn't been adjusted correctly.

If it's the same accross all 4 I think you need to double check all the tappet clearances etc how did you set them? did you use the ruel of 9??

#8 doughbot

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Posted 18 March 2008 - 05:26 PM

yep rule of 9 was used by me , and the mini guy checked them to amke sure,
then checked all connections to and from anything electrical, checked the cam timing, he checked the fuel pump to make sure fuel was getting through, he checked as much as he could in 4 hours and £150 down i'm still no closer




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