Well after running rich for a while, head gasket goin, and a string of odd compression reading, plus some damming comments from guy whos rebuilding my turbo.... I'm worried my engine is not in the best of shapes! Don't know what to think.
Had car remapped and it produced 305 bhp at a measly 1.2 bar ... From a turbo i've since found out to be considerably smaller than what i thought i was running! Its turns out i'm only running a T3 SUPER 60.... they are generaly thought to be well out of puff after 280 bhp and that would be using more than 1.2 bar! As for my compression readings motormech told me i had 30 psi less on the two centre cylinders than the outside ones?? Yet my car runs and idles perfect, and pulls very strong in all gears! My car is mapped for 1.45 bar and i believe its prob running atleast 320 on the road! Would such good power be possible considering such poor compression! Been told i'd be better off doing a compression leak down test than a compression test??? WORRIED! :-( Nick!

What did he say?

the compression is a fairly wide margin, are those wossner forged pistons you are running with gapless rings?

What were the compression numbers?

He just said he could tell by looking at my turbo that he thought the engine had prob seen better days, he's also advised me to get an uprated oil cooler as if reckons my oil temps have been quite high, reckons if can tell this from the turbo!? Trouble with him is that if has an integrale he uses for hill climbs so he reckons everything about his engine is far superior to mine, from parts used to the way its been put together.... Personally i find him quite jealous! All this apart if knows his stuff and is inundated with work! Yes wossner pistons, don't know about the gapless rings! Readings were 125 95 95 125 :'(

Did you do a wet compression test?

A wet test will confirm if its the rings / pistons, but either way, those compression results are terminal - what are the normal 16vt readings? - even the 125 seems rather low

It will continue to run for a while like that (ie months) but the power will be down and the fuel consumption will be up

having been in exactly the same boat recently, I can sympathise - its a horrible feeling to kill a tuned lump - I still have my knackered CP forged pistons in a box to remind me that they aren't totally bomb-proof

Nick I can't remember for sure what my PSI compression readings were but I seem to remember they were a fair bit higher than that TBH - maybe 150psi?

Of course I am running OE pistons though.

As my wossner pistons are supposed to be 8:1 same as standard! How the hell can an engine thats down 55 psi on 2 cylinders and 25 on the other 2 make over the supposed maximum power possible for that turbo at just 1.2 bar of boost! I could undertand a knackered engine running stupid boost i.e 2 bar, making the power! Paul at motormech even said the same, if was gob smacked when i told him what figures it produced the week before after fleas mapping, if said to get that much power with those compression readings if thought i prob have to run at least 2 bar! Is it possible to get dodgey reading.... And this is why i should try the leak down test?? Nick

Nick, long time (apologies since I was heavily into real work...)

Looks like having a v.similar setup, I've gone through similar issues (except for the low compression that I do get 190psi) and last week opend up the engine to see what's happening expecting for the worse...
Turns out (as you can check in my drinking oil thread also in Tuning) that everything is fine.

Seems that one of our problems is the oil rings on our wossners which are no good (apparently) this could be leading oil in, burning it and reducing performace. In your case it seems that this is not exactly your problem but borewash may have had other effects.
Having used a standard head gasket (iirc) and not having "lowered" the block or the cyl head (that I've done) you definitely have a lower compr.ratio but 95 is too low, I'd expect around 140-150 all around.

A wet test will help in pinpointing the problem, opening the block will probably be the only real solution though. Give it sometime though as I have to find a solution for my oil rings and then you can apply that to yours as well. And btw, what's your oil consumption soon after the rebuilt and right now with the right program on (but on a similar pace, don't compare running it driving slowly with redlining it now...)

Cheers

V.