Gaz-2006 0 Posted November 29, 2007 Hi all, I have been having some issues with my XU5JA engine (1.6GTI) as I have been speaking about in a different thread in the service/repair section.. My current problem is thus: I have had 1.2mm skimmed from my cylinder head, and ran the engine like that without the block being decked. It made good power (124bhp) and didn'y pink. This was using a headgasket thickness of 1.25 (std) Now, I am having approx another 1mm removed from the engine blocks height as it has to be skimmed to match in my cylinder liners which are having the surfaces where they fit in the block re-machined to combat corrosion.. That will be a total of 2.2mm removed, and although I have now got the thickest headgasket I can find at 1.5 mm thickness, it is a total of 1.95mm removed from the engine and I'm worried about 2 things: Piston/Valve contact especially when things get warm.... and also compression ratio going sky high and pinking! Does anybody have any experiences and suggestions to hopefully clear my mind or at least let me know where I stand? It is a race engine, but I don't want to have to adjust the ignition timing to combat mid range pinking and compromise outright power.. I did hear from this forum I think that 2mm is an acceptable skim on these engines.. but just want to be sure as my car has to make it to its first test at Donington on a week saturday! Cheers! Share this post Link to post Share on other sites
projectpug 0 Posted November 29, 2007 Piston valve contact shouldnt be a problem on a XU. You might get pinking and have to retard timing back a few degrees. Depends a lot on other things though like cam your running etc. Share this post Link to post Share on other sites
brianthemagical 1 Posted November 29, 2007 try and work out the compression ratio, it'll be your bast bet rather than just guessing. it might be worth going to mapped ignition anyway, even if it's just a small increase in CR. Share this post Link to post Share on other sites
Gaz-2006 0 Posted November 29, 2007 what is the best way work out the compression ratio? I haven't physically done this myself yet so does anybody know the method to do this? (and how long does it take?) It is running a std type 'control' camshaft from Kent. Cam timing is non adjustable. So a few degrees of igintion retard would be able to sort it out if it were a problem? We have a rolling road here and can 'power time' it, and play with it on the rollers with the standard dizzy.. I think checking the comp. ratio is a good move though to see where we really are with it. Share this post Link to post Share on other sites
snillet 1 Posted November 29, 2007 I think you may just have to retard the ignition a little bit as far as you run on high octane fuel, but you might not have to do that either if you watch out for hot air intake. Like if you´re sitting in slow traffic on warm days, you do not power away like crazy directly when the slow traffic starts to move. I dont´think either that piston/valve contact should be any problem for you on that engine. Share this post Link to post Share on other sites
