Hi forum, Remember so long ago when I pulled figured from my engine that were 120psi +/_ 10psi on all cylinders? Well I knew when I did that test the engine had a lot of issues, had been sitting around for a while and I still had all plugs in and butterflies closed when I did it. I pulled my z aside today and stripped it down (removed the plenum) Desided to have another crack and now im ecstatic! With an engine that was driven to operating temp then sitting around for a while while I removed the plenum. I got these new figures... 150psi +/_ 4psi on all cylinders!!! Cant explain how happy this makes me since I was commited to having to rip the whole thing out. But now I have something half decent to work with I need some advice as to what the next step should be? Keeping in mind the performance was terrible but now must have been something other than compression. What would be the logical things to check while the engine is a little more accessible? And is 150psi enough to justify getting bigger injectors now? im thinking to replace all the connectors before putting it back together as a start... Thoughts? Wayne Update: Also. I just put a drop of oil in the cylinders and the psi went to over 220 :/ that means the rings are whats dropping compression doesnt it? Lastly. The plugs were all charred black. So if this is an indication of any issues that would be good to know. im considering at least taking the heads off and putting new valves in which I already have..
Yep, rings is your problem. Charcoal end spark plugs Is unburnt fuel, if they're wet, oil related, stems etc.
Why would you consider putting larger injectors into an engine with that much wear? Do you want to wear it out faster? While the difference in pressure between all cylinders is quite good, 154 to 146 PSI aren't the greatest compression figures. As Zuul has mentioned, the oil test has indicated the piston ring/bore wear appears to be the cause of compression loss. Why would you consider replacing the valves? It looks like you have put more than a "drop" of oil into the cylinders to gain the increase in compression. It would definitely be a good idea to "recondition" any suspect wiring connections while the top of the engine is removed. The spark plug colour is a concern. Further investigation is required.
150 is great compression for a tt motor boost her up . Make sure your timing belt has been changed and had the proper 100k service
Would the plug fouling be from over fueling? Possibly because im using a chipped ecu not 100% tuned to my engine? 98% sure im going to pull the engine and throw in some rings. Might reco the heads at the same time. Then put it back together with 660cc injectors And tidy up the harness with new connectors.
This makes sense :agree: Your compression figures indicate there is a considerable amount of life left in your engine before a teardown is necessary. You may be quite surprised how well your engine will perform if you can sort out any issues. There is an excellent write up on TwinTurbo.net Proper Preparation Prevents Piss Poor Performance Read about the 6 P's here: http://www.twinturbo.net/net/viewmsg.aspx?forum=technical&msg_id=813994
Good artical... Ok. I want to make this as easy as possible on myself.. If 150 is a reasonable figure. It it worth concentrating 110% on the top end alone. . ie. reco heads with the new valves I already have. 660cc injectors put back together and then go through the basics ive got boost hoses going everywhere and lots capped off (noticed one completely broken off) so I had an abortion of a vac hose setup. I am thinking if I start with the block how it is and build upwards.. if I can get away without touching the block I dont have to pull the engine.. which means im back on the road faster. Maybe even within a week or two... Reckon its worth putting in that effort to the top end when im only on 150psi? survey says, 150psi is respectable for a TT. Basically the norm even...
I've put together a few engines and Honestly, a zed engine isn't that hard to pull out. I can do it within a couple of hours by myself. The whole thing comes out with gearbox. Put it on chasis stands, drop the bolts on the front cross member (shocks will hold it in) this gives you the extra room to pull it all out at once. Maybe it's just me, but I can pull the engine out, change heads and get it back in, in half the time that it would take me to f@#k around with the engine still in there! Yes I've tried both methods. Only reason to leave the motor in is if you don't have the room. If you're going to the trouble of doing heads, I'd strongly consider spending a bit more time and sort out your bottom end. At least this way you'll have it right the first time.
I don't know why people like to make life hard for themselves. 150 compression is pretty standard for a used TT. Yes a new TT will see higher, but I wouldn't be concerned about compression until you either have one that's significantly lower, or they're all down around 120 or less. Leave the engine as is, sounds like there's nothing wrong with it. Figure out what is causing it to run shit, fix that. Then start looking at improvements. You don't need to touch the engine to run bigger injectors, bigger turbos or bigger boost, up to probably at least 300rwkw (personally I wouldn't touch internals until up to 350/400). Yes great if you've got heaps of money to burn and happy for your car to be off the road for months (or years), but it's not necessary to make decent reliable power with our engines.
Agree with Shane001...... Nothing wrong with 150psi across all cylinders (especially with only 5psi variation)...... I would throw some larger injectors in (for safety), do hoses and connectors, bypasses etc and maybe a 100K kit if it hasn't been done..... tweak the boost up to no more than 14psi and enjoy driving it This will give you plenty of time to save up for the rebuild..... or you could pick up a tired donk and do your rebuild as money permits and just do an engine swap when the time comes.
Its probably good. But realistically you will be relying on your turbos for all the power.. 150psi would have to be quite a bit slower off the line until your boost spools up Compared to a 171psi engine.. Thatd my take on it anyway.
I cut 1.6 60fts on a 150psi engine with stock turbos and dumps. true story. Make sure your timing belt and all the other maintnance issues are sorted then get it tuned. you will have a blast.
i dont agree. lower compression means u can run more ignition timing. it all balances out within reason. Also you could start talking about dynamic compression ratios , those figures on stock cams for example could equate to the same dynamic figures on an engine with 170psi test readings and long duration cams. Dont worry about the test numbers. maintain it, boost it, tune it and enjoy
also dont worry about upgrading thw stock injectors if u still have stock turbos, they will be pretty much tapped out too
