Leakdown results....your opinion?

[Frozen240]

I have a 92 240 with a KADE-T. I put on the Nsport turbo kit earlier this year. I was quite confident that I had a solid engine as it never used any oil (or dripped for that matter) and when I did a compression test before going turbo it was 180, 170, 180, 180. Pretty even across the board I'd say. It has about 120 k miles on it.

After about 2k miles with the turbo kit installed I start noticing that it is using a little bit of oil and is blowing out blue puffs of smoke between shifts and mostly under boost. It has progressed to the point where the puffs have become clouds of smoke. I always thought it was blue smoke but my buddy was driving beside me the other day and he said that when I was on the gas it was black smoke (good) and when I got off the gas it was white (not good).

It is using an incredible amount of oil now, about 1 litre (i don't know what that is in imperial as I'm Canadian, eh) for every tank of gas. It is also using a little bit of coolant. I've had to top off the overflow container twice in the past 5-6 tanks of gas. I've also got some oily residue in the overflow container which never happened when it was naturally aspirated. I'm running the car at 5.5 psi of boost and have never noticed any detonation. So, my suspicions are that the head gasket has a leak. Here's what I found with compression, 130, 130, 125, 135. This was not done with the same gauge as I did the first test. A lot lower but still even across the board. The plugs did not show any signs of fouling and where all even in wear (they were new when i put the turbo on). As for the leakdown I got 20% leakdown cyl #1, 20% #2, 28% #3, and 12% #4. The mechanic I had do the test thinks I have bad rings on cyl #3, he said that during the test he could feel and hear the air blowing out of the oil fill cap.

What do you guys think? rings, headgasket, both?

I think I'm going to rebuild it and use 8.5:1 compression pistons, will using the low compression pistons require any mods to the ECU?

[Structure240sx]

yea that is alot of leak. my cousin that builds high end engines told me anything UNDER 10% is ok. your rings are going.

lower compression pistons wont require any changes to the ecu. im running 9:1 pistons with a stock ecu and safc. the safc is jsut for my bigger injectors

[huguetpj]

As Structure said... you don't need an ECU retune to account for lower comp pistons. I ran 8.5CR pistons on a stock everything for a while.

I'm thinking your problem could be headgasket related... since all 4 cylinders have low measurments now but evenly accross the board. I just thnik it would be too much of a coincidence for all 4 rings set to go at the same time on the same amount....