993 rebuild for Supercharger

[mmasse]

Today, I went for the first track day of the season, and with my recently installed TPC Supercharger on a 993 '97 engine ('76 911 chassis)

There was plently of track time including a couple of 1 hour sessions. The car with the Supercharger was a BLAST........ until it blew off on the last session of the day!!!!

Until that point, there were no signs of any problem with the SC or the engine. There was no heat soak, HCT temp was 300F during runs, and engine oil temp at 200F.

I exited the last session noticing some lost of power and when I arrived to the pits I realized that there was plenty of white smoke coming out of the exhaust, and the engine sounded BAD.

So now, time for the rebuild and I will need your help!!!!.

I want to keep the Supercharger setup, so what would be the recoomended build for this engine.

I would assume that lowering the compression ratio would be recommended, but that's how far I can go. So these are some of the question that come to mind, but welcome any additional suggestions:

Can you recomnend specific piston/cylinder size?

Should I also replace the piston rods/ pins?

What work should I do on the heads ( assuming keeping them is recommended)? Valve guides?

Please, add whatever you deem necessary for this build.

Engine is originaly a 3.6 '97 993 Euro Varioram.

BTW, this will be a track only car...so go crazy!!!


Thanks for your inputs

[sjf911]

Sounds like detonation, probably blew one or more pistons. How much boost were you running, did you have an intercooler, and how did you handle ignition advance?

[mmasse]

I installed the TPC Supercharger kit. The kit came with a piggyback Computer which is supposed to adjust the timing to avoid detonation. No intercooler. I was adviced by the people at TPC not to buy the intercooler. They said it was not needed for my application/ use ( DE events). Tom at TPC said that if the computer detects high temp at the intake, it would adjust the timing to avoid detonation and that as a consequence you would loose power but not damage the engine. I will hold my views on this until I disassemble the engine and see what happened.

Now, I am looking to move forward and understand what's the best way to build an engine that would be Supercharger safe.

One thing I don't know is if I would haveto change the ECU in case I change the compression ratio or displacement. Anyone comment on this?

Thanks

[rsscotty]

I would not hesitate to contact Geoffrey Ring...he is an expert regarding engine management...probably just what you need for this engine to survive long term, among other things. It would be nice if this was the last engine tear down you have to do.

EFI and Data Aquisition Specialist - Above the Standards

[mmasse]

Now am CONFUSED !!!!

I teared the top en o the engine apart to see what was worng and found NOTHING!!!! Everything look pefect..too perfect. No signs of valve damago, not any signes of scratches or even wear on the cylinder walls, rings at not broken or stack.

I did perfomed a leak test before dismantling and I I got the same sign on the first 3 cylinder. Leak going to the case( I heard the air coming out of the oil breather hose), so I figured out I have blown piston and or rings were failing.

Please, experts jump in.

I am nowinto the rebuild and not too worry about that. My oncern is that I have not found anything wrong. So what the heck was the reason for massive white smoke coming out of the exhaust, and even oil dripping from the muffler!!!!!

BTW, i did find traces of oil in the intake, but I doubt that was enoug to create the situation mentioned above, unless the supercharger was sucking oil from the tank...only think I can think of.

Please, HELP!!!

[sjf911]

Still sounds like piston or ring issue. What percent leakdown did you get? You'll need to measure ring gap and ovality of your cylinders. How are you venting your crankcase possibly overfilled with oil or failure of the scavenge side of the oil circuit? Is it possible you are pressurizing the crankcase? What is the oil circuit for the SC and is there anyway it is pouring oil into the intake?

[mmasse]

Thanks Steve,

Well, thats my concern. There is one breather hose which goes from the top rear of the engine to the side of the oil tank filling cup. And there is another breather hose going from the rubber hose that conects to the throttle body to the other connection bsides the filing cup. I though about this second one and wondered if the SC could be generating enough vaccumm to suck oil from the oil tank., but this is the way it is sppossed to be connected!!!

But, the engine was still failing the leak down test, so I guess there has to be a problem somewhere. I got no read out all on the compression gauge. The air was going directly to the crankcase

[sjf911]

That sounds like you might be pressurizing your crankcase via the second hose mentioned. Which oil tank are you using and can you post some photos of your plumbing.

[sjf911]

I don't know how you could get leak down like that with intact pistons and rings unless the rings have "collapsed" or severe ovality of cylinders has developed. I wonder if your not just blowing oil by all of the rings from a pressurized crankcase and loosing ring seal. Someone with more experience than I needs to answer that.