txhokie4life

I've been sorting my recently acquired an '86 951 track car.

I picked it up earlier this summer and had some track prep work done (crankscraper, rod bearings, timing belt, fuel lines, brakes, etc).
The engine was rebuilt a few years back and has iron sleeves.

When tracking the car I have noticed that I was blowing oil smoke.
I have a LR Super 75 setup with a LR MAF and Wastegate.
The car idles high, about 1100 RPM, but otherwise ran great and pulled like a freight train, topping off about 18# of boost. Butt dyno relative to my local buddies says she's running fine and pumping out the HP.

Possibly unrelated, my blow off valve flutters, so I replaced it, and the new one flutters too. When I first got the car I checked vacuum at the blow off valve and I had 16# of vacuum. Thinking I might have some turbo seal issue I also pulled the MAF off and checked my turbo shaft play and I (and others) believe it is fine. I found some oil in the plumbing there, but it was hard to determine a source.

After a couple trips to the track.
I was able to isolate the oil burning to having oil appear to be entering from what I thought was my AOS return line. I pulled that line and my oil burning stopped. I did have a good bit of oil spray from that hose as the temporary shop glove over the hose trick didn't hold up. I needed to get a catch can and sourced one last weekend. I shoe horned the installation and had two connections that were press fit on, but not secured.

First session on Sunday I blew the line from the hard pipe next to the throttle body that was now routed to my catch can (which I didn't have a hose clamp on). Lacking said hose clamp at the track, I zip tied the hose so that it would not come off easily.

Next session out I smoking like a freight train. Not our the exhaust -- but in the slip stream. I also get a Oil idiot light, but still have oil pressure, so I nurse her back to the paddock. I open the hood to find the dipstick has blown out of the tube -- and oil is everywhere. Check my oil level and I'm down at least a court. I clean up as much oil as I can and call it a day, top off the oil and hope I can make it the 30 miles back to the house. I do.

I'm considering many worst case scenarios through out the week.

Surely I must have some blow by going on and I'm in need of new rings.

So tonite I get some time to run out to the shop and run a compression test.
135/140/140/130. I must be honest and say I'm thrilled with those numbers.

I consider the possibility that somehow the car has the ICV and AOS lines misrouted. Things look right as they travel under the intake -- but I'm don't have enough time tonite to pull the intake and have confidence to get it all back together to drive home tonite. I decide to swap the ICV and AOS line connections. I pull the AOS line from the catch can and run it to the ICV connection on the intercooler return pipe. I go to start the car (I had left the original ICV valve line open). It fires up, but dies immediately, classic no idle. I search the shop for a big bolt that will fit the ICV hose diameter and plug the line. Car fires up and now idles at ~700RPM. Note it used to be 1100RPM. Hmmm, that seemed positive.

I decided to call it a night on what I was thinking a positive note and headed home. Noticed I still had my blow off valve flutter, but it seemed to run just fine, if not a little stronger -- and I could swear once I got on the freeway she pulled a little harder -- every bit of 18#, maybe a tad more.

However I noticed shortly after that pull, a good plume of smoke was trailing behind me. Not really from the exhaust -- once again in my slip stream. When I stopped at a light, it billowed around the whole car.
Yep, popped the dip stick again. Oil all over the place.

My local 944 Turbo buddy and I are at a loss. Surely there seems to be some blow by or something. But those compression #'s certainly seem to suggest a healthy engine and good rings. Oh and there is still that fluttering bypass valve (brand new).

One other data point is that my oil is pitch black -- which I've read is often from exhaust gases introduced to the oil.

Is it possible that the turbo exhaust side bearings/seals are bad and exhaust gas is entering the crankcase that way? Is there an easy way to check?
I'm not super inclined to pull the turbo unless I really have to.....

Sure appreciate any thoughts/suggestions?

Mike

MooreBoost

have you done a leak down test?

thingo

I have been through a very similar ' enjoyable' set of problems, after changing the rings. Mine was solved by putting a restrictor on the turbo oil feed. This was with a gt30r turbo.

1987Porsche944WithRealLongName

I saw a similar issue with a car that had scoring in the cylinders. Compression was fine for whatever reason.

My car came with a vented oil filler cap, just a couple of layers of wire mesh over the center. Hell it was even on the parts list from the dealership that was in my records. Think something like that might do anything to help or would losing the vacuum do more harm than good?

White_951

Did you put in that external oil cooler? If so, did you pull the oil filter console? Could be a prob with the OPRV....I'm just buttoning up a similar job and it looks like I may have the same prob, not sure yet as I've only tested it at idle for leaks so far....keep us informed....

Chris Prack

This is why I don't do compression tests. For the gauge on the tool to hold a measurement it has to have a check valve in it. Typically this is a Schroeder core. I have seen engines pump the needle to an acceptable value but once you do a leakdown on the cylinder is has more than a 30% loss.

That is why. A compression test was a follow up to a poor leakdown test.

txhokie4life

I don't think there is a restrictor to my turbo oil feed.

How does this act like pressurizing the crankcase?

Unless your suggesting that the lack of restrictor blew the seals
and now the result is blow through backwards of these seals under boost?

thanks,

Mike

jlturpin

Not sure if I read your connection to the catch can correctly but it sounds like you are sending boost pressure instead of being on the j-pipe. This would definitely cause excessive crankcase pressure and possibly blow out a few seals. Post a photo of your hose routing.

txhokie4life

I was prepared to do that -- but when I saw decent numbers I moved on.

I'll add it back to the list.

m

jlturpin

Nothing in a catch can scenario should be hooked to the hardpipes.

thingo

In my case I think changing the rings increased the oil pressure to the extent that it was yes blowing through the seals under boost, but after you try changing rings, catch can you are just glad it stops smoking(had the dipstick popping out to). Oil used to pool in the intake of the turbo, so for a while we just thought it was the turbo. But this was just my experience, I have seen a few 951's smoking at the track...

txhokie4life

Sorry, I'm a little confused about your terminology -- just to be clear what i think you are saying was:

You had your dispstick popping, oil burning.
you changed your rings -- no solution
you added catch can -- no solution
you rebuilt your turbo and added a restrictor to the oil feed line to the turbo -- all was good

or did I misunderstand you

I of course and trying to figure out my plan of action.

thanks,

Mike

jlturpin

Mike

Check the hose routing, post a photo. Check the basics before you start dreading pulling engine for rebuild. You specifically stated you had hose routing to hardpipes. THIS WILL PRESSURIZE YOUR CRANKCASE TO BOOST PRESSURE.

txhokie4life

Hopefully some photos will help here....

The hose with the **** (which no-one can quite figure out -- it's just a cap)
connects from the left front hard pipe under the intake to the return intercooler line as shown with white Zip tie.

the line (AOS?) by the TPS was connected to the post MAF inlet that is now open by the yellow zip tie.

In this configuration I would blow smoke out the exhaust under heavy boost.
Pulled the MAF et al and found oil residue and sometimes a small amount pooled in the bottom of the lines, esp near the turbo inlet -- but the shaft play was minimal.

I then pulled the AOS? line and tried to cap it with a glove and zip tie -- (it's all I had at the track). No more smoke -- but then the glove blew and I got a good amount of oil all over the MAF/Filter area (which it was aimed at).

Got a catch can -- hooked it up to the AOS line, it was somewhat restricted
due to the hose lengths I had. First time out it blew at the hardpipe connection by the TPS. I zip-tied it for the next go round. -- This is when I popped the dipstick.

Last night I took the AOS? line and connected it to where the line with the Twist Cap. At first I left the TwistCap (ICV?) line floating open. Car would start but immediately die. I plugged the ICV? line with a bolt -- car fired up and held idle at 650RPM.

Drove home in this configuration -- but blew the dipstick again assuming when under boost.

Maybe someone with a little knowledge of how these lines should be routed can tell me what an idiot I am,

nothing like trying to debug someone else hacks :-)

Mike

Chris Prack

What a mess. The hose with the flush tee looks like it may be connected to the AOS. It needs to go to the MAF pipe if that is the case.