keith

Hey guys, I ran through 3 QUARTS of oil this week in Pop's 951! (of course, I have been on boost a bunch, but sheesh!)

So I had my wife drive the car while I followed, and I observed dark grey to black smoke, followed by grey-white smoke, upon moderately heavy to heavy acceleration. Idle and and regular driving show no evidence of smoke, light to moderate acceleration show wisps of dark smoke.

Of course, the Huntley chipset should explain the dark smoke (fuel). However, the quantity could be an issue, I suppose...

However, I am obviously concerned and cofused about the oil, as I've just rebuilt the head, and replaced the turbo with a (supposedly) low mileage one... If the rings were that bad, wouldn't I be seeing smoke all the time driving?

HELP! How do I know conclusively where the oil problem is?

...and no, there are no obvious leaks...

<img src="confused.gif" border="0">

Russ Murphy

Whatever condition your rings and cylinder walls are in, oil consumption is going to be a lot worse with your foot in it than not. My oil consumption on one track day is equal to two weeks of daily driving.

Bri Bro

Get a leakdown test done, that will ID were the problem is.

Jeremy Martin

More than likely there is no problem, period. You own a porsche, they burn oil. all of them. even the new ones. my car burns about 1.5 liters a week (about the same as 1.5 quarts) and i drive it about 1000 miles in a week... and it's just fine. porsche's factory manual on the 951 states that max oil comsumption is around 1.5 liters every 1000km; this converts to 1.32 quarts every 622 miles! this means you can use up 1 quart every 470 miles and you will be perfectly within factory tolerances! this is porsche speak for if it doesnt smoke all the time, boosts well, and runs generally fine otherwise then just leave well enough alone. these cars smoked when they were new, and they will smoke now... my problem is i burn about 6 quarts between oil changes, which is roughly the sump size. if i were a little more trusting in the recirculation system to properly move all the oil in the engine i'd only change the oil once ever 10k miles; however i know that the zinc in the oil will be uneven with the less moved oil having a higher concentration, which is useless for the engine parts that actually touch, as well as useless for the turbo. so, change your oil and filter once every 4k miles (porsche reccomend interval) and enjoy your car... on some models "check oel" is printed on the rubber gas tank fold that protects the paint from the pump nozzel; this couldnt be more true a reminder. check your oil every time you gas up.
Cheers,

Olli Snellman

It's possible there's nothing wrong with your car.But if you want to be sure make a leakdown test.Most likely the first items to fail are valve stem seals.They can be broken or they are just popped of from valve guides (mine had).If it is not a valve guide stem seal problem it can be a worn out valve guide.

Olli
'88 951

Ahmet

I'll bet on the turbo.
Ahmet

keith

Guys, I feel pretty confident about everything in the head (I mean, I did the valve stem seals myself - new guides, valves seated well, good machine shop, etc.)

I still don't understand how this could be rings, if it doesn't smoke at startup and regular driving.

3 quarts in one tank of gas is excessive, compared to my own 1986 951, which has more miles.

I don't understand how a leak down would diagnose the turbo or oil/air seperator problems (as other Rennlisters have suggested).

I will do a compression test and a leak down test, check my fuel pressure (to verify that it isn't too high, thus thinning the oil), and check the throttle body/intake pipes for excessive oil - this car has only been running for 2 weeks, since the head job and turbo replacement...

Keep them ideers a'comin'!

Peckster

[quote]Originally posted by keith:
<strong>

I don't understand how a leak down would diagnose the turbo or oil/air seperator problems (as other Rennlisters have suggested).
</strong><hr></blockquote>

A leak down would only help diagnose problems in the engine.

Jeremy Martin

you're right, 3 liters in one tank is quite excessive. it should be no more than 1 every tank... do a leakdown first. that will tell you if you have a problem with your rings (air going into the oil pan), your head (air going into the head / valve cover area), or your headgasket (air bubbles going into your coolant). check your spark plugs for carbon and oil buildup. if it's not pretty uniform across all four cylinders, the oil leak is indeed in the engine somewhere... after that, check the turbo. do this by taking off the intake up to the turbo, including the afm and j-boot. then, measure the play in the bearing. it should be no more than 1mm (according to the factory manuals) in any direction, including in/out. if the turbine is still relitivly play free (there will be a little play and there will definitly be oil in your air intake, even on a properly functioning turbo) you should inspect the seals on the front of your engine by taking off the timing belt cover. if there is alot of oil in there, that is probably your problem... that leaves the last big possibility as the seals on the rear of the engine, around the clutch/flywheel. this is hard to inspect, but you can diagnose it by removing the clutch inspection plug under the engine (might as well measure the remaining clutch while you're in there)... the problem i have with all that oil being brunt in the engine is you're not smoking constantly. these cars will smoke under acceleration.. and burning 3 liters in 400 or so miles means you're competing with iraq on how much oil you can burn in a week. also, what weight oil are you using? brand? synthetic? did you switch recently?

Jeremy Martin

there's also one more thing to remember that i learned from working on ferrari's: if the car works, dont fix it. if it's burning 3 liters a week, and each liter costs 3.00$, thats 468 dollars in burnt oil a year. if you have to do a head job, fix the clutch seals, fix the front seals, or fix the rings you're looking at anywhere from 1000$ to 2500$ for the job (even if you do the labor yourself your time is worth money). it would take 2-5 years to burn that much oil, and in 2-5 years at around 20k miles per year you'll probably need a rebuild on an engine that has 100k+ miles on it now... although i would caveat against letting seals near a timing belt go as this can cause the belt to slip or to degrade and break apart... but for clutch seals, just replace the seals when you next replace the clutch; the oil will cause the clutch to fail sooner but if it's oil soaked now you'll need to buy a new one anyone, you might as well get the rest of the life out of this one. also, replacing the turbo is a 10 hour job if you've done it before and have few broken bolts. Porsche quotes a 16 hour book time to pull a turbo and put in a new one. this is 16 hours of labor plus 500$-900$ for another kkk-k26; what i cant stress enough here is if a turbo doesnt smoke constantly and builds good boost, dont bother replacing it.
Cheers,

keith

Hey Jeremy, and thanks for the response. Let me lay out the background of the car (should have done this before, I suppose)

I talked my Dad into buying this "deal" 2 years ago for $2000, running. I've been working on it in my spare time since then to get it up to snuff mechanically for him (he'll take over with the rest of the finishing, interior and exterior stuff).

So far, I've resealed the front of the engine, R&R'd the belts, waterpump, rod bearings, and oil pan gasket. New radiator, cycling valve, lots of vaccuum lines, plug wires, cap, rotor, A-arms, fuel filter, electric water pump for the turbo, FPR, damper, and injectors.

As of 2 weeks ago, I've put a rebuilt head on the car (I set the spring heights and installed the stem seals myself. The head got NEW valve springs and guides, and a 3 angle job.)

I also repaired the turbo downtube and replaced the K26/6 with a used (supposedly low mileage on a recent rebuilt) K26/6.

I had the head and oil pan off at the same time last year, and really should have doen the rings at that time, I suppose...

The car now runs good, and pulls pretty hard, but emits the fuel and oil smoke as stated previously. I was attributing the fuel smoke to the Huntley DME chip we're running.

The oil smoke, in my mind, has to be rings, or valve stem seals (and it had better not be!) orOR turbo-related, right?

However, some guys on the email list have suggested the Oil/Air Seperator as the culprit, although I don't know enough about the way it functions to wrap my brain around that.

I'm guessing I need to start with the compression test, and if it's low, do the oil in the cylinder compression trick. I'll do a leak down at the same time, and report back to you guys with the findings.

BTW, I'm running Mobil 1 15w50 in this thing, but am replacing it with 20w50 dino as it dissappears...

PorscheG96

What is the oil/air seperator anyway? <img src="confused.gif" border="0">

Jeremy Martin

the oil in the cylinder is a poor man's leakdown trick. save yourself the time and just get a leakdown kit and hook it up.
Cheers,

keith

Hmm. Guess you're right.

I have the leak-down gauges as well, so i just need to do it!

Olli Snellman

When you changed your valve stem seals did you use old or new style seals? The old style ones pop off very easy.Also i have seen machine shops still install old style valve guides as well (without grooves).If it is not stem seals it might be a turbo problem.Since you are using thin synthetic oils your oil consumption will be higher than with Dino.I use dino 20W50 (Valvoline Racing).

Olli
'88 951