Vince964T

Hi,

I am looking for some tips.

What would cause very high oil consumption on track on a stock 993TT engine ?

I am talking about VERY high consumption, like 3l or so over 30mins !
Oil is being sucked into the intake then burned.
Some smoke while driving hard but not an enormous amount (or I would have stopped right away, as it is i didn't see anything in my mirrors but heard comments from other drivers afterwards). What could cause that ?

Driving normaly I didn't get any oil consumption of that sort.

So far a lot of things have been checked and the diagnos I have is bad turbos.
Could that cause such a huge oil consumption ?

Thx for your input. I am not a technical guy so please make "simple" comments

Rgds

Basal Skull

How many miles. My guess would be turbos too. And yes you can loose a lot of oil if your bearings fail.

Marcus S.

I have almost the same issues on my 993 Turbo with high oil consumtion, but even oil in the intercooler and MAF after every track day. I have went to the local turbo shop here in Gothenburg Sweden and have the turbos checked, and there is no problem.

I also speaked to our local FVD dealer in Sweden, and together with the technicians at FVD we will try to change the air/oil seperator in the throttle body. The AOS valve I will change has part number 99311013850, nr 45 at the picture below.



I was told that this valve also controlling the preassure in the crankcase, if it fails, oil will be ventilated thru the crankcase ventilation that is connected right after the MAF.

I will change this AOS valve on monday 30th of june and hopes this will solve the problem. If someone has other ideas i will be thankful for yor replies

Regards!
Marcus

Vince964T

Thanks. You seem to track your car regularly with no issues. Always reassuring to see it CAN work !

62k kms on the engine. Engine topend has been rebuilt. And it has been opened again post high oil consumption to check everything was in order. It looks like new apparently.

Turbos are standard K16, 18 years old. Just got them back last week after rebuild.

air/oil seperator in the throttle body you mentionned Marcus was apparently fine on mine. Was one of the 1st thing my technician checked.

Only "bad behaviour" I had previous to this was a puff of white smoke when firing the engine. Just a puff and on every start, didn't matter if the car had been sitting 1 week or 1 minute.

Mike J

that is interesting - its normal to get a puff once in a while to no puff at all, but not on every single startup, especially if the engine was just shut off. I think on my car I have gotten one or two puffs in the last two years of operation.

To generate smoke, some oil must be introduced into the combustion chamber. Since you have done a top end, we can eliminate the valves, so it must be the Turbos or some other places.

cheers,

Mike

Vince964T

I reread the sticky about turbo chargers failure and it could be turbos...(filter, oil type, check valves all done as well).

Could be something was not done correctly with top end rebuild but they measured rings again and they were as new. So hopefully not !

They are puting everything back together during the week and checking everything is in order with oil circulation. Fingers crossed the turbo rebuild does the trick.

Marcus S.

Now the AOS valve is changed on my car, and cleaning has been done of the Intercooler and MAF... again. The car feels good but the real test will be at the swedish racetrack Gelleråsen this sunday, the story continues...

Vince964T

How did it go ?
Hope I get my car back this week before week-end track day.

Marcus S.

This problem is a little bit strange. On the way to the track, I felt sometimes under full boost some issues so I was a little bit concerned how it will go.

On the track, all was gone and the car and engine was going as it should, hopefully this little valve solved all the problems. I will take the intercooler down this week again and have a check and I have my fingers crossed that I will not found any masses of oil

Marcus S.

Now I have been driven two trackdays with the new AOS valve and everything works just perfect. Strange that thos valve coused this problems, but now it's fixed , so happy

Vince964T

Good news the turbo rebuilt took care of the oil consumption (Edit - Thx Rennlist/sticky post)
But now I have some new symptoms I didn't have before.

I have some kind of overboost issue
My boost gauge goes a bit above 0,8, then I feel an hesitation/shudder may be missfire ? the boost then drops back to 0,8 and then she runs well again. Happens in 3rd, 4th, 5th, 6th irrelevant of rpm but only at woot and when I reach max boost. If I go 90% the engine runs great. Obsiously the ECU is saving the engine from overboost.
The car seem to be running lean at max attack. After a hardish session on track (I wanted to really test oil consumption) the exhaust pipes were really white so I stopped driving.
And finally she runs like crap between 2k and 3k rpms in every gears. Iddle is fine.

I did some research about what could cause this. Here is my list:
Sparks (they were changed and it didn't solve the issue) / ignition.
MAF (it got sprayed with a lot of oil)
O2 Sensors especially the ones before cats. Could explain really warm exhaust as cats would not work correctly.
N75 Valve, nber 34 on Marcus diagram above - But would not explain how poorly she runs at 2/3k rpm ?
Waste gate actuators (though it seems I would have problem geting high boost rather than having to much boost?)
Bad ECU - Unlikely, I didn't have that issue before...

After new plugs I have ordered a new MAF and new O2 sensors. Thinking the previous turbo issue and oil bath may have damaged the MAF.


Anything else you guys can think off ?
Anyting turbo side that could be set wrong after the rebuild ?
Understand this is a bit of a special build (964t track car with TT engine in it) and i have no way to read fault codes.

Basal Skull

It's probably one of those things. If your thinking you may not be getting enough fuel, don't forget the fuel filter. I assume you have an external boost gauge if you can read numbers above .8

Basal Skull

Have you tried wot after shutting down? It sometimes takes a ignition off or two period for the ecu to adjust if the battery was disconnected.

Vince964T

Yes correct about the boost gauge.
Thanks for the suggestion about the fuel filter. Would be easy and cheap for once.

I have a circuit switch for the battery (good for track use) so I disconnect from time to time, but that has not been an issue before and the problem stays after turning her on and off a few times.

OverBoosted28

I couldn't find if your car is completely stock (in post) or not. If you're exceeding .08 bar I assume it's not. I had a hell of a time trying to figure out hesitation at 5200+ rpm. Hit everything, plugs, wires, dist/rotor, fuel filter to no avail. Eventually went with a "Crane E-core LX91" coil and brought gap down to .021-.022. That was it. After that I was blowing every hose that was met with boost. Changed/upgraded all (5) hoses, and car has never run this good. If you're running more boost and have standard gap on plugs, the boost pressure will extinguish the spark prematurely. Good luck