GregBBRD

Alex:

Very nice information...that almost confirms that they knew what they were doing, when the holes got left undrilled. They replaced a fair amount of GTS engines, under warranty, that used excessive amounts of oil. It always made me a bit crazy to think that they never took any of those engines apart to see what was wrong. They apparently did.

Also cool to know that Kolbenschmidt made pistons, for the GTS. I've only ever seen Mahles. Why anyone would need/want two different pistons manufacturers for such a small quantity of engines is really interesting to think about.

Thanks for that!

GregBBRD

Nothing. Porsche used the same parts in the 968 engines as they did in the 928 engines. I think he meant 944S2.

GregBBRD

No doubt about that. That makes us both happy.

I'm just talking about how your oil level drops, in the tank, at higher rpms. That is significant for this discussion...another sign that the heads fill up. Luckily, you have enough volume, in the tank, to compensate for the loss of oil.

Joseph has an Acusump..and prayer.

Cheburator

Greg,

Care to share how much oil Mark A has in the tank? In litres, not in quarts for the benefit of us metric people... I went with 10ltrs, but that clearly was not enough. On the other hand, the Aston Martin V8 engine, which is very close to ours - 4.7ltr, 32v only uses 10ltrs of oil in the dry sump, the LS7 - I know it is a small block, push rod and only 16v also uses 10ltrs... How do they get away?

Thanks

Alex

Darklands

The publication with the oil return valves is from 2010.I think it´s a failure of the writer after 15 years.
After speaking with Jochen yesterday his meaning is with a normal 5 l block you should build a complete new crankcase venting.
Porsche did the improved venting holes in the GTS block but these engines have more problems than S 4 engines with oiling.
So stroking to 6.5 l puts the bar even higher.
He´s not a fan of the GTS engine and has the most stress with these in his shop.

daveo90s4

This really is a fascinating thread.

I wonder if the air / oil volume of the valve train area of the heads on the 32v motors can be reduced with some precision machined 'billet' that fits inside the cam covers? If this could significantly reduce this volume, is it possible that this would prevent / help prevent the loss of such high volumes of oil from the sump at sustained high revs, without having to either scavenge the heads or risk using different cylinder head oiling check valves? In other words, the heads would still fill with oil - but with much much less oil.

Just a thought.

Mark Anderson

My tank is 19 liters ( 5 gallons) and I keep it 1/2 full

GregBBRD

I'd guess that Porsche's change with the ventilation system, in the GTS, had more to do with burning oil at low and mid range rpms, where the governments regulate the emissions out of the tailpipes and less to do with how much they reduced the breathing of the crankcase and how much oil "packed" into the heads at higher rpms.

I now have several ideas for improving the air/oil flow through the GTS engines.

Testing will follow.

GregBBRD

But how much oil does it take when you fill it, the first time and how much oil does it take when you change oil?

Seems to me that the "initial fill" is about 16 quarts, with a dry engine, dry coolers, etc.

You would have a better idea on how much oil it takes, when you simply change the oil.

123quattro

Once the catalyst is lit, it should easily deal with the burning oil emissions. Porsche was probably just trying to lower the oil consumption.

GregBBRD

Yes, the catalyst can probably deal with the oil, but the GTS models ping and rattle so much (when they get hot and it is hot outside), that the NOX usually is screaming. If you mix oil in the combustion chamber, it reduces the effective octane of the fuel.

I've had these cars ping so bad that you can hardly drive them.

blown 87

That has to lead to a lot of carbon build up also, which will further degrade the ability to resist knock.

John Veninger

I keep mine 3/4 full!

123quattro

I agree.

IcemanG17

Hmmm....... I wonder how much "pressures" increase in GTS and Strokers compared to stock stroke engines?

Is the pressures in the engine correlated more to engine stroke-RPM-Piston speeds, or is it something else? For example a stock stroke 5.0L at 6600rpm (cutoff) has a piston speed of just under 57 fps....a GTS with its longer 85.9mm (not sure of exact stroke)stroke at the same cutoff is 62fps...but a stroker at 95.75 is 69fps......

So how much more crankcase pressure does a 21% increase in piston speed cause? Doc mentioned he started noticing the problem at about 5,000rpm which is around 52fps....or about 6100rpm in stock stroke engines?