Oil drain in valve-cover?

[beepbeep]

We are on our way to rebuild certain hot 3.6TT engine. As you can see, original engine builder opted for dual 930 turbo-sump oil pumps. There is one pump on each side, sucking oil from turbo oil-sump and dumping it into top valve cover.

Engine has history of blowing oil from every orifice which we are trying to cure. This is one of first steps. For some reason, I don't like having hot turbo oil being dumped into valve cover. My reasoning is that oil drainage from valve tower is dimensioned for oil that drips off the cams and that extra flow of hot oil that just went trough a pair of Garrett GT35BB's isn't helping. Plan is to plug those drain hoses and let oil go into sump or (trough separate hoses) into oil tank.

Problem is, oil tank is going to be moved into front compartment so it's not just a matter of dumping two oil hoses into oil-tank.

What do you think? Where should we dump oil coming from turbochargers? (It's a turbo-converted 3.6 engine )

[sammyg2]

edit, just re-read the post, my suggestion of pumping it into the tank does not apply. never mind

[Grady Clay]

Goran,

Just run the oil outlet from those two scavenge pumps through a
screen filter and Tee into the engine out oil line. This runs that
oil through the normal filters and coolers.

I am not a fan of a front oil tank. When I raced 935s, I could turn
on the oil light under severe braking no matter how full the OE
K3 935 tank was. I think the best solution is the GT3 oil tank
set-up.

It feeds the inlet of the pressure pump with very little inertial effects.


Try this link:
Oil Tank location


If you are trying to move weight to the front, there are other ways.

Best,
Grady

[Porsche Doc]

Hey Man!
Run to returns into the lower valve covers directly in line oil return tubes. That works great for us.
We also had to watch the oil level in the tank. If to high it blows oil into tank vent line and makes a mess. We had to run the oil level at the MIN line. We were using one of the stock tanks that Smart racing deepened for us. It added 3 Qts. with it at the min line
Here is a couple of pics of how we did it on a 3.8L 965 T engine.
Good Luck!

[beepbeep]

Grady: great input! Thanx!

Reason of moving oil-tank up front is shortage of place in engine compartment. Right turbocharger wastegate is hitting OEM oil-tank which forced last builder to shorten the tank. This reduced oil capacity to approx. 60% of original one. Engines healthy apetite for oil and small amount of oil in tank led to costly and specatcular failures. (a pair of these custom build hybrid Garrett turbochargers costs a fortune).

I was also thinking about inertial effects of having oil tank up front but "senior builder" thinks 20 quarts oil tank up front is a good idea. I'll try to change this design detail based on your input.

Engine worked well on dyno but everything changed once it got strapped into car, so we need to rebuild lot's of stuff. Amount of power from 3.6 and dual GT30/35BB @ 1.4 bar is insane.

[beepbeep]

Don: thanx for input!

This is a custom engine with GT2 oil pump. One if it's problems is that they never really stabilized oil pressure. It kinda goes out of whack when revs rise. I suspect that pressure-reducer valve bottoms out.

To put things in perspective: these ball-bearing turbos need reduced oil-flow. That's why there are oil-reduction valves on their oil feed. But as unregulated oil pressure went out of whack, custom-build turbo oil sump thingies got filled with oil that 930 pumps couldn't evacuate so their breather lines started to blow out excess oil. So oil flow to turbochargers got reduced even more (which I suspect led to oil starvation at lower revs which forced owner to replace turbocharger five (!!) times ).

Oil-tank breath line spews oil as well. We'll tear into engine in few weeks, I'll post pictures of potential carnage. I suspect broken piston rings to begin with (it was used with 2 bar of boost from time to time). There is lot's of stuff that needs to be fixed here.

[911pcars]

You have two issues: Engine venting and turbo oil dumping.

If the chain box configuration is the same as earlier engines, try that location. The chain box provides a direct oil drain path to the engine sump.

Oil leaks indicate not enough breathing area to relieve internal pressure. The piston rings have more of a challenge controlling the pressurized charge in the chambers. Blowby on these engines is potentially greater than on normally aspirated engines, thus I'd suggest you use large diameter vent hose to a suitable vent tank; perhaps vent both the oil tank and the engine crankcase into a common vent tank to atmosphere.

I haven't seen this applied to Porsche engines yet, but many domestic V-8s use a vacuum pump to help reduce crankcase pressure and increase piston ring sealing.

Sherwood

[Grady Clay]

Goran,

What chassis?

If it is an early chassis, some creative work on the rear shock mount cross-member will work to fit the GT3 tank.

If the GT3 tank doesn’t suit your application, consider putting the tank in the RR seat area if that is possible in your application. That will let you run a LARGE hose to the pressure pump inlet. It is very worthwhile to make sure there are nice transitions in diameters. Sudden steps and sharp bends restrict the flow.

Keep in mind the importance of a centrifugal oil-air separator in the circuit.

Take a step back and look at the entire system. There is no reason to leak oil or have engine failures.

Best,
Grady

[beepbeep]

Grady: chassis is modified 930 -78 (coilovers, G50, full cage).

I just talked to owner and briefed him on my concerns about G-load induced oil starvation under braking. He's still confident that front mounted tank should would be OK as he doesn't plan to use slicks and will thus have lower G-loads on braking? He says most modern racing Porsches have front mounted oil tank?

We'll discuss these details further on during the winter. I understand your point and would gladly have oil tank on rear seats. Unfortunately, this is show/street car, not pure race car so complicated arrangments of oilsystystem in back seat is to be avoid, to keep "stockish" looks.

P.S.
What do you think about replacing OEM 3.6 N/A fan with 930 one? I heard 930 fan flows more air. OEM fan is geared higher now and is using flat belt with tensioner, but we still have problems with it falling off from time to time.

[Grady Clay]

Goran,

“He doesn't plan to use slicks and will thus have lower G-loads on braking”
Is there some reason to not use the best grip? If there is a class specification, I understand.


“He says most modern racing Porsches have front mounted oil tank?”
Au Contraire, the most modern 911 base race cars (GT3 Cup & GT3 RSR) have gone away from the front tank to the engine mounted tank. My speculation is the exact reason of the inertial influence on the oil feed to the engine. The GT3 tank also doesn’t have to use 25+ liters of oil; a significant weight savings there.


I totally agree with the difficulty finding space to put things. I think the image I posted above is a GT-2TT configuration. That oil tank would solve several of your issues: Proven design, no extra space, lighter weight and keep the “stockfish” look. The issue you will have to address is clearance to the shock cross-member. That should be easy in your application.

I think it would be very beneficial to configure the engine installation to fit any GT2/GT3 engine/trans, including rear suspension.


“What do you think about replacing OEM 3.6 N/A fan with 930 one?”
As I understand it, the 993 (964) 1.6:1 fan is designed to produce less noise at the expense of less mass air flow. Yes, use the 930 high flow fan arrangement – 1.82:1 and more with custom pulleys – will produce more net HP and better reliability.
I think the “Rubbermaid Solution” would be best for track if legal in your series. It can also provide additional cooling to the intercooler. Including that and more, yes – you need the most cooling possible. There is significant performance and reliability to be gained having the intake charge, heads and cylinders cooler.

Best,
Grady