993tt

kojo911 · 02-12-2013, 11:01 AM

Looking for the scavenge pump pressure for a 993 twin turbo. That is the pressure that the oil is pumped from the crank case back to the oil tank or cooler. Any help would be greatly appreciated.

Ken

geolab · 01:33 AM

Hello, I do not know if I understand the question well...
The oil pump in the 993 turbo has a two stage configuration,
One stage is for engine, pressure is 5.2 bar @ 2200 rpm (warm engine) up to max 6.5 bar at 5500 rpm.
Second stage is return oil to tank. Since it is not pressure related, it is measured in liters per minute, and the rate is 65 liters per minute. But for your info, at the exit with same outlet diameter on pump, is more or less 9.2 bar for the return to oil tank
regards

kojo911 · 02-13-2013, 03:44 AM

Thanks, Geolab. I think you understand the question. It's the pressure of the return line (more specifically the flow of the return pump) that I'm interested in. I guess I'd have to figure out what the plumbing diameter is on the return line to figure out what the pressure is.

racing97 · 02-13-2013, 06:38 AM

When my Flow Turbines were functioning on my Dyno I would see 14 GPM on the return side of a Porsche engine with a 993 style pump

regards

kojo911 · 02-13-2013, 06:45 AM

Thanks racing97. So I guess the question is what would be the pressure given the diameter of the return side lines. I nosed around for the formula but I'm not smart enough to plug in the variables. I'm going to assume that with -16 lines it's significantly less than the 5/6bar that the pressure side sees. I'll make a new post when I pop my oil cooler!

racing97 · 02-13-2013, 07:47 AM

Pressure is a function of the restriction. The first restriction from the scavenge would be the exit port of the pump than the case exit. The port size for the exit fitting on the case is 15.8 mm or .625 which would correspond to a -10, I personally have never used less than -12 which is around .725 on the return lines but it is probably a personal preference rather than a imperative. The 993 964 front mounted coolers used on the 3.8 rsr would see well over 100 lbs on start up and I never saw a leak. that being said in the earlier cars with very expensive behr units you had to be very carefull.
regards

kojo911 · 02-13-2013, 02:40 PM

Thanks for your help "97" I probably don't won't have a problem I just want to avoid one if I replace the Parker thermostat. Im running a BB front mount oil cooler like this one:

The reason I'm considering replacement is that oil temps even on the track never get above 150-160f (I've confirmed my temp gauge and sender are working). It's a combination of large oil cooler plus excellent venting.

The valve is it's opening as it should at 160f, I think that's too low. I'm ordering a new valve that opens @ 180f. These valves have a pressure relief circuit in them that can be ordered with various "crack pressures". Currently my 160f valve relief circuit opens at 50psi. It's probably fine but I can order them with higher crack pressures (or lower). This is what led to the initial question. I guess the question I should be asking is what crack pressure should I be ordering.

Probably the smart thing to do would be to leave it alone. I'm not sure that a change from 160f to 180f (the max Parker offers) will make much difference. It's a PITA but I could just mess around with taping the cooler off.