I've been having a significant issue since intalling my current turbo and engine combination: high crankcase pressures at over 19 psi.



I am trying to understand everything that can contribute to the problem since I'v been blindly slapping parts on and off trying to address it.



The motor is a Pineapple with special port by Rob. It's a stage III with all the oil mods. At idle (1000rpm) I see 30 psi on an aftermarket gauge. At above 3500rpm I peg the oil pressure at 100psi and it stays that way.



The turbo is a GT40R from Aspec. All lines going to the turbo are SS, and I am using a .030 oil restrictor which seems to have helped in slowing the filling of the catch can.



I get full boost, 19psi, at 4600rpm in 4th gear very easily. Then I hit the crankcase venting and the power drops.



The boost controller is a Greddy Profec SpecIIb. I can hold targeted boost from 14-17 from initial target to redline, as long as I don't get into crankcase venting.



The venting has its own sound, similar to tone like blowing across a bottle top.



The top of the oil cap has an AN-10 90 degree elbow which connects to 2' of 5/8's webbed clear plastic hose to near the radiator where it connects to a Greddy oil catch can. The vent hose goes to atomsphere via another hose, about 10' long at the rear of car behind the gas tank.



When venting, trying to hold +20psi boost, the catch will fill very quickly...usually after half a dozen 3000-8000rpm pulls.



The motor has about 4K miles on it, break-in took over 1600 miles.



Wastegate is a Tubronetics NewGen with the stiffest spring (about 13psi) in it.



Cars pulls fantastic until the venting starts, then it stops building power.



The addition of the turbo oil restrictor made an impact on turbo spool-up...faster by near 200 RPM in 4th gear.



Could some of advanced oil mods and high oil pressure contribute to the venting?



What internal engine issues could I be having and how would I diagnose?



No dyno sheet, no compression check, but both are planned in the next week.



I have been thinking of venting the rear iron, where the stock rear oil drain went, and tying that to the catch can.



Appreciate your insight.









Tony

 

ok, I had the same problems and the same turbo. I tried all the venting in the book; rear iron, 90deg fitting on the top of the oil filler neck. I even made a baffle for the oil filler neck which didn't help. Anything above 12psi and I would overflow my catch can.



Sean said it wasn't the turbo as Garret has such a low failure rate. He said to check the motor. When we did a compression check, we got a 1 point lower reading from one of the front rotor faces (7.3/7.3/6.3) we figured a side seal was sticking. Anyway, we have had to pull the motor apart and fond some rotor wobble wear marks that were not there prior to the rebuild. My motor was rebuilt at the same time as I ordered the turbo. I put about 2000 miles on it when we finally had to tear it down for this same issue.



It seems odd that you are having the exact same problem as me with the same exact turbo. Your motor is from a reputable builder and I imagine that you won't find anything wrong. Even with my slightly low compression, which was still in tolerance by Mazda specs, my engine builder could not find a direct cause of the crank case overpressure.



This has led me to wonder if the problem might lie with this turbo. Boost pressure might be slipping past the seals in the turbine housing and getting into the crank case. once there it will push out the oil to the catch can. Once it fills and/or the vent gets obstructed, you should see the james bond smoke screen as well when letting off after getting on it.



I also think others have been fighting venting and smoking problems with this turbo. I haven't checked in a while.



Mike

 

Sounds liek you are getting a lot of blowby. Check the motor out

 

Take the oil filler cap off. See if it smokes out of the filler while the engines running.

 

Excessive engine seal clearances

Excessive turbo seal clearances

Excessive oil temps

Excessive oil vapors due to oil chemical content





-Ted

http://fc3spro.com/

 

I would suspect the turbo.



Rob's oil pressure mods caused a bit of trouble w/ my plain bearing turbo and I have read ball bearing units are much more succeptable to this.



I ended up putting the sump under vacuum to help the turbo drain fast enough.



Find out what oil pressure the maufacturer recommends for the turbo and make an electric pump/regulator set-up just to supply the turbo w/ oil at recommended pressure.

 

tony, any new news on your problem. I could use the info.



mike

 

[quote name='mfilippello' date='Aug 5 2005, 09:16 AM']tony, any new news on your problem. I could use the info.



mike


[/quote]



Update: target boost (21 psi) I can hit by 4200 in 3rd gear. Wastegate was swapped out. The original had many defects that are being addressed by the manufacturer.



Motor is solid, guys. It is the LAST variable in this equation that I will consider.



Talked to Mike on the phone, I am trying something and he is too.



Based on another high boost application on a piston engine local to me, going to add vacuum to the vent to assist pulling the vapors out. Based on what has been seen on the piston engine the point at which I would see the same symptoms should more up the boost range.



Also, the oil restrictor has made a 5 fold decrease in venting. With over 10 tanks of gas through the car, I am confident that this is not a fluke.

 

[quote name='RONIN FC' date='Jul 11 2005, 10:20 PM']Take the oil filler cap off. See if it smokes out of the filler while the engines running.


[/quote]



No smoke while running.

 

this is a little late in the game but the rednecks put a fitting into the exhaust so it pulls a vacuum on the crankcase, apparently that helps seal the piston rings better.