I have a strange problem with the 13b turbo in my racecar that I hope you can help me with. The car is a Datsun 510 and is used strictly for autocross and hillclimb. It makes absolutely no attempt at being a street car.

In the center housing, there is a breather tube near the oil filler tube that points rearward(horizontal). Within a few seconds of starting the engine, a substantial amount of oil fumes start coming out of this tube. Once there is sufficient heat in the exhaust header, there is a lot of oil smoke coming out of the exhaust. Also, I have a mechanical Autometer oil pressure gauge and the engine pegs the gauge at 100psi even at idle. I've tried 20w50 and 10w40 oil with no real change in pressure. I am running the stock turbo oil pump and stock relief valves.

The engine has been completely de-smogged, runs stock primary injectors and 750cc secondary, 55psi fuel pressure, AEM engine management, modified Hitachi turbo with Garrett compressor. I am running 14psi boost and it is putting out 300 rwhp. I am still getting the fuel tuning dialed in. It starts well when cold but still needs a shot or two of starter fluid when hot. It has always burned some oil but seems to be getting worse. Also, I run pre-mix and no metering pump.

 

The stock breather pipe on mazdas has never been big enough to support much above a fast idle. Pull the filler neck out of the block and weld in at least a 5/8" tube or better a 3/4" tube running uphill a bit. Run a hose to a catch tank. A tee may be added to run into the air cleaner.

The larger pipe and hose will reduce the velocity of the breather flow and reduce the amount of oil that flow can carry away.

It sounds like the oil scraper rings are worn out and allowing too much oil to slip by and make the smoke.

Get a higher reading oil pressure gage and find out what the actual oil pressure is. Up too 110 is fine for top RPM operation. 100 pounds is adequate. Change to a straight weight synthetic in 30 weight. if the super high pressure worries you. Much better film strength as well.
If it turns out that the oil pressure is over 115 pounds. Remove the stock relief valve and plug in a early relief valve you can take apart and add some washers to get the pressure you want. They start out at 71.9 pounds.
Lynn E. Hanover