Another interesting article on vacuum pump assisted crankcase ventilation from the Supra forums, pasting over here (
http://www.supraforums.com/forum/sho...se-Ventilation) :
Vacuum for Crankcase Ventilation
All cars have combustion gases blow pass the rings into the crankcase. In the old days, Breathers on top of the engine vented the excess gas, more or less keeping the crankcase at atmospheric pressure. Racecars had really big vents. Turbocharged cars could blow even more gases past the rings. However with combustion pressures of 10 atmospheres, all engines do it.
For emissions reasons, the gas was recirculated, drawn by intake vacuum through a check valve. On the Supra, the system has two check valves, and vents into the intake on either side of the turbo depending on the boost level. Rather small tubes though.
On this board are stories of front seal failures...a sign of an over pressurized crankcase. There are also pictures of very small filters on the end of small tubes; can they have enough capacity for a 600hp 3 liter? And there are configurations with those tubes vented to a tank, and then to the intake. Can than create enough pressure to draw excess gases through that circuitous route?
In oval racing there is a story (told as having happened at Stef's), where an engine was dyno'd, but they didn't have the right valve covers. So they put on some covers that didn't have breathers installed yet. When they put on the covers with breathers, the HP went down. When they put the closed covers on, the power went up.
This engine had a dry sump system. The dry sump positively scavenged the air in the crankcase. When it had the sealed covers it created a vacuum, and that raised HP.
In NASCAR today, engines run with around 20-psi vacuum in the crankcase. Dry sump pumps have their scavenge sections designed to create vacuum. A check valve is added to suck air into the crankcase to prevent excess vacuum. In lower racing classes, my dry sumped late model is limited by the rules to 2 scavenge stages, limiting the amount of vacuum.
Virtually no one dry sumps the Supra. Owners have found the stock wet sump adequate for road racing, drag racing, and who knows what else. However, would a vacuum pump help?
These pumps are a single, large vacuum stage off of a dry sump pump. It could scavange the air into a surge tank that vented to the intake. If the tank was baffled, presumably oil would separate and only air and gases would return to the intake.
ATI lists a damper with a dry sump pump adapter. My search has not found any pumps or mounting kits. And it looks like a tight fit around the engine.
Has anyone successfully mounted a vacuum pump to the Supra?
Thanks,
David
P.S.
This a link to Moroso's vacuum pump catalog page