Carnut
March 20, 2008, 4:09pm
20
Currently I am using venturi or slashcut tubes in my exhaust to create a vacuum for crankcase ventilation. I ran this setup last year and was not happy with the results. It did pull a decent vacuum but it was shooting alot of oil into the exhaust which resulted in alot of smoke. When the car was idleing it would randomly let out a cloud as oil entered the exhaust. I could put in a catch can to prevent this but I think I want to ditch the setup all together. This method is best used for car running a open header in nonturbo applications. The check valves are prone to failure when running in high temp turbo applications which could result in exhaust dumping straight into the crankcase.
To replace my setup I was thinking about going with a vacuum pump setup, specifically a electric vacuum pump for crankcase ventilation. This would remove the parasitic loss that occurs with a belt driven pump and would not require modification to fit it into the current drivebelt assembly. I think the only way I could run a belt driven assembly would be to remove the ac compressor.
I found some info on the net, specifically from dpecorvettes.com . Here is his setup
He listed all the benefits
Prevents oil leaks from seals and gaskets by eliminating crankcase pressure.
Reduces parasitic losses from pistons pumping against crankcase air.
Improves piston ring seal.
Increases HP and makes your engine last longer.
Eliminates your PCV system and the possibility of oil being sucked into your engine keeping your intake system and combustion chambers clean.
Eliminates the need for mechanical belt driven evacuation pump that robs some HP and needs rebuilding frequently.
Superior to valve cover breathers and exhaust path suction type pcv systems which contaminate your exhaust system and mufflers with oil.
Pump can be set up with the filtered crankcase exhaust routed to air filter housing instead of out to breather if desired for a closed loop system (emission friendly).
Fits in factory battery tray for easy access to engine. (Battery must be relocated to trunk or rear compartment).
Ideal for Turbo, Supercharged and high compression engines which create higher crankcase pressures at high RPM’s/Loads.
Creates 5 inches of vacuum in your crankcase with a very high CFM air flow when needed at high RPM’s, exhausting and filtering all blowby, while still maintaining its vacuum for ring seal.
The waste oil level is easily seen through sight hose and drained through a valve on the side of catch can. If any oil vapors pass the modified Catch can, they will be condensed and caught in the Air Dryer before reaching the pump to ensure long pump life.
Sooo now I just have to find the right pump which is not too easy. He used a M3 secondary air injection pump which seems to be the perfect fit. Also I need to find the boost switch to activate the pump when I hit boost.
This is a great example of a well thought out crankcase ventilation system. Any GM secondary air injection pump can be used and they are fairly easy to come by. Visit any junkyard and look for any 98-01 blazer or jimmy. It would be nice to see this made and enclosed in a box with just the fittings on the outside using bulkhead connectors.
I know alot of GM guys that have run this for years. When I worked in the dealers we used to get these pumps all the time for warranty repairs because GM wanted you to replace everything in the SAI system. The pumps still worked so guys used them. They saw 7" of vacuum on their small blocks from the dipstick tube.