1985-1998 [Subscribe to Daily Digest] |
Simon S,
FACT - Many manufacturers since the 1960's have had closed crankcase ventilation systems since the era of the down draft tube (i.e. venting combustion gases out of the crankcase with a tube hanging very low and getting vented while the vehicle is in motion). A typical closed PCV system would include the design of a "fresh air in" into the crankcase which id behind the air filter assembly and the "blow-by gases" would then be directed back to the intake manifold = your closed PCV system.
The problem I am having (specific to the Saab 9000 B234 engine) is - where is the fresh air intake? I would you think you need a fresh air intake (because not only does the crankcase's PCV valve design regulate flow of the blow-by gases, it also regulates the lubrication for the bearings in the crankcase... blow-by gases exit to fast = to much oil taken from the crankcase = take out your bearings) like a gas tank needs fresh air intake. As pressures and temperature change for your gas tank, the vent valve in the EVAP system prevents your gas tank from expanded or contracting in unwanted ways. In my mind, with similar logic, you want to be able to control the changes in temperature and pressures in the crankcase with the help of fresh air being introduced so you have proper control over flow as well as lubrication for the bearings. Hence my confusion with regards to no "fresh air intake".
If Saab engineer's decided not to use a fresh air intake for the B234 engine, then I don't understand how (from an engineering/science perspective) that system works when considering your typical "fresh air in" and "blow-by gases directed back to the intake" crankcase venting design.
As always - thoughts appreciated.
posted by 70.181.172...
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.