Saabscene Saab Forum - Saab Technical Information Resource banner
1 - 6 of 6 Posts

·
Registered
Joined
·
4,215 Posts
Discussion Starter · #1 ·
When I was setting up the bailey dump valve I noticed when the car was idling the dump valve was opening ..no problem just bleed some vacumm away.. however on idle there was a definite volume of air coming out the valve..
My guess is that abbott sets up the base boost so that at idle there is always a positive pressure
i guess for quick spool up and minimise lag:
the next thing observed was when road testing it woulld only go into the yellow and it lost all its boost ...(the vacumm pipe to the dump valve had fallen off)replaced it ,tied it down no problem..boosts into the red ..it got me thinking
the vacumm acts to open ,it .pressure from the manifold pushes it open against the spring..so what keeps it closed on high boost ?
 

·
Registered
Joined
·
1,261 Posts
Diaphragm dump valves do let in air at idle/vacuum - it's a flaw in the design that lets air bleed past. They are usually not recommended or fitted to cars where they need to be fitted upstream of the air metering system.

Piston type dump valves overcome this problem
 
1 - 6 of 6 Posts
Top