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Good info. And in addition to that:
All saabs uses the recirculating bypassvalve. Cars equipped with airmass meters (LH2.4 DI/APC and Trionic 7 cars) must/should use bypassvalves, not dumpvalves (non recirculating valves). Trionic 5 cars can use dumpvalves without any problems. There are some dumpvalves (non recirculating valves) that work on AMM cars as well. The HKS unit is one example. For most other dumpv you have to use so much spring force in the valve (to keep it closed on idle, deaccc and shifts) that it will affect valve performance (it will open too slow).
Dean, there really is no difference in how and when the dumpvalve and bypassvalve are open. Absolutely none. Both types of valves are controlled by the difference in pressure over the trottle plate. The *only* difference btw a (recirculating) bypassvalve and a (non recirculating) dumpvalve is the fact that one of them recirculate air into turbo inlet hoose, while the other dumps it into free atmosphere.
I think that there are not as many different design of valves as we might think, there is just a lot of names for the same thing....
1. Turbo Bypassvalve (functionallity nicely described by D above), A recirculating valve.
2. Dumpvalve (same function as the bypass), could also be called a non recirculating bypassvalve.
3. Pop off valve - something completely different. This is a safety valve that will release air at a preset level. During normal operation this valve is closed. This is not a substitute for a bypass och dumpvalve.
4. Blow off valve - I have seen this be used as an alias for all of the above.
...so I dont think you will find any other types of valve than these three. And the pop off valve is not used on modern cars, the ECU handles this overboost protection instead.
Regards,
/Mathias
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