my (long) speculation - Saab Performance Bulletin Board - Saabnet.com
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my (long) speculation
Posted by dave n (more from dave n) on Tue, 10 Apr 2001 22:12:03
In Reply to: Cruising down the Highway, tech question!, Jeff Cunningham, Mon, 9 Apr 2001 15:58:03
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I've always figured the bypass valve starts opening at slightly below zero boost on the gauge. I'm sure it opens more with more vacuum. But I don't yet know at what vacuum it is fully open. Don't forget the turbo is a viscious cycle. The exhaust (turbine) side only gets turned hard when the engine is under load, like when you floor it. While cruising down the road there is little air compression needed, due to open bypass valve, but also little driving force to the turbine from low engine load. A certain size turbo turbine provides a certain amount of work to the turbo shaft, which is affected by the amount of exhaust gas. But the compressor side requires a given amount of work depending on what it's compressing and it's size, etc. I've tried to calculate each separately which is not easy. But when you consider the output of the compressor eventually affects the exhaust gas to increase the work of the turbine.. it's a little too much! I've been researching turbo theory to figure out which upgrade turbo I'll eventually install in my spg. Don't think about it too much or you'll end up like me! Actually studying non-required sections of thermo books for saab info. I'm no "supposed expert"!
dave n
Posts in this Thread:
- Cruising down the Highway, tech question!, Jeff Cunningham, Mon, 9 Apr 2001 15:58:03
- my (long) speculation, dave n, Tue, 10 Apr 2001 22:12:03 <-- Viewing This Message
- Yes it is, George D, Tue, 10 Apr 2001 11:46:57
- Re: Cruising down the Highway, tech question!, Beaudreau, Mon, 9 Apr 2001 20:53:50
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