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jt1 jt1 is offline
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Join Date: Jun 2006
Location: Western NC
Posts: 121
Check Valve in Diverter valve line?

I'm working on my 83 Euro 930, which is stock except for cams. It's primarily used for DE events with a few street miles. The problem I'm chasing is that boost threshold rises as engine temp rises. By the end of a DE session, there is a 4 or 5 second delay from throttle application until boost begins to build. My first thought was the wastegate was sticking, but after purchasing another wastegate and replacing it, that possibility has been eliminated. Next thought was that the diverter valve is sticking when it gets hot. Today I removed the diverter valve and cleaned and inspected it. It appears fine. The piston moves freely under its own weight, and there are no scars or scratches on the piston or housing. The end seals appear to have been recently replaced.

I also have a complete CIS system off an 84 Euro 930. Comparing it to the 83 system on the car, I discovered the 83 has a check valve in the line from the intake to the diverter valve, which is not present on the 84. The check valve is oriented so that vacuum from the intake will pass to the diverter, but no air under pressure can go from the intake to the diverter.

Is it possible that the check valve could be holding the diverter valve open? If so, how could engine temp be a factor? And lastly, does anybody know if this valve is supposed to be there on an 83, but not an 84?

Thanks for your help.

Old 10-05-2008, 12:22 PM
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