Two tier performance
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Scooby Newbie
Joined: Jun 1999
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My (unmodified) car most of the time will only boost to 0.4 bar max but occasionally it will boost to 0.7/0.8 bar (the performance matches this). Weather conditions do not influence when the engine will boost correctly and when it will not. I have tried a straight through exhaust but this produces the same results. I have even seen the boost drop from 0.7 bar to 0.4 bar as I pull through the rev range.
Also I did have a bleed valve fitted a while back but the problem remained on low boost but more boost was seen when it boosted correctly.
Can anyone explain what may be wrong?
[This message has been edited by Mark Howard (edited 16-03-2000).]
Also I did have a bleed valve fitted a while back but the problem remained on low boost but more boost was seen when it boosted correctly.
Can anyone explain what may be wrong?
[This message has been edited by Mark Howard (edited 16-03-2000).]
Scooby Regular
Joined: Jul 1999
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You might try modifying the restrictor in the feed from the compressor outlet to the wastegate; its in the rubber tube, compressor side of T-piece.
If this is too big it lets the wastegate control fill too quickly, the wastegate is open an very limited boost is supplied. Conversly if too small it doesn`t let enough pressure act on the wastegate and you get boost overshoot.....
Just a thought - but you need to modify the hole by only 0.1mm increments.
It sounds like yours is too big (low boost) try filling with solder and re-drilling....
If this is too big it lets the wastegate control fill too quickly, the wastegate is open an very limited boost is supplied. Conversly if too small it doesn`t let enough pressure act on the wastegate and you get boost overshoot.....
Just a thought - but you need to modify the hole by only 0.1mm increments.
It sounds like yours is too big (low boost) try filling with solder and re-drilling....
Thread Starter
Scooby Newbie
Joined: Jun 1999
Posts: 8
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This problem happens in all gears and it doesn't matter how you try to drive around it unlike the 2nd gear problem. This problem is intermittent; but the possible cause/solution you suggest would mean consistent low boost or have I missed something.
Also quite often if I drive hard for 5-10 minutes the boost will not go beyond 0.4 bar but all of a sudden the boost increases to 0.7 bar - very strange!
Also quite often if I drive hard for 5-10 minutes the boost will not go beyond 0.4 bar but all of a sudden the boost increases to 0.7 bar - very strange!
Scooby Regular
Joined: Nov 1999
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Hi Mark
It sounds to me like your boost control solenoid might be sticking shut.This would produce the intermittant low boost you are suffering from.
It is easy to check the solenoid operation by connecting a 12v supply to it.With no power connected you should not be able to blow through it,and with 12v connected it should be free flowing.(This applies to the later two port solenoid if yours is the earlier three port type it may be different)
Also if it is the three port type it could be piped back to front,I remember somebody else having this problem.
Hope this helps
It sounds to me like your boost control solenoid might be sticking shut.This would produce the intermittant low boost you are suffering from.
It is easy to check the solenoid operation by connecting a 12v supply to it.With no power connected you should not be able to blow through it,and with 12v connected it should be free flowing.(This applies to the later two port solenoid if yours is the earlier three port type it may be different)
Also if it is the three port type it could be piped back to front,I remember somebody else having this problem.
Hope this helps
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