[urq] (urq) What can cause over-boost?

[Buchholz, Steven]

... the thing is, if you suspect overboost put a pressure gauge on the manifold line and see what you see ... 

Based on the report that a "chipped" ECU still failed makes me tend to believe that the problem is not overboost.  Since I don't know what was done to this "chipped" ECU I can't say that it is guaranteed not to be an overboost issue ... 

Page 7 of the IST doc shows the allowable boost curve ... from what I see it should allow up to full max boost at 3k RPM ... 

Steve B
San José, CA (USA)
> 
> I my experience, there have been two causes of over-boost.  On my stock
> WX, I had a torn wastegate diaphragm that prevented the wastegate from
> opening on time.  I also had a bad wastegate on my new MC.  I forgot to
> check it before I installed it and got great boost and then a cut-out at
> 3k.  When I removed and examined the wastegate, the piston did not move
> very smoothly and was obviously sticking shut.  I put my good WG from
> the WX back on and it was fine.  So, I would check the WG for diaphragm
> leaks and smooth operation.  Hope it helps.