chipped 1.8t and diverter valves

[Jukka Majanen]

Hi

A question, please.

Mark wrote:
>...Basically, when the valve fails, it can let your turbos 
>overspin and mildly overboost your engine the turbos...  
>It has been suggested that the turbo failures on the 
>1.8T engine are a direct cause of bad bypass (diverter) 
>valves, but without a boost gauge, you'd never know...

I believe the by-pass that keeps open, can cause overspeed
of turbo. But how can it overboost the engine? Isn´t regulating 
elsewhere ( wastegate )

#1If it sticks closed, there can be stalling problems, when the throttle
is closed fast after the full power, like having no valve.
#2If it sticks open turbo will make more job = revs for same measured
engine boost, because part of the flow recirculates. For compressor
the situation is like having a broken pressure hose after the turbo.

Both can cause damages. Stalling ( on highly tuned cars ) can be
very violent, I´ve heard about broken turbine shafts.

regards
j-pm