Blow off valve control

[Jörgen Karlsson]

Hi Chris

The idle and low load problems can probably be solved with an aftermarket
valve, a real HKS POP off valve might be a good choice. I don't like their
'super sequential' blow off valves, they only have a separate vacuum
connection, the pressure control is internally connected.

This caused some problems for me when I had the valve installed on the
outside of a bend, the pressure control line somehow saw a higher pressure
then it was supposed to. This meant that it opened a bit at high boost...
When it was installed on a straight tube it worked fine.

My car also has an up stream air meter, you will probably not have any
problems with very rich mixture at shifts and liftoff, both the TPS and MAP
sensor reports 'idle like' conditions, and the air meter is probably not
fast enough to react during shifts anyway.

You might also see a problem while driving at high speed and low manifold
pressure, for example my car does this on slight downhills where the turbo
boost a lot even if the manifold is at vacuum, I had to set the pressure
difference at around 1bar on the blow of to minimize this. This leaned out
the car until it could not ignite the mix, then the turbo of course spun
down, and the car started running ok again, two seconds later the turbo had
spooled up again, the valve opened and then it started all over again. This
was at 100 to 120mph, below or above that either the manifold pressure was
to high or the exhaust energy to low to spool the turbo.

Now I use a blow off valve from ATR (Applied Technology and Research), works
great and is a bargain compared to the jap stuff.

Jörgen Karlsson
Gothenburg, Sweden

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