overboosting --> my 86 5ktq

Brian Devlin bdevlin at stanford.edu
Fri Nov 30 13:27:10 EST 2001


My main goal is to get more boost quicker, rather than higher
pressures. As it is right now, the turbo barely has a chance to work
in first gear before I shift, and there's noticable lag at every
shift.

Part 1: the frequency valve
What interests me more about this is that the claim that boost comes
on sooner. If I understand correctly from things I've read here, the
wastegate setup in these cars bleeds off some pressure all the time.
So it seems that modulating this tube/valve would be a way to get
boost quicker. I'm just not sure how the frequency valve is actually
working.
Part 2: the spring
My car did come with a boost spring, in the glove box. If I install
it, I was thinking of using a 4kq relay (probably any NA relay) for
the fuel pump. This type of relay uses a signal from the coil to turn
on and off, so it wouldn't be as dangerous as jumpering the relay.
Anybody out there try this?
Part 3: the "chip"
Anybody have btdt on the chip mods vs jumpers? Like hp vs engine damage?
-Brian

this all started with:

>On the way home from the QCUSA driver's school at Sears Point (my car
>was just parked there, I was taking pictures) my car developed a massive
>overboost problem. Perfectly drivable as long as I keep my foot out of
>it, but boost comes on much stronger and at lower RPMs than usual...at
>minimal throttle I hit 1.8 bar on the gauge and hit overboost (qlcc
>chip, Scott Mockry 1.8 bar spring...like a Charlie spring). I made it
>home fine, in fact didn't hit overboost once after realizing what was up
>and keeping my foot out of it.
>
>I stopped to take a peak at a gas station, but not much light. No
>obvious hose problems at the WG lower chamber so I am guessing it is a
>sticking WG (doubtful, this came on all of a sudden), or more likely, a
>torn WG diaphragm.



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