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Re: [turbobike] American Turbo Systems

Dave Morrill (david.p.morrill@fairchildsemi.com)
Thu, 22 Apr 1999 11:34:36 -0400

    I have my popoff valve located on the intake plenum.  Not sure how other
ones work, but most of them are similar, a spring loaded diaphragm with intake
before carb slide on one side, and intake after carb slide on the other.  The
idea is when your throttle is open the intake pressure before and after the
carb slide are equal, and the diaphragm is closed and you can build manifold
pressure.  When you let off, you get vacuum on the valve side and huge boost
on the other, the diaphragm opens and lets the huge boost out, so the turbo
keeps spinning at full speed, instead of slamming into the huge boost and
    I have found on my bike that the pulsing on the valve side causes the
popoff valve to chatter on and off at idle, which will eventually destroy it,
and makes it harder to build boost initially.  During transistion around 7000
my bike is sputtering a little here and the popoff valve is opening in a
feedback loop and causing probs here also.
   I am planning to try a stiffer spring, and possibly removing the vacuum
side of the diaphragm connection.  Basically a popoff valve may be more
trouble than its worth, especially if your planning to run low boost.
    I've actually seen some homemade ones that are slick, and RB racing makes
a combo popoff/priority air intake that is awesome, but they are jerks and
wont sell one.

  Why do you want two pressure settings?


Jurgen Mausch wrote:

> I was looking for a turbo kit for the 96-97 GSXR-750.
> I came across ATS and was wondering if anyone had any experiences with them
> Good, bad or indifferent.
> The kit is rather costly at $5000.00 (w/o FI), I was thinking that I could
> put some
> together for much less. Do you think I'm wrong by the time one gets all the
> bugs worked out?
> Is there any one else in North America that is making a kit for this bike
> that anyone
> knows of?
> Where is the best location to bleed off the excess boost in a blow through
> system; at the turbo, before the intercooler, after the intercooler, or at
> the intake plenum.
> One finial question is there a pop off valve that can be set at two
> different pressure settings and then switched between the two the pressures
> with an electrical switch?
> Thanks
> Jurgen