Partial success

[Carl Summers]

Hi,
     I had to read that a couple times to get it as it seemed
backwards....duh you did say blow through.....The easiest thing you could do
is to install the TB on the inlet of the supercharger and use a vacuum
operated bypass valve so while in vacuum the supercharger doesn't make
excessive heat...bypass is after the TB and after the SC with vacuum line
anywhere in the intake plenum...If you are going to leave it the same all I
can suggest is a vacuum operated bypassing valve that releases to atmosphere
whenever the TB is in vacuum...vacuum line in plenum also.....btw have you
had a chance to measure the IAT after the SC....gotta be pretty high at that
low throttle high kpa stuff.
-Carl Summers



-----Original Message-----
From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
Behalf Of dzorde at erggroup.com
Sent: Monday, August 21, 2000 5:09 PM
To: diy_efi at diy-efi.org
Subject: Partial success


Hooray, I've finally got my Fiat 850 sport running on fuel injection,
however I'm now in need of some suggestions for the next part.  I have a
Toyota MR2 s/c connected in a blow through configuration with the throttle
body (it should be geared for 120kPa full boost, 17psi), my problem as it
stands:

At idle the ecu reads a vacuum (-21kPa to be exact) while the s/c side is
seeing 90kPa (throttle blade shut).  At higher revs (no load) the boost
will build up even more (over 250kPa) as the throttle is only just opening.
Obviously if I keep going like this the s/c is likely to blow a seal
somewhere.
Now here's my question, do I just fit a blow off valve and let it bleed of
any excess boost above say 140kPa ?
And what sort of blow off valve would I use, the ones I have seen on turbo
cars are very small and the s/c has like a 62mm outlet, so that is a lot of
air to remove ?
I have looked at a few available blow off valves (greddy, hks, etc), but
they are all specced as turbo applications, isn't there anything for s/c
applications ?

I'd appreciate any light people can shed on this unknown area I've ventured
into.

Dan  dzorde at erggroup.com

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