<VV> Turbo Flat Spot

[kevin nash]

Message: 6
Date: Mon, 17 Oct 2016 20:22:51 -0400 (GMT-04:00)
From: Grant Young <gyoungwolf at earthlink.net>
To: "virtualvairs at corvair.org" <virtualvairs at corvair.org>
Subject: <VV> Turbo flat spot?
Message-ID:
        <14401465.23985.1476750171401 at elwamui-ovcar.atl.sa.earthlink.net>
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I have a customer whose LM 180 is still experiencing a "flat spot" after swapping carbs and
increasing the jet size by .05". I have very limited experience driving turbo Corvairs
and am looking for some suggestions on where the problem could be?
Thanks,
Grant

Grant- Assuming that the timing is 24 degrees, and the boost retard is working and the throttle is opening all the way, the flat spot is probably caused by being too rich at the wrong place on the
metering rod, or just too rich everywhere. Ideally, you want the carb to be close to 14 a/f when at
part throttle cruising and be at around 12.5 when hitting boost (right around 0 on the gauge)
and gradually richen to 11.5 in boost. There are metering rods and jet combinations that will get it
to do roughly that.  Might not be a bad idea to put a wideband O2 sensor on to verify those a/f
targets, because it is possible that what the customer feels is a flat spot, is actually just how they
run- the stock timing and distributor is responsible for those kind of flat spots.

Kevin Nash 63 Spyder, Efi daily driver