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Date: Mon, 13 Dec 2004 15:57:41 +0100
From: Frode <>
Subject: Re: 99 Turbo update - vroom vroom

Dave Hinz wrote: > Well, the beastie runs & drives. After building one good engine out > of two bad ones and more than a little creative merging of newer > parts in an older car, the '78 99 Turbo I've been working on is > driveable. > > So, the inevitable questions. Where is the overboost sensor on > this thing? It seems to be cutting out the ignition just as I > get into the "red" on the turbo gauge, rather than up a ways as > I would expect. Where is that beastie, and/or might it be > something else like a stuck turbo bypass valve? I installed a 900T engine in my 78 99 some years ago, but didn't get any such luxury as overboost protection -- still I did experience the symptom as you describe, I think it was the warm-up regulator that was stuck, leaving too little fuel at high loads. If you haven't already, try to increase the fuel/air ratio by turning the adjustment screw 1/4 turn clockwise at a time and see what happens. Also check the so-called "control-pressure". If it is too high, as I said, the engine will run lean at high loads. more than 4 bar is too much. The Haynes manual for the 99 is quite informative on this part. When cold, it is approx. 1 bar, increasing steadily to around 4 when fully warm. PS: Until you get the fuel mix mostly correct, you may find it convenient to use a set of "hotter" NGK-s than specified, I think I still use BCP6's, but then in Norway, continuous operation at highway speeds in hot summer days is soo rare! -- Frode

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