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Registered
Join Date: Dec 2000
Posts: 80
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'88 930: fluttering & gasping noise under boost
Car is my friend's '88 830. At 3500 rpm full boost, it's making fluttering / surging / gasping noises. It's fine at sea level.
Sounds like compressor surge and/or the bypass valve periodically venting and/or overboost protection intervening. The boost goes to 1.0 bar on the stock dash gauge and oscillates slightly during this. It has a Fabspeed K27 and long-neck intercooler. I believe this intercooler deletes the clunky stock air bypass system with the later simpler one. I wish I could post the video clip of the phenomenon instead of having to describe it but here we are. |
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05-27-2024, 11:03 AM
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Registered
Join Date: Dec 2000
Posts: 80
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More on this. I posted the video clip to rennlist here.
The engine is effectively rev-limited (at 3500) when this happens. You can see the boost gauge fluctuating. It's acting like the overboost protection is intervening, but the overboost sensor has been disconnected, soooo.... Car runs 1.0 bar happily at sea level. Again this problem only occurs at altitude. It also blows black smoke when this happens so it's (also?) running rich and/or misfiring, too, FWIW. |
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05-28-2024, 09:41 AM
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What are your fuel pressures?
Rahl
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1976 930 turbo Carrera, "Ubich". Mostly stock, lightly sweetened. She’s an angry schwierigkeit. She doesn’t want flowers, she just wants to dance! And when she does, she shakes her hips to the rythem of the road. Drive her like you hate her! |
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05-28-2024, 11:23 AM
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1976 Porsche 930
