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What gas are you running? Posted by Larry West [Email]  (#1140)  [Profile/Gallery]
(more from Larry West) on Mon, 15 Sep 2008 13:04:46
In Reply to: No Overboost? 2000 Aero, Dave F., Sun, 14 Sep 2008 18:22:46 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The Aero and Arc require premium fuel. If boost is going towards 12, then settling back, that *could* be a sign that the Trionic is pulling back the boost because if detects knocking (pinging), which can happen with less-than-premium fuels.
As for the "overboost", if I understand that correctly, what it does is enable you to maintain the maximum manifold pressure, regardless of your altitude. Normally (and this is the mode on pre-T7 Trionic systems), the turbo is set up to allow you XX psi of boost over your ambient pressure. As your altitude increases, that pressure drops, and so does your maximum manifold pressure. T7 maintains the sea level max manifold pressure at altitude.
Example: at sea level, you get 10 PSI of max boost (remember, this is just an example, I'm not quoting actual spec). Add this to the nominal 15 PSI of atmospheric pressure, you get 25 PSI of absolute manifold pressure (pressure in the manifold relative to a complete vacuum). Now, take your 9-5 up to the mountains of Colorado, at a bit above 10,000 feet, and the atmospheric pressure is about 10 PSI. Normally on T-5 and earlier Trionic systems (NG 900, some early 9-3s, 9000), all you could expect is an absolute pressure of 20 PSI (10+10). But Trionic T7 (9-5, later Classic 9-3 & Viggens) will still allow you the maximum sea-level absolute manifold pressure of 25 PSI, and that "extra" 5 PSI is considered "overboost".
_______________________________________ Current: 2002 9-5 Aero Kombi Cosmic Blue 2000 9-5 SE sedan, Imola Red 1990 900S Rose Quartz, Auto Past: 1999 9-5 LPT Combi 1999 9-5 LPT sedan 2002 9-5 Arc 1990 900 5-speed 1986 900 turbo Convertible 1991 9000 turbo 1980 99 GLi 1986 900 turbo 1986 900 S 1991 900 turbo 1984 900 turbo 1976 99 GL
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, Mon, 15 Sep 2008 07:13:24
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