On the T5's the air mass flow is calculated with from the manifold pressure, temperature and RPM's. This is a speed-density arrangement. It is fine tuned by the O2 sensor when at moderate throttle positions. At boost, when the mixture is deliberately rich the fuel mapping is not corrected by the O2 sensor and is thus open loop.

If you used a voltage divider, the ECU would deliver fuel at a the level that corresponds to the reduced voltage. You would get higher boost, a lean mixture, and knocking would be detected, and the boost would be reduced. The net gain would probably be zip, and the possibility of destructive knock would be high.

I don't know the exact setup for a T7 on 9-3's.

I drove a 9-5 170HP loaner. I looked under the hood. It appears to have an air mass meter. In a situation like this, one might expect that the air mass meter would control the mixture, and that the absolute manifold pressure meter would be used for boost control only. This would be like the C900 turbos. On some arrangements such as these, you can fiddle with the manifold sensor voltage. However, the T7's have so many sensors, I don't know if you could get away with such things.

However, you can add an external boost controller and increase the boost, with the ECU's fuel cut pressure as a limit. The ECU maps fuel properly to that point. This will increase the power and change the engine's response characteristic from mild to wild. You can do this for $100. But you need to get a low restriction exhaust, air filter, and should make other mods, depending on your model and year. For more power that that, you need to get a modfied ECU such as Abbott's HO offering.

• 9-3 Boost question for the gurus, Ravi, Wed, 3 Jan 2001 21:12:31
  • There are very few people who understand the, jj, Thu, 4 Jan 2001 14:45:19
    • Re: There are very few people who understand the, ChuckS, Mon, 8 Jan 2001 21:50:39
    • Re: One answer, Stratmoen, Thu, 4 Jan 2001 20:29:04
  • Re: 9-3 Boost question for the gurus, Dean, Thu, 4 Jan 2001 12:06:23 <-- Viewing This Message
    • I can see the gears turning in your head now..., Richard P., Thu, 4 Jan 2001 14:29:51
      • Re: I can see the gears turning in your head now..., Dean, Thu, 4 Jan 2001 15:01:32
        • Thanks. What about water injection ?, Ravi, Thu, 4 Jan 2001 15:48:36
          • Re: Thanks. What about water injection ?, Dean, Thu, 4 Jan 2001 17:37:41
            • Re: Thanks. What about water injection ?, Craig, Fri, 5 Jan 2001 05:05:21
              • ..... LONG, Dean, Fri, 5 Jan 2001 09:58:31
  • I'm no expert, but that seems like it would..., Richard P., Thu, 4 Jan 2001 08:13:06

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