So it sounds like you are using a mini popoff/relief valve so that the MAP sensor does not see pressures above ~15 PSI. So when your MBC is not malfunctioning, the same amount of fuel is delivered for 15 PSI and 18PSI pressure overshoots. So at pressures over 15 PSI the mixture will be less rich. This sounds dangerous. Great if it works, but I don't recommend that others do this unless they feel that damage is a positive learning experience.

Such methods are often used when there is a air mass meter that controls the mixture and the relief valve is used to avoid the MAP sensor triggering a fuel cut.

If a pneumatic or electrical mod it used to create a linear modification of the MAP sensor signal, then the ECU can adapt, withing limits, and will scale it self to the modified signal. So while the adaption gets used to the modified signal, the ECU still does fuel cuts at the old absolute map sensor output voltage. So the net result is low boost indicator readings, higher real boost pressures and fuel cut pressures. This will work to a point but the fuel pressure regulator does not create a high enough fuel pressure to control mixtures if this technique is pushed to far. The ECU signals an adaption error as it feels that the injector duty cylce is out of bounds for nonboost closed loop operation, or the ECU cannot get the O2 sensor readings it wants within its injector duty cycle bounds... same thing.

A mild MAP sensor signal hack can be used to eat pressure spikes, or a popoff valve can be used for the same purpose. But a popoff valve alone cannot be used to increase the fuel cut pressure, only to allow setting closer to it.

Note that Eric is running the Viggen IC. The way that he was playing with the higher boost pressures might have had a much different outcome with the stock IC.

posted by 208.24.179...

• How much boost can a stock ECU handle, 22 psi! (long), ERP, Tue, 11 Jun 2002 00:22:31
  • Re: How much boost can a stock ECU handle, 22 psi! (long), Dean, Tue, 11 Jun 2002 09:11:48 <-- Viewing This Message
  • my friends Aero did the same, nickR, Tue, 11 Jun 2002 00:40:24

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