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, Thu, 5 Apr 2001 10:48:18
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Too bad!
With an air flow meter, an engine control system can actually perform better than a speed density system. But if the ECU is designed to compare boost pressures achieve to dynamic target levels, then it can be interpreted as a problem. But that is strictly a design decision.
The T5 ECU attempts to control boost, but does not care what pressures exists, and will map fuel and timing to suit any pressure. If the timing exceeds the range of the map, or an arbitray limit, then it can cut the fuel.
With any ECU, you can remove the ECU from boost control, and set up an external cotroller. Then you can set up for any level of boost that you want, and the ECU has to accept it. The ECU can map the fuel to suit the boost, or do a fuel cut, which simply means that the injectors are not triggered. The ECU cannot lean the mixture to reduce power, as this would cause knocking. The only other recourse is extremely retarted ignition timing, but that caused other problems. The only other option is to do a partial fuel cut which would not fire the injectors on all cylinders. This would produce a limited amount of power. If the ECU has control over the thottle plate, drive-by-wire, then there is a completely good way for the ECU to control power ouput when it wants to. This sounds like what might be happening.
With a diesel engine, the fuel can simply be reduced if an ECU wants to reduce power.
So an ECU can monitor boost and boost targets and intervene if so programmed. The solution then is to use a modified ECU, where the target boost levels that the ECU expects to see are themselves modified.
The other option, is to use an electrical or mechanical bleed on the absolute manifold air pressure sensor. This will make the ECU increase the boost for you. With a speed density system (T5), tne mixture would go lean and knocking would occur. But with a MAF sensor, the ECU will map to the air mass flow. For some vehicle ECU's this works great. But the ECU might be cross checking sensors, and could still stop things from working as desired. There are pressure bleeds designed to go inline with the MAP pressure sensor, designed explicitly for this very purpose. With this technique, one does need to monitor the air fuel mixture to determine how much boost can be safely achieve for each vehicle-engine combination. Might work with T7, might not.
, Thu, 5 Apr 2001 10:48:18, Thu, 5 Apr 2001 15:02:23
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