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Wastegate actuator vs 1.0bar Chip


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A 1.0 bar wastegate actuator has recently become available for the 996TT. It's being sold as an upgrade for cars that have already been chipped - but I've been thinking... The stock ECM measures boost and controls the wastegate actuator through a solenoid. Both the spring in the actuator and the solenoid via ECM and MAF open at 0.7bar. The idea is there may be slightly improved response if both the ECM and wastegate are set to match at 1.0bar. This seems especially the case if there are some leaks in the solenoid or vacuum lines, since what does the actuator's setting matter when it's the solenoid actually running the show.

The ECM uses 1.4 bar as an emergency boost cut, I would guess this is because you're hitting 100% duty cycle on the fuel injectors at the stock fuel pressure. The fact the limit is so high suggests the factory ECM, unchipped, can run over 0.7bar maybe even up to ~1.3bar.

Has anyone ever tried to change out just the wategate actuator for the 1.0 bar unit rather than chipping the ECM? The part difference is about $1000, excluding the cost of a more complex installation.

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I talked with Kevin at UMW about the boost levels the stock fueling system can handle and he uses 1.285 bar as the threshold. My car was boosting over 1.3 bar and I can tell you it was dumping boost and pulling timing to try to keep from knocking with its tune. I haven't changed to Kevin's tune yet for a number of reasons, but I will prior to taking the car to the track.

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The two work as a system. Changing the actuation of the wastegate without changing the programming could be inviting disaster. Think of lean running conditions brought on by having the boost come up faster than the fuel programmed for the given condition.

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