Lifting boost cut in a 940 turbo

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Lifting boost cut in a 940 turbo[ALL/1998] posted by Edward Foo on
Sunday, 8 June 1997, at 9:26 a.m.

Hello all!

I just currently bought a 1993 940 turbo (auto)...having boosted it to 0.8 bar...and changing the filter, the power has been great. However my intial intentions was to run boost up to 1 bar. But guess what...i have hit the irritating build in boost cut defencer. As i have been working on japanese cars most of the time...i was looking for a map sensor..but cldn't find one. Does anyone know how locate the boost cut sensor or at least bypass the defencer the run higher boost?

Secondly i can't seem to run a after mkt blow off valve even with the factory one disconnected. The idel up sensor will always pick up a vacum leak and go into limp mode. shld i than run my blow-off before the intercooler or what?

Pls help for everyone plays with the 850s and 70 series and the new volvos...has anyone not played ard with a 940 turbo?

Thanks folks! Ed

p.s.: anyone know where to get a touring car body kit for a 940?

Re: Lifting boost cut in a 940 turbo[ALL/1998] posted by abe crombie on
Sunday, 8 June 1997, at 2:33 p.m.

The boost cut-out you are encountering is a function of the ECM comparing Mass Air Flow Sensor (MAFS) signal to engine RPM and determining if the boost is within limits. There is no way to defeat it. To make more boost possible you would have to replace PROM in ECM but I know of no one that re-programs PROMs for that particular ECM. The valve on the turbo is not really a pop-off valve but it is used to recirculate air when you lift off throttle so that MAFS does not read the air pressure wave that bounces off throttle when you lift suddenly. When you defeat this valve the ECM gets a high MAFS signal while also receiving a closed throttle signal and the ECM is entering a "limp-home" situation for idle air control due to the errant signals. MORAL OF THE STORY: you can't run excessive boost unless you can find a source of a modified PROM. The head gasket will be a limiting factor if you do find a way to obtain a higher boost limit PROM.

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