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Discussion Starter · #1 ·
Hi there,

ok it was easy on classic 900 - to tweek the overboost switch (which cuts out fuel pump at some pressure) you needed a screwdriver only.

Now as I am to fiddle with my 9000 2.3T `92 (jetronic apc+DI) with a view to increasing max boost I need to cheat the safety system again. Stock fuel cutout level is set silly low. Only that there seem to be no pressure switch any more.

Questions:
1. Where does jetronic system get boost info from? Wouldn`t it be the sensor on the aluminium turbo-to-throttle pipe?

Changing the readings here (additional resistor i.e) might do the job.

2. I understand instead of a switch now it is ECU that sets the boost limit and cuts out fuel pump. Is it Jetronic ECU or APC ECU?

Changing the EPROM data (yes, I know an electronic magician capable of doing the job)

Any other ideas how to tweek the cutout?

cheers
 

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Saab Mad
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3,053 Posts
As far as I understand it...

1)it extrapolates the boost level by flow reading (from AMM) and engine rpms. The sensor you're referring to is the intake air temperature sensor

2)Jetronic ECU. Bad news is that it's not fuel pump being stopped (running another cable to power it would get rid of cutoff) but injectors.

Glad to be corrected by anybody who knows better...
 
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