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Old 13th October 2012
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rawill rawill is offline
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Join Date: May 2006                                                
Location: near Riverton - New Zealand
My Saabs: 93 2.3 9000griffin, 92 900s LPT vrt
Posts: 3,303

Originally Posted by VT9000CSE View Post
My fuel cut is definately turned OFF. I set the MAP pressure for fuel cut in T5 Suites from 0xFE (1.54 bar) to 0xFF (1.55 bar) which turns off fuel cut. My old T25 would overshoot past red line on boost gauge in 5th at 2000 rpm on the highway when going up hill and flooring it. But it used to hit fuel cut due to this overshoot. Once I turned off fuel cut the overshoot still occurs, then the APC system corrects it and brings it to a stable boost level. This overshoot acts like a little extra power initially then settles down to the correct level. The fuel cut really is a joke cause the little baby T25 cannot keep up boost levels after the rpms hit around 4000+. Stage 3 tune with a max pressure limit set to 1.35 bar ~19 psi. SWEEEEEEET.
I wonder why it overboosts?
and if the T25 is going too high I thought that all it would be doing is heating up the intake charge, not providing extra boost, but causing overheat which would create 'knock" conditions.

Correct me if I am not understanding the process correctly.

And I would have thought, like JZW, that there is something wrong with the BPC/APC valve, to cause the overboost.

I have read, and had 2nd hand experience (from a guy whose ECU I did a wizard tune on) of this valve performing much better after the valve ports have been cleaned.
Some have said, clean it about every 6 months, at other regular intervals, like oil change time.

03 V6 Renault Laguna! (best worst car I have owned!) 06 Merc E350, 11300km, 93 9000 griffin 2.3 St-II. 93 9000CSI na man,370,000km. 92 900 S LPT vert.
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