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Discussion Starter · #1 ·
i have a theory and feel free to rip it apart,but be nice about it!! .
a standard ecu in lets say a 9k aero,is set up to keep the a/f ratio correct from idle to max boost.useing an mbc could be dangerous with this as it allows over boost that goes beyond the caperbillity of the ecu to keep the a/f ratio correct,so possible big bang!!.in a fiddled with ecu the a/f ratio is maintained at that higher boost level.thus no big bang.so far so good .now,dulux and i had this problem that it was only possible to attain that overboost useing an mbc and wasnt possible with the boost control valve on the rad,as even with a stage one ecu it still only boosted to the red and not beyond.now the most probable cause is a faulty solenoid,but could it be the ecu.is it possible that only the part that controls the a/f ratio is changed and not the part that controls the action of the solenoid?.in a nutshell,one could have an uprated ecu that can cope with higher boost,but be unable to produce it!.
im now waiting to get lampooned!!
simon
 

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I also may be wrong but here goes,
At present I am running no APC just an MBC/bleed vavle, I was told by local saab guy that the APC unit works by reducing boost from the maximum down, where as the setup I have limits the boost from low down to a certain point, that seems to make no sense but I can understand it.
The APC seems to suffer from atmospheric changes and breaking hence why the MBC is fitted to my car as done by Abbott, the car covered thousands of miles with no problems as the boost level was set at a sensible level, upon turning up the boost the car seems to not really gain, very funny seeing gauge go off the red but bot all that because the car is all out of the ecu range??
Upon installing stage 3 the car is then able to run more boost due to the changes to the ECU mapping allowing the modification of its previous limits thus more fuel/air/boost more

Unfortunetly with mine she did not perform as first thought although on further inspection by the local saab guy, cam timing out slightly, the car is much better but still slightly lacking, also when upgrading to 3" downpipe+exhaust the wastegate needs adjusting to allow for a reduction in back pressure? so with a little help we got covered in oil and adjusted the wastegate, wether mine would benefit from an uprated unit or just more adjustment I am not sure.
But thats wear we are currently at, awaiting an hour on the rolling road see what the output is.
When the car is boosting higher and holding I will be reinstalling the APC with the MBC vavle on the wastegate side, my saab guy says this is his prefered setup.
Hope this means something to someone????

Dulux
 

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Ahhh but if you're running stage 1 type software from whoever, and you had FPT before hand, you may find overall max boost has changed little, but it now tails much less at the high end.

i.e torque below 3000 may be little changed, but above 3000 may climb or stay stable.

Andrew
 

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Discussion Starter · #6 ·
so it looks like im missunderstanding how the upgrade works then? .it doesnt give more boost,but keeps the boost that you have up for longer up the rev range.am i getting there?
simon
 

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With my speedparts stage three my rev limiter is approx 6,400 rpm, but I am running more boost than before due to the fact the gauge goes right through the red rather than just to the end of the red dashes.

All ecu upgrades most apply similar principles to gain more power, the more fuel/air the engine can get the more power, but different tuning developers seem to be able to alter the dynamic of how the power is applied, wether it is at the higher end of the rev range or lower torque.
 
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