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I have one of 900Aero's modified apc boxes... and your same question came to my mind the other day...
...is the pressure transducer even involved anymore in the operation of the APC box after the modifications have been done?
I also bypassed my fuel cutoff sensor... like you, so i can run higher boost.
however, i am not having any problems with my apc system..I am getting 20-25 psi on a t3/t4 turbo which 900aero (dave) rebuilt for me recently...
I think if you're getting a modified apc box eventually, you could get one now, or whenever you want...
but there IS a way to test the pressure transducer... and if you tested yours with the stock apc box it should work as follows... ASSUMING the apc solenoid is working correctly, which the other posters have suggested that you do, and i agree, if you're not getting full boost..
test the resistance accross the pins of the sensor and i THINK it should be 88ohms... if it's not open or shorted, that's a good sign... open or shorted circuit and it's definately bad...
then... next step is to get a hand operated pressure pump with a gauge, you can rent one from advance auto parts, and from the hand pump run a vacuum hose to the pressure solenoid. with the car on, pump it up to a high pressure and the apc solenoid should react... simulating an overboost situation...
as to what pressure it will react at? i don't know i've never tested the stock box... above 14.7 bar? however this begs the question, why have a fuel cutoff switch AND an pressure transducer seperately to act as overboost protection???
they couldn't put these together in one sensor?
to be honest, I'm not sure what the purpose of the pressure transducer is in the stock system...
but if it is more than opening the wastegate in an overboost condition, it MUST be, in my opinion, the thing that limits boost in first and second gear by the APC... which my car does even WITH a modified APC box..
i was TOLD the modified apc box that i have will allow boost to raise to whatever you want, until it detects knock...
i have yet to hook up a knock led to my apc box, which i will do... but i get maybe 10-12psi in first and second gear and 20-25 in 3rd through 5th...
which is fine with me, so i haven't looked into the operation of this system further, but...
in your case...
start with the apc solenoid, which is THE device that is limiting your boost and then as long as that is working (lots of write-ups on how to test it) then test the pressure transducer, then replace the APC with whatever one suits your fancy...
or just go stand-alone, which i am heavily weighing my options on now :)
-gavin
, Thu, 28 May 2009 13:56:50
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