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APC Bypass

5K views 9 replies 6 participants last post by  BoostedSwede 
#1 ·
I've heard some funky reactions some Saab's exhibit when the APC is messed with, however I would much rather run my own setup, which would include the complete removal of the unit.

I have a '94 900SE-Turbo Trionic5, and my boost is flux, it'll pass in, and out during WOT and all it does is irritate me, while I do currently have the GT25, I have a TD04 from an Aero I plan to rebuild and install this spring, and also wish to simplify the boost control, and omit the current setup entirely and replace it with a simple brass "Tee" (Compressor housing -> Boost Controller -> Wastegate).

Any further insight to be had?
I've read it could blow your motor, disable the car and even make the ECM run open loop "Limp" mode.

I'm not entirely convinced, I see nothing more than a possible DTC, but want to see if anyone here has had success or knows of success in this.
 
#2 ·
pretty sure T5 doesnt have the APC box that the c900s do.

in this you need to reprogram the ecu, using t5 suite or some of our great tuners on here you should be all set to run pretty much whatever you like.

unless you want to redo the entire fuel delivery system etc (IIRC) theres really no reason to bypass it.

i used mikeD for my tunes which included a couple of T5s.

a few people have tried the full bypass but i dont they are running anything close to daily drivers or stock. and most have had some sort of major setback in doing it
 
#3 ·
pretty sure T5 doesnt have the APC box that the c900s do.

in this you need to reprogram the ecu, using t5 suite or some of our great tuners on here you should be all set to run pretty much whatever you like.

unless you want to redo the entire fuel delivery system etc (IIRC) theres really no reason to bypass it.

i used mikeD for my tunes which included a couple of T5s.

a few people have tried the full bypass but i dont they are running anything close to daily drivers or stock. and most have had some sort of major setback in doing it
I can't seem to get T5Suite or CarPC to run on my computer, it crashes every time I try to open it, I'll try with the wife's laptop soon.

I guess it's a good thing I didn't just try it myself, however this begs the question of, what part of the APC would cause the fluctuating boost...?
 
#4 ·
I ran a MBC on my ng900 with no issues, although I did have a T5suite stage 3 tune, so fueling was adjusted to compensate. I was tired of the issues presented by the stock boost control valve always acting up, so I just bypassed it. That said, I wouldn't suggest it with a stock tune.
 
#5 ·
Well, due to some unfortunate circumstances, and a forced move back to Colorado, I've gotta sell the car anyways, I'll be repairing what I can and passing the car to someone with money, hopefully someone here since I want it loved and cared for, it's a sad shame to see it go since it's been so damn good to me, and it pisses me off to sell it, but life doesn't wait.

How hard was that MBC to install? and how did you do it (new to going farther than just driving these cars)

There are a lot of T7 Saabs at the local yard that I could grab one from.
 
#6 ·
...
How hard was that MBC to install? and how did you do it (new to going farther than just driving these cars)

There are a lot of T7 Saabs at the local yard that I could grab one from.
It takes about 5 minutes to install an MBC, after you spend 30 minutes building it. Then another half our setting the boost level.

Grab one what from a T7? You can't use a t7 BPC without some programming of the ECU. Some guys do that because it's a much cheaper part.
 
#8 ·
OK, thank you very much, I'll run to the local yard when the weather gets better and grab what I need.
 
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