apc inline switch

[9000kev]

ok it might be a weird question,

i have a stage 2 9000. 230bhp @ 18psi.

i wanted to fit a switch to the apc wires, (i have the t7apc)
i sometimes unplug my apc for long journeys so i am only boosting to 6psi, this is when i need reliabilty rather than performance.

i have sussed out a way (and a route) to fit a switch in the dash board, which disengages the connection on the apc wires at the switch on a button. this is simply so i dont keep having to lift the bonet to connect the wires i can simply turn the apc on/off by a switch.

my question is, Am i doing any damage/harm to my engine by unplugging the apc and runnign the engine only on baseboost? will it fool the ecu within time?

[DanF.]

I don't see how it would harm the engine at all.




Silly question... is bhp a measure of HP at the wheels or the flywheel? I only ask because, 1.) I'm confused, and 2.) I had my Aero dyno'd with only a stage 2 software upgrade and it made 227hp @ wheels.

[KPAero]

BHP is at the flywheel

[Robinb]

Posted by 9000kev: my question is, Am i doing any damage/harm to my engine by unplugging the apc

Many years ago, a Saab mechanic once failed to reconnect my APC after some work. Everything seemed OK for a day or two, then the Check Engine light came on, code analysis was "multiple misfirings".

Cleared the error, changed plugs, checked all vac lines, same thing 2 days later. Nobody knew what to do about it.

Eventually, I reconnected the APC and hey presto, problem gone.

[9000kev]

wat car was this on may i ask?

[Robinb]

A 1996 Saab 9000 Aero automatic. It was Stage 1 at the time.

[9000kev]

ok, thanks for your help.
maybe i wont wire in a switch then.

[Robinb]

I think that's a good idea.

Of course, if you want to live a little dangerously, you could just disconnect the APC for a few days and see what happens!

[rawill]

Originally Posted by Robinb

Many years ago, a Saab mechanic once failed to reconnect my APC after some work. Everything seemed OK for a day or two, then the Check Engine light came on, code analysis was "multiple misfirings".

Cleared the error, changed plugs, checked all vac lines, same thing 2 days later. Nobody knew what to do about it.

Eventually, I reconnected the APC and hey presto, problem gone.

Mmm, strange that that would happen, I drove for ages with a blown BPC valve and didn't know it.

I got no CEL light.

I will be interested in other responses.

I was going to do exactly the same thing, put a switch in line.

/R

[Robinb]

Posted by rawill: I drove for ages with a blown BPC valve and didn't know it.

Not quite sure what you mean by "blown".

If you mean "malfunctioning" there's a fair chance you won't get a CEL error. Just like a "blown" turbo. CEL errors are primarily associated with emission (and potential emission) problems. A jammed ECU or turbo may not trigger a CEL light.

If you mean "electrically disconnected" then your experience hasn't been the same as mine.

Try it - disconnect the APC for a few days and see what happens! I can't imagine my stage 1 was that different from the orginal ECU.

[rawill]

I had no reading on one leg of the BPC valve, I should not have used the word "blown".

Not accurate.

But for the last 3 days I have disconnected it.
This is on my 97 9000CD, I have the valve bypassed and only using base boost.

I have also run my 93 griffin with a blown fuse for an unknown amount of time, when the BPC had failed.

Hope we get some other responses to this, I am intrigued.

Correct I can not imagine a Stage 1 tune would make any difference. But then I am a noobie.

However think about this.

I put a knock led in my griffin, no light on when using the Stage 2 ECU, however, when I put the original (unmodified) ECU in the led came on all the tiime, even when the key was on but the engine was not running.

What is going on here, I have asked about this on the ECUproject yet.
More fish to catch before I worry about that.

I am thinking the resistor I have put in is not big enough, but why is it different between the ECUs.

[Robinb]

Posted by rawill: Correct I can not imagine a Stage 1 tune would make any difference. But then I am a noobie.

Compared to the likes of Superaero, Wily Coyote, Skint, Boxman and others on this forum, I too am a noobie. I'm just relieved I didn't blow up my engine while I was running various "tests" a few years ago after reading up on the theory of turbochargers.