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APC Valve Blow Test

15K views 18 replies 6 participants last post by  mark e 
#1 ·
Hi

Just checking my APC Valve this morning as in certain driving conditions I can get my Stage 3 to overboost ocaisionally. Now I havent got the 3" exhaust system on yet so not pushing it too much, but the main times I can get it to Overboost is changing down FAST into a high rev band.

Now doing the 'blow' test:
Blow through the 'C' port (top) it freely comes out the middle 'W' port, BUT, if I block the middle port with finger, it will come out of the bottom port 'R', not freely but will leak out. Also it does the same if I blow through the middle 'W' and block the top 'C'.
Does that mean the valve is knackered!??

My thoughts is that although I have to 'force' it by blocking the 'W' port to get it out the 'R' port, this surley means its bleeding a little off the 'W' port on boost therefore causing overboost on odd ocasions??

TIA

Anthony
 
#4 ·
Ordered new APC Valve today.

Just thinking out loud, but you would have thought that one of the decent tuners - Abbotts / Maptun / Speedparts etc would have come up with an alternative to the Saab one that is prone to failure, without having to go to the Manual Boost controller option.
e.g. something that the Tronic ecu can still use the APC as it should, but just a better one!
 
#5 ·
OK, new one just arrived, and I have done the 'blow' test:

Its exactly the same as the one on the car, if I block the top port with my finger and blow through the middle, it will slowley leak out of the bottom!. With the top unblocked air freely comes out of the top.

This is with it totally disconnected from the car,

So, is the new one also knackered, cant believe that!??

Just thinking, but its nothing daft like the electric plug needs to be connected to the car and the car running to seal the valve or something is it>???
 
#6 ·
OK, new one just arrived, and I have done the 'blow' test:

Its exactly the same as the one on the car, if I block the top port with my finger and blow through the middle, it will slowley leak out of the bottom!. With the top unblocked air freely comes out of the top.

This is with it totally disconnected from the car,

So, is the new one also knackered, cant believe that!??[/b]
?? Curious to know the outcome of this one too..
 
#7 ·
OK, a bit more theory first... the valve is a two state device i.e. it flip-flops between a flow from C to W and R to W. It's just possible that it's in the middle of a change-over. To confirm proper operate you need a 5V power supply. With one lead from the supply connected to the centre pin of the valve, alternately dabbing the other on either of the outer pins will force it to operate as described- you will hear a click. You should be able to blow through either path according to which way the valve is.

In the car the APC system modulates the valve state to achieve the desired boost pressure.
 
#11 ·
It's not as simple as a two state device, as the valve (disc of metal) moves between the extreme ends of the (short) tube it's enclosed in. It's drawn either way by the magnetic field of the two coils either side of it that are alternately energised by the ECU at a frequency of 90Hz. The duration of each movement is varied (Pulse width modulation) giving varying overall pressure to the wastegate actuator.
So I would think when de-energised the disc could sit either way (or in between) unless there is a permanent magnet involved.
 
#12 ·
Well I put the new APC on this morning before I drove to work. It would (dare I say it) seem to have resolved the problem!!!!!
I couldnt get it to overboost when it would normally. Easyest way for me to get it to Overboost was to 'go for it' off the mark, stretch 1st gear out and then fast change into 2nd and floor it, and it would overboost pretty much straight away. Well I did that once this morning as thats all traffic permitted and all was good (except for the needed trouser change!!
)

So, fingers crossed, its all good!!!

And I have just had an email from Giles @ Abbott saying that I will get my full 3" exhaust system next Tuesday!. Excellent!

THanks guys

Anthony

p.s. If the Actuator was weak, that would cause under boost, correct?????
 
#13 ·
Will I thnk I have definatly confirmed that all is now well..


No overboost, just very strong boost all the way.. And it picks up soo much better now so my other one must have been goosed!!

Thanks elkparts for gettingt it to me so quik. Happy again now. and will be even happier Tuesday when the exhaust system is fitted!!!

ta
Ant
 
#16 ·
Blow through the 'C' port (top) it freely comes out the middle 'W' port, BUT, if I block the middle port with finger, it will come out of the bottom port 'R', not freely but will leak out. Also it does the same if I blow through the middle 'W' and block the top 'C'.[/b]
Q:
What are the, respectively 'C', 'W' & 'R' ports, and why are they so named?

Sorry for the series of dopey questions, but I don't just want to be able to work on something, yet not understand exactly what it does, why, how etc.

Regards,
Jack
 
#17 ·
The 'C' port is the line that goes from the APC Valve to the Compressor of the Turbo
The 'W' port is the line that goes from the APC valve to the Wastegate Actuator on the Turbo
and the 'R' port is the line that goes from the APC valve to the inlet again - Return

Very basically this device allows the ECU to control the amount of boost presure that the turbo outputs. By directing the airflow to the wastegate / return etc it can measure and change turbo boost.

A failed one will cause Overboost, or just base boost etc.
 
#19 ·
.5bar, thats about right isnt it if I adjust back up to that?[/b]
Yup, spec is 0.37 - 0.43bar for 2.3L/FPTs and auto Aeros, 0.42-0.48bar for manual Aeros


So I would think when de-energised the disc could sit either way (or in between) unless there is a permanent magnet involved.[/b]
I've tested a few now, Nick
and whilst it can sit a little inbetween if it's been left around for a bit, the forcing it either end then checking immediately afterwards has proved 100% accurate.
 
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