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Discussion Starter #1
Bit of an odd one this - most people only want to increase horsepower, not decrease it.

So does anyone know, if I fit an upgraded ECU & APC hardware to my LPT, would it then be possible to 'insert' an extra switched circuit to the APC solenoid to give either:

1.Normal ECU controlled fuctioning.
2.Overidden - ie fully open( or close) the solenoid ,allowing air from turbo straight through to wastegate as per normal LPT function allowing base boost only.


If this would cause problems for the ECU could it be done by having a parallel connection in the hoses between turbo & wastegate fitted with a remotely switchable valve.Then the ECU would be no wiser

I only ask this because there are occasions when LPT power is sufficient ( like most winters & when my better half is driving the car) & it would be handy just to be able to push a button & turn the extra power on or off.

I don't want it to be adjustable, just on or off.
 

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It should be a doddle to create a switch to limit you to base boost.

Options are to wire something to the APC valve, or to utilise the brake pedal feature which does the same.

Also, some models of saab restrict to base boost when the cruise is set too.

ECU should be able to cope as the variouis sensors (Map) will only see base boost and fuel accordingly, likewise, if you have Lambda it to will be adjusting fueling levels.

Andrew
 

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Originally posted by Griffin #341:
[qb]Engstrom-Chicago has an incar switchable device that allows up to 5 different mappings of the ECU including the stock settings. Here is the link:    http://engstrom.net/  
Might want to check it out    [/qb][/b]
1. It needs OBD-II, which most of the Euro-Saabs have not. And Saab is not yet supported...

2. Switching ECUs is a problem on all Saabs featuring a TWICE immobiliser (all Trionic 7 cars, many Trionic 5) because the ECU needs to be married to the TWICE unit using Tech 2.

Yours,

Philip
 

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Discussion Starter #5
Someone has suggested that all I need to do is connect an in-line switch to the earth lead of the APC solenoid

I don't have a grasp yet of APC solenoid operation - I know exactly what it does ,but not the 'logic' of it's operation.

Is turbo to wastegate connection in APC solenoid normally open or normally closed with zero volts applied?

If it's normally open then a simple switch would seem to be the answer. With switch off,and solenoid open, I would only get base boost .With the switch on the solenoid would be under ECU control, and I would have more boost.

Any thoughts?
 

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Seams reasonable to me - the APC solenoid is normally open, ie. disconnect it and the car reverts to 'LPT mode' with the wastegate actuator connected to the pressure side of the turbo via the open APC solenoid.

Therefore your switch idea should work.
 

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Yup, disconnecting the power to the APC solenoid is the easy way to go. An easy place to pick it up is the APC fuse, or at least pulling the APC fuse will mean that you get no more than base boost, if you follow my meaning.

i.e. I don't have the wiring diagram to hand but if you pull the APC fuse (#5) you only get base boost. I'm assuming it's an in line fuse to protect the ECU from a fault in the APC solenoid.

I hope that makes sense
 

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Discussion Starter #8
Well it all works!

Heat plate out, modded air filter housing, stage 1 Speedparts ECU with 'LPT/aeroish' on/off button

As recommended, I cut into the lead out of the APC fuse ( No 5) and ran a cable to a air conditioning on/off switch that fitted into a spare slot on the dash ( switch very kindly supplied by local Saab dealer free of charge & they even photocopied dealer APC & Ignition system wiring diagrams so I didn't cock it up).

I plugged in my new Speedparts ECU and plumbed in the APC solenoid.

Went & did a few adaption runs &


It's a long time since I've driven a car that requires both hands on the wheel when you floor the throttle

Around town the car is as quiet as ever but above 2500 rpm it's an abosolute blast. If I try hard enough I can just about make my rear mudflaps drag on the ground.

But for those sensible moments, like winter or when the wife is driving I can just press my little air con switch and revert back to LPT which loses me more than 65 hp and a bucket load of torque. It's a bit like having a traction control system that works!
 

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Discussion Starter #11
If anyone wants full details please feel free to ask.

I can't promise that I can get you any free switches off the Saab dealer though.
 

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This sounds great - I already have Stage 1 on my 1999 LPT auto but like you I'd like to be able to switch it in and out. I did a similar thing in my old 205 GTi 1.9.

Couple of questions:

Which fuse #5 do you mean - passenger compartment or engine bay bulkhead ?

And what colour is the wire that you tapped into ?

Cheers
 

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Discussion Starter #14
The APC fuse on my 9000 is in the main fusebox (passenger compartment) and was marked as such.

The cable leaving the fuse ie the protected circuit was green/red and this was the line that I inserted my switch into.

If you find the APC fuse in your car you can check with a multimeter which the protected circuit is , just pull the fuse, turn the ignition on and check between either side of the fuseholder and earth.The power supply side will have 12 volts, the wire you need will have 0 volts .

Sorry if I'm teaching you how to suck eggs but it's the easiest way for me to explain it.
 

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Originally posted by Penport:
[qb]Oops just noticed that Whitesaab drives a 9000.
Does anyone know which fuse controls the APC on a 1999 9-3 ? [/qb][/b]
IIRC, it is fuse no.23 (for 9-3 M99) - but there should be a list of fuse no.s and functions on the inside of the fuse cover.

If you do not have it, let me know and I will go and take a look to confirm
 

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Originally posted by Saabman:
[qb] QUOTE
Originally posted by /john:
[qb] Doh!    :rolleyes:    

Try no.26 EPC Engine ECU [/qb][/b]
But surely by pulling/by passing this fuse will make the car a Stage Zero as it won't run [/qb][/b][/quote]Well the 9-5 needs both ECU fuses to run... so your probably right!
 
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