Boost controller

[nine-fiver]

Hi guys,

The Linear Sport estate is getting near to 200,000km in the next few months. It is running really well these days and I have even taken to making it my daily drive. Love the seats, the practicality with the kids and the dog. Brilliant thing all up but TLC on a regular basis is a must, as we all know. But there is that lingering inconsistency with boost levels under acceleration and She thinks that there is something sinister lurking under the bonnet. I don't. But I have a point to prove. I reckon it is the boost 3 way valve sticking and the bypass valve misbehaving. No codes, of course but some days there is just 'nothing'. Others, it is very urgent and quick. Maybe too quick. I think I will pop in decent SH younger parts to see if there is an improvement. It can't hurt.
Suggestions welcome.

[sgould]

You can by-pass the three way valve.  Car will still work.  And it will eliminate that if it makes no difference.

The three way valve on the bulkhead has pipes to the dump valve at the front, the throttle body & the inlet manifold.

Take the pipe from the dump valve straight to the inlet manifold. Block the pipe coming from the throttle body.  Leave the rest abandoned.


You might also have sticky valves in the fuel tank EVAP system.  The "bolt mod" will eliminate one.  I would make that mod permanent anyway.  Saab removed it from around 2006.  To do the mod, remove the top of the three pipes on the valve at the front that's attached to the turbo inlet cobra.  Block the rubber pipe with a bolt.  Leave the top pipe on the valve itself, open to air.

[nine-fiver]

Will do on the weekend. Ta.

[sgould]

Here's a picture of the EVAP system.  Saab removed the pipe marked in red on later 9-5 models and the connection on the cobra went from the back of the cobra to the top connection of the three, with no tee piece.

[nine-fiver]

So, what is the effect of doing the mod? Better boost levels or is it related to some other factor?

[sgould]

It just eliminates one non-return vale.  The two valves have a history of sticking.  If one sticks open, you can lose some boost.

[nine-fiver]

The Bolt Mod seems to have made a bit of a difference. It is certainly boosting more off the line, on gentle throttle. When the sport button is on it is even better there too.

The vac lines to the valves on the firewall are confusing though. There are lines going everywhere and I am struggling with them TBH. There are two small black units mounted on the firewall, above each other. Each with a three way vac line setup. What can be disconnected without creating an open to air issue? Not sure. Doing that 2006 re-route and isolating the line to the throttle body creates other open ends that saw it run worse.

What do these two units actually do? Especially the bottom one?

I tried the direct line from the dump valve to the manifold, but maybe not to a good place. It was to the top pipe above the little vac line to the fuel rail but boost was less consistent and the car seemed more retarded when accelerating. So that was a backward step.

Any chance of a photo showing how it all can be connected up?

[sgould]

I've not done either.  The EVAP mod was already done by Saab at the factory from around 2005.

Here are two pictures showing the pipe from the top connector of the plastic valve around to the back of the cobra.  This is on my car with the "red" pipe in the earlier post deleted.

[nine-fiver]

The evap line from the T to the blue valve behind the RHS headlamp has a small superficial spilt in the line where the pipe changes diameter. Wondering if that is doing the damage.
Then that line appears to go back to the tank, not the throttle body.
So what is in my engine bay doesn't seem to make sense against the diagram. Sorry. Might be an Aussie model variant too. Not sure.
Boost levels have dropped back a bit now, as T7 adapts, no doubt.

[Audax]

The evap line from the T to the blue valve behind the RHS headlamp has a small superficial spilt in the line where the pipe changes diameter. Wondering if that is doing the damage.

You have an M02-05 car? The pictures that sgould posted are for a later car. Anyhow, if you have a split in that pipe that changes diameter then you will notice. I repaired mine by removing it, glueing it and then wrapping it in duct tape to hold it together. The cause for a split appearing there can be when someone has had it apart in the past and not realised that the pipe that connects to it via the blue valve is very slightly handed and gets pulled if it's the wrong way, most often when a turbo has been replaced.

[nine-fiver]

Agreed Audax, thanks. That split is looking like the culprit for sure. I have done several water pumps and the cobra has been off many times. The rubber is not as pliable as it once was. Another one going on this weekend.
Will's photo is helpful though, and I am wondering if that set up can be done on an '02 car. Maybe...

The car is running better, she says, but I am not convinced as yet. It is still a little bit hesitant and reluctant on take off, and you can 'feel' the computer fighting with the turbo a bit. If you know what i mean.
Getting there bit by bit though. At least it doesn't Leak coolant anymore. Happy about that one at least.

[sgould]

I posted the pictures of my car to suggest that you set yours up in the same way.  It's what Saab did.  And it's a much better version of the "bolt mod".   I had a few odd bits of running and thought that I would try the bolt mod.  When I found out that Saab had already done it!

[nine-fiver]

Thanks Will. Yep, not really happy with the bolt mod at this point. Still trying to get my head arounf the diagram and what's under the bonnet. It doesn't seem to correlate, but i may be looking at the wrong pipes. The T pipe that goes to the blue joiner then hives off to the back of the engine bay near the master cylinder and runs off to somewhere else. Not the throttle. Confused still, sorry.

[sgould]

I'm not sure if they changed the pipe routing after they deleted the extra line.

But on my car the purge valve is directly under the MAF sensor at the front and the non-return valve is tucked in against the wing nearby, but it was wrapped in foam tubing and it took a while to find.

Found an old picture which I have written over in red.  This is the 2007 9-5.

[sgould]

Forgot to say that the pipe from the purge valve ends up connected to the rear of the throttle body at the bottom on the right hand side.  That's RHS of the car (LHS if you are looking into the engine bay from the front of the car).