Saabscene Saab Forum - Saab Technical Information Resource banner
1 - 14 of 14 Posts

·
Registered
Joined
·
597 Posts
Discussion Starter · #1 ·
I've just had a custom exhaust fitted to the 9-3 and the guys at Topgear (Doncaster) put it on the rolling road. It hits 194bhp at 3300rpm then drops off abruptly. Boost is always too high though the actuator is set to a minimum. If I unplug the plug on the magnetic valve there is no change. Is it possible to test the valve off the car, since a fault could be in the ECU, wiring, vacuum system, etc?

 

·
Registered
Joined
·
8,948 Posts
I'd check that you can blow through both the C and R ports and gwet your 'puff' out the W port.

Also check the resistance from pins 1-2 and 2-3, they should both be about 3 ish Ohms.

If you unplugged the connector, boost should have dropped to base boost.

Are you hitting over boost?
What boost peak and drop off are you seeing?

Andrew
 

·
Registered
Joined
·
1,086 Posts
Yes, it sounds to me like the boost solenoid may be at fault. I believe that they are interchangeable, so if you can get your hands on a known good one, you can put it in your car and check it out.
 

·
Registered
Joined
·
14,305 Posts
Although boost values are not recorded, the shape of the boost curve normally follows that of the torque curve.

It's interesting that you say it doesn't change when you unplug the solenoid. I say this because normally that sort of shape of boost curve is due to the ECU detecting too high a rate of rise or the onset of knock and then reducing the boost.

Having said that setting the actuator to a minimum may not be helping.

Your steps to diagnosis are to check that the base boost with a calibrated gauge; to do this connect the pipe that's on the C port of the solenoid directly to the actuator. This should give you base boost at all revs, and also confirm your actuator is OK. Then, as has been suggested, check the solenoid.
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #6 ·
Test results:

Base boost = 0.3 bar (adjusted down several weeks ago due to hitting fuel shut-off)

Solenoid:

Resistance = 2.9 ohms
Blowing through R exits through W
Blowing through C DOES NOT exit through W

Solenoid hums with ignition on, but does not change the above results.

Whether soleniod is plugged in or not, boost sometimes holds at around 1.4 bar, but sometimes drops back after around 4 secs to 0.9 bar.

Does this suggest a faulty soleniod, or whatever sensor controls it?
 

·
Registered
Joined
·
8,948 Posts
Nick,

It doesn't sound good.

Base boost is set too low so will be effecting the speed of your turbo's spool up. Also, this low boost will be allowing the wastgate to blow open, limiting your peak boost levels (and thus stopping your over boosting).

The solenoid sounds dead (assuming you couldn't blow through C to W when it was not powered).

The Solenoid valve is a free floating disc between 2 electromagnets ( see http://www.ashill.org/saab/apc1.jpg
http://www.ashill.org/saab/apc2.jpg
http://www.ashill.org/saab/apc3.jpg
http://www.ashill.org/saab/apc4.jpg
http://www.ashill.org/saab/apc5.jpg
http://www.ashill.org/saab/apc6.jpg ) so should allow yoy to blow though from either end to the middle with no problems.

2.9ohms sounds a little low too, I was expecting 3.2 to 3.6 ish.

How was the base boost set if this valve is dead? was the W pipe just disconnected and it set that way?

Finally, I see you have a modded/exchange ecu. Was your boost OK before the ecu change? There are a few of us around who have ecu's (trionic T5) which have a failed component in them which fries APC solenoids in about 5 seconds flat...

The T5 controls boost by earthing pins 1 or 3. pin 2 is a constant live from the fuse box. if one of the transistors (??) dies in the T5 ecu, instead of occilating at 90hz between pins 1 and 3, one will be shorted to earth full time, melting the internals of the solenoid valve.

Hopefully this is not your problem and it's just a failed valve (mine wasn't but I did get the pleasure of cutting it up )

Andrew
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #8 ·
Thanks for the info Andrew

Base boost was last set by a rolling road tuner, though he gave up on it as he was getting odd results (perhaps the solenoid was taking its last few breaths). One day boost was low, the next it was high. Now it's always high!

Fortunately, since my car is lpt, the solenoid came as part of a stage 1 BSR package. I only bought it in May, and I registered the boost problem with them in November. I see no reason why they shouldn't replace the soleniod FOC.

Thanks again to everyone who's helped me on this and other threads - it's much appreciated
 

·
Registered
Joined
·
14,305 Posts
Yes, sounds like a good plan to get the solenoid replaced. Whilst speaking to BSR, you could also check what the recommended base boost for their software is.
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #10 ·
The new solenoid is now on and working, and while the perceived performance has been blunted, the controlled boost has overcome the traction problem in first and second gear (I was getting 1.4 bar at 1/2 throttle with the faulty solenoid).

To benchmark performance, I measure 50-75mph in third (BSR quote this as 4 secs on their website). Recent results are:

4.3 sec with solenoid fault
5.0 sec with new solenoid (BB = 0.28)
4.1 sec with BB increased to 0.34 as suggested by supplier

I've just changed the rediculously expensive platinum champion plugs (0.8mm gap) to BCPR7ES (1.1mm gap) and get 4.5 secs. This seems contrary to the platinum/knock debate.

I don't fully understand how the ECU adaptation process works, and wonder if I'm making changes too quickly for adaptation to take place. I'm also concerned that changing the exhaust to a custom one may be having a negative effect.

For the cost and time, I'm expecting 230+hp at the Emerald Rolling Road day, but still feel I'm some way off.
 

·
Registered
Joined
·
1,448 Posts
The size of the plug tip effects both how hot the spark is, and how long it takes to create the spark. Having a larger tip diameter is like pulling a couple degrees of ignition timing; it's good if you need to, but bad if you don't.

Normally Saabs already have some timing pulled due to knock and so when a larger diameter tip is fitted they advance the timing a few degrees; it all ends up about the same. It doesn't always work that way on tuned Saabs.

Platinum really does have some poor characteristics involving knock on Saabs ... but it has the good characteristic of grounding well on Aluminum heads. However it's bad characteristics don't usually show up until power is over 300 hp on most Saab engines IIRC.

Adrian W~
 

·
Registered
Joined
·
778 Posts
Whoa - you've broken the cardinal rule Chouet! You should never use anything but NGK's. It's no wonder that you have concerns about adaptation - you have to use plugs that have the proper resistance. Experience has shown that NGK's consistently give the resistance that the computer demands for its' adaptations, and anything other than NGK's will give poor results. The other thing is for modified, that is higher boost, engines, a narrower gap is best. 1.1 mm is at the high end of tolerance. The gap will increase w/time. I'd try setting them narrower, maybe .9 mm and work your way up to 1.0 mm, recording the results and finding the sweetspot. By the way, is your 9-3 a T5 or T7?
 

·
Registered
Joined
·
1,086 Posts
BCPR7ES is a NGK. But you are correct about the gap. Hirsch recommended this to me when I first got my ECU reprogrammed. Also, the narrow gap helps maintain the life of the DI by keeping the required spark power down compared to the larger gap.
 
1 - 14 of 14 Posts
Top