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Discussion Starter · #1 ·
Hi Chaps,
Any ideas what could be causing a lack of torque around 2000-2500 rpm?('94 model Aero non-TCS)
The boost/apc gauge is up in the red/orange striped section (at 2k), but does rise a little more to the end of the sector by 3000rpm, (is this normal boost behaviour?).
My specialist has put an ISAT on and the Trionic has no faults detected.
Could fuel pressure be a possibility? Or would that affect the top end power more than the torque???
Thanks in advance.
Nick.
 

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Hi, Chap.

It's a manual, if I remember, yes?
A few things I can think of:

1) Ignition
How long have the plugs been in? I find that, at least in the Aero, they don't last as long as Saab would lead us to believe, and when they deteriorate, they can give false knock signals and reduce boost. I change mine at every 12K mile service (that reminds me - must do one soon). I had seen suggestions that a smaller gap (0.8-0.9mm) can help extend the life of the DI, so tried it for a while. I found that this gives anaemic performance at low RPM compared to the proper 1.0-1.1mm gap. Perhaps Saab know what they're doing after all.

2) Turbo
Is the base boost pressure correct? It should be 0.42-0.48 bar (preferably towards the high end). This is considerably higher than other 9000s and perhaps someone set it too low in the past by mistake (I've had this happen even with a main dealer). I found that too low base boost again makes the car feel anaemic at the bottom end, although it can still take off at high RPM.
Assuming your bypass valve is working correctly (you aren't getting stumbling at junctions?), the wastegate actuator could be weak, allowing the wastegate to open too much and keeping boost down until high RPM. There's also an outside chance that the boost control solenoid is faulty, although that usually gives less subtle symptoms.

3) Fuel
Last summer, my Aero was not pulling well at all, despite decent boost (doesn't sound quite like your problem). Then it failed the MOT emissions test for high lambda (weak mixture). After the dealer had had a look, to no avail, I did a bit of reading up on how Trionic works to find out what could cause the mixture to be weak. I figured out that one of the parameters used to measure air mass (and hence to meter fuel) is the intake air temperature sensor. I measured it against Trionic data found on the web and it was just out of limits. A new one brought back all the old torque and power, and as I was heading off to do an adaptation run, a guy in a tarted-up BM made my day by trying to race. He couldn't have picked a better day and even went for a rolling start. I hadn't had so much fun in ages!
Anyway, the beast sailed through the emissions test this year. Perhaps you can pop down to an MOT station or your Saab garage and ask for an emissions check. I'm sure they won't charge much - the MOT place I went to last year, having managed to scrape the car through on the re-test with the fault still there, offered to check it again free of charge once I'd found and fixed the problem.

So that's a few things to keep you occupied for a while
 

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Discussion Starter · #4 ·
Hi Bill,
Yes, just a few things to check
Talking of the adaptation run, I tried removing my ECU for a while and then went for a run. Unlike with my previous DI/APC equipped Carlsson the boost never went into the red sector which puzzles me. Is this an indicator of an underlying fault not allowing the boost to rise too far?
I have the tech data for the temp. sensor so I will check this first.
The plugs are only a few months old and are gapped correctly, although I will check this again.
Nick.
 

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Well, while there is a variation between boost gauges on different cars, my Aero boost gauge did go into the red and stayed there, even with the standard ECU. My car did have the heatplate, so to compensate, it didn't taper back so far at high RPM, but yours should still behave similarly to mine at low RPM. If changing the plugs didn't make any difference at all, then it's probably not ignition. A failing DI cassette will usually give a noticeable misfire under boost.

It does sound as if your "low-torque" problem is a "low-boost" problem, but from what you describe, you are not stuck with base boost.
 

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Discussion Starter · #6 ·
Thanks again Bill,
I've had a dodgy DI cassette on my Carly, which gave a pronounced missfire at or around peak torque (say 3000 rpm). This doesn't appear to be missfiring, but it MIGHT be.
I'm certain that I'm getting far more than base boost. As said the boost whilst under full throttle is up in the red/orange zone, (about half to three quarters of the way up this zone at 2000-2500 rpm), but goes up to the top of the red/orange zone by 3000 rpm. Could you confirm if this is normal behaviour? Or am I lacking full boost at 2000 - 2500 rpm?
Could it be that the ECU has reprogrammed itself due to some dodgy fuel way in the past, and now I can't get it to re-adapt itself??
Oh, and as a final request. My data for the temp. sensor related to the LH system. Is the trionic sensor the same? Either way would you be good enough to post your data for the sensor so I could check it?
Thanks for all your help.
Nick.
 

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Hi, Nick.

I'm pretty certain we're chasing a boost problem here.

Base boost on my Aero is towards the top of the yellow, but definitely clear of the broken red.

It does sound as if you are lacking boost. When standard, my Aero boosted well into the red on decent fuel (Optimax). A dodgy DI cassette can make the ECU think there is detonation when there isn't, with a resulting retardation of the ignition and reduction of boost pressure.

You should be getting the same boost at 2000rpm as you are at 3000, although you might have to be going up a steep hill to keep the engine revving this low for long enough for the turbo to spool up.

I once did an experiment to determine how much boost I could achieve at various RPM, and how fast the turbo would spool. This was with the JT exhaust, but with no other modifications. I used a graduated boost gauge (I won't stretch credibility by calling it "calibrated"). It cost about £20 and goes up to 2 bar. As far as I can remember, 1 bar is a bit into the red. I think you should be able to achieve at least 1 bar steady state.

Bear in mind that your spool-up might be slower without the JT exhaust. If anything, however, it shows I could achieve full boost at 2000 RPM.

I did the following in 5th gear on various steep inclines (except the 1000RPM test) at an ambient temperature of about 22 deg C. The inclines were so I could maintain almost constant RPM.

I decelerated slowly to each of the following engine speeds to ensure the turbo was idling, then put my foot to the floor and watched what happened to the manifold pressure:

1000RPM - got just above atmosphere. No more.
1500RPM - took a few seconds (5 or more?) to spool up to about 0.3 bar. Couldn't get any higher.
2000RPM - took about 3 seconds to spool up to 1.0 bar (seemed to be my limit on that particular day)
2500RPM - getting better, only took about 2 seconds.
3000RPM - now we're getting somewhere, less than a second.[/b]
The temperature sensor data is what I found on the Townsend Imports site. You can measure the voltage between the two sensor wires with the ignition on, but it would be difficult to make a connection. I removed the sensor and measured the resistance at ambient temperature (as measured by the cars outside air temperature display). I couldn't match this up with any of the temperatures listed in the table, so I went back to "O" level maths, drew the curve on some graph paper and interpolated.

Here's the table:

Deg C Voltage Resistance (KOhm)
-30 4.5 20-30
-10 3.9 8.3-10.6
20 3.2 2.3-2.7
40 1.5 1.0-1.3
60 0.9 0.56-0.67
80 0.7 0.30-0.36

Looking up the invoice, the sensor was part number 9174442 and cost £23.82. I took a 19mm spanner with me when I went to collect it and fitted it in the dealer's forecourt (despite them not having the fibre washer that goes with it - I got a new one later in a local car parts shop). By the time I had driven the 10 miles back to work, the ECU had adapted and I could feel an amazing difference.

Other potential culprits, in order of likelihood, are a weak wastegate actuator and a dodgy BPC valve.
 

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Discussion Starter · #8 ·
Bill,
Have taken the No.5 fuse out for a while then gone for a run...
Boost now goes a tiny bit higher once above 3000rpm, but something must be keeping it down,(as it doesn't adapt into the red), will be checking up on your ideas.
Thanks
Nick.
 

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Discussion Starter · #10 ·
Hi Bill,
The ECU is said to be an Abbott modified item, BUT there is no way of telling as they reprogram the ECU rather than replace any part.
All the mods were done by the previous two owners, most are visable (Koni shocks, Abbott discs, Mintex pads etc.) but this one is not...
Abbott have kindly sent me a graph of their Trionic upgrade versus the standard ECU, and it states that they use 1.25 bar boost versus 0.95 max boost for a standard Aero. Whether this is acheived without a manual bleed valve I'm not sure.

On another note, my plugs are NGK '6ES not the '7ES as stated in my owners manual. I will be changing them tommorrow as I can't go any further without trying this first, just in case it is something that simple. I know the Trionic system can tell a lot from the monitoring the voltage at the spark plug during firing, so it could be that it's getting false information...
Nick.
 

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Spot on, Nick. As you point out, the plugs are such a sensitive item that further diagnosis is impossible without putting the right ones in.

Do Abbott really only go up to 1.25 bar on an Aero? When we met in the middle of nowhere (but close to the New Forest), I saw Andy Bowles's Abbotted 9000 clear the end of the red. Must have been his manual boost controller. Honestly, a non-Aero with that kind of boost. Do some people have no respect?

I'd be sure the Abbott upgrade would achieve its stated maximum boost purely by electronic means. My Maptun Stage 2 upgrade (which requires the JT exhaust to keep the exhaust gas temperatures down) achieves 1.6 bar without the use of a manual controller.

Keep us posted. You may have to do another adaptation run after changing the plugs in case the wrong plugs caused the Trionic ECU to enter "maximum negative adaptation".
 

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Discussion Starter · #13 ·
Have now changed the plugs for the correct BPCR7ES II plugs. Tryed removing fuse 5 for a few minutes, but still the adaptation doesn't seem to kick in. Humph....
I wonder if unplugging the APC solenoid would allow unlimited boost, just so I could check to see if it is a engine managemnt thing that is holding the boost down?
Nick.
 

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If you unplug the electrical connection to the solenoid, then take it out and accelerate hard in say 3rd gear, then the boost should go off the end of the gauge and you will get fuel cut off. If it doesn't, then it's most likely that you have either a) a leaky solenoid valve or B) a weak/split wastegate actuator. You could help confirm this by putting a brake hose clamp on the W hose to the actuator, and you should get the overboost described above.
 

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Mark, you sure you don't mean unplugging the electrical connection will give base boost, and disconnecting/clamping the "W" hose will give unlimited boost?

I'm sure that's what you meant to say

If interfering with the "W" hose doesn't give fuel cutoff-inducing boost, then I'd say it could be a very weak actuator diaphragm (allowing the exhaust pressure to blow the wastegate open against the spring pressure) or the turbo is not spinning up properly, indicating a bad turbo. Or, and I really have heard of this happening, the wastegate valve-plate-thingy (what's the word?) is lying in the cat, so the wastegate is open all the time.

Anyway, unplugging the electrical connection to see where base boost is on the gauge might not be a bad idea anyway. It's all potentially useful information.
 

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Discussion Starter · #16 ·
Well, where do I start?
By disconnecting the W pipe at the solenoid, the boost was allowed to go off the end of the gauge. Also it appeared that the boost at 2000 rpm was far higher than with the solenoid all connected up. So it appears that the engine management IS holding the boost down... But why?
I then reconnected the W pipe and removed the electrical connection to the solenoid. The boost behaved the same as with the solenoid connected, no difference, and certainly no base boost!!?
So could the knock sensor be faulty?? (Remember the ISAT detected no fault codes) I think not as I believe that would create a base boost symptom.
Also have I tested properly for base boost? If I have then why is it so high?? Has someone adjusted the wastgate rod so much as to render the APC inoperative??
Nick.
 

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Well, Nick, it sounds as though the wastegate isn't stuck, otherwise you wouldn't have got massive overboost. Removing the "W" pipe removes makes the wastegate actuator totally unaware of the pressure the turbo is producing. This has nothing to do with the ECU and even a simple non-electronically-controlled turbo installation will display this behaviour if its boost pressure feedback path is removed.

As long as there are no leaks, with the solenoid connector disconnected, you must get base boost. Base boost on the Aero is very high compared to other 9000s. On mine, it reaches most of the yellow. Boost gauges vary, and it might not need base boost on yours to be much higher than spec. to reach the broken red. Remember that if there was a problem, someone might have fiddled to try to compensate for it.

If you suspect that the solenoid valve is leaking or there is a leak somewhere else, then remove the "W" hose from the solenoid, the "C" hose from the turbo compressor and plug the solenoid end of the "W" hose onto the turbo compressor where the "C" hose came from. This will make it an "Aero LPT" and you absolutely must be in base boost now! Note the position on your gauge.

You don't have a knock sensor as such. On Trionic cars, knock sensing is achieved by measuring ionisation current across the plug gap.

It could well be that the engine management is not "holding back", but rather is not increasig boost beyond base. It is conventional to think of the APC system reducing boost when it sees a problem, but in fact its job is to raise boost when it thinks it is safe to do so. This is what the solenoid valve does - when not energised (or unplugged) it has no effect and all you can ever achieve under these conditions is base boost. It is only when energised by the ECU (when it is safe to do so) that the valve bleeds pressure away from the wastegate actuator to fool it into keeping the wastegate closed and therefore increase boost pressure.

You might have a dead solenoid valve. This will not, so far as I know, throw up a fault code. The best test is to replace it with a known working one. You also really should check (or have checked) the base boost level so you know where you are. One way to compare on your standard boost gauge is to drive the car at around 3000rpm, say in 3rd gear and, with one foot still on the accelerator, brake quite firmly, holding enough throttle to maintain 3000rpm. With the brake pedal depressed, boost is limited to base boost and maintaining 3000rpm with the brakes on will load the engine enough that it will be producing as much boost as it can (i.e. base boost).
 

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Discussion Starter · #18 ·
If I do have a dead solenoid valve then it would explain why the 'adaptaion run' doesn't produce a higher boost than before.
Should it be possible to hear/feel the solenoid buzz at idle, I believe they operate at 8 Hz, but is this at all times??
With my existing solenoid disconnected the boost was exactly the same as with it all connected. The boost was up into the broken red sector. I can't believe this represents base boost, unless the wastegate rod really has been adjusted by someone who (once the solenoid gave up the ghost, for instance) didn't know better than to adjust it to overcome the lack of boost.
Is base boost for an Aero 0.48 bar, that strikes a note with me?
I'll be trying to clean the solenoid out with some carb cleaner as a first point of attack.
Thanks for all your help.
Nick.
 

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Bill,

Nope, I meant what I said first time about the effect of unplugging the electrical connection to the solenoid and it's effect on boost- because that's what happened on mine with the standard ECU, although not with an Abbott one (I have both, long story...)!

However, main point of exercise achieved...

BTW mine's an (early) Trionic and does have a knock sensor. I didn't think they stopped using them on later cars. I thought that the ionisation measurement was to measure combustion efficiency.

No, you don't get a fault code when the solenoid valve dies. Nick, why don't you buy the Abbott manual boost control valve- it's not too expensive (circa £50 incl p&p)- certainly a lot cheaper than the electrical one and you can then set things up how you like.

Tell you what... I recall there's a test you can do by blowing/sucking on the various ports of the solenoid. I'll do that a bit later for you, cos I know mine is working and report back.

PS Bill
"the wastegate valve-plate-thingy (what's the word?)" errm... I'd have said just "wastegate" or flap myself
 

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OK, here's what I found on the solenoid...

If you blow into the "C" port (top one), the air should only come out of the "W" port (middle). If you block off the "W" port, you should go blue in the face trying to blow and most importantly, nothing should come out of the "R" port (which all makes sense).

i.e. in "resting" configuration it allows the full pressure of the turbo to be applied to the wastegate. Thus if you disconnect the electrical connector, you should get base boost- however this does somewhat knock on the head my experience I recounted earlier about disconnecting the electrical connector . Wierd!

Thus, if the eletrical actuation of the valve is faulty, it won't open up the path to the R port, thereby meaning that you can only get base boost.
 
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