Saabscene Saab Forum - Saab Technical Information Resource banner
1 - 20 of 34 Posts

·
Registered
Joined
·
597 Posts
Discussion Starter · #1 ·
Here are the dyno results I got at LPS yesterday. Opinions on the day were that I may have a fault with either the throttle position sensor or the MAP sensor.

It was suggested that I could test the MAP sensor using a bike pump. Can I measure resistance, or do I need to measure voltage?

Can anyone explain how to test these sensors in detail, or shed more light on the results below?



 

·
Registered
Joined
·
24 Posts
Yes you can test the MAP sensor. With this MAP sensor you have to measure voltage. The voltage must raise/lower in a nice straight line when you use a vacuum tool. When you give me your mail adress I will send you a picture of the tabel/graphic what you must measure.

regards,

Sander
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #3 ·
I have reduced base boost by 0.05 bar to 0.33 bar and the boost fluctuation has all but gone. I think the blip on the fuelling on my dyno result is a fault on the dyno sensor and not the car.

In terms of performance, I'm getting sub 4 seconds for 50-75 mph in 3rd (I think well over 200 bhp), though not consistently. It varies between 3.9 and 4.6 seconds on the same stretch of road on different days.

Since performance is variable and deteriorates quickly after a few bursts of acceleration, would I be right to suspect that the IC is not sufficient for the state of tune? Reading one of /John's posts on another thread, I see that Saab fitted the Viggen IC on 200 hp+ 9-3s.

I don't want to do further upgrades to ECU/exhaust, etc until I have consistency with the current state of tune.

Am I on the right lines?
 

·
Registered
Joined
·
4,215 Posts
sounds as if you are getting core saturation with the i/c

donno about saab fitting the viggen i/c to 200 + cars but the standard i/c does not look very efficient imho
there are much better alternatives out there at good prices
 

·
Registered
Joined
·
11,343 Posts
The intercooler is not the root of your problem. You need to turn your boost back up to the standard 0.45bar and resolve the issue with the mapsensor (if that is the cause of the troubles).

Once that is sorted, a crossflow intercooler will prove more efficient than the dual-pass IC.
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #6 ·
/John

BSR say that base boost should be as stated by Saab. My supplier said that this is 5 psi (0.33 bar). Is this not correct? The car is performing far better at this setting, and not displaying the characteristics that made me suspect the map sensor. However, if I can source a MAP sensor for a reasonable cost, I'd be happy to give a new one a go.

Nick
 

·
Registered
Joined
·
11,343 Posts
Originally posted by Chouet:
[qb]BSR say that base boost should be as stated by Saab.  My supplier said that this is 5 psi (0.33 bar).  Is this not correct?  [/qb][/b]
This is what I am trying to say: ensure that your base boost is at the correct setting as stated by Saab.

I think that your supplier is wrong. AFAIK the correct base boost for a GM900 is 0.4bar to 0.45bar. The 0.33bar figure that your supplier quotes is, IIRC, the setting for 9000 lpts?
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #8 ·
Hi /John

Mine was originally a 9-3 lpt. Is the base boost spec the same as for the GM900?

Thanks

Nick
 

·
Registered
Joined
·
11,343 Posts
Originally posted by Chouet:
[qb]Mine was originally a 9-3 lpt.  Is the base boost spec the same as for the GM900?
[/qb][/b]
Sorry Nick, I thought it was a 900. OK, 9-3. Well, the base boost on my 9-3 was 0.45bar on a B204R. Perhaps someone can clarify for a B204E, but I think that 0.4-0.45bar is what you need.
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #11 ·
Um, at the risk of stating the obvious, have you asked BSR what the base boost should be set to?
--------------------------------------------------------------------------------[/b]
Yes. They told me to set base boost to "the standard setting specified by Saab".
 

·
Registered
Joined
·
11,343 Posts
Originally posted by Chouet:
[qb] QUOTE
Um, at the risk of stating the obvious, have you asked BSR what the base boost should be set to?
--------------------------------------------------------------------------------[/b]
Yes. They told me to set base boost to "the standard setting specified by Saab". [/qb][/b][/quote]...and your supplier is telling you that the standard is 0.33bar?


Here is Saab's specified settings:

Engine: B204E
Base boost: 0.40bar
Max boost: 0.45bar

Engine: B204L
Base boost: 0.40bar
Max boost: 0.75bar

Engine: B204R
Base boost: 0.40bar
Max boost: 0.95bar

Engine: B235R
Base boost: 0.45bar
Max boost: 1.00bar
 

·
Registered
Joined
·
14,305 Posts
I'd be inclined to say that it's a poor show if the tuner doesn't know/can't tell you what the correct base boost setting is!
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #14 ·
I'd be inclined to say that it's a poor show if the tuner doesn't know/can't tell you what the correct base boost setting is!    [/b]
...and I'd be inclined to agree with you!

Nottingham Saab are going to check everything out for me in a couple of weeks - they are not overly familiar with BSR but seem to have good experience of tuning. Im hopeful they'll shed light on what is going on.
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #15 ·
The car has had a day of testing at Nottingham Saab (who I would highly recommend - loaned me a 9-3 for the day, too!).

Throttle position sensor, MAP sensor, etc all tested ok, DI and APC soleniod replaced with new to test, intercooler etc pressure tested, engine condition tested, etc, etc. The engine is not detecting knock.

A few minor things were found and fixed (inc. a valve leaking under boost), but the performance loss is still there. Nottingham Saab have questioned the ECU.

However (perhaps due to adaptation after the fixes) things have deteriorated. If I accelerate from 2000 rpm in 4th, boost climbs to 1 bar at 3000 rpm, then oscillates between 0.9 and 1.2 bar, then drifts back to 0.5 bar at about 4500 rpm.

Is this a weak wastegate actuator or could faulty software do this?
 

·
Registered
Joined
·
1,597 Posts
If it were the Actuator I would have thought it would leak before getting to 1Bar and wouldn't be rpm related. (i.e. it doesnt know the rpm, just the pressure)
Can you get hold of an ECU to try? - would at least close out that area either way and its quick to change over.
 

·
Registered
Joined
·
14,305 Posts
Base boost is dictated not just by actuator spring tension but also the force on the wastegate resulting from exhaust backpressure. This varies with flow and RPM.

I'd say trying another actuator has got to be worth a shot, then you can be confident you've eliminated a further mechanical possibility.
 

·
Registered
Joined
·
8,216 Posts
I'd expect a weak actuator to be sensitive to RPM because it is exhaust gas pressure that will blow it open and this will increase with RPM for a given throttle opening. The original boost fluctuation may also have been a symptom.

Oops - Bubbles just beat me to it...
 

·
Registered
Joined
·
597 Posts
Discussion Starter · #19 ·
I replaced the wastegate actuator with a 2nd hand one, and this made no difference at all.

I have now replaced the ECU (stage 3 to keep things moving forward - I hope to find or have made a 3 inch downpipe and have my highflow cat grafted in to replace my 2.5 inch dp).

Boost now holds for longer but still drops back to 0.7 bar at higher revs, and power seems to come in waves (surging). While the car is slightly better at higher rpm, it's still way off the mark.

I've also noticed a fairly loud metallic squeek when I lift off the throttle.

Any ideas?
 

·
Registered
Joined
·
1,086 Posts
The squeeking sound is probably the wastegate closing. A surging boost problem can be caused by a wastegate actuator that is not strong enough.

I had a surging boost problem after my second custom re-map at Hirsch. It was solved by a uprated wastegate actuator that they sent me. I did not, however, have a problem with the boost pulling back at higher revs like you do. I had over 330 Nm from about 2100 rpm all the way to around 5500 rpm.
 
1 - 20 of 34 Posts
Top