Saabscene Saab Forum - Saab Technical Information Resource banner
1 - 16 of 16 Posts

·
Registered
Joined
·
96 Posts
Discussion Starter · #1 ·
I've suspected for a while that my turbo wasn't giving as much
as I thought it should. Even under hard acceleration the boost gauge needle hardly gets into the red area. So, after searching on the site and following most of the advice re: checking hoses and wastegate actuator etc [including purchase of new 3-tonne trolley jack - my old one barley lifted the front of the car and then buckled and popped an oil seal - fortuneately, no underside damage to Drakken!] I disconnected the battery for 15 minutes and then went off to do a calibration run.

Improvement in response noticeable almost straight away
but last night coming home along a dead straight stretch of road I pushed the pedal to see how well she could respond. Well, needle on boost gauge goes past the 3 red lines and into the full red area, but then bounces back into the yellow, then bounces back into the red etc, with no throttle movement from me
. She did this a couple of times so I backed off and didn't push it again.

Any ideas what to look for? I'm going to re-check the hoses and other usual suspects again to see if I've missed anything.

BTW, I fill her up with Optimax on an irregular basis but my wife tends to fill up with tesco's finest as the Shell garage is too far to go!!
 

·
Registered
Joined
·
11,343 Posts
I would not expect any non-modified car to boost into the red zone. Following disconnection of the battery, any boosting into the red is likely to be happening whilst trionic is readapting.

The behviour of the boost gauge on your car sounds completely normal to me.
 

·
Banned
Joined
·
693 Posts
RE:I would not expect any non-modified car to boost into the red zone.

My '98 Annie FPT manual, which AFAIK is bog-standard, will boost into the red from low revs. Additionally, if I slam the throttle open from low revs, it will hit the (fuel or ignition? - can't recall which)cut-off to limit the boost. This is not a problem for me - I usually drive fairly sedately, and rolling open the throttle prevents it from happening anyway - but does it indicate a problem somewhere? I'd be grateful for any advice.

BOF
 

·
Registered
Joined
·
11,343 Posts
Originally posted by Dennis Eves:
[qb]My '98 Annie FPT manual, which AFAIK is bog-standard, will boost into the red from low revs. Additionally, if I slam the throttle open from low revs, it will hit the (fuel or ignition? - can't recall which)cut-off to limit the boost.
BOF [/qb][/b]
This does not sound normal. Your Saab is possibly modified, but the symptoms described could also be caused by the incorrect setting of base boost.

Bill Jones describes the procedure to check base boost

Even under spirited driving you should not be hitting the overboost cutoff.
 

·
Registered
Joined
·
204 Posts
Originally posted by /john:
[qb]I would not expect any non-modified car to boost into the red zone.  [/qb][/b]
My standard aero goes in the red zone everytime at WOT. On a calibrated boost gauge this equals to a peak of 1.05 bar followed by a steady 0.95 bar which is exactly what a 9k aero should boost.
 

·
Registered
Joined
·
222 Posts
My unadulterated (yet) '94 Aero always boosts into the solid red on hard acceleration and after a few seconds will drop back to the top of the yellow (as normal, the APC cuts down the boost after a brief overboost period) but then stays steady.

The only way to get the fuel cut out to operate is if you're accelerating hard and suddenly let off the gas and then jump back on again as the fuel pumps can't keep up with quick changes in demand like this so you get pressure spikes in the fuel line.

Have you checked if you have an exhaust leak around the exhaust manifold, a loose or broken stud could cause variable boost as the exhaust gas escapes in different conditions (hot/cold engine).
 

·
Registered
Joined
·
11,343 Posts
Originally posted by Marky:
[qb] QUOTE
Originally posted by /john:
[qb] I would not expect any non-modified car to boost into the red zone.  [/qb][/b]
My standard aero goes in the red zone everytime at WOT. On a calibrated boost gauge this equals to a peak of 1.05 bar followed by a steady 0.95 bar which is exactly what a 9k aero should boost. [/qb][/b][/quote]I read the original post as expecting to be boosting consistently into the red and maintaining boost in the red area, thus my comment that this is not to be expected. Boosting slightly into the read and falling back to the red/yellow border is about right.
Originally posted by Bu:
[qb]My unadulterated (yet) '94 Aero always boosts into the solid red on hard acceleration and after a few seconds will drop back to the top of the yellow (as normal, the APC cuts down the boost after a brief overboost period) but then stays steady.
[/qb][/b]
This is the sort of behaviour I would expect.

In my experience the yellow/red border equates to 1bar and the top of the red equates to 1.5bar. Of course, the Saab turbo gauge is not graduated, let alone calibrated, so can only give an indication of boost. Your best bet is to get hold of a graduated boost gauge to measure boost pressure (better still, check with a calibrated boost gauge.)
 

·
Registered
Joined
·
14,305 Posts
Originally posted by Drakken UK:
[qb] Well, needle on boost gauge goes past the 3 red lines and into the full red area, but then bounces back into the yellow, then bounces back into the red etc, with no throttle movement from me    :eek:   . [/qb][/b]
I'm afraid this is not normal behaviour. An initial peak in to the red, then dropping back to the yellow is, but repeating it is indicative of a problem.

It could possibly be a problem with a worn wastegate actuator, struggling to hold the boost.

Your first step is to check the base boost is correct with a graduated gauge. BillJ's 9000 site at the bottom of this page list the procedure for doing this and the right specs.
 

·
Registered
Joined
·
227 Posts
Having the same problem as Drakken UK at the moment I have just upgraded to a S/P stage 4 T28 turbo complete with wastegate actuator etc.

From 2nd to 5th gear when floored boost goes up to 1.3+ bar then quickly drops to 0.7 then back up again etc. This continues at about 1 second intervals until I reach just over 4000 rpm at this point it calms down and stays at 1.0 bar.

Base boost is set at 0.4 as per S/P. I have done a few adaption runs but with no success, double checked all fittings to ensure everything is tight,have not had a chance to contact the supplier yet as I only fitted it this weekend so i shall do so in the morning.

Steve
 

·
Registered
Joined
·
181 Posts
My Aero was doing exactly this fluctuating boost thing, sometimes it would hold good boost, other times, it would mess about surging the boost on and off.

Last week I replaced the 3mm vacuum hoses. There didn't appear to be any leaks, but they were fairly deteriorated.

Now I have good solid boost up to just into the red zone and no heart-stopping surging just when I'm trying to overtake something.
 

·
Registered
Joined
·
227 Posts
A quick update, swaped the wastegate actuator for the one on my old T25 today as I know it will hold boost at 1.1 bar still boosts upto 1.3 bar but only drops down to 0.9, also swapped the ecu back to stage 2, same problem but will only boost to 1.1 bar.

My guess is as bubbles suggested ,the wastegate actuator is not holding boost, will possibly have to go down the route of an uprated spring.

Very annoying when you go down the route of upgrading with a well known tuner/supplier with a supposidly tried and tested package only to find that some of the parts are not up to the job, although I must stress all the previous upgrades have been above my expectations and Elkparts have been first class
trying to sort out the problems I have encountered with this upgrade.

Steve
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #13 ·
Thanks everyone, plenty to think about within all the replies.

/John, as Drakken is an MY92, isn't she pre-trionic? Would this change your comments at all?

Bubbles, thanks for the feedback - will try and do all the checks as per BillJ's site this coming weekend.

Tricxy - I've been thinking about replacing all the hoses, having read your post I think it's an obligatory change now!

Commiserations Steve-Stg2, it really is frustrating when you pay out for the goods and they don't perform. Hopefully you'll continue to get good support from your supplier.
 

·
Banned
Joined
·
693 Posts
Re: This does not sound normal. Your Saab is possibly modified, but the symptoms described could also be caused by the incorrect setting of base boost.

Bill Jones describes the procedure to check base boost

Even under spirited driving you should not be hitting the overboost cutoff.

Thank you for the response, /John. I'm 90% sure the car is not modified, so I intend to check the base boost sometime soon. Is there anyone local who is willing to lend/hire me a boost gauge? Hoping to hear from someone..anyone, really.....on 01628-525838 (Marlow area).

Dennis Eves
 

·
Registered
Joined
·
227 Posts
You may also want to try a known good APC valve, I have narrowed my fault down to this, don't buy a new one to see if it solves the problem.....not cheap and may not work! I have just been sent a new one from Saab FOC only to find it was a dud only getting base boost with it. Off to find another one

Steve
 

·
Registered
Joined
·
89 Posts
I am having the same problem with my 96 2.3fpt auto. Intermittently it boosts right into the red then surges noticably with the boost gauge flicking between the red and orange sections. Other times under full throttle the needle just sits in the graduated section and pulls smoothly.
 
1 - 16 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top