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Discussion Starter · #1 ·
The 1996 Hirsch 2.0LPT 9000 is running a little rough of late under acceleration. When under boost the boost gauge is showing fluctuating boost thats erratic and increases and decreases boost pressure ands creates a strange rough acceleration and it doesnt feel very fast or clean boosting at all. What could cause this? The previous owner mentioned that the Turbo Actuator is a bit weak when I purchased it and might need changing soon. What does the actuator do and how much am I looking at for replacement if it is this that could be causing it. If it isn't what could it be chaps.....I've just fully serviced it and it cannot be anything else but something associated with the turbo (I dont think....but maybe I'm wrong!)

Many Thanks

 

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Sounds like an interesting 9000 there mate.


The actuator is an electro-magnetic "valve" which controls the opening/closing of the wastegate so it effectively governs the boost pressure. If the actuator is working correctly the APC system (part of Trionic on the 96 cars) can set the boost pressure by modulation of the actuator.

If the actuator is duff the APC is unable to control boost properly and can cause over/under boosting and in some cases the boost "pulsates". This sounds like the problem your having. So a new actuator WILL probably solve the problem. HTH.
 

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Sounds like it may be wastegate actuator to me, rather than the APC valve. The symptoms are just like I had on mine and the cause turned out to be not enough pre-load, although it could equally be caused by a failing spring or diaphragm.
 

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There's only two small bolts/screws that hold the actuator to the compressor housing. The clip has to be removed from the rod to disconnect from the wastegate lever. The usual mode of failure is for the spring/diaphram arrangement breaking so that the rod can be pulled out too easily - there should be some resistance when you pull on the actuator rod. When you say it was recently serviced, did it include new plugs and what are they gapped at? I've seen wide gaps cause vascillating boost, also.
 

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Apart from checking the hose connected to the actuator and pulling the rod (no pun intended)
to check the resistance there is not a lot that can be checked.
Your best bet is to swop it for a known good one and see if that makes a difference.
Don't know if there is anyone close to you with an actuator for the T25, if your interested I have 2 spare for the T25 and they both hold boost at 1.1-1.2bar, it will cost you a beer though
PM me if your interested.

Steve
 

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Discussion Starter · #8 ·
I have recently changed the spark plugs (the recommended NGK ones) but i was always under the impression that they come pre gapped for the 9000....but I'm here to be proven wrong. Being a Hirsch modded Saab wouldnt it be worth me changing the actuater for a performance one to enable the extra performance or would an original one be just as safer bet?
 

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Discussion Starter · #9 ·
I have recently changed the spark plugs (the recommended NGK ones) but i was always under the impression that they come pre gapped for the 9000....but I'm here to be proven wrong. Being a Hirsch modded Saab wouldnt it be worth me changing the actuater for a performance one to enable the extra performance or would an original one be just as safer bet?
 

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There's no need for a 'performance' actuator. The stock OEM is more than sufficient for the Hirsch ECU - I'm sure Hirsch doesn't raise the basic boost pressure and maintains Saabs' APC settings.
 

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Also, if the NGK's are '11's, then they're gapped to 1.1 mm which is the upper limit of their gap tolerance. As they tend to widen over time/use, I set mine at 1.0 mm and change them every year/12k miles, as they're only a quid each and don't take long to change.
 

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Discussion Starter · #12 ·
Right I fitted the new actuater today kindly supplied by Steve for a very reasonable price. It has sorted most of my problems except under extreme acceleration in 3rd gear it overboosts still and loses most of its boost and hesitates and also this somtimes happens in 1st gear when accelerating hard. Any ideas peeps?
 

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Originally posted by The Scrappy formerly known as KSow1:
[qb]... except under extreme acceleration in 3rd gear it overboosts still and loses most of its boost and hesitates ... [/qb][/b]
Have you checked the base boost setting? If it is doing this then it sounds like base boost is set too high.
 

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Originally posted by The Scrappy formerly known as KSow1:
[qb]Steve set the base boost just right for me with my Hirsh set up. [/qb][/b]
The actuator was set at 0.4bar for my previous T25, however as per my PM you may need to adjust it using a graduated boost guage Billj has a good artical on how to do this on his website.

It sounds as though it may be set too high for your turbo, if you don't have a guage you may want to lengthen the rod i.e turn the turnbuckle one complete turn anti clockwise, take it for a spin and see if it has helped overboost...you may have to do this more than once as one full turn is approx 0.03bar

Hope this helps.

Steve
 

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Discussion Starter · #17 ·
Turned it back 3 whole turns and still the darned thing overboosts....It's doing mine and my missus's head in! Does anyone else have any guesses what could be wrong other than keep winding the actuator back....as that doesnt apear to be doing anything to help at the minute.
 

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Originally posted by The Scrappy formerly known as KSow1:
[qb]Turned it back 3 whole turns and still the darned thing overboosts....It's doing mine and my missus's head in! Does anyone else have any guesses what could be wrong other than keep winding the actuator back....as that doesnt apear to be doing anything to help at the minute.      [/qb][/b]
If you haven't done it already, try replacing the hoses from the APC solenoid, starting with the Wastegate ("W") hose first and see if that helps.
 

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Are you sure it's overboost? Overboost is violent, disconect either the pressure hose from the turbo or the hose to the waste gate from the APC actuator and go for a drive. It's like going in to a brick wall. It may be the DI cassette that has failed. Mine went the same way, on upper boost pressure. It was ok in the rest of the rev range.
 
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