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Hi everyone - more worries reflecting my deepseated insecurities - the group has become my blue security blanket.

2.3 Stg1. In 4th gear max boost shows as 1.3 bar or there abouts.

Almost straight away the boost falls to 1 bar and fluctuates between 1 and 1.2 bar cycling in about 3/4 of a second and then stabilizes at 1 bar after 3 or 4 seconds. The turbo can be heard spooling up and down.

Spool up is almost instantaneous - max boost is reached very quickly.

In lower gears accelerating hard from low revs there is a slight tinkle/rattle - Pinking? only lasts half a second or so - no back off in boost.

is this normal behaviour or is it indicative of a fault? - perhaps a weak wastegate actuator?

Cheers

Alyn
 

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sounds completely normal...
boost is backing off because the trionic is sensing that it should
the noise you hear is also typical (well mine does it!) and I guess it is something like onset of pinking...

don't worry be
 

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I've just been informed by Abbotts that I need a 8psi wastegate capsule to curb my spiking which constantly hits the overboost cutout. Its okay if I rev the engine thru the gears but just putting my foot down in a high gear causes masses of boost and the headbutting the steering wheel syndrum. Anyone else experience this using a Abbott MBC valve?
Anyone got any other ways of modifying the actuator on the cheap as I don't have £195 to give to Abbott.
 

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Simple, just tune the MBC to not hit the fuel cut in 5th gear. The lower gears won't be quite as strong but it will cure the boost cut problem.
 

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I had already done this last year but as the MBC valve is fixed and hasn't been moved I couldn't work out why it was starting to overboost. Abbott reckon the actuator is getting weak and cannot repond fast enough to the sudden increase in pressure. As i want to run a constant max safe high boost I need to look at the underlying problem not have to keep adjusting the MBC valve to compensate for some other part wearing out.
How difficult would it be to modify the wastegate actuator, can it be done?
 

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It could just be weather related. Or prehaps the mbc could be changing a bit, i.e. wearing out or falling out of adjustment. A long time ago when I had a TurboXS MBC, I had to adjust it quite often to keep top performance without the boost spike induced fuel cuts.

But then again, Abbott could very well be correct. I personally don't know how to modify a wastegate. I would think you would have to purchase a stronger one.
 

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There are no moving parts in an Abbott MBC valve it is designed like a crude needle valve arrangement and in thoery once set should never lose its adjustment setpoint.

Is there a spring inside the actuator which gives it the lift setpoint?
 

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I don't know about Abbotts design. I previously had a TurboXS and then a Dawes. Sorry, I guess I can't help you.

You should adjust it in as high a gear as possible though.

I gave up on MBCs for the reasons of constant need for adjustment and really bad high rpm boost taper. An upgraded ECU works much better.
 

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Is there a spring inside the actuator which gives it the lift setpoint?  

 [/b]
Yes, there is a spring inside it.. but the capsule is sealed.

I've replaced the actuator on my 9000 for an up-rated one.

A lot of companies do up-rated actuators.. Forge for example.
 

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The actuator could indeed be getting weak- the cheap alternative to fitting an uprated actuator is to shorten the rod a little, although it's not as good as an uprated actuator- see my previous post here for a more detailed explanation.

And as a summary of how it all works together:

The APC solenoid or any MBC have essentially the same function- to prevent the wastegate "seeing" the full boost pressure, thus enabling it to stay shut, allowing the higher boost (that's bit cyclical I know
).

Like maximum boost, overboost cutoff is also adaptive, and (presumably) because it is a protection mechanism, each time it happens the threshold lowers slightly. So, Mark, you may find that disconnecting the ECU for a while then re-adapting could cure the problem.

Having been through all the MBC combinations, my personal recomendation is to treat them with great caution, especially if you do not have a modified ECU. This is because they remove the valuable APC protection that makes Saab turbo systems so inherently reliable.
 

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I did a quick check on the way back to the digs last night.....50mph in 5th, foot flat to the floor, a few seconds to wind up then overboost at 1.4barg. Slow back down to 50mph, now in 3rd, foot flat down, boost pressure climbs rapidly to 1.7barg, no overboost! Why does it see the cutout in 5th but not 3rd??
 

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Originally posted by Mark E:
[qb]Having been through all the MBC combinations, my personal recomendation is to treat them with great caution, especially if you do not have a modified ECU. This is because they remove the valuable APC protection that makes Saab turbo systems so inherently reliable. [/qb][/b]
And even if you do have a modified ECU
 

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Originally posted by Mark in Ireland:
[qb]50mph in 5th, foot flat to the floor, a few seconds to wind up then overboost at 1.4barg.  Slow back down to 50mph, now in 3rd, foot flat down, boost pressure climbs rapidly to 1.7barg, no overboost!  Why does it see the cutout in 5th but not 3rd??    [/qb][/b]
You got me there... the standard MAP sensor does not read beyond about 1.6 bar. If you look at it on Tech 2, there's a scale from 0-255 (that'll be an 8 bit system then, sir) and anything above 1.6 bar registers as 255.

I certainly can't see any logical reason why that shoud happen- unless you gauge is not reading properly?

Remind me of your setup, Mark -ie what ECU etc...
 

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Its a standard 1992, 2.3 Carlsson, Abbott head, dump valve and MBC valve, 3" JT Exhaust no cat.
Gauge is brand new from Speedparts and goes to 2.2barg.
I've been inquiring about APC/DI upgrades and have had different info from the specialists. I spoke to Giles at Abbott and he said it would be a waste of £395 for their upgrade as I wouldn't see much gain for the cost, however Swedish Dynamics said, quote 'The DI/APC control unit performs the task of providing information relative to turbocharger activity and ignition timing/control. Your 1992 vehicle also has a separate control unit for the LH fuel system which controls fuel delivery only. Our DI/APC EPROM will enhance both providing boost levels towards 20 psi. Ignition timing will also be reformatted to be further curve retarded under
the additional boost pressures. Our LH EPROM will enhance fuel curves but is not always required with the DI/APC EPROM update.
Our Fuel EPROM would be highly recommended with the DI/APC but end result is generally a 5-6 bhp provision per psi boost increment (8-9 psi gain would render a 40-55 bhp provision).
These EPROMS could be easily shipped to Ireland.
So different opinions and I'm still no clearer on the way forward.
 

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Originally posted by Mark in Ireland:
[qb]I did a quick check on the way back to the digs last night.....50mph in 5th, foot flat to the floor, a few seconds to wind up then overboost at 1.4barg.  Slow back down to 50mph, now in 3rd, foot flat down, boost pressure climbs rapidly to 1.7barg, no overboost!  Why does it see the cutout in 5th but not 3rd??    [/qb][/b]
The boost spikes at onset very quickly. In a higher gear like 5th, the engine accellerates slower so the spike is notreduced as quick. In 3rd, the engine uses the air more rapidly as it accellerates faster and therefore the initial boost spike is used before it gets too high. Try going into 5th and slowly moving your throttle down to the floor. You will probably get higher sustained boost without the fuel cut.
 
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