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I will be checking my basic boost pressure over the weekend on my '86 9k turbo. Any ideas what the value should be? According to Saab9000.com it should be ~5.5 psi. Please confirm!

What effect would increasing the basic boost pressure have? Engine damage? Would it run hotter due to higher fuel consumption? Damage to the head gasket, valves or rings?

If I set the basic boost pressure on a hot and humid day as opposed to a cold dry day is this bad?
 

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It will cause the oil seals in the turbo to leak and also the weaker mixture will cause the pistons to melt as it will be much hotter if you go to high. My coope turbo should run at .5 - .6 bar but i run at 1.2 max using a pressure bleed valve and have had no ill effects yet.
 

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Do you need to set base boost if you run a MBC valve?  [/b]
Not unless your base boost is already out.

Don't Abbott turn up the base boost with their uprated actuators as part of their upgrade kits?

It really all depends on whether your fuelling is capable of supplying the engine with enough to cope with the increased boost pressure. The downside of increasing base boost always going to be that you don't leave the APC system with much room for manoeuvre.

PS: welcome to SaabScene "Still looking for one"
 

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Is your 86t equipped with the 2.5bar fuel pressure regulator or do you have the 3.0bar?
If you have the 3.0FPR you should be able to increase the base boost by 2lbs without any problems that I am aware of. 2lbs=4 clockwise turns,i.e. shorten it.
 

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It really all depends on whether your fuelling is capable of supplying the engine with enough to cope with the increased boost pressure. The downside of increasing base boost always going to be that you don't leave the APC system with much room for manoeuvre.

Fitting the Abbott MBC Valve bypasses the APC, the only protection I think I have left is knock and overboost. I don't know how the knock sensor works exactly on my car now the APC is bypassed, anybody know??
 

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Originally posted by Mark in Ireland:
[qb]Fitting the Abbott MBC Valve bypasses the APC, the only protection I think I have left is knock and overboost.  I don't know how the knock sensor works exactly on my car now the APC is bypassed, anybody know?? [/qb][/b]
It only partially functions... Under normal conditions, the first stage of knock protection is to alter the timing... if the APC can't reduce knock this way it reduces the boost.. which it can't do anymore if you use an MBC
.

When I ran an MBC I also used water injection to guard against knock. Now I'm using software control, my base boost is comparatively low- 0.5 bar but I have 1.6 bar peak, and hold 1.5 bar to above 5000rpm. I still keep the water injection for extra "protection", even though it takes a few hp off the top end.
 
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