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Porsche Crest Unbalanced boost

Just today, when I took my 930 Slant out for a drive, I've noticed that my boost seems to be unbalanced whenever I'm accelerating. At full boost, it's supposed to stay around the 1.1-1.25 bar range, but for some reason it keeps moving from 1.0 to 1.2 and back to 1.0 when I accelerate. The engine also goes "waa waa waa" when the boost is unbalanced, or for those of you who have musical knowledge, my engine seems to do a "vibrato" when that happens. It sounds as if I'm letting on and off the throttle, even though I'm holding it straight. My car usually only does this when I hit a bump while accelerating, but today it's doing that on flat ground. I checked the engine, but there didn't seem to be any problem, and my car normally doesn't do this. Is this normal or do I have to get it checked out?

Thanks,
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Jason

1987 930 Slantnose Cabriolet, 545 hp, Guards Red- Weekend cruiser
1986 944 Turbo (951), 350+hp, Guards Red- Track car
2005 Toyota Tundra SR5 Double Cab 4x4, stock 282 hp, Silver- Daily driver
Old 03-09-2014, 01:01 PM
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Check all lines running to the wastegate. You have a boost controller?
Old 03-09-2014, 01:06 PM
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Quote:
Originally Posted by Tippy View Post
Check all lines running to the wastegate. You have a boost controller?
Yes, I have a boost controller. It's set at the maximum boost rating (1.25 bar) for my car and I've never messed with it since I bought it.
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Jason

1987 930 Slantnose Cabriolet, 545 hp, Guards Red- Weekend cruiser
1986 944 Turbo (951), 350+hp, Guards Red- Track car
2005 Toyota Tundra SR5 Double Cab 4x4, stock 282 hp, Silver- Daily driver
Old 03-09-2014, 01:19 PM
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That may be where the problems lies.
Old 03-09-2014, 01:25 PM
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Quote:
Originally Posted by Tippy View Post
That may be where the problems lies.
Would that mean I have to reset my boost controller? I don't want less boost since I want the most speed out of my car, since I'm a bit of a gearhead
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Jason

1987 930 Slantnose Cabriolet, 545 hp, Guards Red- Weekend cruiser
1986 944 Turbo (951), 350+hp, Guards Red- Track car
2005 Toyota Tundra SR5 Double Cab 4x4, stock 282 hp, Silver- Daily driver
Old 03-09-2014, 01:27 PM
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What kind of boost controller is it (electronic or a simple adjustable pressure valve), and what pressure wastgate spring is being used?

You are going to have to put some of that "gearheadedness" into practice and troubleshoot your boost control circuit.

1) Check all hoses to and from the wastgate, controller, and where ever it picks up the boost signal (probably the intercooler) - check for loose hose clamps, hoses that are melted, torn, frayed, etc.

2) If nothing in the above checks is obvious, bypass the controller with a double sided hose barb, and then take the car for a drive and see if the problem is still there. If it isn't, then you know the controller is the problem and it either needs to be rebuilt or replaced.
Old 03-09-2014, 01:40 PM
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Quote:
Originally Posted by Ronnie's.930 View Post
What kind of boost controller is it (electronic or a simple adjustable pressure valve), and what pressure wastgate spring is being used?

You are going to have to put some of that "gearheadedness" into practice and troubleshoot your boost control circuit.

1) Check all hoses to and from the wastgate, controller, and where ever it picks up the boost signal (probably the intercooler) - check for loose hose clamps, hoses that are melted, torn, frayed, etc.

2) If nothing in the above checks is obvious, bypass the controller with a double sided hose barb, and then take the car for a drive and see if the problem is still there. If it isn't, then you know the controller is the problem and it either needs to be rebuilt or replaced.
It's an electronic boost controller, and I don't know what pressure spring I have, unfortunately.
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Jason

1987 930 Slantnose Cabriolet, 545 hp, Guards Red- Weekend cruiser
1986 944 Turbo (951), 350+hp, Guards Red- Track car
2005 Toyota Tundra SR5 Double Cab 4x4, stock 282 hp, Silver- Daily driver
Old 03-09-2014, 01:42 PM
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OK, try to re-boot the controller by disconnecting its power supply and then reconnect after a couple of minutes. When you do this, check to see if it has a battery (used to store info when the car's main battery is disconnected), and replace it if it does.

Given that it is electronic, it might be programmed to adjust boost level for varying RPMs, so if you test it with the bypass pipe like I suggested above, use some common sense caution with the throttle when you do so (so you don't overboost, as the factory overboost circuit is likely no longer functional on your car).
Old 03-09-2014, 02:08 PM
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Quote:
Originally Posted by Ronnie's.930 View Post
OK, try to re-boot the controller by disconnecting its power supply and then reconnect after a couple of minutes. When you do this, check to see if it has a battery (used to store info when the car's main battery is disconnected), and replace it if it does.

Given that it is electronic, it might be programmed to adjust boost level for varying RPMs, so if you test it with the bypass pipe like I suggested above, use some common sense caution with the throttle when you do so (so you don't overboost, as the factory overboost circuit is likely no longer functional on your car).
Okay, I guess I could try doing that.
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Jason

1987 930 Slantnose Cabriolet, 545 hp, Guards Red- Weekend cruiser
1986 944 Turbo (951), 350+hp, Guards Red- Track car
2005 Toyota Tundra SR5 Double Cab 4x4, stock 282 hp, Silver- Daily driver
Old 03-09-2014, 02:24 PM
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