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Forced Induction All questions and problems regarding Superchargers, Turbos, NOS, ZEX, intercoolers, water injection, etc.

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Old 04-12-2004, 04:20 AM   #21
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It'* on the front side of the SC. Here'* what the actuator and the BCS look like:

*note the red vacuum line has been removed from the actuator. Your vac line is black.

Located right in the middle of this pic:


The round black thing (bypass actuator) uses vacuum to keep the bypass butterfly valve open/partially open when boost is not needed (light throttle). When the throttle is opened wide, vacuum behind it is lost and the actuator closes the bypass valve, which is between the lower intake manifold where air is compressed and the inlet of the SC. The small black box connected to it with one vac line is the BCS. When the ECU detects a reason to dump boost, regardless of throttle position, it allows vacuum to the under side of the actuator which will open the valve.

I think it can still throw a code and not set the light off. Look for code 57, I think.
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Old 04-12-2004, 04:37 AM   #22
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Based upon your description, I am somewhat perplexed. Please post another image that details the BCS and actuator. If you disconnect the two, does it mean that only the BCS is bad or would both be defective?

Is the bypass actuator the same as a wastegate actuator? If the BCS is bad, should I replace both parts anyway?
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Old 04-12-2004, 04:55 AM   #23
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The actuator rarely goes bad and works normally when not connected to the BCS. Replacing just the BCS is probably fine. The wategate and bypass actuator are the same thing.
Ignore the tictacs. This is someone elses diagnosis procedure. The vac line that makes a sharp turn at the bottom is the one you want to pull off the actuator.
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Old 04-12-2004, 05:14 AM   #24
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Nothing like testing theories at 3:45 am.

I drove the car normally, it started making noise after passing succesfully through all gears. The boost was strong until the noise started, then it dropped down and acted erraticly. The RPM stayed steady. I got on it again, stayed on it for a few moments (after the noise started) to see if I let up when I heard the noise the first time. With the noise going, the boost was less than normal (bouncing around). I disconnected the hose from the actuator. Repeated the same steps, however, it showed no improvement. Apparently, my BCS is not the cause, or is it?

My boost guage reads from -10 - 0 - 10.
At idle, should any boost show on the guage?

What about during WOT?

Any idea where it should be under normal driving conditions?

Any other ideas you think will work?

I also tried to find the oil plug, could not locate it. Please help.

Bill
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Old 04-12-2004, 05:29 AM   #25
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Quote:
Originally Posted by William Aronson
Nothing like testing theories at 3:45 am.

I drove the car normally, it started making noise after passing succesfully through all gears. The boost was strong until the noise started, then it dropped down and acted erraticly. The RPM stayed steady. I got on it again, stayed on it for a few moments (after the noise started) to see if I let up when I heard the noise the first time. With the noise going, the boost was less than normal (bouncing around). I disconnected the hose from the actuator. Repeated the same steps, however, it showed no improvement. Apparently, my BCS is not the cause, or is it?

My boost guage reads from -10 - 0 - 10.
At idle, should any boost show on the guage?

What about during WOT?

Any idea where it should be under normal driving conditions?

Any other ideas you think will work?

I also tried to find the oil plug, could not locate it. Please help.

Bill
I wouldn't suspect the BCS then. If disconnecting it changed nothing, it'* not the problem. Boost should be about -9 or -10 at idle, about +9 at WOT. Cruising at highway speeds will show about -3. Does this problem only happen after the car has warmed up? It could be an ignition coil or a clogged catylitic convertor. Do you have a multimeter? You could check the resistances of the three coil packs. If one is different than the other two, it needs replaced.

The oil plug is behind the nose of the sc. You may have to get a flashlight to see it. It'* about a half inch in diameter with a hex head screw plug (4.5mm allen wrench to get it open). It'* about half way down the end of the left end of the SC, more or less under the plastic cover that holds some wires. Look between the alternator bracket and the SC.
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Old 04-12-2004, 05:35 AM   #26
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Gotta go 2 bed. I'll check again late morning.
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Old 04-12-2004, 05:39 AM   #27
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Does this problem only happen after the car has warmed up? No, it occurs when cold and when hot as well.

You could check the resistances of the three coil packs. I plan on changing all three (down the road) what do you suggest?


I presume that you read the rest of my postings, do you think that it is a faulty SC?

Anyone else have any ideas?

Would a low oil level cause it to make noise?
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Old 04-12-2004, 05:40 AM   #28
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Pic willwren has of plug location, the plug had been removed. You're looking down at the end of the supercharger.

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Old 04-12-2004, 05:46 AM   #29
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Quote:
Originally Posted by William Aronson
Does this problem only happen after the car has warmed up? No, it occurs when cold and when hot as well.

You could check the resistances of the three coil packs. I plan on changing all three (down the road) what do you suggest?


I presume that you read the rest of my postings, do you think that it is a faulty SC?

Anyone else have any ideas?

Would a low oil level cause it to make noise?
I'm not thinking it'* the SC, I don't see how it could not produce boost without being literally broken. When you change the coils, get MSD. A bad bearing could make a whine, but if it comes and goes regardless of temp, I have my doubts. My alternator made a whine when it was going bad, but didn't cause any drivability problems till it totally failed. Low oil could make a whine if bearings aren't properly lubricated.
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Old 04-12-2004, 11:32 AM   #30
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I'll buy alternator whine for sure. If the BCS appears to be good, I'd start thinking about a sticky bypass (wastegate).
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