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Old 08-02-2007, 01:42 PM   #1
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Default low boost? 2000 SSEI

How do you read the boost gauge and what is normal range? My gauge is normally in the -side of the gauge when cruising at 40 to 50 mph. I do not see go into the positive side unless i punch it. At 65-75 mph it sits just below 0 on the negative side. I heard these SC cars are prone to bad boost control solenoids. Can i diagnose this without an OBDII scanner? Thank to all replies.
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Old 08-02-2007, 02:01 PM   #2
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Boost should be negative cruising on level ground. Anytime you give it half throttle, the boost should be around zero, and increase as you push harder. Cruising at 70, mine sits at around -5 psi. It'* difficult to tell if yours is acting up from your description, because it sounds pretty normal.

If you take the electrical connector off the boost control solenoid (BCS) and the boost behavior changes, either the BCS is bad or the PCM is telling it to dump for some reason. And a scanner would tell you more. What is the boost at WOT?
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Old 08-02-2007, 06:24 PM   #3
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Default Re: low boost? 2000 SSEI

Quote:
Originally Posted by howard chaput
How do you read the boost gauge and what is normal range? My gauge is normally in the -side of the gauge when cruising at 40 to 50 mph. I do not see go into the positive side unless i punch it. At 65-75 mph it sits just below 0 on the negative side. I heard these SC cars are prone to bad boost control solenoids. Can i diagnose this without an OBDII scanner? Thank to all replies.
That sounds normal. Most people don't know (i didn't know back then) that your supercharger has a clutch on it. If you drive normally (up to 0 psi on the boost gauge), then you're not really using the supercharger. Anything over 0 on the plus side, then you're getting boost and using the supercharger, but you really have to push down the pedal to get that boost out of the supercharger.
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Old 08-02-2007, 06:38 PM   #4
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There is no clutch. Just a vacuum controlled valve that opens so much based on air pressure difference between the SC inlet and outside air pressure. The further open the throttle is, the closer the SC inlet air pressure will be to outside, and the valve closes appropriatly. The SC is always pumping the same amount of air per revolution, just varying amount get dumped back to the SC inlet. If you look, you'll see that the bypass valve is closed when the engine isn't running because no air is moving and the pressures are equal. Now, the BCS, under the PCMs command, can allow air pressure in the SC outlet to the bypass valve actuator. That will make the air pressure difference greater, and open the valve more than it would have been so it dumps more boost back to the SC inlet.
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Old 08-02-2007, 06:57 PM   #5
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Quote:
Originally Posted by howard chaput via PM
at wot it will increase to 5 lbs. max
I think that is a couple pounds low for a Series II. I could be wrong.
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Old 08-02-2007, 09:52 PM   #6
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Default 2000 ssei

Today i mashed it and maximun boost was 5 lbs. Is this the max a stock unit puts out without mods?
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Old 08-03-2007, 02:24 AM   #7
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7psi is probably normal.

You need to check for vacuum leaks, or any other condition that may cause your PCM to dump boost.

When you're idling, and you pull the vac line off the boost control actuator (the round black device mounted to the front of your SC), does the arm fully extend and retract smoothly?
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Old 08-03-2007, 10:03 AM   #8
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Slight off topic..

Seeing you are in Mass. There is a mini meet going on this weekend where we could help you diagnose any possible issues. 06082 or basically 10 miles south of Springfield Ma. PM me if you are interested.

Another factor to consider is our weather in the area has been extremely humid and quite hot. Under these conditions you may be seeing a slight bit of KR at WOT and I would think 5lbs is probably about right for the weather.
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Old 08-03-2007, 09:41 PM   #9
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Quote:
Originally Posted by J Wikoff
There is no clutch. Just a vacuum controlled valve that opens so much based on air pressure difference between the SC inlet and outside air pressure. The further open the throttle is, the closer the SC inlet air pressure will be to outside, and the valve closes appropriatly. The SC is always pumping the same amount of air per revolution, just varying amount get dumped back to the SC inlet. If you look, you'll see that the bypass valve is closed when the engine isn't running because no air is moving and the pressures are equal. Now, the BCS, under the PCMs command, can allow air pressure in the SC outlet to the bypass valve actuator. That will make the air pressure difference greater, and open the valve more than it would have been so it dumps more boost back to the SC inlet.
I stand corrected.
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