overboost....on a SS/Sc cobalt wtf

[1966 dart wagon]

My friend recently bought a 06 Supercharged SS cobalt, he has had the dealer do some warranty work on it already...stupid chevy, and now he is claiming it is over boosting......my question:

How is that even possible in a supercharged application? :confused:

I just laughed but o well, and after searching google and some cobalt forums ive come up with nothing...thoughts?

[Tony Hanna]

How much boost is it supposed to make and how much is it actually making? Maybe the PO put a pulley on it without the supporting mods? Just a wild guess...

[Tony Hanna]

Just did a little bit of reading. It looks like the SC Cobalts have a bypass valve that's controlled by the PCM.



Operation
Supercharger boost pressure is regulated to prevent engine and drive train damage. When the engine is operating under high boost conditions, the powertrain control module (PCM) limits boost pressure to 83 kPa (12 psi). The PCM disables boost under the following conditions:

• When reverse gear is selected

• When the engine coolant temperature (ECT) is excessively high

• When drivetrain abuse is detected

• When the vehicle is decelerating

• If an intercooler pump failure is detected

• If the intake air temperature (IAT) sensor 2 becomes excessively high

• Under heavy load in first and second gear at engine speeds above 5,800 RPM

The PCM controls boost pressure by using the boost control solenoid. The boost control solenoid is normally an open valve. Under most conditions, the PCM commands the boost control solenoid to operate at a 99-100 percent duty cycle. This keeps the solenoid valve closed and allows only inlet vacuum to control the position of the bypass valve. At idle, engine vacuum is applied to the upper side of the bypass valve actuator, counteracting spring tension to hold the bypass valve open. As engine load is increased, engine vacuum is decreased, causing the spring in the bypass valve actuator to overcome the applied vacuum, closing the bypass valve and allowing the boost pressure to increase. The bypass valve starts to close when the vacuum measures 250 mm Hg (10 in Hg) and is fully closed at 90 mm Hg (3.5 in Hg). When reduced boost pressure is desired, the PCM commands the boost control solenoid to operate at a 0 percent duty cycle. This opens the solenoid valve and allows boost pressure to enter the bypass valve actuator at the lower side to counteract the spring tension, opening the bypass valve and recirculating excess boost pressure back into the supercharger inlet.

Results of Incorrect Operation
An open boost control solenoid control circuit, an open ignition 1 circuit, or boost control solenoid valve stuck open will cause reduced engine power, especially during wide open throttle operation.

The boost control solenoid control circuit shorted to ground, boost control solenoid valve stuck closed or a restriction in the boost source or signal hoses will cause full boost to be commanded at all times and a possible overboost condition during high engine load situations.

A restriction in the vacuum signal hose to the bypass valve actuator or a stuck closed bypass valve will cause a rough idle and reduced fuel economy.

Maybe that could be the cause...

[1966 dart wagon]

Interresting read, i was thinking of it later, going....does it have a form of wastegate that is bad, another caviler guy said they do so I though that is probably the problem, weird.

thanks for the article Tony Hanna :thumb:

[Tony Hanna]

Interresting read, i was thinking of it later, going....does it have a form of wastegate that is bad, another caviler guy said they do so I though that is probably the problem, weird.

thanks for the article Tony Hanna :thumb:

You're welcome.
I thought it was interesting too. I was under the impression the boost from an SC was only regulated by pulley size until reading that. Learn something new every day I guess.:)

[TurboSedan]

yep, 3800 S/C has the BBV too. some people adjust them to get boost sooner (mounting holes are slotted) but that usually ends up with excessive KR on stock cars. not to mention bad MPG.

------------------------------------
Joshua Mitchell
'91 Dodge Spirit R/T
'87 Shelby CSX #667
'98 Buick Regal GS

[skitzo_inc]

I was upset when I looked at one. SS but not super charged, not turbo charged. Ecotech crap. :(

[anokabball24]

Just a case of a supercharger trying very hard to be a turbocharger. Poor thing.

[Tony Hanna]

I was upset when I looked at one. SS but not super charged, not turbo charged. Ecotech crap. :(

I believe Dodge did the same thing with the SRT appearance package on the Neons.
Supposedly the Ecotech isn't a bad little engine. I'm curious to see how the TC versions do. Might buy one in a few years when they can be had used for a decent price.

[Kevin]

The ecotec IS a good little engine... Pretty much better than any TD engine past or present.

When was the last time the Chrysler engineers published a book on how they took the 2.4l engine and made 1000hp? There's also loads and loads of SAE papers that GM engineers have out about various aspects of a turbo on the ecotec.

[CDNTurboZ]

I'm curious to see how the TC versions do. Might buy one in a few years when they can be had used for a decent price.

guys are getting now over 300 hp with just a tune

[BigAl]

My Auto Electrical teacher had an 06 SS that he traded on a 09. He had done a bunch of work to the 06 and said the 09 turbo was a lot faster stock.

[neongary]

I wonder how the PCM detects "drivetrain abuse"?