I am an ASE certified mechanic and I have the 2006 Cobalt SS/SC G85 package, 12000 miles, CAI is all.

I noticed reciently that when I gunned it the boost would go up to 12.5 at 4000 rpm's then as the rpm's climbed the boost would deplete down to 4 or 5 psi?

I thought it might be the belt and tensioner causing SC belt to slip dealership replaced for free.

That didn't fix it. I did some troubleshooting of my own and found if I took the plastic boost cylinoid out of the vacume loop the boost would work great! Carefull cause the car is smart and will put you in limp mode!!!!!

Meanwhile I always had a problem with 5th and reverse found that GM put out a tech article on the problem. with the 2006 ss/sc the 5th / reverse syncro's where fualty and should be replace while under warrenty!

If there is anyone else out there with this problem let me now so I can submitt it to GM!

 

Mine would do the same thing, under heavy acceleration boost would jump to like 12psi, then quickly drop down. But I ended up finding out my clutch was toast instead.

 

Cool Thankyou for your in put anyone else?

 

If its not a slipping belt it may be a slipping clutch. hahaha. something is slipping around here!

 

no problems. but good tip.

 

his clutch is good, his belt is tight, it goes great sometimes and other times it boosts strong and then it just lets go of the boost. the rpms still climb at a very slow rate but the boost is gone. any more ideas

 

Holy S^&* a light bulb came on! I checked a thread on how to install EBC. I saw how they by passed the boost control solenoid. Low and behold it worked!!!!!!!! I placed a vacume cap on the output of the solenoid and pulled the vacume hose off of the bottom of the boost actuator leaving it open to atmosphere, and whalla 12.5 lbs at 3000 and beyond to redline! I can finaly enjoy the Cold AIR Intake. I drove the car for 30 minutes and no CEL and I scanned it and no codes. Wholly **** does it pull HARD I got on the highway and gunned it from 30-140 in about 14-16 seconds. I mean to tell you it pulls with this intake! So more importantly what made my car limit boost? Why did by passing the boost solenoid fix the problem? And what do I tell GM/dealership when I go back? Please feed me back! Also, is it true when you get an HP Tune done they electricly by pass the boost solenoid anyway?

 

whats the deal with the tranny i have 3000miles of warrenty left and what should i tell them when i go there my reverse sucks ass it always grinds

 

Greate question they told me that was normal at Bob Valenti chevy in Mystic, CT! And did not fix my car yet I'm currently trying to talk to GM corporate a Mr. Charles Furry!!!!! Good look with that little time let?>

 

I did that bypass thing and like idk if it worked I maybe got like .75 psi I'm suppose to be getting 17.5 why the he'll am I only getting 16.25..and is it fine to drive with it bypassed

 

whats the deal with 5th and reverse? mine grinds or doesnt want to go in at times?

 

Not being a dick, but I see your sig says 305 hp With a 2.79 and 42's??

 

Yes I make 305hp if you had your car tuned at corvettes of westchester youd understand I have a very good tune can someone answer to my post?

 

Altitude and temperature?

Maybe he means at the flywheel.

 

I dont make 305hp to the ground

 

Oh, to the flywheel seems logical than. Was gonna say "BS!" (or you had N20) cuz I have the HTV1320 and it's WAY more efficient than the m62

 

yea man 305hp hp to the wheels that's pretty crazy I wish lol but anyway I mean ppl say they get 17.5 psi on 42# and I'm only getting like 16.25 I did the bypass not much difference..why is this could getting 62# give me the extra boost

 

Location, elevation, and weather/atmosphere play a part in psi. you're only .75 away from where you "should" be on the 2.79. My 3.1 on my TVS hits 20-20.5 and my friend hit's 20.5-21.5 on a 3.1

 

ok but will larger fuel injectors help to..and how about the dual plate intercooler any one have it and what do you think of it

 

Its not elevation and temp yesterday was hot out my car for some reason was acting faster..was hitting 17.25 psi

 

boost byepass mod is bad!!!! I have seen one motor already crack a piston from that. If i where you i would hook it back up.

 

wat is so bad about boost by pass

 

Heres some reading for you.
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.


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arite good enough for me I'll hook it back up..it does give me alil more boost though but w.e will 60# give me alil more boost

 

The only problem is, I've taken it to the dealership and they cant find the problem! I don't understand I have a GM scanner with alldata and I was unable to find an issue the only thing I can think is my actual electric control cylinoid vacume diverter is ripped so under perportionate boost the diaphram leaks by causing the issue however not sending a signal to the ECU. Without a CEL the dealership wont fix it and I'm just to cheap to do it my self!