I have an 06 cobalt ss/sc. I recently bought the car with zzp downpipe, catless exhaust and intake, a lean code, and a hesitation around 2800 rpms. So I bought a new filter for the cai, because it was super dirty, and I also cleaned out the throttle body. After that, the car would not idle and was running even leaner than before, And also the boost would not go above 5 psi. So first thing I did was a compression test and smoke test, mainly because I was curious and to make sure I didn't have a vacuum leak. Both turned out good. Then I put a new maf and map sensor(on the supercharger) on the car. Still didn't idle or run well. Now during all this time I had been watching the live data on a scantool. I finally figured it had to be in the tune. Me and a Good buddy made a custom tune with hptuners, After multiple data logs (no maf, only speed density) and the car is back to running right. Only problem now is boost. Can anybody give me some advice or share an,experience they had? Thanks

 

Bypass actuator on the supercharger. Do the bypass mod and see if it fixes it. If not, problem is elsewhere.

 

sorry, I forgot to mention it, I did that as well

 

if you did the boost bypass mod and it didnt fix the issue the bypass valve in the blower is likely jammed open.

 

which I'm guessing there is no repair to that, only blower replacement?

 

usually what happens is the bushings in the case seize to the shaft of the bypass shaft. with the blower off you can spray some penetrating oil into them and work the valve back and forth till it moves freely again.

 

If this is what's wrong, you should be able to watch the shaft to see if it moves when the engine is started then shut down

 

well I got on motologic and performed every step on the trouble tree for the boost control system. The actuator, the solenoid, and vacuum pressure seems to all check out fine. Also since I hooked up the boost gauge, I've started to notice that sometimes it will hit 6 or 7, but once it hits the peak boost, the boost level starts to drop off after that. So my guess is that it needs a new sc. Any other suggestions or opinions will be taken though.

 

My supercharger does a have a small rattle forming. Not sure if it's the coupler or the timing chain. If it does happen to be the coupler, could that cause my low boosting issue?

 

You might want to have someone with an HP Tuner log a drive. Timing and fuel also help control the overall boost. Chances are the timing or fuel is being cut back due to ECT or IAT temps.. Boost should only go up and level off once its peak efficiency is achieved.

 

I have hp tuner software and just made a custom tune myself, for the idle issue after exhaust and intake. Timing and fuel are right, ect and iat temps are good too. I have the aeroscan iat temp gauge. And also logged the iat temps during multiple drives throughout this past week with the hp tuner while doing the tune. It is a speed density tune, and not a maf tune. I have also done the boost solenoid bypass. Still the same issue. As I said earlier I also did every step to the trouble tree to the boost control system and the actuator and solenoid tested out fine. Which if the boost control system all tests out fine, and the tune is fine, then it leads me to think the sc has an issue.

 

even if the valve is moving it could be hanging open a little. doesnt take much to loose the boost your missing. id pull the blower off, remove the bypass actuator and have a good look at it.

the blowers themselves do get some wear on the rotors and the case, but they dont generally lose that much boost. its usually an actuator issue or a leak.

you didnt mention what pulley you have, along with other mods.

 

stock pulley, it's got 50# injectors in it for some reason. Aem cai, zzp catless downpipe, zzp headers, And zzp catless exhaust. I have smoke tested the motor 4 Times and no leaks, not even an evap leak. I vacuum tested the solenoid and the actuator according to the trouble tree and they both tested out fine.

 

pull the blower off and have a look at the bypass valve itself. only takes 10 minutes to pull it off.

 

the actuator arm moves freely. We took the actuator off and the valve rotates freely in both directions. (from stop to stop) my buddy ziptied the actuator arm closed thinking the spring was to weak to hold it down under boost. But still nothing get 5 or 6 psi.

 

You could post your tune and a log file.

 

I don't have the computer with me right now or I would. But I can promise you the tune is fine. Its a gm stage 2 tune, just slightly modified for the upgrades.

 

Is this the highest boost you have seen the car do?
Do you have an evap smoke machine or a high pressure unit. The evap units only produced 1/2 pound of pressure.

Maybe post a pic of your Torque management / Supercharger settings. I think these are the stock Stage II settings.

 

no. When I first bought the car is was hitting 12/13 and holding steady. Which is a big difference from 5 or 6 and bleeding off through the rpms. When going to 5 or 6, it doesn't hold boost anymore. Yes. My buddy works at a shop and has all the necessary scan tools, smoke machines, etc. We have smoke tested the intake and evap systems 4 times each. I can't post a pic because my buddy has the laptop with hp tuners on it, he's tuning his ls.

 

I pretty much remember that chart from looking at it so many times, but it all looks the same besides my etc boost is at 100%. What I'm saying is, if you take off the 2 vacuum hoses from the actuator and plug both of them, and ziptie the actuator arm in the closed position, then the supercharger should have no choice but to boost, because there is no longer a way the computer can control it. Right?

 

The bypass valve is just one aspect of overall boost. Fuel and timing are also pulled back to adjust overall boost.

 

I don't think you're understanding. the computer would realize timing and boost Are off and then would decrease boost through the computer telling the boost solenoid to. With the boost solenoid not even connected to the actuator and the actuator arm ziptied closed, it has no choice but to boost. There is literally no way for the computer to Tell the supercharger to stop boosting. Its all mechanical at that point.

 

You're forgetting the ECU can close the throttle body limiting the air to the supercharger.

 

I understand that you have zip-tied the valve, but that is not the only thing controlling power.
Did you not know that the valve is not the only item controlling boost? Fuel, Timing and the Electronic throttle all are used in controlling overall boost.

If there is an input telling the PCM to cut back boost, it can be done with the valve, timing, fuel and the throttle motor. As ECaulk mentioned, you can have your foot to the floor but the throttle body can still shut the throttle plate.

The reason I am pointing this out is you are blaming the SC and the SC is likely not the issue.

 

It could be the supercharger is if something damaged the rotor pack or the air filter is completed caked (but OP said he had a new one installed).

Could also be the MAP and bar sensor connections are backwards.