Henry3959

Im trying to put this into a timeline... So it sounds like it ran well with 13 psi of boost?

Did you still have good boost pressure before doing this?
How could the tune have changed? If it is only creating 5 psi of boost it isn't running right unless your boost hose is leaking.
How did you disable the MAF?
So it wasn't rattling before and is now? The worn out coupler will not limit boost as it still turns the same rpm.
You put a new MAF sensor into the CAI and a MAP sensor on top of the supercharger? Was it setting codes for either?

Josh Williams

Im the op's friend that works at the shop. The car boosted and ran fine other than the hesitation before throttle body cleaning and new air filter. Then immediately would not idle or boost past 5psi after those 2 things were done. Was running filthy lean so we had it tuned with hp tuners to richen it up a bit. The car idles now but still limited to 5-7psi. We have put a new maf, 02 sensor 1, and map sensor (one on top of supercharger inlet) on it to no prevail. With ignition on engine off, the throttle body opens to 99% via scan tool. I need to check it while going down road at WOT I guess. Actuator valve rotates freely and even with valve held shut with zip tie and boost solenoid plugged, boost is still limited to 5-7psi. One thing a little concerned about is WOT air/fuel ratio is only 13.2. I think it needs to be a little richer like 11.5. Either way for a supercharger it should provide boost regardless of fuel injection, given that the actuator is held shut with zip tie, there are no boost/vaccumm leaks, the engine rises to commanded rpm, and the throttle plate opens fully.

Josh Williams

I did another smoke test today and then immediately chased it with compressed shop air (regulated) and still no smoke presence (other than at the air filter). Seems to rule out any boost leaks so there's that.

Henry3959

You do not understand how total torque is provided. If the PCM is cutting back fuel and timing, little lone shutting down the throttle, you will not have enough performance to build rpms which won't let you build boost. This is how traction control also works. You can go full throttle in snow here and barely get the tires to rotate so he'll yeah, the PCM can shut down boost whether the bypass valve is wired open or not.

I diagnosed issues for GM for over 20 years when the Dealer failed to repair the vehicle prior to a buy back. Although it is very hard remote it is not impossible. Post your tune file and a lot of us will be able to help.
Is it not setting any codes?

Josh Williams

Your theory on timing and fuel works in a turbo application because a turbo is spooled up by exhaust gas velocity and volume, however a supercharger literally is only dependent on engine rpm and throttle position. The car has no problem achieveing redline under load (although it does seem slower than normal). Seems like simple physics to me. I will check throttle position at WOT under load tomorrow and post results. Thanks.

Josh Williams

If you were saying that fuel and timing are off and causing the throttle to not open fully would make more sense. But the fuel and timing alone are not the direct cause of low boost on a supercharger especially when boost management is bypassed.

Josh Williams

If the throttle opens fully tomorrow and we know it's working properly, I will try to get a data log/tune file from my tuner uploaded.

Henry3959

That would help a lot!
Ask your tuner to disable all forms of PCM Torque Management and retest. If there is an issue that the PCM sees and it is pulling back timing and fuel this will disable that... to a point

chevygirl2006

We don't really build boost. Sounds like your describing turbo applications. We floor it and our max boost is pretty much there. And you can take away as much timing as you want and the same amount of boost will be there. Same with fuel. I always have 22-23 psi no matter what the afr is or timing advance. Now when you change vvt settings it can change boost by a few psi.

Henry3959

I'm betting you like I have torque management disabled from retarding timing, pulling back fuel and shutting down the throttle as also used in traction control. I'm thinking he has an issue other than the SC limiting boost. With only 5 psi and a wired open valve I would expect expensive noises coming from the SC as he said it just started.

Josh Williams

Josh Williams

Throttle opens completely. Engine load seems low (WOT 3rd gear on flat road). Air/Fuel at 12.7

ECaulk

iTrader: (6)

Is your belt slipping?

You dont have any codes right?

ECaulk

iTrader: (6)

Also that AFR is commanded, the LSJ doesn't have a wideband sensor only a narrowband

Josh Williams

No codes now. How would you know for sure if belt is slipping? Would it be glazed over? Is 12.7 on narrowband rich enough?

ECaulk

iTrader: (6)

The narrow band isn't reading that. That is what the ecu is commanding no guarantee that is what it actually is.

As far as belt slip goes not sure how to tell other than by how much tension you have on the belt

Josh Williams

So just wanted to let you guys know since I hate a forum with no solution. The problem was the air filter that I installed was entirely too small to supply the supercharger with enough air to boost 12 PSI

Sharkey

iTrader: (1)

got pics of said air filter?

ECaulk

iTrader: (6)

Qfe

chevygirl2006

That does make much sense because when you restrict air flow boost increases.

Henry3959

On the exhaust side, not intake side. I would also like to see how small of a filter it takes to knock a 2.0 to it's knees.

Henry3959

If this was the case, shouldn't a log file have shown a vacuum at WOT on the incoming air pressure sensor?

Sharkey

iTrader: (1)

it would have. we could have picked up on that had we had a log file posted.

Josh Williams

Dont put these on an anything boosted... The map sensor (vacuum sensor) was still reading 6psi of boost as the op states and fuel trim values looked good somehow so i dont see how you could have pinpointed air filter restriction through a log file if you had one.

Josh Williams

There is always vacuum on incoming air??