No matter why it was ENGINEERED for the car, it serves a purpose.
If you are looking to play, treat your car right and tune it properly, don't rig it and hope it isn't hurting anything

 

That dyno was runnin weird that day alex...

 

I don't understand the point of this.

 

well it seems like no one knows exactly what the system does or what this mod bypasses...so until then ill just keep it the way it was meant to be

 

I work with vacuum every day. We have vac tanks where I work to stabilize vacuum supply. Our cars have the tank for the same reason, I assume.

 

Per your comments (and others) this is what I had assumed as well. Those guys started using the Dejon spring to hold boost but I'm not sure if(or exactly how)this is related on our cars. Maybe an engineer will chime in-I'd love to have a definitive answer how Dejon spring/tank delete/downpipe wi cutout (or combination thereof) affects bpv operation/compressor surge. I'm currently on stock spring and I've never used the cutout-I hope I get more than extra noise and a cel,lol.

Regarding the tank delete: I bypassed tank only(not solenoid) and my results have been the same stock/stg 1-the car has less lag. Not sure how this traslates to better dyno #'s though?

1 more thing-if you do this mod keep an eye on your vac hoses-mine developed a leak at the solenoid and threw a post cat lean code; a little trimming/reclamping took care of it.

 

i did this mod 3 days ago and after driving my cra around it did change performance. less lag and it is holding at 15 and peaking at 17-18 before i was opeaking at 15-16 so there was an obvious improvement

 

From GM ..... Read part thats bolded


Service Information
Home Publications Number Search New Bulletins Bulletin Search Feedback Help
2009 Chevrolet Cobalt | Cobalt, G5 (VIN A) Service Manual | Document ID: 2324723
#PIP4669A: Intermittent DTC P2261 Setting - (Aug 10, 2009)

Subject: Intermittent DTC P2261 Setting

Models: 2008-2010 Chevrolet Cobalt SS
2008-2010 Chevrolet HHR SS

This PI was superseded to update model years. Please discard PIP4669.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:

A technician may find DTC P2261: Turbocharger Bypass Valve Stuck Closed set with no problem found. It may be intermittent in nature or they may find the dtc will set after a hard acceleration, usually in third gear. DTC P2261 is a type B dtc and will not set on the first drive cycle the dtc sets, therefore multiple test drives should be performed to confirm repair.
Recommendation/Instructions:

SI diagnostics for this DTC states that the ECM compares the measured MAF reading to the modeled MAF and has detected a series of pulsations in the induction system that exceed a calibrated threshold. A snapshot of "Induction Data" will show the fault, however the tech may need to compare the snapshot data to another vehicle if they are unfamiliar with the readings. They should note a fluctuation and or a difference in the desired versus requested boost level. When diagnosing this dtc pay close attention to Circuit/System testing step #1. This step has you inspecting for any vacuum leaks, damage, restrictions, improper routing or connecting of the vacuum hoses on the charge air bypass valve solenoid, the charge air bypass valve, and the charge air bypass valve vacuum tank.

We have found leaking vacuum tanks causing this dtc. When testing the vacuum tank, care must be used or the results may not be valid. The vacuum tank has an integral check valve not noted in SI. To check the Vacuum Tank operation, disconnect the hose that runs from the tank to the Bypass Valve Solenoid at the solenoid and apply vacuum to the tank. The tank should be able to maintain vacuum with no decay. Note: If you remove the vacuum hose from the intake manifold and plug it and the decay stops the check valve is leaking, if the decay continues the tank itself is leaking.

Note: Front wheel drive platforms using the 2.0 Liter RPO (LNF) incorporate a charge air bypass valve supplemental vacuum tank. The purpose of the tank is to provide an instant source of vacuum to the bypass valve via the bypass solenoid (when it is commanded open by the ECM). This results in less pressure buildup under closed throttle conditions, thereby reducing compressor noise, surge and spool time.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.


WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
Š 2010 General Motors. All rights reserved.

 

I would be scared to remove it... Seems like it is their to improve performance. If it is deleted is it easy to re-instal?

 

What are the procedures on doing that mod?

 

Hmmm.

Seems to be a placebo mod

 

No dyno close to me

 

I'm thinking about testing it out. Seems like it is designed to slow you down. I will need to talk to Vince

 

that write up made it seem to REDUCE spool time, the opposite of what people are claiming.
If someone is running BOV to atmosphere, I can see it working, but they are claiming improvement when stock.
That GM document makes it sound important IMO. Reduces dead air in the tubing, which decreases surge, thus reducing spool time.

Unless the bypass somehow still allows proper blow off...

 

Rukkee FTW(again)
I'm trying to wrap my head around this,lol. If the tank is bypassed wouldn't it be getting a more direct vaccum source(when commanded)? Maybe the mod helps when the bpv is moving in a certain direction,idk.
Regardless how the car felt this is straight from the horses mouth so I'm thinking F it. Still doesn't explain why it's not on the rwd's.

Unnecessary in vaccum/necessary in boost ?

 

This sounds like you had a leak somewhere in the section you bypassed.

 

I just received my adjusted tune file back from Vince. Ill load it and try to get to the track this week and let everyone know how it runs.

 

What are the results after you inserted the new tune from Vince??? Do you feel better performance? I am wanting to do this tonight. Please reply back! Thanks

 

I havnt gotten to the track yet but this thing is a FN beast. It pulls so hard that its a bit scary. It spikes 26 PSI at full throttle and I think it holds 24 but I will get it to the track after I get back on the 27th. Leaving this suckass weather for 2 weeks in Arizona

 

Do you think i should do this mod and have vince update my tune? If you give me the go i will do it tonight.

Thanks!

 

Wow, I had no idea this thread was still going.
To clear some things up:

I only did the vacuum tank bypass. Not the entire solenoid bypass.

My car definitely pulls harder and has zero lag thanks to the vacuum tank bypass.

If the vacuum tank is there for a reason, my guess is to simply create lag, curbing torque steer, something magazine editors HATE. Seriously, read any magazine comparison of our car with other fwd turbo cars and they will whine and moan about torque steer (I'm looking at you mazdaspeed 3's). Better reviews=better sales. Or maybe the turbo lag is just a byproduct of this vacuum tank.

Also, why doesn't the solstice gxp, sky rl have a vacuum tank? (rwd=not having to worry about torque steer)

All I know is that my car is still running well and I have yet to throw any codes. The only bad side effect of this mod is slightly lower mpg (simply because I stay in the boost more often. )

 

I've had this mod done for quite a while. Only thing I get is the BPV goes off more often. I don't have turbo lag, and i do have more torque steer but good tires is for that

 

Did Vince tune you for this mod? Or did you just do it after you installed the tune?

 

well, i got the tune then did the mod however i did a data log afterwords and sent to vince and he said everything looked good so. Now I'm waiting for a update from my CAI so ill let you know what he says.

 

Thanks alot man! I'm thinking about doing this mod tonight. Very cool stuff!