Kuntryboy865
New member
mine does that if im just grannying around but if im giving it some.gas it sounds normal.
Sent from my KFTT using Tapatalk
Sent from my KFTT using Tapatalk
Bypassing the the bypass valve solenoid.
- Thread starter MPFab
- Start date
2014 Blue RS
Active member
This is my experience as well. Car seems much happier under throttle then putzing from light to light.
CheapFuneral
New member
I just did this, didn't feel a noticeable difference. Im stock so not sure if that's y. Going to the track Friday, but I doubt I will see any difference in numbers.
Mikeygoolsbay
New member
How bad is it if it does this. It's does it in at city speeds with about 50% throttle in high gears. But it also does it intermittently on the highway
ReeseLightning
New member
I honestly don't know enough about it however if you can tell it doesn't sound right maybe post some pics and vids so we can help assess the situation
CheapFuneral
New member
I hear my turbo spooling but i don't hear the blow off with the windows open. How loud should it be? (Not sure if it was there before or not)
Mikeygoolsbay
New member
I have a ddm intake and heatshield
CheapFuneral
New member
Lol I dont think I have flutter dumb just asking how load the stock blow off is and if I should hear it after this mod. I'm completely stock other than this mod.
CheapFuneral
New member
Ok thanks. I just wanted to be sure. Also no noticeable difference, I'm guessing for the same reason.
Preloader
The M32 Martyr
A full understanding of what this bypass bypass does will help you know what you should be feeling. It's not gonna add peak power to your car.
The intake manifold has a vacuum reservoir molded into the bottom. This way The ECM has a vacuum source, when the intake is under boost and is unable to provide vacuum.
It then applies this stored vacuum to the BPV to keep it cracked open after a shift or a blow-off of boost to "cushion" the effects of returning to full boost when mid-full throttle is requested.
So you pretty much won't feel much difference in lower RPM where boost is slow to build anyway. You will be more inclined to feel it after a shift in the higher (above 3k) rpm shifting where this little turbo is ready/willing to supply full boost.
With this bypass solenoid bypassed, you should feel an immediate return of acceleration, where stock, you would get a "cushioned" return to peak power.
The intake manifold has a vacuum reservoir molded into the bottom. This way The ECM has a vacuum source, when the intake is under boost and is unable to provide vacuum.
It then applies this stored vacuum to the BPV to keep it cracked open after a shift or a blow-off of boost to "cushion" the effects of returning to full boost when mid-full throttle is requested.
So you pretty much won't feel much difference in lower RPM where boost is slow to build anyway. You will be more inclined to feel it after a shift in the higher (above 3k) rpm shifting where this little turbo is ready/willing to supply full boost.
With this bypass solenoid bypassed, you should feel an immediate return of acceleration, where stock, you would get a "cushioned" return to peak power.
Preloader
The M32 Martyr
The difference in sound, if you have an aftermarket air intake is not so much that it is louder, but that it is crisper. Because the BPV is actually going from fully seated/sealed, to blow-off (recirc). Stock.... the BPV is often prevented from fully seating by this controlled vacuum source, so when it blows-off (recircs) it doesn't make such a sharp release of pressure; softer sound.
CheapFuneral
New member
Ok thanks 
Tried The Bypass Mod
I tried the bypass mod yesterday and went back to stock today.
I read the complete thread about it on this site and also ventured over to Cruze Talk to get some input. It seemed logical that bypassing a solenoid which bled off boost at the ECU's command would increase power. In all actuality I experienced slower response and decreased power after the mod. The car was noticeably quicker after the bypass mod was reversed.
This got me thinking about the auxillary vacuum system GM put in place on the 1.4T Ecotec. Why would they develop an elaborate, separate vacuum system just to control boost and power delivery? That doesn't seem very cost effective considering they can effectively control boost with the boost control solenoid which is already in place and a necessary component for the production engine.
Also, I recognized the sound the compressor bypass valve (bov) was making after doing the mod. It was reminicant of the sound I heard after "crushing" the factory bov on my old Lancer Evolution. Depressing the hat on the factory metal valve would increase the spring pressure resulting in less acuation. Meaning, it was harder for the valve to open. This bypass mod on the 1.4 Ecotec produced the same result.
The difference is the Sonic valve isn't harder to open because of a stiffer spring, it's due to a weak vacuum source. I believe Chevrolet designed this auxillary vacuum system on our cars to aid in proper function of the bov. The intake manifold does not have a large plenum and isn't enough to actuate the bov on its own. Increasing plenum volume would shift the powerband where the average consumer would find less desirable. And a weaker bov spring wasn't the answer because it wouldn't hold enough boost pressure to reach production power goals. Hence, the vacuum chamber and control solenoid.
Now, this is only my theory derived from a little automotive knowledge and experience, and my own personal test bed. I do not have any numbers nor data to back up my theory but I can say with complete certainty that this mod decreased performance.
I tried the bypass mod yesterday and went back to stock today.
I read the complete thread about it on this site and also ventured over to Cruze Talk to get some input. It seemed logical that bypassing a solenoid which bled off boost at the ECU's command would increase power. In all actuality I experienced slower response and decreased power after the mod. The car was noticeably quicker after the bypass mod was reversed.
This got me thinking about the auxillary vacuum system GM put in place on the 1.4T Ecotec. Why would they develop an elaborate, separate vacuum system just to control boost and power delivery? That doesn't seem very cost effective considering they can effectively control boost with the boost control solenoid which is already in place and a necessary component for the production engine.
Also, I recognized the sound the compressor bypass valve (bov) was making after doing the mod. It was reminicant of the sound I heard after "crushing" the factory bov on my old Lancer Evolution. Depressing the hat on the factory metal valve would increase the spring pressure resulting in less acuation. Meaning, it was harder for the valve to open. This bypass mod on the 1.4 Ecotec produced the same result.
The difference is the Sonic valve isn't harder to open because of a stiffer spring, it's due to a weak vacuum source. I believe Chevrolet designed this auxillary vacuum system on our cars to aid in proper function of the bov. The intake manifold does not have a large plenum and isn't enough to actuate the bov on its own. Increasing plenum volume would shift the powerband where the average consumer would find less desirable. And a weaker bov spring wasn't the answer because it wouldn't hold enough boost pressure to reach production power goals. Hence, the vacuum chamber and control solenoid.
Now, this is only my theory derived from a little automotive knowledge and experience, and my own personal test bed. I do not have any numbers nor data to back up my theory but I can say with complete certainty that this mod decreased performance.
Reading your description leads me to believe you may have accidentally done it wrong. I had someone contact me with similar results initially, but after figuring out that he had a couple vac lines wrong it fixed the issues. My advise is to try again and double check everything.
Your theory as to why the chamber/solenoid are there is not correct. It is there as a form of torque management. It can and will open the valve and hold it open to prevent ANY boost from being made. Put your Sonic on a dyno and try to do a pull without pulling the ABS fuse. The car will initially start to build boost, then after sensing the front wheel are turning and the rears aren't, it will open the BOV and hold it open. It will stay like that too for several minutes. You will not have any boost until it decides to release the open BPV. A boost solenoid can only drop boost to the base rate of the actuator which will degrade power to the drive wheels. The ability to hold the BPV open utilizing the solenoid and vac chamber, destroys power to the front wheels.
The vacuum in the plenum is more than enough to actuate the valve. My car idles with 22" on the gauge. Vacuum developed by the engine is a function of the pistons moving in the cylinders, and timed events of the valve train. It isn't dependent of the volume in the plenum..
Your theory as to why the chamber/solenoid are there is not correct. It is there as a form of torque management. It can and will open the valve and hold it open to prevent ANY boost from being made. Put your Sonic on a dyno and try to do a pull without pulling the ABS fuse. The car will initially start to build boost, then after sensing the front wheel are turning and the rears aren't, it will open the BOV and hold it open. It will stay like that too for several minutes. You will not have any boost until it decides to release the open BPV. A boost solenoid can only drop boost to the base rate of the actuator which will degrade power to the drive wheels. The ability to hold the BPV open utilizing the solenoid and vac chamber, destroys power to the front wheels.
The vacuum in the plenum is more than enough to actuate the valve. My car idles with 22" on the gauge. Vacuum developed by the engine is a function of the pistons moving in the cylinders, and timed events of the valve train. It isn't dependent of the volume in the plenum..
I did run all new vacuum hose. I ran a line directly from the bov to the intake manifold. The factory line from the chamber to the solenoid was left alone and the other two ports on the solenoid were capped.
