V1 Mikes Extended, Full Frame Goblin - 2009 Cobalt LS with 135k donor

[mike_sno]

And now I am completely confused, but convinced that I have something wrong wired. Seems like A is the bypass valve actuator?
The boost control solenoid is what I have labeled as the Air bypass valve? This is in bypass mode when the PCM commands 0-98 which is 0V at the plug and is closed when the PCM commands 99-100 12V at the plug??

 

[Ross]

Your car should have the green hose connected like in the picture... but I don't think this will fix your low boost issue. It will allow the PCM to stop boosting under the conditions you listed in the article.
The SC bypass valve is what you called "A". The bypass takes about 5lbs of force, but it moves by hand pretty easily.

...
And now I am completely confused, but convinced that I have something wrong wired. Seems like A is the bypass valve actuator?
The boost control solenoid is what I have labeled as the Air bypass valve? This is in bypass mode when the PCM commands 0-98 which is 0V at the plug and is closed when the PCM commands 99-100 12V at the plug??

You got it right.
After reading the Boost Control System Diagnosis article (many, many times), this is what I got out of it:
- 12V (actually PWM 100% duty cycle) at the bypass valve actuator = SC Boost. 12V will allow atmospheric pressure to the blue hose, allowing the bypass valve to close from its' internal spring pressure, giving the engine boost. (Both sides of the diaphragm are nearly the same pressure, so the spring succeeds at pushing the rod out), If the engine is at idle, boost will stop, as the intake vacuum will compress the spring in the diaphragm.
- 6V (actually it is a PWM signal with 50% duty cycle) at the bypass valve actuator will half open it, half boost to the engine.
- 0V = no boost. 0V will open the bypass valve, allowing boost pressure to go down the blue hose, which opens the bypass valve, and stops the SC from building boost, by recirculating the excess air.

My thoughts/guesses/2 cent opinion:
- Is your intercooler laminova tube's fins plugged up?
- is your bypass valve out of adjustment, and not closing all the way? This would allow boost pressure to recirculate, diminishing boost.
Your boost line (green line in my picture) being disconnected would have stopped the PCMs ability to shut off engine boost... Only leaving idle intake vacuum able to shut off boosting.
- is your SC wore out? If the SC bearings wear out, the lobes can contact the outer SC casting, and then your SC isn't sealed well enough to make decent boost numbers.
- is there a leak in the post-SC gaskets that is letting out boost?

 

[mike_sno]

Your car should have the green hose connected like in the picture... but I don't think this will fix your low boost issue. It will allow the PCM to stop boosting under the conditions you listed in the article.
The SC bypass valve is what you called "A". The bypass takes about 5lbs of force, but it moves by hand pretty easily.
View attachment 44877


After reading the Boost Control System Diagnosis article, this is what I got out of it:
- 12V (actually PWM 100% duty cycle) at the bypass valve actuator = SC Boost. 12V will allow atmospheric pressure to the blue hose, allowing the bypass valve to close from its' internal spring pressure, giving the engine boost. (Both sides of the diaphragm are nearly the same pressure, so the spring succeeds at pushing the rod out), If the engine is at idle, boost will stop, as the intake vacuum will compress the spring in the diaphragm.
- 6V (actually it is a PWM signal with 50% duty cycle) at the bypass valve actuator will half open it, half boost to the engine.
- 0V = no boost. 0V will open the bypass valve, allowing boost pressure to go down the blue hose, which opens the bypass valve, and stops the SC from building boost, by recirculating the excess air.

If I understand that right I took away the possibility of the ECU to remove boost from the engine. The Boost Solenoid duty is logged in the log ans is always at 100%. It was never necessary to take away boost, because I always had pressure on the side where the blue hose is connected.

It make sens to me that the 0V is No boost. Whatever could go wrong, the engine would run with no boost. (Cable broken, solenoid defect, fuse,...)

 

[mike_sno]

I blew with my compressor on one side of the valve. It is moving, just not very much, I thought there is a hard stop and it would move to the other side when I did it by hand.

 

[Ross]

Your bypass valve barely moves. Is it stuck on boost only? Look how far mine rotates when I push on it with a screwdriver.
The green side is longer than the red side on my bypass valve.
Your compressor just put 100 PSI boost in the diaphragm, and ruptured the diaphragm???

SC bypass open, No boost:

SC bypass closed = making boost.

 

[mike_sno]

SC bypass open, No boost:
View attachment 44878

SC bypass closed = making boost.
View attachment 44879

Mine is definitely not moving that far.

 

[Ross]

Push on it with a screwdriver... see if it is just a bad diaphragm (screwdriver moves it all the way down),
or if it is a bypass valve issue (screwdriver can't move it anymore than the diaphragm can).
Your bypass seems to go to full boost, so this doesn't explain why you are only getting 5psi boost.

 

[mike_sno]

I removed the bypass valve. The shaft which comes out of the Supercharger is not moving. I guess I have to take the SC off and see what's going on.

 

[mike_sno]

It is moving, but only a few degree, then it has a hard stop at both sides. Way less as yours is moving.

 

[Ross]

Maybe cleaning the laminova tubes will give you more boost pressure. Also pulling the SC will give you a chance to see how worn your SC lobs are.

 

[mike_sno]

This is the problem, I just don't see anything which is blocking the movement. https://youtube.com/shorts/C-e_lZgKoyA?feature=share

 

[mike_sno]

Well, brute force and some oil got it working. I had to use pliers with not to much force, but to much for moving it by hand. Then rotating up a few times and not its easy to turn.

 

[Ross]

So the bypass valve wasn't closing or opening! Glad you found the issue, and already have it fixed. New boost numbers coming soon!
The SC lobs look good too, you still have the black coating on them, so the SC bearings are doing there job.

 

[mike_sno]

Everything is back together and installed. Tomorrow morning I will make a test drive. I took a video of the lobs. https://youtube.com/shorts/or7NWmMbmy8?feature=share I saw them when I repaired the Head, but did not take a video. I think they look decent ?

Yes, the valve was not completly opening or closing. It was stuck somewhere in between. Now it almost makes a full turn, with no resistance and is sitting nicely on the hardstop. I adjusted the hardstop in a way that it is at the point where the valve is completely closed.

I think I also did not damaged anything with the compressor. I pushed the rod manually in and out and closed put my finger on either of the hoses. The rod just moved a bit until the vacuum / pressure in the hose stopped it from moving. Seems like, I was lucky this time. Thanks for all the help !!!

New log file coming soon. If that was just 5psi, I am on pins and needles !!!

 

[Rauq]

Seems like things are pretty well sorted, I'm looking forward to hearing the results. Here's to hoping it makes good boost now- that bypass actuator hose routing was certainly stopping it from making boost.

 

[mike_sno]

Well, now we have boost. At least some sort of. I took the car for a ride this morning. In the attached log file you can see at minute 17 and 45 sec. that the boost gooes up from 3psi under 5300rpm to about 14psi above 5300rpm. I can feel a decent kick in the back when this happens.

When I stopped I looked at the bypass valve in the SC again. And it IS stuck again half open. I put some more oil on it, but it seems there is another problem. Might be that the valve gets closed when enough Vaccum is gone, but this is for sure part of the issue. I wonder if this is fixable. I did not take the shaft out yesterday and looked at the bearings/bushings.

Maybe even more in the tune.

Speedometer is still off.

 

[mike_sno]

FYi, I made a roundtrip and while the engine was waruming up. I did not push it to hard. But I can see that in the logfile, I have more boost lower. That was what I felt as well. I guess the shaft of the valve must have locked up later on.

 

[Rauq]

The valve does have stops of some sort. I know you can't get much more than 90° of rotation out of it. If they're not solid stops, I could see them getting gunked up and stuck. I seem to remember that you could jam it stuck in one direction or the other, but I can't remember which.

That the boost gooes up from 3psi under 5300rpm to about 14psi above 5300rpm. I can feel a decent kick in the back when this happens.

That does sound like it's sticking.

Speedometer is still off.

What tire size are you running? If the speedometer is running 10% high, you can use the Gear/Tire Wizard in HPT and Manual Scale it with a 0.91 multiplier to adjust it down.

 

[Dale E]

So, now you have your hoses hooked up properly, but do you have the by pass valve adjusted properly? There should be a set screw (stop/limit) for the flapper and there should be at least one mounting hole slotted for a fine tune adjustment. Also, unhook the by pass valve and operate the rod by hand. measure the travel. Then on the car place a zip tie on the shaft and as you drive it will move so you can measure the working travel of the shaft.

https://video.search.yahoo.com/search/video?fr=mcafee&p=SC+bypass+valve+adjustment&type=E210US370G91821#id=2&vid=869b643f45849e857b55744604ebecd9&action=click

 

[Gtstorey]

For wheel size, you can't just use a calculator for your labeled tires size to get diameter. Best way is to measure circumference and divide by PI. Or measure the distance traveled with one rotation. But as Rauq said, you can just tweak it until it reads correct.