Author Topic: Turbo Bypass Valve (Read 12203 times)

Brazen17 · « **on:** July 09, 2010, 04:52:34 PM »

What is the turbo bypass valve and what does it do? Anyone know where it is located? If it were to fail what types of symptoms might it produce? Today I soldered the GMPP Stage 1 connectors and it made no difference in the performance of the car. Max psi of 12 and after driving it a few minutes won't make more than 5 psi. Still waiting for the dealer to call and tell be the valve is in (back ordered almost 3 weeks ago) so they can install it. Hope this fixes my car. It is getting lonely sitting out in the garage!

DeepBlueGXP · « **Reply #1 on:** July 09, 2010, 05:14:42 PM »

We have a surge valve and it's located on the front of the turbo. It has a tan cover and 3 10mm bolts with a hose coming off it. You can see it here under the elbow on the top left

shabby · « **Reply #2 on:** July 09, 2010, 07:04:39 PM »

Quote from: Brazen17 on July 09, 2010, 04:52:34 PM

Today I soldered the GMPP Stage 1 connectors and it made no difference in the performance of the car. Max psi of 12 and after driving it a few minutes won't make more than 5 psi.

When you installed those gmpp sensors... did you load the gmpp tune? Because without the gmpp tune those sensors do you no good.

Brazen17 · « **Reply #3 on:** July 09, 2010, 07:38:11 PM »

Quote from: shabby on July 09, 2010, 07:04:39 PM

When you installed those gmpp sensors... did you load the gmpp tune? Because without the gmpp tune those sensors do you no good.

Yah. I bought the kit about a year and a half ago and it worked fine the first year. Then it would lose boost, making maybe 5-7 psi. A restart would clear it up. Hell, when it first started doing it, it would clear up on its own within a minute or two. The last couple of months it's been really bad and now all a restart will do is get me to 12 psi for a short time before it drops back to 5 psi. That is why I was wondering what this turbo bypass valve did and if it would cause the symptoms I am having. I went ahead and soldered the wires just to see if that might clear it up but it did not. Took it for a drive and could only hit 13 psi and about a mile later back down to 5 psi. Just gonna leave it in the garage and wait for the nationally back ordered valve to come in. I thought these turbos were used in several different manufacturers cars? Oh well...

shabby · « **Reply #4 on:** July 09, 2010, 07:48:31 PM »

Take out the diaphragm from behind the cap cover of the bypass valve and inspect if its cracked/worn. If not then do a boost leak test and check the wastegate arm to see if the nuts are still secure.

Brazen17 · « **Reply #5 on:** July 09, 2010, 07:57:12 PM »

Is there a procedure for the boost leak test and if so where can I find it? I will inspect the diaphragm tomorrow. Will either procedure invalidate my extended warranty?

shabby · « **Reply #6 on:** July 09, 2010, 10:00:00 PM »

The idea of a boost leak test is to pressurize the intercooler pipes by capping off the turbo and pressurizing the pipes with air to around 20psi or so. I have a cap that i put on the turbo that has a pressure gauge on it, i simply apply pressure through a fitting and watch the pressure rise and listen for leaks.
Now since one of the pcv lines is directly connected to the turbo you're going to have to take it off and cap that too otherwise it'll leak. Personally i wouldn't bother with all this if you're worried about warranty, let the dealer figure it out.

Brazen17 · « **Reply #7 on:** July 10, 2010, 01:38:26 PM »

Does the turbo bypass valve operate the same or similiar to an after market BOV? Took the wife to breakfast this morning and on the way over the car would hit and hold 13 psi. On the way back it would only make 5 psi but would not hold it. It would bleed back down to 0 psi every time.

Gentleman Jack · « **Reply #8 on:** July 10, 2010, 02:16:58 PM »

Brazen,

Your problem sure seems like a leak somewhere, where it is though....??

Shabby
The leak down test is intersting. Any chance of a pic of the cap you developed with the gauge in it? I would like to try that on mine as I continually get the dreaded P0101 which is almost always a leak / weak point, but I can't find it.

Do you disconnect both ends or do you leave the last rubber hose connected to the Throttle body?

Thanks,

GJ

shabby · « **Reply #9 on:** July 10, 2010, 02:33:41 PM »

Quote from: Brazen17 on July 10, 2010, 01:38:26 PM

Does the turbo bypass valve operate the same or similiar to an after market BOV?

Its the exact same thing, except the stock one is built into the turbo while an aftermarket bov is external. Start checking all your hose/clamp connections, and try to take a peek on that wastegate rod, maybe the nut came loose.

Quote from: Gentleman Jack aka Bubble Gum on July 10, 2010, 02:16:58 PM

Shabby
The leak down test is intersting. Any chance of a pic of the cap you developed with the gauge in it? I would like to try that on mine as I continually get the dreaded P0101 which is almost always a leak / weak point, but I can't find it.
Do you disconnect both ends or do you leave the last rubber hose connected to the Throttle body?

You can buy one for $25 here http://www.boostpro.net/prodtester.html
I didn't disconnect any hoses from the throttle body, the pcv hose needs to be capped off from the turbo if you want to pressurize the turbo. Otherwise you can just disconnect the passenger ic pipe and cap it off there and pressurize it while bypassing the turbo, its a bit of a pita getting that hose off from the turbo.

Gentleman Jack · « **Reply #10 on:** July 10, 2010, 02:36:24 PM »

If you do the test both ways, you could determine if the leak is the wastegate or the IC plumbing right? Unless they both leak. By separating the turbo from the test, then doing the test thru the turbo, the wastegate could be identified as the culprit.
I think?

GJ

shabby · « **Reply #11 on:** July 10, 2010, 03:20:32 PM »

The wastegate is on the exhaust side, you're thinking of the bypass valve. The problem with the bypass valve is that its built into the turbo, so even if it would be leaking you would not hear it. You have to inspect the diaphragm for tears/cracks.

Brazen17 · « **Reply #12 on:** July 10, 2010, 05:28:01 PM »

Quote from: Gentleman Jack aka Bubble Gum on July 10, 2010, 02:16:58 PM

Brazen,

Your problem sure seems like a leak somewhere, where it is though....??

Shabby
The leak down test is intersting. Any chance of a pic of the cap you developed with the gauge in it? I would like to try that on mine as I continually get the dreaded P0101 which is almost always a leak / weak point, but I can't find it.

Do you disconnect both ends or do you leave the last rubber hose connected to the Throttle body?

Thanks,

GJ

If it were a leak I think it would be consistent. When the car is "working" it will hold 13 psi, when it's not "working" it will go to 5 psi then bleed down to 0 psi. By working I mean in its current condition. On the plus side I did get it checked out at the dealership and they are saying it is the bypass valve. Bad news is it's on national back order so who know when it will get here. If this is truly the problem it has been going bad for about a year or a little more now. It's to the point I don't like to drive it anymore. Just got to be patient and wait for the valve to come in....

Soldered the 3-bar sensors on the wifes redline and took it for a 50 mile drive with nary a hiccup so maybe we got one of 'em back to working properly! Was hitting and holding 25 psi. Never the less it didn't seem to be making as much power as it should have. Didn't stop me from beating down a WRX-sti. Of course her ambient air temp gauge was reading 111/113 degrees! Her coolant temp was as high as 235 degrees. Does that seem to be near the danger point? That was in city driving at 45 mph or less. On the highway it would drop back to 205 degrees.

Uranium-238 · « **Reply #13 on:** July 10, 2010, 06:02:04 PM »

Not nessicarily...

I had similar problems with my car. Wastegate took a crap and had to be replaced. Once that was done, I had similar symptoms to what you are describing. Sometimes it would boost, sometimes not. Dealer ended up replacing the entire CAC system, apparently there was a leak. So, as strange as it sounds just because boost levels are intermittent it doesn't mean you don't have a leak.

Brazen17 · « **Reply #14 on:** July 10, 2010, 07:41:06 PM »

Tricky little rascals! What is the CAC system?

LatinVenom · « **Reply #15 on:** July 10, 2010, 08:59:22 PM »

You can check the diaphragm as Shabby is suggesting and at least you would know for sure the dealer is correct.
If the diaphragm is good then you have a leak or your IC tubes are bad (mushroom).

Uranium-238 · « **Reply #16 on:** July 10, 2010, 09:25:17 PM »

CAC=charge air cooler. It's the intercooler and all the pipes attached to it.

Brazen17 · « **Reply #17 on:** July 10, 2010, 09:59:26 PM »

I'll take a look in at the diaphragm in the morning - it's 103+ in the garage right now!

Graywolf · « **Reply #18 on:** July 10, 2010, 11:38:04 PM »

Above 235 degrees the car will go into a limp mode and a light will show

Brazen17 · « **Reply #19 on:** July 11, 2010, 01:09:52 PM »

Quote from: Graywolf on July 10, 2010, 11:38:04 PM

Above 235 degrees the car will go into a limp mode and a light will show

Wow! I was right at the limit. Good info.

Brazen17 · « **Reply #20 on:** July 11, 2010, 01:11:55 PM »

OK, down to 94 degrees in the garage so I guess I can get a little work done before it gets hot! I may just have to buy one of those portable A/C units. Then I could get some wood work done too. Or else wait 'til September.

Brazen17 · « **Reply #21 on:** July 11, 2010, 01:44:52 PM »

Is there a gasket or some type sealant under the cover of the turbo bypass valve? Just thought I should know before I remove it.

LatinVenom · « **Reply #22 on:** July 11, 2010, 05:28:58 PM »

I believe the diaphragm itself is part of the seal. It has been a while since I remove the Dejon spring from it.
Just take the 3 screws off then the spring and finally take a look at the diaphragm.

Brazen17 · « **Reply #23 on:** July 17, 2010, 04:43:56 PM »

Ok. Dealership replaced turbo bypass valve and MAF sensor on Friday. Pulled out of parking lot and seemed to be much better and was hitting 20/21 psi. Stopped to get gas. I mixed ~3.5 gallons of 100 octane and the rest 91 octane. Drove away and could not get more than 14 psi shortly followed by max of 5 psi that would not hold and would bleed back to 0 psi. Dealer said they did a pressure test on the system and found no leaks.

Today was a repeat of yesterday as I drove over to dealership. They said to drop it off Monday morning. Any ideas on what is the problem? By contrast my wife's redline with the GMPP tune hits 25 psi and holds it a bit before slowly dropping to 23 or so. She was having similiar though not exactly the same issues as mine but when I soldered her MAP sensors all her problems seem to be fixed. Soldering didn't make a difference on mine. Beginning to get very frustrated.

Is it possible the software has somehow been corrupted? Maybe a reload of the GMPP tune...?

scanner · « **Reply #24 on:** July 17, 2010, 04:59:53 PM »

Get a technician with a tech2 in the car with you and demo the problem. The tech2 can "see" all the inputs and outputs that the ECM uses. If full boost is commanded and not delivered there is a leak. If full boost is not commanded when you WOT then there is a reason the ECM "thinks" it's a bad idea. The ECM could be being "lied to" by a faulty input. Your professional tech will understand this. Guessing about this and that is not nearly as effective as a scan tool applied by a skilled operator.

Are Detroit to LV tickets cheap? I have wanted to visit Frontsight's place for a while....

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Author Topic: Turbo Bypass Valve (Read 12203 times)