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Inconsistent boost?

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
Looking for turbo expert advice and feedback here. My '12 GS has always had this issue. Sometimes, at WOT, boost just doesn't build to where it normally goes, and the car just doesn't pull like it usually does.

I have a Trifecta tune and a boost gauge, so I know that 'normal' boost is right at 22.7-22.8psi. But when it acts up I maybe get 14-16psi. The car still goes pretty good at 16psi, but it's not the same. I monitor knock retard, so I know that is not the issue. And it's not temperature related as it will come one moment and then be gone immediately after (no time for anything to change temperature).

I noticed at first that it seems to happen a lot when getting on the throttle right after a turn. I thought maybe it was a super-aggressive stability control intervention, but it happens even with stability control turned off, and sometimes happens in a straight line too.

I thought about it some more and realized that this tends to happen when I get completely off the throttle at maybe 3000-4000 rpm (like I might do when making a turn after downshifting to 2nd gear) and then get back on it.

Sure enough, I can get this to repeat pretty easily by finding an open road, getting up to about 60 in 3rd gear, slowing down (full off-throttle) back down to about 40, then getting back on. About one in three times I do this: low boost. The rest: full boost.

So, something is probably getting stuck. Since I never get 'overboost' issues, I doubt it's the wastegate. So I figured maybe the BPV. I sent a log to Trifecta but all they could confirm is that they are not getting the air flow they are commanding and nothing seems different to them (in terms of commands) when the boost is low, so it's 'mechanical' and not a problem with the tune or control software.

So, I recently put in a Forge BPV (recirculating), and it's exactly the same problem. I also confirmed all the plumbing for the BPV. This car has a vacuum source (via a vacuum reservoir) and a pressure source (nipple just ahead of the intake throttle) and a control solenoid that decides which (vacuum or pressure) is sent to the BPV. All the lines look good, and the solenoid seems to work properly on my work bench.

Still thinking this seems like a BPV issue, I re-plumbed the system. Now I put manifold vacuum (without the reservoir) directly to the BPV, eliminating any ECU control of the BPV via that solenoid. Three days later, I have yet to get the low boost situation to come back. Not 100% conclusive since it is intermittent, but it was happening a lot before, especially if I tried to make it happen, and now I can't make it happen.

Sorry for the long post. Anyone have any other ideas or comments? Any idea why GM needs to 'control' the BPV instead of just having it open when intake manifold pressure is low (a pretty robust indication that the throttle has closed and surge needs to be prevented)? I don't hear any surging with this 'mod', and I'm not setting 'surge' faults, so I don't think I'm being hard on my turbo. I'm wondering if I just leave it this way or try a new BPV control solenoid?

Maybe this solenoid is only needed as part of that catalyst warm up thing our cars do when you first start them up.. I need to check if my car still makes the same vacuum cleaner sound when I start it up with this mod.

Anyone else notice low power once in a while and not sure why, or low boost if you have a boost gauge?
 

jester435

Full Member
458
4
0
Salt Lake City, Utah
Buick Ownership
2012 Buick Regal GS
Walt, I had my regal gs in the dealership over the weekend for a weird noise after I take my foot off the accelerator. They explained it to me that the bypass valve is letting out too much pressure. The system and turbo in the GS needs a certain amount of pressure in the system. I am going to pull off the bypass valve this weekend and put the stock one back on. See if it solved the issue and noise.

Just thought I would give you my experience.

good luck!
 

QSilverGS

Full Member
374
4
0
Holland, MI
Buick Ownership
2012 GS, 2006 Rendezvous
The only thing I can think of is the control of the boost for "no lift" shifting gets confused when decelerating, down shifting and then trying to accelerating again. Bypassing the solenoid took that out of the process.
 

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
Walt, I had my regal gs in the dealership over the weekend for a weird noise after I take my foot off the accelerator.
Never heard of that one. Usually a 'weird noise' when taking your foot off the accelerator would be a bypass valve that isn't opening... that noise is turbo surge. But you have an atmospheric bypass valve according to your signature, so don't those make a very loud noise when they vent? Let us know how this turns out for you.
______________________________
 

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
The only thing I can think of is the control of the boost for "no lift" shifting gets confused when decelerating, down shifting and then trying to accelerating again. Bypassing the solenoid took that out of the process.
I definitely didn't think of the 'no lift shift' feature, and there isn't much documentation on how that works. But if it was part of a control strategy, I would think that if I repeat the same steps over and over, it would happen every time. Within my ability to do everything the same exact way, it was happening about every 3rd time on average. But I suppose I could be right on the verge of triggering some logic and just happen to hit it about 30% of the time.

I like the brainstorming. Keep it coming.

But if it's part of a strategy, does anyone else notice it?
 

jester435

Full Member
458
4
0
Salt Lake City, Utah
Buick Ownership
2012 Buick Regal GS
Never heard of that one. Usually a 'weird noise' when taking your foot off the accelerator would be a bypass valve that isn't opening... that noise is turbo surge. But you have an atmospheric bypass valve according to your signature, so don't those make a very loud noise when they vent? Let us know how this turns out for you.
correct. the vent is very audible on shifting and acceleration when the excess boost blows off. This is a weird noise right after I take my foot off. Buick claims it is the turbo making the noise because of too little pressure in the system. They said it isnt hurting anything, but it is making that noise.

I am going to swap out the bypass valve for the stock one and see if the noise goes away. I love the woosh sound, but not worth the other noise.
 

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
kinda changing the subject a bit, but did Trifecta supply you two tunes (with and without atmospheric bypass)? If so, did they charge you extra to have two tunes?
 

jester435

Full Member
458
4
0
Salt Lake City, Utah
Buick Ownership
2012 Buick Regal GS
kinda changing the subject a bit, but did Trifecta supply you two tunes (with and without atmospheric bypass)? If so, did they charge you extra to have two tunes?
they did not charge me extra for any additional tunes, but I did allow them to use my car as a demo for a few items. I am not really the normal customer. I am actually not really sure how much I can divulge in the forums.
______________________________
 

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
Well, the low boost situation happened to me again today. Favorite spot/situation... waiting at a red light a couple of cars back, planning on turning right (no turn lane, so I must wait behind the cars going straight). Light turns green, I slowly accellerate in 1st, shift early to 2nd, back off the throttle as I make the tight right turn, then hit full throttle as I straighten out... no boost (well, 13psi today instead of 22.7psi). And it stays like that all the way through 2nd gear.

CRAP!

So, no one else has ever experienced this???
 

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
I found myself at a stoplight with open road ahead, so I grabbed my phone and shot a quick video of this.

http://youtu.be/9SjkR2-OTeQ

I make my way up to third and have good boost available (short shifting... just trying to get up to third gear... I did have wheel spin in 2nd). Then I leave it in 3rd and come back down to about 3000 rpm and get back on it. I do this three times. The first and third I've got full boost and it's pulling like crazy. The second time it just feels flat and you can see the boost reading on my scangauge only hitting maybe 14psi instead of 22.8psi.

Even if you've got no opinion on this, some might like the location I've got my scangauge now. It blocks the top half of the coolant and fuel gauges, but the needles only move in the bottom half anyways, so it really doesn't block anything.
 

bnebel15

Full Member
115
1
0
Bay Area, Ca
Buick Ownership
2013 Regal GS Smokey Grey Metallic. Trifecta tuned
I found myself at a stoplight with open road ahead, so I grabbed my phone and shot a quick video of this.

http://youtu.be/9SjkR2-OTeQ

I make my way up to third and have good boost available (short shifting... just trying to get up to third gear... I did have wheel spin in 2nd). Then I leave it in 3rd and come back down to about 3000 rpm and get back on it. I do this three times. The first and third I've got full boost and it's pulling like crazy. The second time it just feels flat and you can see the boost reading on my scangauge only hitting maybe 14psi instead of 22.8psi.

Even if you've got no opinion on this, some might like the location I've got my scangauge now. It blocks the top half of the coolant and fuel gauges, but the needles only move in the bottom half anyways, so it really doesn't block anything.
Sorry for a subject change. What kind of boost gauge is that. I like it

OK I see it's a scangauge. But from their site I can't tell how to get it to read boost. Their site says nothing about boost reading. Is it an add on to the gauge to make it read boost. Cause from their site I can't tell if the scangauge2 reads boost on its own
 
Last edited:

kranz38

Full Member
1,626
10
38
Crown Point
Buick Ownership
Regal GS
Does it do it with stock tune? The car will adjust boost to make x amount of power, is it pulling timing? What are your fuel trims at. Id Put an analog boost gauge on it and have it dyno tuned.
______________________________
 

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
But from their site I can't tell how to get it to read boost.
All ScanGaugeII's from when they first started making them were capable of reading whatever is available on the OBDII port. That always included 'MAP'. At some point they updated their software to be able to display 'boost' by taking MAP and adding in atmospheric pressure. I sent mine back in about a year ago to have the software updated so that it could do this.

So, if you buy a new one, you'll have Boost as an available reading for sure. If you buy a used one, you might only have 'MAP' as a reading depending on how old it is, but they offer a software update that was pretty cheap.

Here is the page on their website that explains the 'standard' available readings: http://www.scangauge.com/products/scangaugeii/digital-gauges-2/

Then you can add in others (like the 'knock retard' I'm showing) if you know the necessary CAN information and configure your ScanGauge to request the data and display it properly. They have instructions on their website on how to do that too. They call that 'X-Gauge'.
 
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Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
Does it do it with stock tune? The car will adjust boost to make x amount of power, is it pulling timing? What are your fuel trims at. Id Put an analog boost gauge on it and have it dyno tuned.
Stock tune: it does it with my 'select a tune' turned off, but I have not flashed back to totally stock to check. I'll do it at some point, but Trifecta says they can't see anything in the data logs. They are calling for more air but are not getting it.

Is it pulling timing: I've got 'knock retard' on the display, so it is not pulling timing due to detonation (at least not in these runs... it does happen sometimes). For a while I was looking at spark timing on the ScanGauge and it is different when the low boost happens, but it's a chicken and egg kind of thing... do I have low boost because timing is wrong, or is the timing just different because the engine is running at 14psi instead of 23psi?

Fuel trims: I have not looked, but I think the ScanGauge can read them if I reconfigure it. I'll try giving that a shot too.

Why the analog boost gauge? I know it would be much faster responding and easier to get good readings, but this is definitely NOT an instrumentation problem. The car is just flat sometimes, and other times it pulls like a freight train. The low boost readings correlate to when it's just not running right.
 

bnebel15

Full Member
115
1
0
Bay Area, Ca
Buick Ownership
2013 Regal GS Smokey Grey Metallic. Trifecta tuned
All ScanGaugeII's from when they first started making them were capable of reading whatever is available on the OBDII port. That always included 'MAP'. At some point they updated their software to be able to display 'boost' by taking MAP and adding in atmospheric pressure. I sent mine back in about a year ago to have the software updated so that it could do this.

So, if you buy a new one, you'll have Boost as an available reading for sure. If you buy a used one, you might only have 'MAP' as a reading depending on how old it is, but they offer a software update that was pretty cheap.

Here is the page on their website that explains the 'standard' available readings: http://www.scangauge.com/products/scangaugeii/digital-gauges-2/

Then you can add in others (like the 'knock retard' I'm showing) if you know the necessary CAN information and configure your ScanGauge to request the data and display it properly. They have instructions on their website on how to do that too. They call that 'X-Gauge'.
Thanks for the clear up. I'm new to scangauge but loved the way it looked. And much cheaper than the p3 vidi. I was a little confused on how to add knock retard. Is it simply adding a can code to the gauge
 

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
Thanks for the clear up. I'm new to scangauge but loved the way it looked. And much cheaper than the p3 vidi. I was a little confused on how to add knock retard. Is it simply adding a can code to the gauge
You actually have to enter in 4 'codes', plus the 'units' and the 'name' for the thing you are adding (so units for knock retard are 'degrees' and the name I gave is 'KR'). The information is on ScanGauge's web site, and although it is tedious, after you add these once you never need to add them again. They just show up as available parameters.

And it's easy to change the parameters you're looking at. If I didn't want to see 'ECT' anymore and instead wanted to look at 'IMT' (intake manifold temp), I just press the little button next to where 'ECT' is showing now, and it scrolls through all the available parameters. Stop pushing the button when IMT is showing.

The backlighting is also adjustable. I've got mine set to match the color of the rest of the cluster (that 'teal' color GM likes to use), but you can adjust it to many different colors.

Of course, it also reads and clears codes, calculates fuel economy, and has some performance monitors too (like 0-60 times and 1/4 miles and stuff, which frankly I have never tried using).

In the video you can see the velcro I've got holding it in place, but from the driver's seat you can't see that, unless you are a little old lady in Florida and look up through the steering wheel when you drive.

I used to have it sitting in the ash try spot, where it really fits well, but I found that spot too difficult to glance at while driving, especially if you are accelerating at WOT and want to glance at your boost... it took me to long to change my focus to the ash-tray area and then back to the road, so I moved it.
______________________________
 

bnebel15

Full Member
115
1
0
Bay Area, Ca
Buick Ownership
2013 Regal GS Smokey Grey Metallic. Trifecta tuned
You actually have to enter in 4 'codes', plus the 'units' and the 'name' for the thing you are adding (so units for knock retard are 'degrees' and the name I gave is 'KR'). The information is on ScanGauge's web site, and although it is tedious, after you add these once you never need to add them again. They just show up as available parameters.

And it's easy to change the parameters you're looking at. If I didn't want to see 'ECT' anymore and instead wanted to look at 'IMT' (intake manifold temp), I just press the little button next to where 'ECT' is showing now, and it scrolls through all the available parameters. Stop pushing the button when IMT is showing.

The backlighting is also adjustable. I've got mine set to match the color of the rest of the cluster (that 'teal' color GM likes to use), but you can adjust it to many different colors.

Of course, it also reads and clears codes, calculates fuel economy, and has some performance monitors too (like 0-60 times and 1/4 miles and stuff, which frankly I have never tried using).

In the video you can see the velcro I've got holding it in place, but from the driver's seat you can't see that, unless you are a little old lady in Florida and look up through the steering wheel when you drive.

I used to have it sitting in the ash try spot, where it really fits well, but I found that spot too difficult to glance at while driving, especially if you are accelerating at WOT and want to glance at your boost... it took me to long to change my focus to the ash-tray area and then back to the road, so I moved it.
Thanks for the clarification. I contacted the company direct and they couldn't even tell me if the scangauge would read map on my 2013 gs. they said 50% of the cars display map readings through the obd port and they couldn't confirm if the 2013 regal gs showed map.
 

bbronner413

Full Member
136
5
18
Chicopee, MA
Buick Ownership
2013 Buick Regal GS
I wanted to chime in because I had a similar boost issue right when I got my new 2013 Buick Regal GS and it may provide some insight to your problem.

What was happening within a couple thousand miles of having the car was intermittent lack of power/lack of boost, particularly after a hard acceleration. It wasn't always there, but it certainly happened enough to the point where I felt like something was wrong. Basically, at times it felt like there just wasn't enough "juice" to propel this heavy ass car.

Dealer found out that the vacuum hose that goes from the bypass valve to the solenoid valve in front of the engine was crimped/kinked causing this. Since this is a recirculating bypass valve, it wasn't sending the whole relief pressure from the bypass valve to this solenoid/switch and causing a limp mode like condition.

They just ordered a new vacuum hose and the problem has since been solved.
 

12blkgs

Full Member
24
0
0
Buick Ownership
Buick
I wanted to chime in because I had a similar boost issue right when I got my new 2013 Buick Regal GS and it may provide some insight to your problem.

What was happening within a couple thousand miles of having the car was intermittent lack of power/lack of boost, particularly after a hard acceleration. It wasn't always there, but it certainly happened enough to the point where I felt like something was wrong. Basically, at times it felt like there just wasn't enough "juice" to propel this heavy ass car.

Dealer found out that the vacuum hose that goes from the bypass valve to the solenoid valve in front of the engine was crimped/kinked causing this. Since this is a recirculating bypass valve, it wasn't sending the whole relief pressure from the bypass valve to this solenoid/switch and causing a limp mode like condition.

They just ordered a new vacuum hose and the problem has since been solved.
my 2012 gs has this same condition from time to time as well and my car is completely stock, I will have to take a look at this hose you wouldnt happen to have any pics of it for a reference would you?
 

Walt G

Full Member
815
39
28
25 miles SW of Chicago
Buick Ownership
'12 Regal GS
I'm just relieved to finally hear that I'm not the only one that has ever experienced this.

In my case though, it's not the lines from the BPV to the BPV control solenoid. I've thoroughly inspected those, plus I even tried driving around for a while with the BPV plumbed directly to my intake manifold (with a new hose I provided). But I have NOT looked at any of the lines that control the wastegate yet. I need to do that.

But if anyone wants to check their BPV lines, it's pretty simple. First, pop off the plastic engine cover (it just pulls straight up after unhooking the rubber hose that runs along the front). The BPV control solenoid is sitting on top of the intake manifold, just left of center. Can't miss it. Three vacuum lines running to it. The one going out the left heads around the left side of the engine and to the actual BPV. The other two lead either to a vacuum reservoir under the intake manifold (which has another line that lead back to a connection right on top of the intake manifold), or to a nipple located just ahead of the intake throttle on the plastic pipe that attaches to the intake manifold.

All (except the connections on the reservoir) are easy to see and access. I hope you find your issue. I'll keep looking for mine and report back if/when I find the proverbial smoking gun.
 
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