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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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Discussion Starter · #1 ·
Sigh. I have been getting the dreaded P0299 codes again for the last couple of weeks and the car is going into limp mode as a result.
I have pulled the charge air system apart, quintuple checked for leaks or loose connections, pulled the nose cone off and re-inspected the CAC / IC. Cleaned the sensors, double checked the wire connections, shortened the wastegate rod by a single nut turn and retested the car the next day, 3 days in a row.
Double checked my torque on the intake manifold, throttle body and turbo to make sure I covered all the bases.
Flashed the tune and all to no avail.

I emailed Trifecta a week ago after doing some datalogs and actually recorded the event in one of the logs. Haven’t heard from them in a week.

reached out to Dave at PAW and he offered up that with the Big Wheel turbo on his tunes, he disables that code as it is a known thing on this turbo.
I forwarded that info to Trifecta and still nothing.

I gotta say I am really and truly at wits end here.

here is the current (and mostly) reproducible scenario that triggers the wastegate to pop (I can usually here it when it happens).

I am driving in the freeway in some open traffic.
I go wot in a gear that is just on the edge of being to tall / high for the situation. (Example I am in 4th gear and a downshift would get me the boost I want but instead I just wot in 4th) I am not so high a gear that it’s inappropriate just when you are in the edge of downshifting.
Invariably the car starts to accelerate in build boost then “pop” goes the wastegate, loss of boost and I can only get it back if I cycle the motor off then back on.
it doesn’t throw a cell every time it’s goes into limp mode.
Once it happens, it seems highly likely to happen again even with an engine cycle on off, or if I clear the code.

so far it never happens for the first time (codes cleared) in 1st, 2nd or 3rd. Only in the above scenario in 4th or 5th. After it has happened I am able to trigger limp mode in lower gears, until I clear the code and then we start all over again.

the first time I went through this I discovered a loose washer stuck in the intake manifold. Then I had a bad coil and then a had a shredded turbo compressor wheel on a new BWK04 back to back to back.
After replacing the Turbo with another new one and sussing out the bad coil I have not touched the motor or changed anything (brakes don’t count)

this is starting to drive me mad as I’d like to move past this but am at a complete loss as to what else to check or do.

absolutely looking for any ideas or thoughts on what I should do or where else I should look. At this point no idea would seem crazy to me..
 

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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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Discussion Starter · #2 ·
I should add, is there a clue in the fact it is only happening in the above scenario?
Like is the motor stressing under more sustained torque in that scenario and that I should be looking for a physical issue because the motor moves more in that scenario? (I don’t know that is does move more just throwing darts at a dart board at this point)
 

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where you do have the preload set on your waste gate?? The closer the nuts are to the actuator the more preload there is.

Because the waste gates are not poppet style and they are a flap if you wot the engine that means that the engine is moving a lot more air. I believe the factory waste gate actuator has something like a 5 or 7 lb spring in it. That spring inside that actuator does 2 jobs, the first job is it controls the crack open pressure. that means that the pressure on the output side of the turbo needs to exceed that spring pressure before the gate will start to open.

It is also responsible for holding the gate closed. This is where having a big wheel turbo comes into play. While you do not have higher boost pressures you are able to get more air into the cylinders and that additional air once heated from combustion is going to cause a higher pressure inside of the exhaust manifold. If the pressure inside of the exhaust manifold exceeds the pressure of the waste gate spring the waste gate is going to get blown open.

Now you can add more preload by shortening the waste gate actuator arm. Doing this can cause another issue called boost creep As you add preload you are also shortening the range of motion of the actuator and by doing that you will restrict how far the waste gate can actually open. If the waste gate is unable to open far enough to let enough exhaust bypass the turbine to throttle how fast the turbo is able to spin the boost is going to creep or keep on going up.

It is hard to get just the right balance to control the waste gate not blowing open and not ending up with boost creep.


And this is why you love me!!!!


These waste gate actuators are upgraded versions of the ones that come with BorgWarner turbos. They have a maximum boost pressure of 26 PSI and the K04 pretty much taps out at 24ish. The spring inside of the stock waste gate is going to be set to get you to about 18 PSI or so max pressure. Decent rule of thumb is 1/2 boost pressure = waste gate spring pressure. The preload adjustment will give you a 2-3 PSI swing. So stock spring is probably in the 7 psi area. So if at any point the exhaust manifold pressure is above that an the gate is closed well guess what?? it's going to blow open. If you preload adjust to keep it close you will reduce how far it is able to open at say max boost and if it is not able to open far enough to slow the turbo down the turbo will keep on spinning faster and faster until it breaks apart.

Those aftermarket actuators allow you to open them up to change the springs to dial in a better crack pressure without effecting how far the gate is able to open .
Different tension springs are sold separate and the rating they have on them is because of the spring they include with it.

If you are running 22 psi of boost I recommend using a 10 or 11 lb spring.

I want to say the stock spring is either a 5 or a 7 lb spring... so if you go with a 10lb spring and h preload all the way out your max boost is going to be in the neighborhood of 20-22 lbs of boost 11 lb spring is going to give you 22 -24 lbs of boost.
 
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If the above is hard to understand I have a spare K04 turbo and I can make a video that will demonstrate the problem so you can actually see what I am talking about.
 

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Discussion Starter · #5 · (Edited)
If the above is hard to understand I have a spare K04 turbo and I can make a video that will demonstrate the problem so you can actually see what I am talking about.
I actually have the nut on the wastegate a full 3 turns shorter from "stock" at this point, as sent to me by Dave Gilbert. Other than not fixing the issue with limp mode, I will say the first turn did make a difference in response on the turbo. The second and third turn did not. I did each turn on a separate day to space out the results.
Either way it did not address the issue. I am planning on going back two turns as the initial first nut turn felt like i had landed in the sweet spot.

I am certainly not the only one with a BWK04 + Trifecta tune so I am baffled as to why this is happening. Unless PAW switched to a different turbo vendor since the older ones?

And... now that you mention it. The replacement BWK04 that PAW sent did not have a BPV on it (the beige plastic part on the front). Since PAW was kind enough to replace it, i didn't want to be a pain in their but, so i just transplanted the one from my working OEM K04 as they looked identical...
Hmmm....

-KG, I realize you are talking about the actuator so the BPV is tangential to your point but maybe they put an upgraded spring in the BPV when they convert to a Big Wheel?

PS> Just emailed Dave at PAW to get his comments...
 

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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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Discussion Starter · #6 ·
Just heard back from Dave,
Here was his response regarding the BPV (PS: i checked my BPV when i pulled it from the OEM K04 and it looked mint)
The BPVs usually are just fine unless the diaphragm is torn of the spring has fatigued. We use the stock BPVs on 6758 EFRs that are running 29psi making 375-400whp and they are fine. I don’t think this is your issue but it never hurts to try.
-Dave Gilbert
 

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Discussion Starter · #7 ·
Update, Trifecta just posted a new tune. Will download, flash and report back... fingers crossed.
 

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There is a waste gate control solenoid that the ECM controls. this solenoid helps to control the crack pressure and the speed in which the gate opens. I am not sure how = Dave is using the EFR6758 actuators on the K04 because the bracket that holds the actuator on the K04 is welded to the actuator and on the EFR the actuator is bolted to the bracket so they aren't interchangeable. The actuators cannot be opened up as the housing is bot bolted together but has a rolled seam to hold the 2 halves together. The spring inside cannot be changed without causing damage to the housing.


I friend of mine is having the exact same issue you are having tho it is on a different vehicle. He has a Ford 3.0l v6 twin turbo and both turbos had larger compressor wheels put into them. They are BorgWarner turbos and have a similar design for the waste gate actuators. and his waste gates are also blowing open. The thing that sucks about his setup is that his actuators pull to open the gates unlike the turbo you have which push to open the gates. So there is no aftermarket actuator available to solve his problem...

There is something you can do to test if the waste gate is actually being blown open. You need to get a 1 to 2 lb per inch extension spring and hook it onto the waste gate linkage where the actuator arm attaches and attach the other end to the bracket that holds the actuator. by adding that spring it is going to make it a little bit harder for the gate to open and it will not effect the range of motion at all. So you can increase the crack pressure while retaining the ability for the gate to fully open. It's a simple 50 cent test to see if that solves the problem. The other way would be to add a pressure sensor to measure the pressure inside of the exhaust manifold. If the pressure inside the exhaust manifold exceeds the spring rating then the gate is getting blown open.

The turbine housing is nicknamed the "snail" and it is nicknamed as such because of the shape of it. Think of a conch shell it spirals getting smaller as the spiral gets to the center. In a turbo that decrease in size increases the exhaust pressure as the exhaust travels to the center. This is why turbos works so well. Not only do you have exhaust bowing onto the turbine wheel but that exhaust has been pressurized. So say it has been pressurized to 14.696 psi gauge pressure and you live at sea level. When the exhaust exits the end of the snail to blow onto the turbine wheel it expands to equalize to barometric pressure which at sea level is 14.696 psi. if you take 12" x 12" x 12" volume of air at sea level and compress it is 14.696 psi that air now has a volume of 6" x 6" x 6" or 1/2 the size. When the air exits the snail to "blow" on the turbine it expands back out to it's original size which moves the turbine wheel at 2 times the speed it would if the air was not compressed.


In the case of a big wheel turbo you are moving a larger volume of air and once you get to the turbo that larger volume of air is going to translate into a higher exhaust manifold pressure.
 

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This is an oversimplified version of what is happening but it gives you the idea of how it works.

When you adjust the waste gate rod the correct verbage is adjusting the waste gate preload.. The spring inside of the actuator is a compression spring and compression springs are rated in pounds per inch. The waste gate actuator has close to 1" of travel. So if you put in a new spring that spring will be partially compressed during the assembly of the actuator. If you buy say a 10lb waste gate actuator that is full open at 20psi and if the actuator has a total of 1" of throw/movement the spring that is inside would be 2" long and is a 10lb rated spring. The spring gets compressed down to 1" so there is a starting point of 10psi. That spring sits on a diaphragm and the rod is attached to that diaphragm. The boost pressure created by the turbo gets put into the actuator on the back side of the diaphragm and when that pressure exceeds 10psi the spring will compress causing the rod to move and the gate to start opening.

So if you adjust the preload by using the nuts on the rod you are compressing that internal spring more. By doing that you are decreasing the throw or how far the rod is able to move. And that limits how far the waste gate is able to open. The turbo and the waste are designed to work together. What that means is the size of the waste gate is made so it can hold the turbo at it's maximum when the gate is fully opened up. There is some fudge factor there but not a whole lot. Changing the compressor wheel to a larger one is messing about in that fudge factor area. If for whatever reason your engine has a higher VE (Volumetric Efficiency) you can end up just outside of that fudge factor area and end up with the waste gate getting blown open or boost creep issues because the physical size of the waste gate is not large enough to allow enough exhaust to bypass the turbine.

It is a really delicate balance and very hard to dial in the settings without having a pressure sensor in the turbine housing on the turbo. Without that it's really a guessing game and trial and error on replacing springs in the waste gate actuator. The OE actuator which is what you have does not have replaceable springs so the only adjustment you have is seen in this table.

Font Screenshot Parallel Number Slope



You will be i the medium boost category.


With the rod adjusted to full length the crack pressure of the waste gate is going to be 8.8psi and with the rod shortened up all the way he crack pressure becomes 15.9 psi.

8.8psi is approx 43% of the full stroke pressure. That is going to allow the waste gate to move the most.
at 15.9psi crack pressure that is 77% of the full stroke pressure.. so if 43% is gate close and you move that to 77% you will end up seeing a 34% reduction in how far the gate is able to open. Doesn't sound like a big deal but it is. If the gate at full open allows 40% of the exhaust to bypass the turbine and say the turbo is designed to reach peak output at 100 cfm if your engine puts out 140CFM hen setting the preload to 8.8 would allow the turbo to function properly. But that 8.8 psi could occur at a low RPM and this would cause you to loose power sooner. But if you change the preload to 15.9 psi that means 100% of the exhaust gases are going to power that turbine until the boost pressure hits 15.9 psi. Sound better right? well it is kind of. Until you run the calculation on how far the gate is now able to open. a 34% reduction in how far the gate is able to open means 34cfm is able to flow past the turbine. that puts the volume spinning the turbo at 106cfm which is 6cfm above the 100 peak. That means the turbo will not slow down it will keep on spinning faster and faster. boost creep!!!

The waste gate size was designed for use with the original compressor wheel. by increasing the size of the compressor wheel you are moving more air. more air can cause the gate to open too soon so an adjustment of the preload needs to be done to keep the gate from opening before it should. Too much adjustment and the gate will not open far enough to control the speed of the turbo. too little and the gate is going to open when it shouldn't


Small adjustments to the preload. as in 1/8th turns of the nut. not 1 thread. If you look at that table it shows you how much of a change 1 turn of the nut can cause. almost a 1 psi change to the crack pressure which means the waste gate is going to loose some 2-3% of its movement range.

I suggest the TurboSmart actuator because ideally you want tobe able to get the crack pressure as close to where you want it without limiting how far the gate is able to open. Because of the larger compressor when you are going to be right at that line on the gate when fully open being able to keep the turbo at speed properly without having boost creep. increasing the crack pressure to stop the gate from blowing open by using the nut is going to increase the possibility of getting boost creep.

The TurboSmart actuators allow you to change the springs to get as close as possible to the ideal crack pressure and exhaust manifold pressure without changing how far the gate is able to open.

This is one of the more difficult adjustments to get correct. There is a tool you can buy that will allow you to apply pressure to the gate so you can adjust the preload precisely.
 

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Made a boo boo above.


a 34% reduction in the waste gate range of motion if the gate is able to allow 40CFM through with 100% range of motion if there is a 34% loss of range of motion because of the preload being maxed out the wastegate is now only going to allow 25.6 cfm through it and if your engine is outputting 140cfm and the turbo maxes out at 100cfm there is going to be 14.4 cfm of air that is going to end up going through the turbo causing the boost to increase when you don't want it to.
 

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Now the Solstice does have a boost control solenoid. This is a bad name for this specific part and it can be misleading. All this part does is it limits the amount of pressure the waste gate actuator sees. If the output pressure from the turbo is 10psi and the control solenoid is set to allow 80% of the pressure through then the waste gate actuator is going to see 8 psi.. If the turbo is outputting 10 psi the ECM cannot make the actuator see anything more then that 10psi. It doesn't create pressure it only limits the pressure. The only thing the boost control solenoid can do is alter when the waste gate starts to open and nothing more If your exhaust manifold pressure is blowing the gate open the only way a tune could fix the issue is to have the boost control solenoid open the wastegate before it gets blown open providing there is enough boost pressure to do so.
 

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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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Discussion Starter · #12 ·
Well I sent trifecta the email from PAW.
I am paraphrasing here as I am on my phone right now and not in front of the email but essentially they indicated they did not recommend PAWs approach as “possibly unsafe”. However reading between the lines it sounds like the finagled those numbers a little bit from the tune I hadto see if it would eliminate the problem.
They asked me to flash the new tune and data log some “lug pulls” (never heard that one before but love the term) in alignment of what I originally described as reproduce-able limp mode triggers.
I am certainly will to give it a go.
I am also going to return the nut back two rotations to the sweet spot I found on the first turn.

I will start with the current tune and the lengthening of the wastegate rod actuator and see if I maintain limp mode, then reflash and try the new tune.
 

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It's a damned temperamental thing. so when adjusting do no more then 1/4 turn adjustments at a time.

rod getting shorter = more preload = increasing the crack pressure on the waste gate = waste gate not going to be able to open as far.

Just remember that line above.
 
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If you have a way of logging outside of trifecta I would love to have a look see. I would need you to log

barometric pressure,
MAP kpa,
MAF gsec,
engine speed,
throttle plate position,
throttle plate desired/commanded,
accelerator pedal position,
waste gate duty cycle,
intake pressure,
commanded/desired waste gate duty cycle
boost pressure,
commanded/desired boost.
air load
VE


with those I could tell you if the gate is being blow open or not.
There is no sensor for the turbo RPM, if there was it would be easy to see if that is what was happening.

I can send you my HPTuners adapter if you want to get some detailed log files.
OR
you can ask Trifecta to send you a CSV file of the logs you are sending them and I can write up a program that will graph the information to you can see what is happening.
 
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Discussion Starter · #16 ·
Well I have the Tech 2 not sure that it can log all those things simultaneously…
 

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IDK what the output format is or if you can even export the data from tech 2

You would have to mess around with it to see what you can do with it.
 

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Discussion Starter · #18 ·
Hmm. Well step one is to lengthen the wastegate actuator rod.
Clear the codes and get a baseline.
Step two is flash the new trifecta and do some “lug” pulls.
If that doesn’t resolve it I will PM ya on step 3….
 

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I love you guys! Reading this made my eyes cross, it is so out of my job description, but makes sense, kind of...I'll be in the corner with the mop and dustpan until the broom and pail get fixed. Keep it coming and good luck. There's a book in this saga you know. I see KG as Dr Emmett Brown and HH as Marty. No Delorean but a fine Solstice with a happy turbo!

Richard
 

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Discussion Starter · #20 ·
I love you guys! Reading this made my eyes cross, it is so out of my job description, but makes sense, kind of...I'll be in the corner with the mop and dustpan until the broom and pail get fixed. Keep it coming and good luck. There's a book in this saga you know. I see KG as Dr Emmett Brown and HH as Marty. No Delorean but a fine Solstice with a happy turbo!

Richard
I am just happy I learned a new term “lug pulls”
:)
 
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