Bah Humbug - 991.2 low boost pressure - Cobb install
12-30-2019, 10:04 PM
#1
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Bah Humbug - 991.2 low boost pressure - Cobb install
So I bought my 991.2 C2 a Cobb AccessPort for Christmas and, after the family cleared out, I went ahead and installed it. Everything went smoothly with the self-install, except for the fact that the error messages on the dash screen during the install process scared me a bit (the manual doesn’t warn you about that part of the process). Well, here’s the bah humbug part - the car wasn’t any faster. Turns out that I had a boost leak preventing my boost pressure from going above 10-11 PSI max. Until I did more research, I thought that the behavior was normal for stock, but it turns out that it is a few PSI low and I didn’t realize it before I installed the AP. Cobb has been great to work with, but the behavior and the fault codes are pointing toward a boost leak between the turbos and the engine. What a bummer... Other than the low turbo pressure, the car drives flawlessly.
Oh well, such is life. Does anyone know a good Porsche shop in North Atlanta that I can work with to diagnose and repair the leak? I’d rather not deal with the dealer on this one. I’ll probably go ahead and install some sport cats once I’ve got the leak sorted out.
Oh well, such is life. Does anyone know a good Porsche shop in North Atlanta that I can work with to diagnose and repair the leak? I’d rather not deal with the dealer on this one. I’ll probably go ahead and install some sport cats once I’ve got the leak sorted out.
Last edited by Porschex3; 12-30-2019 at 11:57 PM.
12-30-2019, 11:14 PM
#2
Originally Posted by Porschex3
So I bought my 991.2 C2 a Cobb AccessPort for Christmas and, after the family cleared out, I went ahead and installed it. Everything went smoothly with the self-install, except for the fact that the error messages on the dash screen during the install process scared me a bit (the manual doesn’t warn you about that part of the process). Well, here’s the bah humbug part - the car wasn’t any faster. Turns out that I had a boost leak preventing my boost pressure from going above 10-11 PSI max. Until I did more research, I thought that the behavior was normal for stock, but it turns out that it is a few PSI low and I didn’t realize it before I installed the AP. Cobb has been great to work with, but the behavior and the fault codes are pointing toward a boost leak between the turbos and the engine. What a bummer... Other than the low turbo pressure, the car drives flawlessly.
Oh well, such is life. Does anyone know a good Porsche shop in North Atlanta that I can work with to diagnose and repair the leak? I’d rather not deal with the dealer on this one. I’ll probably go ahead and install some sport cats once I’ve got the leak sorted out.
Oh well, such is life. Does anyone know a good Porsche shop in North Atlanta that I can work with to diagnose and repair the leak? I’d rather not deal with the dealer on this one. I’ll probably go ahead and install some sport cats once I’ve got the leak sorted out.
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Porschex3 (12-31-2019)
12-30-2019, 11:22 PM
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Originally Posted by yoyo711
Try to uninstall and see what happens for Boost pressure and reinstall.
12-30-2019, 11:41 PM
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There is a lot of history on this subject. I suggest you search and do some reading but honestly I am not sure anyone came up with a positive conclusion in the past.
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Porschex3 (12-31-2019)
12-31-2019, 12:01 AM
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Originally Posted by ClassJ
There is a lot of history on this subject. I suggest you search and do some reading but honestly I am not sure anyone came up with a positive conclusion in the past.
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Porschex3 (12-31-2019)
12-31-2019, 12:46 AM
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Originally Posted by Porschex3
Thanks. Yes, I’ve looked through those. It looks like one solved his similar issue by going Cat bypass and the other similar issue had a bad solenoid. Another poster had the issue, but never reported back with a resolution. I think what’s going on in that people are discovering existing mechanical weaknesses when they’re trying to up the pressure - I don’t think the Cobb tune is doing anything wrong. With mine, I’m getting code P0299, which seems to indicate low boost pressure getting to the engine.
One person replaced an ECU without any improvement. Another person I swore replaced their turbos due to stuck wastegates.
End of the day here, the common thread is that their car was fine, it then was tuned, and ended up with boost loss. I don’t recall seeing anyone with low boost on a stock car but I could be wrong.
What baffles me is how a return flash to stock does not seem to remedy things which would seem to point to a part failure.
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Porschex3 (12-31-2019)
12-31-2019, 01:23 AM
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Thanks guys. To be honest, I wasn’t paying close enough attention to the boost gauge before flashing to know for sure, but I’m pretty sure that it was where it is now. I had done several launches and fast WOT accelerations and, while it has been fast, I didn’t have the boost gauge programmed in to look at it (it is now my top line on the gauge). Once I installed the tuning and didn’t feel much improvement (and I didn’t feel any decrease either), I started paying very close attention to boost because I did my research and realized that I was supposed to be getting way more boost than it was showing. The tune gets it up to 10 PSI much faster than the stock tune, but I know it isn’t supposed to stop there.
The car is fast and smooth all-around, but just not as fast as it should be. I think my problem was that I went from my Cayennes to the 911 and, even at less than full boost, it feels pretty darn fast.
The car is fast and smooth all-around, but just not as fast as it should be. I think my problem was that I went from my Cayennes to the 911 and, even at less than full boost, it feels pretty darn fast.
12-31-2019, 09:23 AM
#10
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What year? Is it driven in winter?
The wastegate actuator linkage is prone to seizing on these cars requiring turbo replacement. That would explain low boost if it is occurring.
The wastegate actuator linkage is prone to seizing on these cars requiring turbo replacement. That would explain low boost if it is occurring.
12-31-2019, 09:37 AM
#11
Freed Performance in Cumming has a solid reputation in the Atlanta area for performance and tuning modifications. I have no personal experience with them, but have heard from others that they are the go to place around Atlanta. You could also call German Car Repair in Alpharetta for some guidance. Alan Kidson runs a great shop and has a lot of experience with Porsche and BMW modifications.
12-31-2019, 09:41 AM
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Originally Posted by Porschex3
So I bought my 991.2 C2 a Cobb AccessPort for Christmas and, after the family cleared out, I went ahead and installed it. Everything went smoothly with the self-install, except for the fact that the error messages on the dash screen during the install process scared me a bit (the manual doesn’t warn you about that part of the process). Well, here’s the bah humbug part - the car wasn’t any faster. Turns out that I had a boost leak preventing my boost pressure from going above 10-11 PSI max. Until I did more research, I thought that the behavior was normal for stock, but it turns out that it is a few PSI low and I didn’t realize it before I installed the AP. Cobb has been great to work with, but the behavior and the fault codes are pointing toward a boost leak between the turbos and the engine. What a bummer... Other than the low turbo pressure, the car drives flawlessly.
Oh well, such is life. Does anyone know a good Porsche shop in North Atlanta that I can work with to diagnose and repair the leak? I’d rather not deal with the dealer on this one. I’ll probably go ahead and install some sport cats once I’ve got the leak sorted out.
Oh well, such is life. Does anyone know a good Porsche shop in North Atlanta that I can work with to diagnose and repair the leak? I’d rather not deal with the dealer on this one. I’ll probably go ahead and install some sport cats once I’ve got the leak sorted out.
12-31-2019, 10:32 AM
#13
Probably a chargepipe into the intercoolers, or an inlet pipe. Sucks, but nothing crazy.
If you have warranty, revert back to stock and drive for a few hundred miles, then take it to the dealer.
If you have warranty, revert back to stock and drive for a few hundred miles, then take it to the dealer.
12-31-2019, 10:33 AM
#14
Originally Posted by Ceepe
I notice on two base 3.0's now I never see boost pressure above about 10-12 PSI. What is the max boost you guys are seeing on non tuned ECU's?
I'm consistent 11ish max for base cars.
12-31-2019, 11:35 AM
#15
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Thanks everyone. I really appreciate your knowledge and advice. In case it is helpful, here is a datalog that I did with the Stage 1 91 map installed (this was with 93 fuel in the tank). It isn't the best pull b/c I had to pull off a little early, but I couldn't find a good place to do a full 2.5k - redline. It should be enough data to see how everything is functioning though.
