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-   -   Question for 991.2 owners that have installed the Cobb tune (https://rennlist.com/forums/991/1145893-question-for-991-2-owners-that-have-installed-the-cobb-tune.html)

991.2GTS 06-01-2019 10:30 PM

Question for 991.2 owners that have installed the Cobb tune
 
Last week i installed the Cobb tune stage 2 on 2018 GTS. My car has ak exhaust, fabspeed 200 cel and header. Question is do you guys that have the Cobb tune feel like the pull less after 6000rpm, cause this is what happened to my car. I feel my car has a boost drop after 6000rpm, especially 3rd and 4th gear, I know the gauge in the car is not as accurate but it dropped to 12psi after 6000rpm. Anyone experience the same problem? Thanks guys

i did change to stage 1 map and it seems the boost drop not as much but probably because the stage 1 pull less before 6000rpm

arter 06-01-2019 11:07 PM

connect up your cobb unit in datalogger mode and see what is happening during a pull

Rennolazine 06-01-2019 11:29 PM

Doesn't sound right. Possibly the boost tables messed up due to your specific exhaust mods not working well with the OTS map. Happens periodically to my friend with cobb on his base after exhaust install.

LargePuppy 06-02-2019 09:47 AM

I loved the power from the tune, but the drive became clunky.... did a transmission reset and the drive quality improved significantly, can give that a shot

Cyberbug 06-02-2019 10:45 AM

With those mods you will need a pro tune
You can confirm that by just calling cobb

spdracerut 06-02-2019 02:31 PM


Originally Posted by 991.2GTS (Post 15880684)
Last week i installed the Cobb tune stage 2 on 2018 GTS. My car has ak exhaust, fabspeed 200 cel and header. Question is do you guys that have the Cobb tune feel like the pull less after 6000rpm, cause this is what happened to my car. I feel my car has a boost drop after 6000rpm, especially 3rd and 4th gear, I know the gauge in the car is not as accurate but it dropped to 12psi after 6000rpm. Anyone experience the same problem? Thanks guys

i did change to stage 1 map and it seems the boost drop not as much but probably because the stage 1 pull less before 6000rpm

Yeah... the Stage 2 tune was done on a car with only high flow cats, IIRC. So with the headers and exhaust, you freed up some more flow. I bet you're getting a lot of knock and the ecu is pulling ignition timing in the upper rpm range. However, with a COBB tune, it should be doing like ~21psi of boost at redline. So if it's dropping all the way to 12psi, there's some serious stuff going on where the engine isn't happy about something and trying to save itself by lowering boost/power. Or you have a massive boost leak. I'm assuming you have premium gas in it? I suppose it's possible you got a bad tank of gas. If you datalog it to see what the car is doing, it may help the diagnosis.

Cyberbug 06-02-2019 02:51 PM

That's the thing - once you start messing with stock, getting stability and reliability takes some effort.

PCA1983 06-02-2019 03:06 PM

You didn't mention any improvements on the intake side, like BMC and plenum mods. They say Stage 1 requires BMC or equal. For Stage 2 I'd want the BMC and plenum mods. I'd try those first, b4 spending more on another custom tune.

991.2GTS 06-02-2019 03:18 PM

I do have plenum but stock intake filter. After I change it back to stage 0 map everything is fine so I hope is not any boost leak. I will upload a Datalog a bit later and see if you guys can see the problem

991.2GTS 06-02-2019 03:20 PM


Originally Posted by spdracerut (Post 15881594)
Yeah... the Stage 2 tune was done on a car with only high flow cats, IIRC. So with the headers and exhaust, you freed up some more flow. I bet you're getting a lot of knock and the ecu is pulling ignition timing in the upper rpm range. However, with a COBB tune, it should be doing like ~21psi of boost at redline. So if it's dropping all the way to 12psi, there's some serious stuff going on where the engine isn't happy about something and trying to save itself by lowering boost/power. Or you have a massive boost leak. I'm assuming you have premium gas in it? I suppose it's possible you got a bad tank of gas. If you datalog it to see what the car is doing, it may help the diagnosis.


Im using the 91 map because the 94 gas that Iím using here in Canada got like 0 ethanol

minthral 06-02-2019 03:27 PM

I recall reading some GTS turbos dropping off PSI at higher RPMs due to poor lubrication and replacements was fix. It was a really obvious drop though...its normal for all 991.2 turbos to drop 2-3 PSI near redline.

Assuming its less than ideal conditions like hot outside or high altitude, GTS will boost 15/16 PSI in mid RPMs then near redline or past 6k you could see 12/13....so I would consider it normal for stock. Doubt you should go to dealer since its not stock. Your best bet is to call Cobb...they'll probably be more helpful. My 2 cents is that its normal and your guage is not functioning correctly due to tune (its probably boosting to 16 when it says 13 in the meter). Its possible Cobb tune made mid RPMs stronger and than higher RPMs so its a perception thing.

Cheshi143 06-02-2019 04:12 PM


Originally Posted by 991.2GTS (Post 15881681)
Im using the 91 map because the 94 gas that Iím using here in Canada got like 0 ethanol

You can and should use the 93 file.

COBB recommends data logging the car with the AP to verify there is no timing pull. If there is timing pull, then switch to the 91 file.

991.2GTS 06-02-2019 04:50 PM

6 Attachment(s)
The datalog7 and datalog10 one are from stage 2 map and the datalog11 one from the stage 1 map. Any expert here know how to analyze this? The ignition timing seems a bit off compare to other members' datalog

Btw, thank you for everyone's input, you guys have been helpful

Rennolazine 06-02-2019 05:30 PM

If its 94 RON then he needs the 91 octane map. 98 RON is for the 93 map

spdracerut 06-02-2019 05:46 PM


Originally Posted by 991.2GTS (Post 15881825)
The datalog7 and datalog10 one are from stage 2 map and the datalog11 one from the stage 1 map. Any expert here know how to analyze this? The ignition timing seems a bit off compare to other members' datalog

Btw, thank you for everyone's input, you guys have been helpful

Your car is pulling insane amounts of timing.

This is what a so-so timing map looks like. It's still pulling some timing at ~4200rpm as you can see by the step down/retard of the timing. But it's running about 9-10 degrees of timing above 6k rpm.
https://cimg8.ibsrv.net/gimg/rennlis...8c1ed2db2c.jpg

This is what your car is doing. It's running like -6 degrees. And you can see the drop in boost at ~5800rpm as the engine is trying to save itself.
https://cimg4.ibsrv.net/gimg/rennlis...b02552b0ff.jpg

Looking at the data, I highlighted the columns which show timing correction for each cylinder. You're getting massive timing retard for each cylinder which also causes the main ignition timing to drop.
https://cimg2.ibsrv.net/gimg/rennlis...3fa35ec2b3.jpg


I would try different gas. A different station and just the highest octane there is. This beyond a tune vs. parts issues. This is just bad gas in my opinion.



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