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Mk7 GTI High Knock Retard

astrotreb

New member
Location
Albuquerque, NM, USA
Car(s)
2018 GTI S
Hello!

I've been lurking these forums forever, and finally decided to post.

So, I recently bought a used 2018 GTI S DSG with 21k miles. I'm running COBB Stage 1 and a CTS downpipe.

I've been getting high knock retard on all 4 cylinders. No CEL. I have seen up to -6.88 degrees on a single cylinder. The datalog I attached only shows -4.5, but that's still higher than the normal 0 to -3. When I get the knock it's usually in drive mode; I can negate it a lot by running the car in manual and shifting around 2.5k or higher RPM. Another thing I have noticed is I can hear a subtle whistling noise when the knock is occurring. I took the car to the dealer, they scanned the car, and there were no fault codes. They told me it was a tune related issue, but I don't see how that can be the problem.

I'd appreciate all the help and feedback!

https://datazap.me/u/astrotreb/log-1622798510?log=0&data=7-12
 

daconchslop

Autocross Champion
Location
SC
Car(s)
ACS SE/Tech
Cobb maps are trash. Knock is not normal at any levels.
 

oddspyke

Autocross Champion
Location
Delaware
Car(s)
2016 GTI, 2018 ZL1
The Cobb maps aren't fast, but they can run fine with no knock. Time to start troubleshooting.

1. What fuel are you using and which stage 1 map? If you're running a 93 map and 91 fuel, you have your answer.

2. Flash back to stock and see if you still have knock.

3. Check your spark plugs, take a gap measurement.
 

Agray

Go Kart Champion
Location
Washington
Cobb maps are trash. Knock is not normal at any levels.
Isn’t the part of the strategy, especially on pump gas to ride the knock sensor within safe limits? -1 to -3 is really no big deal. Without doing that, isn’t there a lot of power left on the table?
 

daconchslop

Autocross Champion
Location
SC
Car(s)
ACS SE/Tech
If his plugs were that fried, he'd likely have misfires and a CEL by now.
 

daconchslop

Autocross Champion
Location
SC
Car(s)
ACS SE/Tech
Isn’t the part of the strategy, especially on pump gas to ride the knock sensor within safe limits? -1 to -3 is really no big deal. Without doing that, isn’t there a lot of power left on the table?
This is known as the jagged edge...
 

yoffer

Go Kart Newbie
Location
Jacksonville
NM in the summer on stock intercooler? Sounds like its time for upgrade.
 

astrotreb

New member
Location
Albuquerque, NM, USA
Car(s)
2018 GTI S
The Cobb maps aren't fast, but they can run fine with no knock. Time to start troubleshooting.

1. What fuel are you using and which stage 1 map? If you're running a 93 map and 91 fuel, you have your answer.

2. Flash back to stock and see if you still have knock.

3. Check your spark plugs, take a gap measurement.
1. I'm running the 91 map and using 91 fuel. Tried an octane booster, but that didn't change anything.

2. I reflashed to the simulated stock(stage 0) map, and still no change. I need to invest in a data logger, so I don't rely on the AP to log. Will come back to this later with a logger and uninstall the AP.

3. All 4 plugs were carbon fouled. Gaps were normal. I will post pictures tomorrow.
 

astrotreb

New member
Location
Albuquerque, NM, USA
Car(s)
2018 GTI S
Also this, especially since the Cobb stage 1 isn't meant to be run with a DP. But a better tune won't help if his plugs are fried and he's using the wrong fuel. Baby steps...
The map and octane I'm using is correct. The plugs were carbon fouled, but the gaps were fine.

Would running a DP on stage 1 cause -6.88 of KR?
 

oddspyke

Autocross Champion
Location
Delaware
Car(s)
2016 GTI, 2018 ZL1
1. I'm running the 91 map and using 91 fuel. Tried an octane booster, but that didn't change anything.

2. I reflashed to the simulated stock(stage 0) map, and still no change. I need to invest in a data logger, so I don't rely on the AP to log. Will come back to this later with a logger and uninstall the AP.

3. All 4 plugs were carbon fouled. Gaps were normal. I will post pictures tomorrow.

The map and octane I'm using is correct. The plugs were carbon fouled, but the gaps were fine.

Would running a DP on stage 1 cause -6.88 of KR?
Next step would be new spark plugs then and see if that clears it up. Make sure they are factory heat range.

I wouldn't think the DP by itself would cause that kind of knock, but running intake and exhaust parts you aren't tuned for can mess with your A/F ratio and cause things to foul more rapidly. Hopefully one of the guys on here with more tuning experience can chime in with a better answer.

Why would you need something else to datalog?

Edit: are you on the original factory plugs still or did you change them at some point?
 
Last edited:

Daily Driver

Drag Racing Champion
Location
New York
Car(s)
2020 GTI SE
It's suppose to be 0 knock? Well my EQT Custom tune still has knock up to -4 and they said it's not an issue, when I addressed it. They said as long as is not consistent. it's pretty consistent if it's for a whole 1000s of an RPM range. But hey I'm not EQT pro tuner what do I know.

If your car is 21k miles I suggest replacing Spark Plugs for NGK RS7 Plugs.
Then add 1 gallon of E85 and run it for atleast 15miles before you start hitting it. To make sure the gas has worked it's way in. Just so you know I get knock on Normal drive all the time, -2.75 is common and under. On sport mode it's like -1.75. in Manual I wouldn't get it cause I know how to shift better then DSG set points. But when I hit the car doing a 3rd gear Pull to 7000rpm I get knock at 3800 up to 4500 then it fluctuates between Cylinders. #4 has giving me the Most knock up to -4.75

So EQT suggestion to me, it's normal, Nothing to worry about. I put E85 on my own to try and relieve some KR numbers. I don't think it helped. Maybe 2 gallons of E85 would do it.

I've also heard you want 0 knock. Any knock is bad go with a pro tuner! So I went EQT and it knocks same as any other OTS tune, and they say it's fine. 🤷
 

GTI_Owner

Go Kart Champion
Location
USA
Car(s)
2016 GTI
1. I'm running the 91 map and using 91 fuel. Tried an octane booster, but that didn't change anything.

2. I reflashed to the simulated stock(stage 0) map, and still no change. I need to invest in a data logger, so I don't rely on the AP to log. Will come back to this later with a logger and uninstall the AP.

3. All 4 plugs were carbon fouled. Gaps were normal. I will post pictures tomorrow.
Before you purchase a datalogger make sure it will work with the AP tune installed. When Cobb moved to their consolidated ROM it rendered some functionality of my VCDS unusable, unless I flash back to the stock tune, since the ECU is no longer identifiable with the Cobb tune installed.

Also, search for a copy of the funktionsrahmen for simos18, it'll tell you all about how tuners can manipulate the knock retard. Unfortunately Cobb only reports knock retard and not knock sensor voltage so you don't have real knock information to evaluate.
 
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