Hesitation/flat spot around 4500-5000rpm

[Zippaks]

Hello everyone!
I've got 1.8t 20v Leon - APP engine with K04 hybrid turbo from S3, intercoolers from cupra R, 386cc injectors, coils from 2.0tfsi, forge DV, TIP, 3 inch downpipe..no cat etc.. Bought the car with remap - don't know which one. The problem I have is that whenever I go full throttle on 1st, 2nd, 3rd there something like flat spot between 4600-5000+ RPM - the car doesnt slow down but it doesnt really pull and the RPM's go 2-3x slower - it's like there is more throttle but I cant press it. On 4th gear, It still hesitates, but after a moment it goes and can reach 6500-7000rpm. From time to time it revs properly but 1/20 times. Despite the problem the car runs perfectly fine until it goes to the flat spot.

N75 is only electronically connected and I have MBC - set to 1.2bar. It holds the pressure perfectly fine, it doesn't overboost or something ( well with whatever N75 I tried the boost goes crazy on full throttle like 1.8-2 bars... and thats why I run MBC).

Things I checked:
MAF - good readings around 170-180g - it's working properly
DV - Vacuum tested it - everything is fine, tried with the oem one - same.
Leaks - pressure checked everything - no leaks
Actuator - pressure checked it - works fine it opens the waste gate.
I checked the spark plugs - all 4 looked perfectly fine - not wet, not black, they were brown, only one spark was little soaked with oil - maybe the cover there is leaking or someone splashed a little while filling and went in.

VCDS - no error codes...
I am suspecting - coils ? new spark plugs? fuel pump? I suspect the remap as well ? Whatever idea you folks have is well appreciated I am a bit of a noob so please explain into more details. Thank you for your time.

Logs on 4th gear

Logs on 3rd gear

More logs on 3rd gear

 

[mty12345]

Hello everyone!
I've got 1.8t 20v Leon - APP engine with K04 hybrid turbo from S3, intercoolers from cupra R, 386cc injectors, coils from 2.0tfsi, forge DV, TIP, 3 inch downpipe..no cat etc.. Bought the car with remap - don't know which one. The problem I have is that whenever I go full throttle on 1st, 2nd, 3rd there something like flat spot between 4600-5000+ RPM - the car doesnt slow down but it doesnt really pull and the RPM's go 2-3x slower - it's like there is more throttle but I cant press it. On 4th gear, It still hesitates, but after a moment it goes and can reach 6500-7000rpm. From time to time it revs properly but 1/20 times. Despite the problem the car runs perfectly fine until it goes to the flat spot.

N75 is only electronically connected and I have MBC - set to 1.2bar. It holds the pressure perfectly fine, it doesn't overboost or something ( well with whatever N75 I tried the boost goes crazy on full throttle like 1.8-2 bars... and thats why I run MBC).

Things I checked:
MAF - good readings around 170-180g - it's working properly
DV - Vacuum tested it - everything is fine, tried with the oem one - same.
Leaks - pressure checked everything - no leaks
Actuator - pressure checked it - works fine it opens the waste gate.
I checked the spark plugs - all 4 looked perfectly fine - not wet, not black, they were brown, only one spark was little soaked with oil - maybe the cover there is leaking or someone splashed a little while filling and went in.

VCDS - no error codes...
I am suspecting - coils ? new spark plugs? fuel pump? I suspect the remap as well ? Whatever idea you folks have is well appreciated I am a bit of a noob so please explain into more details. Thank you for your time.

Logs on 4th gear
View attachment 45700
Logs on 3rd gear
View attachment 45701
More logs on 3rd gear
View attachment 45702

Hey mate. Timing looks weird on the first Log. You're at -16 BTDC at 4500rpm. That would definitely cause a power dip between 5000 and 6000, and i would guess is a fault with the mapping. The reason is that as engine speed increases, you want the combustion to start earlier and earlier (so more degrees BTDC) so that the air/fuel mixture has more time to start burning, and produces pressure at the right time. With the timing being so close to zero between 5-6000rpm, most of your power will be wasted, the piston will already be half way down it's stroke by the time the pressure increases, rather than being just past TDC which i where you want to peak pressure to be. Hope that makes sense.

Also the lambda values look weird in the 3rd log. The actual and specified are miles apart and the actual is all over the place. Also the specified value is just a straight 0.435v which is not what I would suspect to see. What map is it?

Could run some more logs with the lambda Group 31, and timing Group 3.

 

[Zippaks]

Hey mate. Timing looks weird on the first Log. You're at 16 BTDC at 4500rpm then it starts coming back towards zero, despite there being no evidence of knock! That would definitely cause a power dip between 5000 and 6000, and i would guess is a fault with the mapping. The reason is that as engine speed increases, you want the combustion to start earlier and earlier (so more degrees BTDC) so that the air/fuel mixture has more time to start burning, and produces pressure at the right time. With the timing being so close to zero between 5-6000rpm, most of your power will be wasted, the piston will already be half way down it's stroke by the time the pressure increases, rather than being just past TDC which i where you want to peak pressure to be. Hope that makes sense.

Also the lambda values look weird in the 3rd log. The actual and specified are miles apart and the actual is all over the place. Also the specified value is just a straight 0.435v which is not what I would suspect to see. What map is it?

Could run some more logs with the lambda Group 31, and timing Group 3.

First thanks for your time mate. Sadly I have no idea about the map. But yeah that lambda (o2) shows only 0.435v specified which is strange. Tomorrow I will run more logs of what you said and will come back.

 

[Zippaks]

Here are the logs.

3rd gear: Actually that run went kind of ok

3rd gear: Here I felt the invisible wall around 5000k rpm

2nd gear run:

Another 2nd gear run:

Another 2nd gear run:

 

[mty12345]

It's still got hardly any timing advance despite showing no signs of knock in your other logs. That coupled with the lack of any specified lambda values and the extensive mods, I think you really need to get it on a dyno with a good tuner, especially as you said the boost goes nuts on the N75 and you have to use a MBC etc. Without a known good map, i think you could be chasing your tail on this. Also possuble that some VCDS codes have been coded out of the ECU to avoid failing emissions etc.

 

[Zippaks]

I agree and I tried it all. I don't find any reason to witch hunt and make more problems. It seems that either I need a good mapper to remap the car or I need an exorcist . Thank you for looking into the thread @mty12345 I will try to search for someone - competent map the car and will report back these weeks.

 

[mty12345]

I agree and I tried it all. I don't find any reason to witch hunt and make more problems. It seems that either I need a good mapper to remap the car or I need an exorcist . Thank you for looking into the thread @mty12345 I will try to search for someone - competent map the car and will report back these weeks.

No worries mate, and yh let us know how you get on.

 

[Zippaks]

No worries mate, and yh let us know how you get on.

Btw interesting is that when the problem is happening I saw the boost gauge starts to overboost but a little by little, meanwhile the map sensor readings are just fine. I tired holding for longer my foot on the pedal and the overboost goes back to normal levels on the gauge and at the same time car feels better for 1-2 seconds. I am pretty confident my MAP sensor is totaly fine but... these gauges I am not so sure which should I belive.