Boost/power issues - plots and logging/trouble shooting advice?

[McDub]

Hey all,

I have issues with my golf R underperforming of late.
It seems to be when the air temp is at or above 25 degrees, under load the car feels like a dog on the freeway in 4th/5th W.O.T, like the engine timing is being heavily retarded.

I've tried logging boost with a cheap Bluetooth adapter and the Torque app.

Car had a Stage 1 APR tune, no other mods.
As November came along performance seemed down, this was actually after installing a new clutch with SMFW.
Trying to improve it, I changed the DV to a GFB DV+
Then I added a Volant intake
I put in a new PCV valve (there was some diaphragm bypass)
Changed spark plugs and gapped at 0.028"
Then autotech HPFP (and new cam follower), and changed software to Stage 1+
Still little improvement.

Then today I had a new N75 put in while my timing belt and water pump was done.
The mechanics commented that it felt fine yesterday (when it was 20deg), but it didn't feel like it was boosting right today (25 degrees). I had the exact thoughts as them, it felt beautiful driving yesterday morning, and a dog this afternoon.

I've attached some plots of the boost.
As you can see, it's kind of all over the shop.
Sometimes it struggles to climb, other times it overshoots and drops very rapidly to around 17psi before picking up again.

I've had it smoke tested briefly, but no-one seems to offer pressure testing so I'm thinking of making a DIY pressure tester.


What can I log to help diagnose this problem?
I can't seem to be able to log requested/actual boost on this Torque app, but I might try get a ross tech cable this weekend.

My thoughts on what it could be:
Cat is partially blocked?
A temp sensor is out?
Map sensor?
MAF sensor?
Hose/boost leak?
Knock sensor?
Carbon buildup on intake manifold?

Whatever it is, it seems quite dependent on ambient air temp, however cooler temps could just be masking the problem due to more power, as the boost still seems inconsistent at lower temps.

Cheers!

P.S I'm in the Sydney area (north) if anyone has any mechanics they specifically know are good at logging and diagnosing these hard to troubleshoot issues (preferably an APR dealer).

PPS. With the SMFW in, it caused the whole cabin to vibrate.
I couldn't stand it and went back to a DMF after a few months. Fortunately the mechanic refunded.
I never heard back if the clutch was unbalanced, or if maybe my engine vibrates a bit more than normal and hence doesn't like the SMFW.
The reason I mention this, is if my engine vibrates a bit more for some reason, this could potentially cause issues with the knock sensor?

[h100vw]

Find someone to log it with vcds. Timing retard.

[McDub]

Find someone to log it with vcds. Timing retard.

Yeah it looks like it's out around 8 degrees at WOT on the plots above, I presume that's significant?

Any recommendations for people in Sydney? From memory you're down south a bit (you had a stab at a similar issue of mine on my old MKIV gti actually!)

I might borrow a friends ross-tech cable this weekend if you can suggest things that are worth logging.
I imagine logging requested boost/actual will be pretty key?

[h100vw]

8 degrees would be like someone put 91 in it. Any chance it has contaminated fuel. Could be many things though. I'd put the car back as standard as possible. Certainly the airbox.
Check the fuel trims though, block 032 with VCDS. I have seen Volant intake throw trims out.

[McDub]

8 degrees would be like someone put 91 in it. Any chance it has contaminated fuel. Could be many things though. I'd put the car back as standard as possible. Certainly the airbox.
Check the fuel trims though, block 032 with VCDS. I have seen Volant intake throw trims out.

I've tried changing who I've used for fuel and no difference.
Today it was cool again, but ran like a dog, so doesn't seem to be air temp affected.
I've now got a ross-tech cable and will be doing the logs that APR request for trouble shooting.
APR - VCDS Datalogging Guide
As my tune is meant to be for an intake and HPFP, I think i'll leave it as is, however I was suggested to put the original DV back on.
Just need to find somewhere safe to do the pulls!

[Lucas_R]

Just need to find somewhere safe to do the pulls!

If you are in Nth Sydney - hit the M1 heading toward central coast after 9pm to do some 4th gear pulls.

[McDub]

If you are in Nth Sydney - hit the M1 heading toward central coast after 9pm to do some 4th gear pulls.

4th gear, what's that 140km/hr at redline?
Bit tricky doing that on a road that you can't scope for cops hiding though. Would prefer a stretch where I can loop a U-turn with both sides visible. Hmmm. Or maybe just do 3rd gear pulls on the M1 (about 105km/h?). But yeah 4th gear would be preferable

[Lucas_R]

4th gear, what's that 140km/hr at redline?
Bit tricky doing that on a road that you can't scope for cops hiding though. Would prefer a stretch where I can loop a U-turn with both sides visible. Hmmm. Or maybe just do 3rd gear pulls on the M1 (about 105km/h?). But yeah 4th gear would be preferable

3rd gear will work but i think they prefer 4th gear pulls as the VCDS will get more reference points while the engine revs. I use an industrial estate that's close by to do my logs - at least once its after business hours it gets pretty quiet in there.

My Mk6 R did about 96kph in 2nd so 3rd would be prob 110-120kph.

[McDub]

3rd gear will work but i think they prefer 4th gear pulls as the VCDS will get more reference points while the engine revs. I use an industrial estate that's close by to do my logs - at least once its after business hours it gets pretty quiet in there.

My Mk6 R did about 96kph in 2nd so 3rd would be prob 110-120kph.

Hmmm so 4th gear is looking like jail speeds
A non-public rd would be great, otherwise it's looking like 3rd.


My hunch is knock sensors at this stage.
The SMF I had put in when this problem presented could have caused damage to them.
I've heard they are quite sensitive to their required tightening torque, and no doubt also to vibration I imagine.
The only thing is the mechanics I've spoken say this isn't common.

I did find this mechanic from Ecuador who replaced everything on two cars until he replaced their knock sensors which fixed the problem:
Vw Golf GTI MKV 2.0TFSI unusual fail "HELP"
Sounds potentially very similar, including the inconsistent nature. I'll see if my logs compare to his.

[McDub]

Managed all 5 of the APR runs/rounds tonight.
Car actually felt OK unfortunately, so I may need to redo when it's feeling a bit worse.
Although I rarely redline my car so hard have good judgement here.

Here's a "round 5" in 3rd:

Boost requested seems to be very close to actual

STAMP	Engine Speed - (G28)	Mass Air Flow - Sensor (G70)	Throttle Valve Angle	Ignition - Timing Angle	Timing Retardation - Cylinder 1	Timing Retardation - Cylinder 2	Timing Retardation - Cylinder 3	Timing Retardation - Cylinder 4	Lambda Control - Bank 1 (actual)	Boost Pressure - Control (N75)	Boost Pressure - (specified)	Boost Pressure - (actual)
	 /min	 g/s	 %	 °BTDC	°KW	°KW	°KW	°KW		 %	 mbar	 mbar
0.48	2040	7	5.1	-6.8	0	0	0	0	1.99	0	280	1030
1.12	1360	4.39	3.5	-9	0	0	0	0	1.99	0	260	1020
1.78	1880	5.61	4.3	-6.8	0	0	0	0	1.99	0	270	1010
2.43	1640	5.19	3.9	-8.3	0	0	0	0	1.99	0	270	1010
3.06	1680	27.81	26.3	18.8	-4.5	-1.5	0	-0.8	1.99	0	1460	990
3.71	1840	37.72	99.6	19.5	-2.3	0	-0.8	0	0.95	33.3	1690	1080
4.37	2080	47.61	99.6	17.3	0	-0.8	-0.8	0	0.99	33.7	1690	1230
5.01	2360	63.03	99.6	12.8	0	0	0	0	0.95	36.5	1880	1420
5.65	2720	85.25	99.6	9	-0.8	0	-2.3	-2.3	0.97	51.8	2080	1650
6.3	3120	130.33	99.6	6	0	0	-1.5	-2.3	0.9	64.3	2290	2060
6.99	3640	175.19	99.6	6.8	0	0	0	0	0.88	56.1	2360	2420
7.64	4240	186.58	99.6	7.5	0	0	-1.5	0	0.88	56.9	2430	2450
8.28	4760	209.08	99.6	9	0	0	0	0	0.87	60	2490	2440
8.92	5240	228.69	99.6	8.3	0	-1.5	-1.5	-1.5	0.86	65.9	2460	2470
9.58	5720	244	99.6	11.3	0	-2.3	0	-2.3	0.8	74.5	2360	2500
10.23	6160	245.97	99.2	15	0	0	0	0	0.79	73.3	2230	2390
10.89	6560	250.31	98.8	15	0	0	0	-1.5	0.77	67.5	2130	2310

Here's the "round 2" in 4th:

STAMP	Engine Speed - (G28)	Ignition - Timing Angle	Timing Retardation - Cylinder 1	Timing Retardation - Cylinder 2	Timing Retardation - Cylinder 3	Timing Retardation - Cylinder 4	Lambda Control - Bank 1 (actual)	Accel. Pedal Pos. - Sensor 1 (G79)	Engine Load - (actual Value)	Boost Pressure - (actual)	Rail Pressure - (actual)
	 /min	 °BTDC	°KW	°KW	°KW	°KW		 %	 %	 mbar	 bar
0.09	1600	23.3	0	0	0	0	0.96	99.6	70.7	1010	89.29
0.49	1680	16.5	0	0	-3.8	0	0.98	99.6	83.5	1000	94.9
0.87	1760	18.8	-3	0	-2.3	0	1.02	99.6	88.7	1070	104.36
1.31	1840	18.8	-1.5	-1.5	-0.8	-0.8	0.98	99.6	95.5	1170	106.53
1.72	1920	18	-3.8	-1.5	-1.5	0	0.95	99.6	100.8	1240	108.88
2.11	2040	12	-2.3	0	-2.3	-1.5	0.95	99.6	107.5	1310	110.56
2.53	2160	11.3	0	0	-0.8	0	0.95	99.6	116.5	1390	113.5
2.92	2240	10.5	-0.8	0	0	0	0.99	99.6	123.3	1470	114.18
3.33	2400	9.8	-1.5	-0.8	-0.8	-2.3	0.98	99.6	131.6	1560	114.19
3.73	2520	9.8	-1.5	-2.3	0	-0.8	0.95	99.6	142.1	1670	115.44
4.14	2680	6	0	-0.8	-3	-1.5	0.91	99.6	155.6	1800	115.17
4.53	2840	7.5	0	-0.8	-3	0	0.91	99.6	176.7	1970	115.73
4.94	3000	3	0	-2.3	-3.8	-2.3	0.89	99.6	191.7	2200	116.05
5.34	3200	4.5	-2.3	-0.8	-3.8	-0.8	0.89	99.6	191.7	2430	116.75
5.75	3400	6	-0.8	0	-2.3	0	0.89	99.6	191.7	2410	117.39
6.17	3560	6.8	0	0	-0.8	0	0.88	99.6	191.7	2380	114.72
6.56	3760	6.8	0	0	0	0	0.88	99.6	191.7	2390	116.8
6.98	3960	6.8	0	0	0	0	0.88	99.6	191.7	2420	116.18
7.42	4160	7.5	0	0	0	0	0.86	99.6	191.7	2410	115.81
7.81	4280	7.5	0	-1.5	0	0	0.85	99.6	191.7	2410	115.51
8.23	4480	8.3	0	-2.3	0	0	0.86	99.6	191.7	2430	114.92
8.62	4640	7.5	-1.5	-0.8	0	-0.8	0.86	99.6	191.7	2450	114.01
9.04	4800	9	0	0	0	0	0.85	99.6	191.7	2490	115.22
9.47	4960	9	0	0	0	0	0.86	99.6	191.7	2500	118.52
9.87	5080	7.5	-1.5	-3	-0.8	-0.8	0.84	99.6	191.7	2520	112.92
10.37	5240	6.8	-2.3	-1.5	0	-2.3	0.82	99.6	191.7	2500	113.84
10.76	5400	6.8	-0.8	-2.3	-1.5	-0.8	0.8	99.6	191.7	2540	121.18
11.19	5520	10.5	0	-1.5	0	0	0.8	99.6	191.7	2550	125.85
11.61	5640	9.8	0	-2.3	-0.8	-1.5	0.8	99.6	191.7	2530	122.11
11.99	5760	12	0	-3.8	0	-2.3	0.78	99.6	191.7	2510	116.83
12.37	5880	11.3	-1.5	-2.3	-1.5	-0.8	0.77	99.6	191.7	2490	121.98
12.8	6000	9.8	0	-3.8	0	-2.3	0.77	99.6	190.2	2450	119.99
13.22	6120	11.3	0	-5.3	0	-3.8	0.78	99.6	186.5	2410	112.28
13.7	6120	33	0	0	0	0	0.84	0	16.5	2230	128.16
14.14	6040	33	0	0	0	0	0.95	0	17.3	1330	129.59
14.55	5800	33	0	0	0	0	1.05	0	18	1180	126.17
14.95	5560	6	0	0	0	0	1.27	0	18	1130	87.4

Anything to make of that?

[h100vw]

250gs is just over 300hp at the crank. Boost looks normal imo. So if I was presented with that log I'd be sure it's tuned.