Hi all,

I didn't use my vRS for a few months and now it has a weird boost problem.

It pretty much has all the usual stage1 mods:

Supersprint cat back exhaust

Carbonio induction kit

Baily re-circ DV

Jabba re-map

Uprated wind mount intercooler

It used to run about 17-18psi (1.2-1.3bar) peak and back off to around 14-15psi (1bar). Now it shoots up to way past 20psi (off my gauge) and then drops instantly to below 10psi, then shoots back up again, dropping again etc. It keeps doing this all the way through the rev range. Basically the boost gauge just shoots up and down and never settles.

Fault codes are:

P1297

P0411

I have spent ages searching on here, and so far I have:

Swapped back to the stock DV - No difference

Bypassed the N249 Valve - No difference, but the DV sounds nicer

Looked for obvious air leaks, I cant find any. I replaced the Y shape hose and a few others under the inlet manifold last year due to air leaks.

I don't know what else to try, possibly the N75? Its original so could be buggered?

Thanks

Trev

Also,

Could it be throttle body related? How do I go about resetting the throttle? I have vag-com...............

Many thanks people!!!

Trev

Here's how to do a throttle body alignment:

http://wiki.ross-tech.com/wiki/index.php/Throttle_Body_Alignment_(TBA)

Does sound like a faulty N75 if it's surging, then again the two codes you've got suggest a boost leak and a problem with your secondary air injection system as well.

Cleaning the throttle body and resetting it may get rid of the P1297 code.

Might be worth checking your secondary air system over re. the P0411 code, especially the combi valve on the side of the exhaust as if thats stuck open it could be affecting the turbo (the exhaust gases are escaping through the hole as well as down the exhaust)

Are you getting those boost figures from VAG-Com or from a boost gauge?

Many thanks for your reply Mr Eyebrow!

I just blasted a load of carb cleaner through the throttle body, unfortunately my freeby version of vagcom wont let me do a reset.

My secondary air pump is needs a good bodge up, I did put a few self tappers in where the rivets were a year or so back but it makes noise again from cold starts. Silly design! will bin the whole lot one day if I can be arsed!

I will check the combi valve on the exhasut, any pointers as to how to tell if its ok?

If all else fails, I will have to try a new N75.

Many thanks again

Trev

The code's probably from the knackered pump then rather than the combi valve. You're better off taking the pump off and bolting the two halves together with some 4mm bolts and washers instead of using self tapping screws or they'll just come apart again. Or take the plunge and bin the whole secondary air system.

Could always borrow a working N75 to test it if you know anyone near you with a VAG 1.8T car.

Check the diagnostics section of the forums and see if there's anyone near you with the full version of VCDS that can do the TB reset for you - you need to take it off and clean it properly as well and put a new gasket on rather than just spraying it with a bit of carb cleaner.

I'd go with a dodgy n75 valve. It's the main thing that controls the boost pressure, so if that's not working, you haven't got a chance. When the boost drops, do you hear the dv operating. It could be that the n75 has failed completely, so the ecu is opening the dv instead.

Thanks for the replies

I cleaned the N75 with carb cleaner and seems to have helped a little. It still boosts to 20psi, but not over that. Then rapidly drops to 14-15, shoots back up to 17-18, then drops back to about 14ish again when the revs rise past 5-6k.

Not exactly ideal, but a tad better than before!

I will bolt the secondary air pump together and check the exhaust side works ok and also clean the TB properly.

The DV was not dumping boost with the fluctuations, I bypassed the N249 anyway to check if that was playing up.

Unfortunately I don't know anyone with a 1.8t at the minute, or I would try a different N75.

Does anyone run a manual boost controller (bleed valve, brass monkey or what ever its called) on these cars? I know you would lose the safety features, but it would help me find out the problem and I am sure I have one in the garage somewhere.

I would honestly rather run it at a consistent 1 -1.1 bar anyway.

On all my previous turbocharged cars, using an electronic boost controller (Apexi AVCR for example) seemed the norm but I haven't heard of people bothering on 1.8t cars.

Thanks again!!

Trev

Whereabouts are you? If you're anywhere near Wakefield, I have a working n75 you can try, and have full vagcom too.

They don't tend to run standalone boost controllers as the ECU and the map on it should do it all for you. Unfortunately the only controls between the ECU and the turbo are the N75 and N249 and they do have a habit of going wrong on these cars.

i had a similar problem, mine was a split hose to the n75. the split was right next to the clip so couldnt be seen, give the hoses a good twist and one will come off. mine was the one that goes in the top of the n75 which goes to the actuator irrc

Thanks for the replies

rk696, brilliant offer but unfortunately I am miles away from you!

I went through all the pipes again and one of the pipes that comes out of the bottom of the inlet manifold was a tad oily, probably leaking as the jubilee clip was not properly tight.

Also, the aftermarket DV is definitely buggered, I can blow through it! Don't know about my standard one, seems ok to me but everyone says they are rubbish, It could well be leaking at high boost. I might block it off and go for a run.

Maybe I should forget the bleed valve for the long term, I have found one in my garage though! I might pop in on just to see if the boost is consistent using it.

I suppose it's just a process of elimination, if it's still erratic with the DV blocked off and a manual boost controller then it must be leaking somewhere!

I have also managed to get a full version of vag.com - I done the throttle body re-set and I tried logging the boost yesterday but not quite sure ho to get in on to a graph that makes any sense!

Many thanks again!

Trev

Here's a link that should help with making a graph of your VAG-Com log (assuming you've got Excel)

www.vaglinks.com/OBDII/Vag-com_Data_Logging_And_Graphing.pdf

Or put the figures up on here and I'll graph them for you.

Re. the bleed valve, I'd be a bit reluctant to fit one as I've no idea how much pressure (if any) the standard N75 bleeds out. I suppose you could run a vac pipe direct from the turbo pipework to the actuator with the bleed valve mounted in it, that way you have vacuum keeping the wastegate closed while off boost, but as the boost pressure builds the wastegate opens. I would probably have the bleed valve completely closed to start off with which will mean the wastegate will open really early to be on the safe side, then adjust it until the required boost is achieved. You'd also have to block off the hole in the inlet pipework where the N75 was and leave the N75 plugged in so the ECU doesn't throw a code.

Still a much better idea to find and fit a known working N75 though, that way the ECU has full control based on the MAP sensor readings and there's less chance of the turbo overspeeding.

Re. the oily pipe, did you flex it a bit to see if it's split at all? Mine was like that with lots of oily mess spattered all near it and you couldn't see the split unless you twisted the pipe, but it was a good inch or so long!

Many thanks for all your help people, I really appreciate it!

The pipes don't appear to have any splits in them, I data logs a few runs today with the DV removed and holes blocked up. I am sure there is a problem with both my DV's as the boost is substantially better than before. I have tried to do a graph, but I am useless! Can you please put these figures on a graph? I hope they make sense!

The first run I logged boost, torque and the N75. The second I just logged the boost:

1st Log:

Thursday 5 April 2012 12:38:03 06A 906 032 HN 1.8L R4/5VT 0001 Group A: '115 Group B: '120 Group C: '118 Engine Speed Engine Load Spec. Boost Actual Boost Engine Speed Spec Load Curr Load ASR Status Engine Speed Air Temp In Boost Dut Cyc Actual Boost TIME 700-6800 RPM 15-150% 990-1800 mbar <=1800 mbar TIME 700-6800 RPM 0-399 Nm 0-260 Nm active yes/no TIME 700-6800 RPM <=110 C 0-100% <=1800 mbar MARKER STAMP /min % mbar mbar STAMP /min Nm Nm STAMP /min °C % mbar 0.91 2160 32.3 1000 1070 0 2160 399.8 29.4 ASR OFF 0.42 2160 30 0 1070 2.22 2320 100.8 2070 1400 1.31 2200 399.8 29.4 ASR OFF 1.71 2200 30 92.2 1070 3.42 2720 154.9 2170 2190 2.62 2440 399.8 196 ASR OFF 3.02 2560 30 89.4 1950 4.73 3240 160.9 2210 2200 3.93 2920 399.8 305.8 ASR OFF 4.33 3080 33 74.9 2300 6.05 3760 160.2 2200 2170 5.13 3400 399.8 305.8 ASR OFF 5.53 3560 36 74.9 2200 7.26 4200 157.9 2210 2210 6.45 3880 399.8 303.8 ASR OFF 6.85 4040 38 76.9 2220 8.46 4640 157.1 2150 2160 7.65 4360 399.8 297.9 ASR OFF 8.05 4480 40 76.1 2190 9.66 5040 153.4 2100 2100 8.86 4760 399.8 290.1 ASR OFF 9.26 4960 43 75.7 2090 10.88 5440 151.9 2080 2060 10.06 5200 399.8 274.4 ASR OFF 10.48 5320 45 78.8 2050 12.27 5880 146.6 2010 1980 11.28 5560 399.8 258.7 ASR OFF 11.79 5720 49 81.6 2020 13.69 5440 11.3 1000 1280 12.69 5960 399.8 235.2 ASR OFF 13.2 6080 51 82.4 1950 14.91 4920 160.2 2150 2220 14.09 4840 399.8 113.7 ASR OFF 14.49 4880 47 80 2310 16.2 5160 153.4 2020 2090 15.31 5000 399.8 272.4 ASR OFF 15.8 5080 51 76.5 2090 17.61 5320 132.3 1930 1790 16.7 5200 399.8 248.9 ASR OFF 17.1 5280 54 67.5 1880 19.13 5560 152.6 2050 2050 18.12 5400 399.8 258.7 ASR OFF 18.62 5480 55 80 2080 20.32 5440 11.3 1000 1220 19.53 5560 399.8 149 ASR OFF 19.93 5520 54 0 1410 21.63 5080 12 1000 1070 20.73 5320 399.8 0 ASR OFF 21.23 5200 46 0 1110 22.84 4760 12 1000 1100 22.03 4960 399.8 0 ASR OFF 22.43 4840 44 0 1100 24.25 4560 12 1000 1100 23.34 4680 399.8 0 ASR OFF 23.74 4600 42 0 1100 25.55 4360 12.8 1000 1090 24.65 4480 399.8 0 ASR OFF 25.05 4440 41 0 1090 26.86 4120 12 1000 1080 25.95 4320 399.8 0 ASR OFF 26.36 4240 40 0 1090 28.07 3920 12.8 1000 1070 27.26 4080 399.8 0 ASR OFF 27.66 4000 39 0 1070 29.27 3680 12.8 1000 1070 28.47 3840 399.8 0 ASR OFF 28.87 3760 39 0 1070 30.47 3520 12.8 1000 1070 29.67 3640 399.8 0 ASR OFF 30.07 3560 39 0 1070 31.79 3400 12.8 1000 1070 30.89 3480 399.8 0 ASR OFF 31.39 3440 39 0 1070 33.1 2640 13.5 1000 1070 32.3 3360 399.8 0 ASR OFF 32.7 3200 39 0 1070 34.41 4040 13.5 1000 1070 33.5 2760 399.8 0 ASR OFF 33.9 4040 38 0 1070 35.7 3800 12.8 1000 1070 34.81 4000 399.8 0 ASR OFF 35.21 3920 38 0 1070 37.02 3640 12.8 1000 1070 36.1 3720 399.8 0 ASR OFF 36.52 3680 37 0 1070 38.23 3800 164.7 2250 2310 37.42 3640 399.8 0 ASR OFF 37.82 3680 38 85.1 1470 39.45 4280 161.7 2230 2250 38.63 3960 399.8 301.8 ASR OFF 39.03 4120 44 78.4 2240 40.84 4720 160.9 2170 2190 39.93 4440 399.8 303.8 ASR OFF 40.34 4560 48 77.6 2210 42.15 5160 154.9 2140 2110 41.24 4880 399.8 290.1 ASR OFF 41.66 5000 50 76.9 2140 43.45 5560 153.4 2050 2080 42.55 5280 399.8 266.6 ASR OFF 42.97 5400 53 82 2110 44.68 5880 145.9 2010 2000 43.86 5640 399.8 248.9 ASR OFF 44.26 5760 55 81.2 2030 45.98 4520 9 1000 1170 45.08 5560 399.8 0 ASR OFF 45.56 4680 51 0 1190 47.19 4720 159.4 2200 2260 46.38 4600 399.8 172.5 ASR OFF 46.79 4640 51 79.6 2290 48.49 4960 154.9 2150 2150 47.69 4840 399.8 276.4 ASR OFF 48.09 4880 56 77.6 2160 49.69 5160 154.9 2150 2140 48.89 5000 399.8 268.5 ASR OFF 49.29 5080 57 78.8 2140 51 4080 12.8 1000 1240 50.09 5200 399.8 268.5 ASR OFF 50.5 4880 57 0 1670 52.31 4040 12 1000 1070 51.4 4120 399.8 0 ASR OFF 51.91 4080 49 0 1080

2nd Log:

Thursday 5 April 2012 12:42:27 06A 906 032 HN 1.8L R4/5VT 0001 Group A: '115 Group B: Engine Speed Engine Load Spec. Boost Actual Boost TIME 700-6800 RPM 15-150% 990-1800 mbar <=1800 mbar TIME MARKER STAMP /min % mbar mbar STAMP 0 1480 12.8 1000 1020 0.4 1440 12.8 1000 1020 0.82 1440 18 1000 1020 1.21 1480 40.6 1000 1010 1.62 1480 48.1 1000 1030 2.01 1480 48.1 1000 1050 2.41 1520 48.1 1000 1060 2.81 1520 45.1 1000 1070 3.23 1560 45.1 1000 1070 3.73 1560 40.6 1000 1080 4.13 1560 31.6 1000 1070 4.53 1600 30.8 1000 1050 4.93 1600 31.6 1000 1050 5.34 1600 32.3 1000 1040 5.74 1600 32.3 1000 1040 6.14 1640 32.3 1000 1040 6.54 1600 34.6 1000 1040 6.94 1600 35.3 1000 1040 7.45 1560 38.3 1000 1050 7.85 1560 39.1 1500 1050 8.25 1600 75.9 1480 1100 8.75 1680 80.5 1610 1200 9.15 1720 85.7 1670 1270 9.56 1800 90.2 1750 1320 10.06 1920 99.2 1890 1420 10.46 2040 110.5 2030 1530 10.86 2120 122.6 2050 1670 11.28 2280 133.1 2090 1840 11.77 2440 146.6 2120 2040 12.27 2640 157.1 2160 2210 12.68 2800 166.2 2190 2300 13.18 3000 167.7 2230 2310 13.68 3200 160.9 2200 2190 14.09 3360 160.2 2180 2170 14.49 3520 160.9 2160 2170 14.89 3640 159.4 2170 2150 15.31 3800 159.4 2190 2170 15.79 3960 158.6 2210 2190 16.2 4120 159.4 2200 2200 16.6 4240 159.4 2180 2210 17.02 4400 159.4 2170 2160 17.5 4560 158.6 2150 2170 17.92 4680 157.9 2130 2160 18.32 4840 156.4 2120 2130 18.81 4960 155.6 2110 2080 19.21 5080 153.4 2100 2060 19.61 5200 154.9 2090 2080 20.01 5320 153.4 2090 2080 20.43 5440 151.9 2090 2050 20.83 5520 152.6 2040 2030 21.24 5640 150.4 2020 2040 21.64 5760 149.6 2020 2020 22.04 5840 146.6 2000 1990 22.44 5920 145.1 1990 1970 22.84 6000 146.6 1980 1970 23.34 6120 142.9 1800 1920 23.76 6200 130.8 1670 1780 24.25 6240 117.3 1660 1610 24.65 6280 119.5 1660 1610 25.07 6360 118.8 1710 1630 25.47 6440 121.8 1770 1700 25.85 6000 12 1000 1610 26.36 5040 12 1000 1140 26.76 4920 12 1000 1150 27.16 4760 12 1000 1100 27.56 4680 12 1000 1080 27.96 4560 12 1000 1110 28.36 4400 12 1000 1090 28.76 4320 12 1000 1090 29.18 4200 12.8 1000 1090 29.58 4120 12.8 1000 1080 29.98 4080 12.8 1000 1080 30.47 4040 12.8 1000 1070 30.89 4000 12.8 1000 1070 31.29 3960 12.8 1000 1070 31.69 3920 12 1000 1070 32.09 3880 12.8 1000 1070 32.49 3840 12 1000 1070 32.89 3800 12 1000 1070 33.29 3760 12 1000 1070 33.7 3720 12.8 1000 1070 34.1 3680 12 1000 1070 34.51 3640 12.8 1000 1070 34.9 3600 12.8 1000 1070 35.3 3480 12.8 1000 1070 35.82 3280 12.8 1000 1070 36.31 3120 12.8 1000 1070 36.71 3040 12.8 1000 1070 37.22 2920 13.5 1000 1070 37.62 2840 13.5 1000 1070 38.02 2800 13.5 1000 1070 38.42 2760 13.5 1000 1070 38.82 2680 13.5 1000 1060 39.22 2640 13.5 1000 1060 39.64 2600 13.5 1000 1060 40.14 2560 13.5 1000 1060 40.54 2520 13.5 1000 1060 1 40.94 2520 13.5 1000 1060 41.34 2480 13.5 1000 1060 41.75 2480 13.5 1000 1060 42.25 2400 13.5 1000 1060 42.65 2280 14.3 1000 1060 43.05 1720 14.3 1000 1050 43.45 1520 15.8 1000 1030 43.86 2360 12.8 1000 1040 44.26 2600 13.5 1000 1050 44.66 2480 13.5 1000 1050 45.06 2400 13.5 1000 1050 45.46 2320 13.5 1000 1050 45.97 2280 13.5 1000 1050 46.47 2160 13.5 1000 1050 46.87 2040 13.5 1000 1050 47.27 2040 13.5 1000 1050 47.69 2080 45.1 2070 970 48.09 2080 85 2090 1180 48.49 2200 105.3 2080 1440 48.89 2280 121.8 2100 1670 49.29 2440 136.8 2130 1900 49.69 2560 148.1 2160 2080 50.09 2760 159.4 2200 2230 50.5 2920 166.9 2220 2310 51 3080 166.2 2240 2280 51.4 3240 162.4 2220 2240 51.8 3400 162.4 2200 2220 52.2 3560 160.9 2190 2180 52.61 3720 159.4 2210 2160 53.01 3880 161.7 2230 2230 53.41 4000 160.2 2250 2220 53.83 4160 160.2 2230 2230 54.31 4320 159.4 2210 2230 54.72 4480 158.6 2190 2190 55.13 4600 158.6 2180 2190 55.53 4760 158.6 2160 2180 55.94 4880 156.4 2140 2150 56.42 5040 154.9 2130 2070 56.84 5160 154.1 2130 2100 57.35 5320 154.1 2130 2050 57.73 5440 152.6 2100 2080 58.13 5560 150.4 2040 2070 58.55 5680 148.9 2020 2020 59.04 5840 147.4 2000 1990 59.46 5920 142.9 1990 1960 59.86 6040 143.6 1980 1940 60.26 6120 141.4 1970 1970 60.66 6200 139.1 1960 1900 61.06 6320 136.8 1950 1940 61.46 6400 133.8 1890 1890 61.88 6440 133.1 1820 1900 62.37 6560 127.8 1720 1810 62.77 6280 22.6 1000 1540 63.17 6240 11.3 1000 1290 63.57 5880 12 1000 1200 63.97 5440 11.3 1000 1090 64.37 5120 12 1000 1110 64.88 4760 12 1000 1100 65.28 4520 12 1000 1100 65.68 4320 12.8 1000 1090 66.08 4080 12.8 1000 1090 66.48 3920 12.8 1000 1090 66.88 3760 12.8 1000 1080 67.28 3600 12.8 1000 1080 67.7 3440 12 1000 1080 68.19 3240 12 1000 1080 68.59 3040 12 1000 1070 68.99 2960 13.5 1000 1070 69.41 2800 13.5 1000 1070 69.91 2600 13.5 1000 1070 70.31 2520 12.8 1000 1060 70.71 2440 13.5 1000 1060 71.11 2360 13.5 1000 1060 71.52 2320 13.5 1000 1050 71.92 2280 14.3 1000 1060 72.42 2200 13.5 1000 1050

I cleared the 17705/P1297 code before the runs, and I just scanned the car again and now I have 17705/P1297 and 17608/P1200 -Boost pressure valve mechanical malfunction!

Never had that one before!

Many thanks

Trev

After searching about the 17068 code, its probably logged due to me bypassing the N249 and removing the dump valve completely....................

I've just graphed some of the first log figures for you (I could only use the first 10 or so points as those were the only ones where your revs were continually rising) I will post it up tonight when I get home from work but it looks perfectly normal to me. Peaks about 17psi then drops to 14psi and the actual follows the spec pretty closely, there are no massive fluctuations either.

I'll graph the second log as well and see what that looks like.

Looks like either the DV or the N249 was the fault then.

2nd log was much easier to graph... you'd done a slow buildup of RPM. Interestingly on that one your actual spikes at over 18psi, about 2 psi above your spec.

My guess is your N75 is a bit shonky hence the actual boost shooting up above the spec boost at times, and the ECU was using the N249 to open the DV to vent boost to bring it inline with the spec boost - hence the juddering.

By removing the N249 you've cured the symptom but not the underlying problem. I reckon it probably needs a new N75. Maybe try speaking to Jabba and see if they recommend an N75J or just a new standard one?

Don't run around for too long with the DV blocked off btw, you'll put a lot of stress on the turbo.

Excellent, many thanks again. I look forward to seeing the graph! Can you work the torque out using those figures at all?

Bailey said they will rebuild my DV for £36, so hopefully that should work properly again. I will speak to Jabba about the valve.

Thanks

Trev

Do another run from low revs to the redline preferably in 3rd or 4th gear (private track obviously ) and log block 002 or 101 (so you get MAF figures in g/s).

Post the results up here and I should be able to convert it to BHP and graph it. To get a rough approximation of BHP at any revs you take your MAF figure at those revs and divide it by 0.8 so for a standard VRS at full chat that would be 150g/s / 0.8 = 187bhp. Not quite book figures but close.

Providing we've got BHP and RPM I can also work out your specific torque at various engine speeds as well and add that to the graph.

Excellent, many thanks for that! I did't get a chance over Easter to do any more logging but I will ASAP

Thanks

Trev