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  1. #1
    Yohan87's Avatar
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    More Boost Without N75 (94.5% Duty & Logs)

    My S3 (1.8T AMK) has a stage 2 custom map and when first remapped it would hit approximately 24psi before tailing off to 22psi which it then held across most of the rev band.

    Recently however the car struggles to make anything above 20psi and usually holds 19psi across the range.

    Vag-Com shows no faults.

    I removed the N75 from the TIP and plugged the tip, left everything else on the N75 connected and just left the end that was in TIP "open" as it were.

    Took it for a drive and the car then made 22psi and held it across the range.

    Are these the symptoms of a faulty N75 valve?

    I shall be performing a boost leak test this weekend to rule that aspect out.
    Last edited by Yohan87; 7th December 2011 at 13:01.

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  3. #2
    "Stick a V8 in it!"

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    From what you describe, all you've done is created an air leak?

    All the boost being bled off by the N75 is supposed to be recirculated, hence its fed back into the tip. By removing it from the TIP, the N75 is still controlling the boost, but the bled-off air is just being dumped.

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  4. #3
    Yohan87's Avatar
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    Interesting, so why would an air leak cause my car to boost higher?

  5. #4
    "Stick a V8 in it!"

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    No idea!

    Remember boost is temperature dependant, if its colder outside the ECU requests less boost as it knows the airs denser. Given the recent sharp drop in outside temperatures, its not entirely unexpected that boost request would drop a little.

    You'd need to do some logging to find out if the ECU's requesting more boost and isnt getting it, or if its simply requesting less boost because it doesnt want as much.

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  6. #5
    Yohan87's Avatar
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    That may well be it then.

    When logging in vag-com the ECU is only requesting 1.4 bar (approx 20psi).

  7. #6
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    Quote Originally Posted by Yohan87 View Post
    That may well be it then.

    When logging in vag-com the ECU is only requesting 1.4 bar (approx 20psi).
    Meaning that the turbo is producing exactly what is requested basically?
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  8. #7
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    Exactly, it's just less than it was producing in October so I automatically assumed the worst.

    Here are some logs, hopefully the formatting works.

    Wednesday 30 November 2011 19:32:41:62534 VCDS Version: Release 11.11.0 Data version: 20111111
    8N0 906 018 H 1.8L R4/5VT 0004
    Group A: '114 Group B: '115 Group C: '031
    Engine Load Engine Load Engine Load Boost Pressure Engine Speed Engine Load Boost Pressure Boost Pressure Lambda Control Lambda Control
    TIME (specified) (spec. corrected) (actual Value) Control (N75) TIME (G28) (specified) (actual) TIME Bank 1 (actual) Bank 1 (specified)
    Marker STAMP % % % % STAMP /min % mbar mbar STAMP
    8.42 97 95.5 22.6 0 7.81 760 21.8 970 980 8.11 0.992 0.992
    9.33 97 95.5 21.8 0 8.72 760 21.8 970 980 9.03 0.992 0.992
    10.23 97 95.5 35.3 0 9.62 760 21.8 970 980 9.92 1 0.992
    11.13 141.4 140.3 51.9 0 10.53 1560 45.9 970 980 10.85 0.922 0.992
    12.05 109 107.5 51.9 0 11.44 1920 54.9 970 1020 11.74 0.984 0.992
    12.95 147.4 146.3 54.9 0 12.34 1600 48.1 970 1040 12.66 1.008 0.992
    13.86 116.5 114.9 19.5 0 13.25 2200 46.6 970 1070 13.56 0.953 0.992
    14.78 118 116.4 53.4 0 14.16 1480 41.4 970 1000 14.46 0.93 0.992
    15.66 130.8 129.9 47.4 0 15.06 1720 51.1 970 1020 15.36 1.016 0.992
    16.58 159.4 158.2 45.1 0 15.97 1960 48.1 970 1040 16.26 0.977 0.992
    17.48 140.6 138.8 15.8 0 16.87 2240 46.6 970 1050 17.18 0.961 0.992
    18.38 116.5 114.9 49.6 0 17.78 1600 15.8 970 1020 18.08 0.977 0.992
    19.29 120.3 119.4 53.4 0 18.68 1600 50.4 970 1010 18.99 0.922 0.992
    20.19 129.3 128.4 55.6 0 19.59 1760 54.9 970 1030 19.91 1.008 0.992
    21.1 137.6 135.8 57.1 0 20.49 1880 56.4 970 1050 20.8 1.008 0.992
    22.01 157.9 156.7 51.9 0 21.4 2040 56.4 970 1080 21.69 0.992 0.992
    22.9 169.9 168.7 49.6 0 22.31 2160 54.9 970 1070 22.61 0.984 0.992
    23.82 170.7 168.7 24.1 0 23.2 2280 48.1 970 1070 23.51 0.977 0.992
    24.71 108.3 107.5 14.3 0 24.11 1920 14.3 970 1040 24.41 0.961 0.984
    25.61 122.6 120.9 29.3 0 25.01 1520 20.3 970 1000 25.32 0.984 0.984
    26.52 122.6 120.9 28.6 0 25.93 1760 28.6 970 990 26.23 0.992 0.992
    27.43 124.1 122.4 27.8 0 26.82 1760 28.6 970 990 27.14 0.992 0.992
    28.33 124.8 123.9 27.8 0 27.74 1760 27.8 970 990 28.03 1.023 0.992
    29.24 125.6 123.9 25.6 0 28.63 1760 26.3 970 990 28.93 1.023 0.992
    30.15 126.3 125.4 25.6 0 29.55 1760 25.6 970 990 29.84 1.016 0.992
    31.05 127.1 125.4 24.1 0 30.45 1800 25.6 970 990 30.75 0.984 0.992
    31.95 127.8 126.9 27.1 0 31.36 1800 24.1 970 990 31.66 0.977 0.992
    32.86 130.8 129.9 57.1 2.7 32.26 1840 35.3 970 990 32.56 0.953 0.992
    33.76 143.6 141.8 93.2 94.5 33.16 1920 78.9 1760 1040 33.47 0.899 0.977
    34.67 169.2 167.2 115.8 94.5 34.06 2080 100.8 2020 1270 34.37 0.961 0.961
    35.58 182.7 180.6 152.6 94.5 34.98 2320 124.1 2290 1560 35.28 0.953 0.953
    36.49 188 186.6 177.4 92.5 35.88 2640 168.4 2410 2090 36.18 0.977 0.945
    37.39 191 189.6 176.7 89.8 36.79 2960 178.9 2430 2300 37.09 0.922 0.938
    38.3 191.7 191 188.7 90.2 37.69 3360 182 2420 2260 37.99 0.93 0.938
    39.2 191.7 191 188.7 91.8 38.6 3720 187.2 2410 2260 38.9 0.93 0.93
    40.11 191.7 191 191.7 94.5 39.51 4080 188.7 2390 2280 39.81 0.906 0.883
    41.01 191.7 191 190.2 93.7 40.41 4440 191.7 2370 2350 40.71 0.875 0.86
    41.92 191.7 191 185.7 94.1 41.31 4800 188 2330 2300 41.62 0.836 0.836
    42.82 191.7 191 180.5 94.5 42.22 5120 184.2 2330 2270 42.52 0.828 0.821
    43.73 191.7 189.6 180.5 94.1 43.12 5400 182 2370 2230 43.44 0.813 0.821
    44.63 189.5 188.1 173.7 94.5 44.03 5640 180.5 2390 2220 44.33 0.821 0.821
    45.54 182.7 180.6 168.4 94.5 44.93 5920 174.4 2360 2170 45.24 0.813 0.821
    46.44 177.4 176.1 168.4 94.5 45.84 6160 171.4 2310 2130 46.14 0.813 0.821
    47.36 170.7 168.7 160.2 93.3 46.75 6360 160.2 2270 2250 47.05 0.813 0.821
    48.25 164.7 162.7 164.7 91 47.65 6560 161.7 2180 2140 47.95 0.813 0.821
    49.17 161.7 159.7 153.4 87.5 48.57 6720 154.9 2100 2160 48.87 0.813 0.821
    50.07 161.7 159.7 145.9 87.5 49.47 6880 152.6 2060 2040 49.77 0.813 0.821
    50.97 191.7 191 12.8 0 50.38 6920 65.4 980 2510 50.67 0.813 0.899
    51.88 191.7 191 12.8 0 51.27 4960 13.5 980 1100 51.57 0.867 0.938
    52.77 136.8 135.8 14.3 0 52.18 3120 13.5 980 1030 52.49 1.991 1.047
    53.69 104.5 103 14.3 0 53.08 1440 13.5 980 1010 53.41 1.811 0.961
    54.58 97 95.5 18 0 53.98 1080 14.3 980 990 54.3 1.016 0.953
    55.5 97 95.5 20.3 0 54.88 880 18.8 980 990 55.18 0.938 0.984
    56.4 130.8 129.9 12 0 55.8 800 20.3 980 990 56.1 0.984 0.992
    57.32 191 189.6 12.8 0 56.7 3240 12 980 990 57.01 1.991 1.047
    58.21 191 189.6 12.8 0 57.61 3120 12.8 980 1000 57.91 1.991 1.047
    59.12 186.5 185.1 13.5 0 58.51 3080 12.8 980 1000 58.81 1.991 1.047
    60.01 119.5 117.9 12.8 0 59.42 2120 14.3 980 1000 59.71 1.991 0.945
    60.92 112 110.4 12.8 0 60.32 1360 14.3 980 1000 60.62 1.211 0.945
    61.82 188 186.6 13.5 0 61.22 2600 11.3 980 990 61.52 1.991 1.047
    62.74 186.5 185.1 12.8 0 62.12 2760 12.8 980 1000 62.44 1.991 1.047

  9. #8
    Yohan87's Avatar
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    And here is one with the N75 removed from the TIP.

    Wednesday 30 November 2011 20:08:04:62534 VCDS Version: Release 11.11.0 Data version: 20111111
    8N0 906 018 H 1.8L R4/5VT 0004
    Group A: '114 Group B: '115 Group C: '031
    Engine Load Engine Load Engine Load Boost Pressure Engine Speed Engine Load Boost Pressure Boost Pressure Lambda Control Lambda Control
    TIME (specified) (spec. corrected) (actual Value) Control (N75) TIME (G28) (specified) (actual) TIME Bank 1 (actual) Bank 1 (specified)
    Marker STAMP % % % % STAMP /min % mbar mbar STAMP
    0.86 97 95.5 25.6 0 0.25 1000 24.1 970 980 0.57 0.977 0.992
    1.77 97 95.5 27.1 0 2.06 800 27.1 970 980 2.37 0.984 0.992
    2.67 97 95.5 28.6 0 2.97 800 28.6 970 980 3.28 1 0.992
    3.57 97 95.5 29.3 0 3.88 760 28.6 970 980 4.18 1.016 0.992
    4.48 97 95.5 38.3 0 4.78 1200 40.6 970 970 5.09 0.945 0.992
    5.39 106 104.5 45.9 0 5.69 1480 45.9 970 990 6 0.969 0.992
    6.29 131.6 129.9 50.4 0 6.6 2120 53.4 970 1010 6.9 0.984 0.992
    7.21 185.7 183.6 61.7 0 7.51 3040 72.2 1130 1100 7.81 0.961 0.992
    8.11 187.2 185.1 14.3 0 8.41 2160 14.3 970 1070 8.71 1.008 0.977
    9.02 166.9 165.7 41.4 0 9.32 2360 41.4 970 1010 9.62 0.906 0.992
    9.91 185 183.6 63.2 6.3 10.22 2760 72.9 1230 1110 10.52 0.961 0.992
    10.82 191.7 189.6 122.6 69.8 11.13 3520 130.8 970 1840 11.43 0.774 0.992
    11.74 188 186.6 14.3 0 12.03 2480 13.5 970 1070 12.32 0.93 1.047
    12.63 182 180.6 12.8 0 12.93 2440 13.5 970 1010 13.23 1.991 1.047
    13.53 177.4 176.1 13.5 0 13.84 2320 13.5 970 990 14.15 1.991 1.047
    14.44 162.4 161.2 12.8 0 14.74 2040 12.8 970 990 15.04 1.991 1.047
    15.35 129.3 128.4 12.8 0 15.65 1760 12.8 970 990 15.95 1.991 1.047
    16.25 115.8 114.9 12.8 0 16.55 1040 18.8 970 980 16.86 1.85 0.945
    17.15 97 95.5 33.8 0 17.46 1040 33.8 970 990 17.76 0.977 0.945
    18.06 99.2 98.5 29.3 0 18.36 1000 27.1 970 990 18.66 0.922 0.992
    18.96 97 95.5 30.1 0 19.28 800 30.1 970 980 19.56 1.008 0.992
    19.88 99.2 98.5 40.6 0 20.17 1480 48.9 970 980 20.48 0.938 0.992
    20.79 115 113.4 48.1 0 21.07 1720 51.1 970 1000 21.37 1.008 0.992
    21.69 168.4 167.2 63.2 1.6 21.99 2560 69.2 1010 1080 22.29 0.984 0.992
    22.59 163.9 162.7 15 0 22.89 1800 26.3 970 1030 23.19 0.953 0.992
    23.5 133.8 132.8 55.6 0 23.8 2040 58.6 970 1050 24.1 0.969 0.992
    24.4 172.9 171.6 69.2 0 24.7 2480 71.4 1150 1140 25 0.969 0.992
    25.31 188 186.6 82.7 0 25.61 3080 113.5 1590 1350 25.91 1.008 0.992
    26.21 191.7 191 181.2 94.5 26.51 4160 191.7 2480 2450 26.84 0.875 0.899
    27.12 191.7 191 186.5 94.5 27.43 5520 16.5 970 1870 27.82 0.938 0.938
    28.13 191.7 189.6 13.5 0 28.43 3280 12.8 970 1050 28.72 1.991 1.047
    29.03 188.7 186.6 13.5 0 29.32 2720 13.5 970 1010 29.64 1.991 1.047
    29.92 185 183.6 12.8 0 30.24 2640 13.5 970 1000 30.54 1.125 0.977
    30.84 184.2 182.1 14.3 0 31.14 2520 15.8 970 990 31.44 0.969 0.992
    31.75 183.5 182.1 16.5 0 32.05 2480 16.5 970 980 32.35 1 0.992
    32.65 182 180.6 14.3 0 32.96 2480 14.3 970 990 33.26 1 0.961
    33.55 179.7 177.6 13.5 0 33.86 2400 13.5 970 980 34.16 0.961 0.953
    34.46 176.7 174.6 15 0 34.76 2360 16.5 970 980 35.06 0.938 0.984
    35.36 175.9 174.6 16.5 0 35.68 2360 16.5 970 980 35.97 1.008 0.992
    36.27 172.2 170.1 14.3 0 36.57 2280 15 970 980 36.86 0.977 0.977
    37.18 171.4 170.1 15 0 37.48 2240 15.8 970 980 37.79 0.992 0.992
    38.09 170.7 168.7 27.8 0 38.39 2240 24.8 970 990 38.67 0.984 0.992
    38.99 169.9 168.7 21.1 0 39.29 2240 19.5 970 990 39.58 1 0.992
    267.49 169.9 168.7 12.8 0 266.89 2280 12.8 970 1000 267.18 1.991 1.047
    268.4 166.2 164.2 13.5 0 267.81 2240 13.5 970 1000 268.1 1.991 1.047
    269.29 156.4 155.2 12.8 0 268.69 2160 12.8 970 1000 269 1.991 1.047
    270.21 148.9 147.8 18 0 269.61 2120 12.8 970 1000 269.93 1.039 0.945
    271.1 146.6 144.8 39.1 0 270.52 2040 40.6 970 990 270.81 0.875 0.945
    272.01 143.6 141.8 39.8 0 271.42 2040 39.8 970 1010 271.72 1.008 0.992
    272.92 141.4 140.3 39.1 0 272.31 2000 38.3 970 1010 272.62 1.008 0.992
    273.83 139.1 137.3 39.8 0 273.23 2000 39.1 970 1010 273.52 1.016 0.992
    274.73 138.3 137.3 41.4 0 274.13 2000 39.1 970 1010 274.43 1 0.992
    275.64 137.6 135.8 36.8 0 275.03 2000 43.6 970 1010 275.34 0.984 0.992
    276.54 137.6 135.8 41.4 0 275.95 1960 36.8 970 1010 276.24 0.984 0.992
    277.44 136.8 135.8 39.8 0 276.84 1960 42.1 970 1010 277.14 0.977 0.992
    278.35 136.8 135.8 37.6 0 277.74 1960 39.1 970 1010 278.06 0.992 0.992
    279.25 103.8 103 21.1 0 278.66 1960 32.3 970 1020 278.97 1 1.047
    280.16 101.5 100 21.1 0 279.55 1120 26.3 970 1000 279.85 1.32 0.992
    281.07 97.7 97 19.5 0 280.46 1080 20.3 970 990 280.76 0.891 0.992
    281.97 97 95.5 20.3 0 281.36 920 18.8 970 990 281.67 0.953 0.992
    282.87 115 113.4 13.5 0 282.27 800 21.1 970 980 282.57 0.992 0.992
    283.78 185 183.6 13.5 0 283.18 2520 12 970 980 283.49 0.984 0.961
    284.69 184.2 182.1 12.8 0 284.09 2640 12.8 970 990 284.38 1.991 1.047
    285.6 183.5 182.1 12.8 0 284.99 2560 12.8 970 990 285.29 1.991 1.047
    286.5 181.2 179.1 12.8 0 285.9 2480 12.8 970 1000 286.2 1.991 1.047
    287.4 173.7 171.6 13.5 0 286.8 2400 12.8 970 1000 287.11 1.991 1.047
    288.3 166.9 165.7 12.8 0 287.71 2240 12.8 970 1000 288 1.991 1.047
    289.21 158.6 156.7 12.8 0 288.61 2200 12.8 970 1000 288.92 1.991 1.047
    290.11 150.4 149.3 12.8 0 289.51 2120 12.8 970 1000 289.81 1.991 1.047
    291.03 142.9 141.8 13.5 0 290.42 2040 12.8 970 1000 290.72 1.991 0.992
    291.93 141.4 140.3 42.1 0 291.32 2000 13.5 970 990 291.63 0.969 0.945
    292.85 157.9 156.7 90.2 94.5 292.24 2040 63.9 1280 1000 292.53 0.93 0.992
    293.75 173.7 171.6 119.5 94.5 293.14 2200 100 2200 1250 293.44 0.961 0.961
    294.65 184.2 182.1 158.6 94.5 294.04 2400 131.6 2360 1600 294.35 0.961 0.953
    295.56 189.5 188.1 182.7 93.3 294.95 2720 175.2 2430 2200 295.25 0.938 0.938
    296.46 191.7 189.6 191.7 89 295.86 3080 185 2460 2400 296.16 0.914 0.938
    297.36 191.7 191 191.7 90.6 296.76 3480 191.7 2460 2350 297.06 0.945 0.93
    298.27 191.7 191 191.7 92.2 297.67 3840 191.7 2440 2400 297.97 0.93 0.914
    299.18 191.7 191 191.7 92.2 298.57 4240 191.7 2410 2390 298.87 0.875 0.875
    300.08 191.7 191 191.7 93.3 299.48 4600 191.7 2380 2400 299.78 0.852 0.844
    300.99 191.7 191 185.7 94.5 300.38 4960 191.7 2350 2290 300.69 0.844 0.828
    301.89 191.7 191 184.2 94.5 301.31 5280 184.2 2380 2270 301.59 0.805 0.821
    302.81 191 189.6 177.4 94.5 302.19 5600 185.7 2390 2250 302.49 0.821 0.821
    303.7 183.5 182.1 174.4 94.5 303.11 5880 175.2 2390 2210 303.42 0.821 0.821
    304.61 176.7 174.6 168.4 94.5 304.01 6120 168.4 2340 2260 304.31 0.821 0.821
    305.51 169.9 168.7 162.4 92.9 304.91 6360 166.9 2270 2170 305.21 0.821 0.821
    306.42 163.9 162.7 157.9 90.6 305.82 6600 160.2 2200 2160 306.13 0.813 0.821
    307.33 161.7 159.7 156.4 86.3 306.72 6760 154.9 2110 2180 307.03 0.805 0.821
    308.23 161.7 159.7 145.1 83.5 307.63 6920 151.1 2060 2140 307.94 0.813 0.821
    309.13 191.7 191 13.5 0 308.54 6520 12.8 970 1740 308.83 0.789 0.914
    310.04 191.7 189.6 12.8 0 309.44 4680 13.5 970 1080 309.74 0.93 1.047
    310.93 121.1 119.4 13.5 0 310.33 2800 14.3 970 1020 310.63 1.991 1.047
    311.84 104.5 103 14.3 0 311.23 1360 13.5 970 1000 311.56 1.523 0.961
    312.74 191 189.6 11.3 0 312.15 1120 16.5 970 990 312.45 0.977 0.961
    313.66 191 189.6 12 0 313.05 5560 11.3 970 990 313.36 1.991 1.047
    314.56 191.7 191 12 0 313.96 5440 12 970 1000 314.26 1.991 1.047
    315.47 191.7 191 12.8 0 314.87 4920 12 970 1020 315.18 1.991 1.047
    316.36 191.7 191 12 0 315.76 4280 12.8 970 1020 316.07 1.991 1.047
    317.27 191.7 191 12.8 0 316.67 3760 12.8 970 1020 316.97 1.991 1.047
    318.17 191.7 191 12.8 0 317.59 3560 12 970 1020 317.88 1.991 1.047
    319.08 191.7 189.6 12.8 0 318.49 3440 12.8 970 1010 318.79 1.991 1.047
    319.99 191.7 189.6 13.5 0 319.39 3360 12.8 970 1010 319.69 1.991 1.047
    320.9 191 189.6 12.8 0 320.29 3280 12.8 970 1010 320.61 1.991 1.047
    321.81 191 189.6 12.8 0 321.2 3200 12.8 970 1010 321.5 1.991 1.047
    322.71 190.2 188.1 12.8 0 322.1 3120 12.8 970 1010 322.41 1.991 1.047
    323.61 190.2 188.1 12.8 0 323 3040 12.8 970 1000 323.31 1.991 1.047
    324.52 188.7 186.6 12.8 0 323.91 2920 12.8 970 1000 324.22 1.991 1.047
    325.43 188 186.6 18 0 324.82 2840 13.5 970 1000 325.12 1.031 0.945
    326.33 187.2 185.1 15 0 325.73 2760 17.3 970 1000 326.03 0.938 0.945
    327.24 185.7 183.6 14.3 0 326.63 2760 15 970 990 326.94 0.945 0.945
    328.14 185 183.6 14.3 0 327.54 2680 14.3 970 990 327.84 0.945 0.945
    329.15 184.2 182.1 15.8 0 328.43 2640 13.5 970 990 328.78 0.953 0.945
    330.06 183.5 182.1 20.3 0 329.44 2600 16.5 970 990 329.77 0.938 0.945

  10. #9
    Yohan87's Avatar
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    Those runs were carried out in 4th gear at WOT and sometimes when at full boost I hear fluttering coming from the TIP/Intake and the boost flutters up and down in time with it.

    Perhaps the N75 being turned on and off by the ECU?
    Last edited by Yohan87; 7th December 2011 at 13:03.

  11. #10
    "Stick a V8 in it!"

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    fluttering under load is not good?

    Usually indicates surge, but thats somewhat unlikely on a standard turbo.

    Maybe a leak?

    Looking at the boost figures, the actual doesnt meet the requested over a lot of the pulls... which could suggest a leak, or a fault with the turbo ie worn out or leaking wastegate.

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    It's a standard turbo (K04-023) and the engine/turbo has probably only covered around 30,000.

    There is a fair bit of timing pull and on one occassion I even recorded 10's on one cylinder so I suspect a boost leak.

    Hopefully the boost leak test will reveal all.

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    www.badger5.co.uk

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    10's!

    yowzer.. be safe dude..
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    Quote Originally Posted by badger5 View Post
    10's!

    yowzer.. be safe dude..
    I know :-(

    It never used to do that until my boost went missing.

    I am just hoping there is a boost leak somewhere, which is causing knock, ECU is then pulling everything back and asking for less boost as a result?

    Or am I talking crap.

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    I have experienced something similar.
    Had a smoke test carried out about two months ago and discovered a leak on the charge pipe and on the DP, fixes those and my boost went down from 22 psi to 18, did some logs and found out that the actual boost takes a while to match requested at about 4300 rpm, so i've got a new n 75 and boost returned.
    Went with the car club two weeks ago for a spirited drive and the hose on the end of the charge pipe popped off, refitted again and now boost is at 18 psi.
    It's like with boost leaks my turbo spools quiker and harder!
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    Quote Originally Posted by Rosso TT View Post
    I have experienced something similar.
    Had a smoke test carried out about two months ago and discovered a leak on the charge pipe and on the DP, fixes those and my boost went down from 22 psi to 18, did some logs and found out that the actual boost takes a while to match requested at about 4300 rpm, so i've got a new n 75 and boost returned.
    Went with the car club two weeks ago for a spirited drive and the hose on the end of the charge pipe popped off, refitted again and now boost is at 18 psi.
    It's like with boost leaks my turbo spools quiker and harder!
    Yup its due to the air being able to escape quicker, with less resistance. Just read beachbuggys ko4 hybrid thread

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    I just read that as well.

    In the "flutter video" in that thread I sometimes get the same thing as what happens at the end of the video.

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    Quote Originally Posted by Rosso TT View Post
    It's like with boost leaks my turbo spools quiker and harder!
    The turbo will work harder to match boost if the map sensor is not getting the airflow it's expecting due to a leak. This is also why pressure drop across intercoolers is an important factor.
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  19. #18
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    What would cause the ECU to not request as much boost?

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    its load request would have been met
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    So to make sure I understand.

    If there is a leak, it will hit it's load request much earlier as it's working harder against the leak?

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    surely it would hit load request later?

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    That could also work I guess.

    I'll test for boost leaks first and then take it from there.

    Why is the N75 duty 94.5 and not 100?

  24. #23
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    its the limit its set to... varies slightly between cars/ecu's
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    Thanks for the info guys, i might need a new bigger mofo intercooler then.
    Always suspected mine is a bit restrictive and hot.
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    Quote Originally Posted by Rosso TT View Post
    Thanks for the info guys, i might need a new bigger mofo intercooler then.
    Always suspected mine is a bit restrictive and hot.
    What cooler do you have a t present? I tried 3 different FMIC setups and now run the huge toyosport one, which is very good.
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    At present i have a tube and fin style cooler 450x230x55 63 inlet/outlet.
    I'm thinking of getting same style core but wider and thicker and not necessary taller.
    Today i had the timing settins turned down to 1, starting to get hot down here.
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  28. #27
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    Well today I tested for boost leaks and it appears there are none so the next step is to try another N75 valve. My current version is an F so would a replacement F be the best option?

  29. #28
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    Quote Originally Posted by badger5 View Post
    its the limit its set to... varies slightly between cars/ecu's
    Would setting the limit higher help compensate for a dodgy valve?

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    no... duty cycle is duty cycle.. max'd out is what it is doing.
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  31. #30
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    Ok.

    So if I've no boost leaks then is it common for these N75's to just stop working properly and cause slightly lower boost?

  32. #31
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    thats Not what I have said
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  33. #32
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    Bill, you've lost me...

  34. #33
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    Well this evening I tried a wee test of the N75 valve. Firstly tried to suck air through the longest pipe (TIP side) but couldn't, no air passing through. Also tried to blow air through it and couldn't either. Out of interest sake I sucked/blew the bottom of the N75 valve (from charge pipe) and had the same result, no air passing either direction. However, my MAP sensor is another story.... I went to check the plug was in properly and noticed a crack on it and there is a lot of flex on the plug I took a video so hopefully it shows what I mean. Could this be the reason I can only make 17psi boost instead of my usual 24psi spike/22psi held across the range? The car is showing no fault codes. [img width=528 height=432]http://i694.photobucket.com/albums/vv309/YohanVRS/Project%20Bora%20S3/th_MAPSensor.jpg[/img]

  35. #34
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    you should be able to blow thru the centre (boot in) port of the n75 and it should exit the long (tip) port.
    yours sounds blocked which is'nt good.. but this should create uncontrolled boost if when you blow into the ports nothing comes out..?
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  36. #35
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    Thanks Bill.

    I definitely can't blow through the "boost in" port, nothing comes out. Obviously I can't blow air through at the pressure a turbo does but still doesn't sound right if something should be exiting the TIP port.

    Could it be that the valve is sticky and the turbo can push some air through but not enough to for me to reach max boost?

  37. #36
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    normally you can easily blow thru them as a test, so summats amiss 4 sure
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  38. #37
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    Ok Bill, a friend is popping past with his LCR also with an F valve so I will swap them over and see what happens.

  39. #38
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    Morning Bill,

    I tried an N75F valve from a friends AUM last night and all my lost boost was restored :-)

    Obviously I can't keep his so will be buying a new one and the dealer advises that the E valve has superceded the F.

    Are the characteristics exactly the same?

    Thanks

  40. #39
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    Your dealer is wrong, the F valve supersedes the C valve and is a later revision than an E anyway.

  41. #40
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    I don't think they are, from what I've read and the parts people I've called the E has superceded the F. I believe it went C -> F -> E. Alphabetically it doesn't make sense but the part numbers are: - F = 058 906 283 F E = 06A 906 283 E Either way, I bought a new E valve from them and replaced my valve with it and normal service is resumed and the car is back to how it was. Thanks to everyone who replied (especially Bill).

 

 
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