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Thread: Overboost Troubleshooting

  1. #1
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    Overboost Troubleshooting

    I'm trying to troubleshoot a high end power problem. I'm assuming the ECU is cutting power due to overboost, as I've installed a boost gauge and it's telling me that the turbo overboosts (up to 25psi ), and then (I think) the ECU cuts in.

    I thought I had a faulty wastegate, however, now I don't think so. I've checked the wastegate with an air compressor, and it actuates at 20psi, max (possibly minus a couple of PSI). It happens 100% of the time I've tested it; so could it be sticky? If so, how do you 'un-sticky' it?

    So what could be causing the overboost? I thought intercooler pipes collapsing, but how would that cause overboost?

    What else can I check?

    Cheers
    Current: ‘16 Disco Sport (7seater) aka « Family Bus 2 »
    Sadly Gone: '77 RRC 2 Door aka "Beast"
    Gone: '92 RRC Vogue SE aka "The Family Bus"
    Long Gone: '99 Td5 Defender aka "The TANK!"

  2. #2
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    drover,
    when you setup the boost gauge did you come from the wastegate actuctor???.if so does your gauge jump about when a load is put on the motor??.I have just opened up the exhaust on td5 00mod and its dam near impossible to read gauge under load.
    It seems to spool up much quicker,but hard to check max psi.
    cheers

  3. #3
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    wind your boost back! should be round 17psi!
    if you want to run 25psi you need a little black box of electrickery to fool the ecu.

    make sure there is not holes in the vacume line to the wastegate modulator.
    the ecu is cutting fuel to the engine to limit damage.
    check the length of your waste gate rod.

    cheers phil

  4. #4
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    Quote Originally Posted by tracker View Post
    drover,
    when you setup the boost gauge did you come from the wastegate actuctor???.if so does your gauge jump about when a load is put on the motor??.I have just opened up the exhaust on td5 00mod and its dam near impossible to read gauge under load.
    It seems to spool up much quicker,but hard to check max psi.
    cheers
    i welded mine into the steel tube between the turbo and the I/C, it reads fine, looks like this
    http://www.youtube.com/watch?v=JuSNpCkaVaU
    fluctuation of gauge is directly linked to what your right boot is doing.

    cheers phil

  5. #5
    tombraider Guest
    Discowhite has nailed it....

    Dial the boost back to 18psi max and you'll be fine without a "boost box"

  6. #6
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    thanks Phil,I like the movie,my needle swings wildly ,so much its hard to read psi. Boost gauge is used to check turbo and wastegate ,thats why the temp connection.

  7. #7
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    I think people maybe misinterpreting what I'm trying to achieve...

    I'm NOT trying to overboost etc... I'm trying to figure out WHY it's doing it when it shouldn't!
    I'm getting to 110-120km/h and the car starts kangaroo-ing... I'm assuming it's the ECU cutting in when it senses overboost (as it IS overboosting - as proven by the boost gauge)!

    My mech boost gauge is T-eed into the wastegate actuator piping. It's a VDO, so it's not a crap quality one. No wild swinging of needle, it's smooth and related to right boot pressure.

    I haven't done a thing to change the boost (haven't touched the thread), so I'm wondering why it's overboosting (ie why the wastegate isn't dumping the exhaust when it reaches 17-18psi)...

    The wastegate works (that was the compressor test), but it's not doing it's job when the engine is running...! Is there any way of 'un sticky'-ing the wastegate, or, is there something else to look for???

    Tombraider (aka Mike?), I'm not after any little black box... although, I'd like to know when you plan on getting some more silicon hoses into the country! Don't want to nag (I've sent a PM&email and no response)...

    Cheers.
    Current: ‘16 Disco Sport (7seater) aka « Family Bus 2 »
    Sadly Gone: '77 RRC 2 Door aka "Beast"
    Gone: '92 RRC Vogue SE aka "The Family Bus"
    Long Gone: '99 Td5 Defender aka "The TANK!"

  8. #8
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    there is also another sensor on the intake manifold that can give you this fault check the plug has'nt come loose as mine did once giving that fault.

    Check the small hose going to the waste gate solenoid from that steel pipe before the intercooler,they can get a crack in them where they push onto the nipples this has also happened to me aswell.
    disco seriesII mods so far:-bullbar,hyd winch,
    detriot locker,lsd front,C.D.L kit,chipped and bigger intercooler,2" lift,rock sliders, lsd in transfer case, modified auto trans.

    In the event of nuclear war,Disregard this message

  9. #9
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    Quote Originally Posted by stevo View Post
    there is also another sensor on the intake manifold that can give you this fault check the plug has'nt come loose as mine did once giving that fault.

    Check the small hose going to the waste gate solenoid from that steel pipe before the intercooler,they can get a crack in them where they push onto the nipples this has also happened to me aswell.
    Intake manifold sensor... would this cause overboosting? I thought the turbo/wastegate was a mechanical system...? I'll check either way.

    The hose is fine, that was checked when I put the boost gauge in.

    Anything else?

    Cheers
    Current: ‘16 Disco Sport (7seater) aka « Family Bus 2 »
    Sadly Gone: '77 RRC 2 Door aka "Beast"
    Gone: '92 RRC Vogue SE aka "The Family Bus"
    Long Gone: '99 Td5 Defender aka "The TANK!"

  10. #10
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    ok ,now you have me thinking.
    Mine is plugged in the same as yours,but my needle fluctuatates under hard accellation.It also doesent overboost and goes fine.One think that did happen was the t piece blew off and didthe same thing..quote.( and the car starts kangaroo-ing... )
    I look at Phils post and that is how the boost gauge worked on the tdi,but when we chipped the td5 Stewart (mr) plumbed a boost gauge in and it did the same thing as mine and he didn't seem worried.
    pm me if you want to compare the two discos.
    cya

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