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  1. #1
    Veteran Member Four Rings vinny.dtw's Avatar
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    How accurate are our boost gauges?

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    Awe / Podi / Custom?

    Beside the point, the reason I ask is because after doing numerous logs and research about if I have installed my boost gauge correctly. I've come to the conclusion that the boost gauges are either 1.) Rather inaccurate, 2.) I'm just stupid and shouldn't argue with the vendors.

    So here is my reasonings. After logging my car, comparing them to my boost gauge readings, and an alternate boost gauge connected while I was at the dyno, they were drastically different from each other. And I have some pretty knowledgeable to agree with me that the boost gauges are inaccurate.

    So here is my newest problem with the car that stemmed me to this, while me and Ryan were dynoing our cars, I got about 200whp from my current GTRS setup with T5 B7. Which quite frankly is redonk. I did more logging with some friends just to see what exactly is going on, and found out after Greg told me I'm making about 18psi...in comparison to what my boost gauge said 24 psi. Why? Well thats another story that I'm trying to figure out. But what is driving me nuts is why in the world are they reading different?

    So, am I nuts? or do the gauges really suck? This is where I am asking for some help. Anyone with logs/vagcom and a boost gauge of there car, can they please post and tell me if your boost gauge is accurate in comparison to your vagcom readings? Thanks

    Vince

  2. #2
    Veteran Member Four Rings Capt. Obvious's Avatar
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    Nov 14 2006
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    600hp glorified Beetle, e-tron, 1G DSM
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    Re: How accurate are our boost gauges?

    Have you tried hooking up another gauge just to see what it says? Or maybe even running a T off the feed line for the gauge so you can run TWO boost gauges and compare what they read?
    -Darrick

  3. #3
    Veteran Member Four Rings vinny.dtw's Avatar
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    Re: How accurate are our boost gauges?

    I have the AWE boost gauge, and we used the one at the dyno, and both of them were relatively close. 23.7 psi at the dyno, 24 psi for the awe, and 2270mbar on vagcom which equates to 18psi.

  4. #4
    Veteran Member Four Rings dougyfresh's Avatar
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    Re: How accurate are our boost gauges?

    Your MAP sensor is attached correctly to your intercooler piping?

    Your N75 is hooked up correctly (boost signal from turbo outlet, vacuum signal from TIP, line going to W/G actuator)?

    You've verified (visually and such) that your connection on the intake manifold for the AWE boost gauge is fine and the leads going into your interior are fine?


    Did you re-pressure test your system at your buddy's shop since we spoke last?
    -Doug
    2002 A4 Avant EPL tuned 2.7T K04 6spd

  5. #5
    Veteran Member Four Rings vinny.dtw's Avatar
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    Re: How accurate are our boost gauges?

    Check, check, check, and no pressure test yet. I got too antsy this afternoon and checked everything myself in terms of connections.

  6. #6
    Veteran Member Four Rings yoogene83's Avatar
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    Apr 27 2004
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    2017 Pacifica Limited / 2014 BMW M5
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    Re: How accurate are our boost gauges?

    My theory may need some tweaking, but here's my suggestion, check this line:

    Quote Originally Posted by yoogene83 View Post



    it was connected between the turbo and N75, this is what you could see




    Driving impressions noted after putting in the new line was that the gauge was showing LESS boost than before with a butt dyno of about -10hp. why? i too pondered this and came to this conclusion:

    the hole in the hose creates a leak in which the n75 regulates the amount of boost that the turbo can send to the intake mani, however, since there was a hole in that hose, it would allow air to leak out, thus, making the n75 think there was less boost than what was actually being produced, which in turn led to the n75 actuating the wastegate to allow for more boost. I always noted that was i boosting ~22psi on b7t5, which should have been around 20psi spike with a 18psi hold. i just thought my car was badass and thought nothing of it. little did i know, that the additional boost was from the leak and was also creating a lean condition, which is bad joojoo.

    car drives fine now, as well, although a little less boost, it's feels quicker in 1+2 gears, but 3+ seem to have slowed down. oh well
    possible that the point where your ECU reads and the pressure read from the gauge is at different locations. Then again, i could be talking out of my ass, which happens a lot. But it doesn't hurt to check though.

  7. #7
    Veteran Member Four Rings vinny.dtw's Avatar
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    Re: How accurate are our boost gauges?

    checked that hose in particular when i read your thread. :) thanks Eug for the advice though. :)

  8. #8
    Registered User Four Rings winston@podi.ca's Avatar
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    Re: How accurate are our boost gauges?

    I have bench tested a lot of gauges and the VEI digital units and the Defi units are pretty much perfect when it comes to displaying an accurate reading.

    I have hooked up two boost gauges in parallel with a VEI or Defi in my lab to see how much of a discrepancy there is on average with most good mechanicals gauges +/- 1psi range.

    With a cheap low end gauge I have seen as much as a 4psi difference from that it should be.

  9. #9
    Senior Member Two Rings
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    Re: How accurate are our boost gauges?

    A rather simple way would be to put a vacuum/pressure tester on the gauge. Just about any mechanic would have a tester of some sort with a gauge on it.
    Robbie
    2003 A4 1.8TM
    Motor F21 Turbo, FMIC, Green Tops, Meth Injection, Motoza Tune, Carbonio, Forge DV, Ecode Test Pipe, Neuspeed Catback, 034 Motorsport Solid Mounts
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    Interior/Audio Pioneer D/D Head, JL 450/4, JL 500/1, JL ZR650's, 2 - 8 JL 8W7's

  10. #10
    Veteran Member Four Rings Siggiepop's Avatar
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    Re: How accurate are our boost gauges?

    my defi reads accurately. ^ try switching to a vei gauge ? and pressure test.
    CT4952

  11. #11
    Veteran Member Four Rings martini's Avatar
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    Re: How accurate are our boost gauges?

    if they dyno reading, and two boost gauges are reading 20+, then I would be questiong teh VAG logs more than the boost gauges...
    a4mods.com Stickers!


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  12. #12
    Veteran Member Four Rings dougyfresh's Avatar
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    Re: How accurate are our boost gauges?

    Quote Originally Posted by martini View Post
    if they dyno reading, and two boost gauges are reading 20+, then I would be questiong teh VAG logs more than the boost gauges...
    It just means there is something wrong with either 1) the MAP sensor and factory harness or 2) aftermarket boost gauge


    Vince,
    My boost gauge correlates with the dyno boost gauge but I can not correlate it with VAG-Com since I'm running more than 2540mbar. I could run off the WG spring and see if it correlates. Oh, wait... Now that I remember.. It does correlate. I ran the motor off the W/G spring (~11-12psi) when I broke the 2.0L in: http://www.youtube.com/watch?v=QUzOeTpngYE


    Still convinced something is amiss with either the engine harness/hardware or the AWE gauge. I'm leaning on believing the VAG-Com data since your dyno charts reflect 18psi.
    -Doug
    2002 A4 Avant EPL tuned 2.7T K04 6spd

  13. #13
    Veteran Member Four Rings vinny.dtw's Avatar
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    Re: How accurate are our boost gauges?

    We will see, school sadly starts this Monday, and I'm taking the car in Friday at 7 a.m on the lift to reinspect everything. Its kind of hard in a dark garage a little flashlight and 20 degree weather to inspect everything thoroughly. I'll keep everyone updated.

  14. #14
    Senior Member Two Rings
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    Re: How accurate are our boost gauges?

    Doesn't the computer log the actual boost differently? I thought I remembered reading that it doesn't account for outside are pressures or something like that? Would think account for the differences between a gauge and the vagcom reading?
    Robbie
    2003 A4 1.8TM
    Motor F21 Turbo, FMIC, Green Tops, Meth Injection, Motoza Tune, Carbonio, Forge DV, Ecode Test Pipe, Neuspeed Catback, 034 Motorsport Solid Mounts
    Suspension Statis SS, Antera Type 309 18x8
    Interior/Audio Pioneer D/D Head, JL 450/4, JL 500/1, JL ZR650's, 2 - 8 JL 8W7's

  15. #15
    Veteran Member Four Rings vinny.dtw's Avatar
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    Re: How accurate are our boost gauges?

    Yes, usually the vagcom doesnt give you read out with atmospheric pressure in mind, therefore you have to do the math your self. and subtract atmospheric pressure from the mbar readout it gives you.

  16. #16
    Veteran Member Four Rings dougyfresh's Avatar
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    Re: How accurate are our boost gauges?

    PROBLEM FIXED!

    The AWE gauge was incorrect. The car is boosting 18psi on B7 via SPS3 as VAG-COM has verified.


    Vince tried another boost gauge and it correlates with VAG-Com and says AWE gauge is fubarred.



    Winston... Can you test Vince's AWE gauge for shits and giggles?
    -Doug
    2002 A4 Avant EPL tuned 2.7T K04 6spd

  17. #17
    Veteran Member Four Rings vinny.dtw's Avatar
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    Re: How accurate are our boost gauges?

    Quote Originally Posted by martini View Post
    if they dyno reading, and two boost gauges are reading 20+, then I would be questiong teh VAG logs more than the boost gauges...
    Funny you say that, so maybe even the dyno was inaccurate? I don't know. But thanks Doug for updating. More logging to go! Still though, I don't think B7, T5 or T6 would make up for the 50whp i'm missing, but it certainly is a start.

  18. #18
    Veteran Member Four Rings dougyfresh's Avatar
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    Re: How accurate are our boost gauges?

    Email me the logs once you get some more. I'll take a look for you.
    -Doug
    2002 A4 Avant EPL tuned 2.7T K04 6spd

  19. #19
    Registered User Four Rings winston@podi.ca's Avatar
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    Re: How accurate are our boost gauges?

    Quote Originally Posted by dougyfresh View Post
    PROBLEM FIXED!

    The AWE gauge was incorrect. The car is boosting 18psi on B7 via SPS3 as VAG-COM has verified.


    Vince tried another boost gauge and it correlates with VAG-Com and says AWE gauge is fubarred.



    Winston... Can you test Vince's AWE gauge for shits and giggles?
    I'll hook it up in parallel with a VEI gauge and see what is going on.

  20. #20
    Veteran Member Four Rings dougyfresh's Avatar
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    Re: How accurate are our boost gauges?

    Quote Originally Posted by winston@podi.ca View Post
    I'll hook it up in parallel with a VEI gauge and see what is going on.
    Excellent. Thank You Sir!
    -Doug
    2002 A4 Avant EPL tuned 2.7T K04 6spd

  21. #21
    Veteran Member Four Rings lookaught's Avatar
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    Re: How accurate are our boost gauges?

    I installed a VEI in place of a mechanical Podi (gen1 Stewart Warner) and it reads slightly different values. Less vacuum when off the throttle and coasting (VEI - 22 to 23 inHg, SW - 24 to 26 inHg) but boost was spot on between them at 13-15 max holding pressure.

    I can't say why the vacuum read higher, perhaps the two inline restrictors made a difference... Either way Im much happier with the VEI, its a nice piece of equipment.
    Jon

    go > show

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  22. #22
    Veteran Member Four Rings pondside36's Avatar
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    Re: How accurate are our boost gauges?

    VEI FTW... as stated a great gauge
    Goodwood Green is money...$$$$
    Arclight "You need to post pics already Pondside - enough w/ the prom dress teaser BS!"

  23. #23
    Veteran Member Four Rings QTC's Avatar
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    Re: How accurate are our boost gauges?

    My AWE reads a peak of ~18-19psi (can't really tell b/c it happens so fast). ASP's boost guage (while on the dyno) gave a peak reading of 18.5 psi, and VAG-COM gave me a peak reading of 18.4 psi, so all the numbers line up for me. I have the second version of the AWE guage FWIW
    Dahlback | AWE | Milltek | Vogtland | H-Sport | Oettinger | Thule | OEM+

  24. #24
    Veteran Member Four Rings vinny.dtw's Avatar
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    Re: How accurate are our boost gauges?

    Sounds like an issolated case for me.

  25. #25
    Registered User Four Rings winston@podi.ca's Avatar
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    Re: How accurate are our boost gauges?

    Quote Originally Posted by lookaught View Post
    I installed a VEI in place of a mechanical Podi (gen1 Stewart Warner) and it reads slightly different values. Less vacuum when off the throttle and coasting (VEI - 22 to 23 inHg, SW - 24 to 26 inHg) but boost was spot on between them at 13-15 max holding pressure.

    I can't say why the vacuum read higher, perhaps the two inline restrictors made a difference... Either way Im much happier with the VEI, its a nice piece of equipment.
    The VEI, and most other quality electronic gauges, will read more accurately since you have to calibrate the unit or it self calibrates when you start it up.

    This eliminates atmospheric variables which a simple mechanical gauge can not do.

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