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    Thread: Understanding the N249 and Diverter Valve with Schematic

    1. Member zeusenergy's Avatar
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      04-02-2008 01:17 AM #1
      I don't know if anyone has posted a good schematic of the system (besides the typical vacuum hose chart underhood)
      Maybe there's a good layout in the bentley... I still don't have one. Sorry in advance if "This has been covered already!!!"
      I had fun making it, might as well share the wealth.

      But this should help some of you who either don't really understand the system, or want a better more concise view of the associated parts. The car I used to figure all of this out on is a 2001 New Beetle 1.8T. enjoy!

      And if you would like to download a very nice PDF version, here it is:
      http://shaw-clan.com/beetlepix/N249cutaway.pdf


      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    2. 04-02-2008 01:33 AM #2
      did you personally research this, via dissection of said components?

      excellent work, provided that it's accurate.

      Quote Originally Posted by Travy View Post
      error404: Stance not found.

    3. Member zeusenergy's Avatar
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      04-02-2008 02:21 AM #3
      Yes.
      Testing each part off the car, viewing the internals only on the stock DV. But the N249's design should be close.... most solenoids share the same basic structure.
      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    4. 04-02-2008 02:23 AM #4
      good work.
      Quote Originally Posted by Travy View Post
      error404: Stance not found.

    5. Member zeusenergy's Avatar
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      04-02-2008 02:27 AM #5
      Thanx! Going to bed now, it's like 3 in the AM!
      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    6. Member Chupathingy's Avatar
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      04-02-2008 09:28 AM #6
      You're missing the vacuum resivoir in the diagram. Also I'm not sure about the beetle but on the GTI/Jetta's the n249 never sees the vacuum lines on the charge pipe. There is a direct connection from the charge pipe to the n75.

    7. 04-02-2008 09:50 AM #7
      Nice diagram, however as stated above, I don't recall the n249 having any connection with the n75.

    8. Member zeusenergy's Avatar
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      04-02-2008 11:22 AM #8
      Quote, originally posted by Chupathingy »
      You're missing the vacuum resivoir in the diagram. Also I'm not sure about the beetle but on the GTI/Jetta's the n249 never sees the vacuum lines on the charge pipe. There is a direct connection from the charge pipe to the n75.

      Thanks for letting me know about that! Forgot the simplest part. Fixed! Also, revised the info in the schematic to reflect my car as the guinea pig.
      As you can see from the pic below, there is definitely a connection between the N75 line and the N249! Could it be that other models get their charge-side reference from another source line coming off the charge pipe, or elsewhere before the throttle body?


      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    9. 04-02-2008 01:14 PM #9
      On AWD/AWW/AWP engines the N249 valve has three connections : One going to the DV, one to the intake manifold for reference, and one to the vacuum reservoir (And the electrical connection of course.) I don't understand why your N249 is tied in to the charge pipe before the throttle body?

    10. Member zeusenergy's Avatar
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      04-02-2008 04:45 PM #10
      Is the one that goes into the manifold blocked by a check valve? If it's not, then it gets pressure from there instead of the charge pipe. That's a guess on my part. My car was stock with the crimped clamps when I got to it, so my guess is that it was setup correctly.
      The way it was setup on my car... if it fails, the DV will NEVER open! So I'm glad I pulled it. I do like the simplicity of the NB's vacuum setup up top over the MK4's under the manifold, though!
      I think my motor is an AWV. it's hard to tell, cause the head is dirty where the etched letters should be!
      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    11. Member kaipyroami's Avatar
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      04-02-2008 07:35 PM #11
      excellent write up

    12. Member tyrantanic's Avatar
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      04-02-2008 08:06 PM #12
      Nice how about about one explaining the N75 better haha. Great writeup tho.
      Even a stopped clock gives the right time twice a day.

    13. Member zeusenergy's Avatar
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      04-02-2008 09:15 PM #13
      I've seen the N75 cross-section and I still don't understand it!!!
      Thanks for the props!
      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    14. Member kaipyroami's Avatar
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      04-03-2008 01:08 AM #14
      the N75 is just a variable rate boost leak. It is controlled by a PWM (pulse width modulation) signal. for more info on PWM please google it there is too much info available.

      it leaks the boost pressure from activating the wastegate until the required boost is reached.
      the valve has one nipple from the boost one to the wastegate actuator and one to the intake (before the turbo)
      it will then leak the boost from the actuator to the intake to prevent the wastegate opening.

      in 0% pwm mode or limp mode the turbo will only boost 4psi because the wastegate is set to 4psi. at 0% pwm the valve is fully closed.

      at 25% pwm the valve is open 25% of the time and closed 75% of the time

      at 50% pwm the valve is open half of the time and so forth.


    15. Member kaipyroami's Avatar
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      04-03-2008 01:13 AM #15

      here is a PWM visual





      Modified by kaipyroami at 10:15 PM 4-2-2008


    16. Member kaipyroami's Avatar
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      04-03-2008 01:16 AM #16
      so as you can see the green (boost) is always connected to the gray (actuator).
      and will vent to the purple (intake outlet) when the valve is open. (meaning when the PWM current opens the solenoid)


      Modified by kaipyroami at 10:21 PM 4-2-2008

    17. Member zeusenergy's Avatar
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      04-03-2008 10:55 AM #17
      Well thank you very much for clarifying that!!!!!
      So the N75 is just a solenoid driven N.O. bleeder with a third diversion port. I did understand what the lines do, just wasn't sure about how the ECU controls it. But you've nailed it here for me. The N75 is opened and closed very quickly over and over.

      I was under the impression that there was some sort of controller motor doing analog work, or some other variable process going on inside the N75. Nope! The ECU is just outputting a digital signal for rapid on/off control. WICKED simple. This could also mean replacing the N75 for a regular solenoid is possbile! Sure, the ECU will still control it, but without bleeding air into the wastegate which should make boost build fast. Of course that's crazytalk!


      Modified by zeusenergy at 7:58 AM 4-3-2008

      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    18. Member kaipyroami's Avatar
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      04-03-2008 11:01 AM #18
      you got it.
      it oscillates at around 20hz and the duty cycle is just the pwm
      you can track it in vag-com and log in vag scope to really get a feel for what its doing and when its working

      just a simple solenoid

      by the way good job on the N249 info.
      it took me two weeks of searching just to understand the n75 and its not nearly as complex




      Modified by kaipyroami at 8:02 AM 4-3-2008


    19. Member zeusenergy's Avatar
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      04-03-2008 09:09 PM #19
      Thanks for the props.
      I just bypassed the N75 for kicks, with my MBC. Playing around with it, I find the MBC to be better in feel and response than the N75 will ever be. The part throttle issue other people experience just isn't an issue for me. Yes, it happens, but you can feather the throttle enough to minimize the problem.
      I got the MBC up to 15 spike, and it's now holding at 14 steady all day long. Interestingly, without the N75 I get MUCH less spiking than stock. Must be that tiny bleeder passage on the wastegate side of the N75.
      Without a diode, I get no limp mode...
      Decided to go with a dual MBC using the N249 style valves (2 in parallel for better flow, diode for the higher boost) and leave the N75 out of the loop entirely. The current MBC will be my low setting and the high will be set at 18PSI Don't sound like much to some, but I'm already overjoyed at the 14PSI action!!!


      Modified by zeusenergy at 6:11 PM 4-3-2008
      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    20. Member JWoody's Avatar
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      04-03-2008 09:35 PM #20
      This would be an excellent Thread for the 1.8T FAQ! Excellent work, well thought out and clearly defined on most basic aspects, in fact it almost looks like you recreated the Bentley with better detail...


      J-


    21. Member zeusenergy's Avatar
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      04-04-2008 05:25 PM #21
      Bump for FAQ status!!!!!
      Moderators? ......Bueller?
      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    22. 04-04-2008 07:31 PM #22
      How high have you cranked the boost?

      Is it possible you aren't actually boosting over 1bar?

      You said it holds at 14-15, so it's possible your gauge and MAP sensor are picking up slightly different boost readings and you are not actually over 14.7 PSI yet.

      I'm not sure if that's why you aren't hitting limp, but if the beetles are the same as golfs you can't go over 15 PSI without getting into limp mode. It will spike up to 18 or so, but then it will take it all away.

      Great work though, Dude


    23. Member zeusenergy's Avatar
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      04-04-2008 08:43 PM #23
      Quote, originally posted by middiesman »
      How high have you cranked the boost?

      Is it possible you aren't actually boosting over 1bar?

      You said it holds at 14-15, so it's possible your gauge and MAP sensor are picking up slightly different boost readings and you are not actually over 14.7 PSI yet.

      I'm not sure if that's why you aren't hitting limp, but if the beetles are the same as golfs you can't go over 15 PSI without getting into limp mode. It will spike up to 18 or so, but then it will take it all away.

      Great work though, Dude


      That's what I experienced last night. At 14.some-odd PSI the car shut me down to 5 PSI. Today I went with the diode (it was already pre-wired anyway) and now no more limp. I also tossed a plastic washer in there and now am at 15 steady rather than the 14 I had it at during the day yesterday. I have several of those washers so it will be easy to step the boost 1 PSI at a time if I choose. The guage is read from manifold pressure, so the CTS in the IC sees slightly more I assume.

      The most I want out of my car is 17 PSI, MAYBE 18 PSI but I need an A/F indicator or guage first to see how my stock fueling is holding up. at 15 PSI MBC/diode everything SEEMS fine. I have been told time and again that 16 PSI is safe for stock FPRs and stock ECM software. I'll wait to see how I'm fueling before going overboard!

      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    24. Member zeusenergy's Avatar
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      04-04-2008 10:46 PM #24
      FYI:
      Doing a DV direct to manifold (N249 bypass) is a huge help for response out of the car, N75 or MBC makes no difference. It opens every time the manifold sees vacuum, and makes noise every time. After doing the MBC, it's even LOUDER!!
      Forest Gump: "I like it alot, Ginny."
      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




    25. Member zeusenergy's Avatar
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      04-16-2008 01:04 AM #25
      Just posting an "understand the N75" thread now, with cool schematic....
      I have VCDS and located in New England, PM me!

      Four 1980 Audi 5000s gas and diesel, 1987 & 1988 VW Fox, 1980 VW Mk1 Scirocco, 1987 Audi 5000 TQ, 1988 Audi 5000 Q, 2001 VW New Beetle Sport 1.8t, 2011 VW Jetta MK6 TDI/DSG




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      03-17-2009 11:45 AM #26
      just tossing this out there, should i delete the mo fo, or repair/replace...

      http://forums.vwvortex.com/zerothread?id=4298296

      Turbos, Timepieces and Firearms.

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