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  1. #81
    Veteran Member Three Rings rnagy86's Avatar
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    It is hard to overlay these logs on each other so here is two snapshots.
    The first one is with N249 plugged in, the second is N249 disconnected.
    Both tests were done with two proper DVs with the a piston that does not
    cover any of the ports when fully open.

    BTW: The map that you are looking for SDLDSUA and its axis calculation in ASM.
    Both the ASM axis calculation is done and the values are also divided by two,
    however looking at the M-box, the SDLDSUA values are higher by default in
    that file.

    600g/s, 1.98 FATS, 5.6 seconds 100-200 (1850kg)



    Last edited by rnagy86; 12-08-2017 at 07:26 AM.

  2. #82
    Veteran Member Four Rings wbrunner23's Avatar
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    Boost spike is greater with n249 unplugged, which makes sense, but the spike looks almost identical to the spike with the n249. I agree with previous suggestions that it is actuation speed that is causing the spike.

    You need something that can open the DVs quicker

  3. #83
    Veteran Member Four Rings V1nny's Avatar
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    I had APR original diaphragm (not piston) DV for a while, but after going stage 3, they did not hold more than 22psi, so I called APR, and they sold me heavier springs for about $20. Very happy so far, no need for maintenance ever, also opening faster than any piston.
    https://www.goapr.com/products/r1.html
    https://www.ecstuning.com/b-apr-part.../z1001791~apr/

  4. #84
    Veteran Member Four Rings jibberjive's Avatar
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    01.5' S4, 04' A4 USP, 04' CRF450r
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    It looks like you've verified/logged everything, except for the final thing that actually actuates the valve. Do you have an aftermarket boost/vacuum sensor that you could use to log the actual amount of vacuum applied to the DV's during driving/operation? For example, I have a Zeitronix setup that I use, which could integrate that vacuum data into the logs.

    Also, are your vacuum lines all OEM or are some aftermarket?
    ** GT2860R-7 S4 Build Log--

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  5. #85
    Veteran Member Three Rings rnagy86's Avatar
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    Quote Originally Posted by jibberjive View Post
    It looks like you've verified/logged everything, except for the final thing that actually actuates the valve. Do you have an aftermarket boost/vacuum sensor that you could use to log the actual amount of vacuum applied to the DV's during driving/operation? For example, I have a Zeitronix setup that I use, which could integrate that vacuum data into the logs.

    Also, are your vacuum lines all OEM or are some aftermarket?
    Yes all lines are OEM. Already measured vacuum there and at the vacuum reservoir during driving. I have -.5-6 bar vacuum at the reservoir at WOT and that goes
    fine to the DVs.

  6. #86
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    Here is a graph from some old log b_ldsua as "Diverter Active". I rdrop the throttle on sample 401. I would suggest logging throttle angle as well, maybe there is some anomaly there.


  7. #87
    Veteran Member Three Rings rnagy86's Avatar
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    Do you see how different your B_ldsua is? It keeps open, mine is only active for 1 second.

  8. #88
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    I gave you too small of a window to see full second after the transition, window shows 7 samples past that which is 0.7s in my case. It should shut off unless you gently step on the pedal to remain in part throttle at which point the static state DV control takes over and keeps them open. It is irrelevant anyways because shutting off happens with very little boost left in the intake.

    I wouldn't look into this too deep as yours appears to be opening more or less on time and shut off time is dictated by delta of pressures in relationship to predicted pressure in next 10ms window.

    I would go now and investigate one more hardware part that you probably haven't looked into yet - important if you have aftermarket charge/inlet pipes. Look really carefully at your pipes and more specifically into the hose connector that DV connects to. During manufacturing process, they take shaped pipe, should drill a hole of proper size and weld the smaller pipe connector over it. This is where shortcuts are taken... Normally you'd make the hole as large as possible (especially if there are complicated shapes involved that prevent you from seeing and correcting issues later on due to shape) so that after welding on the connector the resulting hole matches the inside diameter of connector but that requires experience and attention to details. Make the hole too large or position the pipe inaccurately and you have a scrap piece of door stopper.

    So what they really do? They make a much smaller hole and weld the pipe onto it... They created an awesome flow restriction which is hidden from view. Here what should happen is somebody should go in with grinding bit and enlarge the hole to match inside diameter of connector but that obviously doesn't happen these days because we don't want to pay for quality workmanship so we get chinese crap.

    I've seen Y-pipes with what seemed like 1/4" hole behind the pancake connector (coming from SRM) etc. Imagine how well that worked when you're WOT and want that crankcase pressure to go back into Y-pipe (bye bye seals)...

    If you have turbo inlets which are aftermarket and don't utilize silicone "Crab" connectors for DVs then you must also inspect these for the same possible issue.

  9. #89
    Established Member Two Rings
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    I just wanted to state, the spike after letting off the throttle has always bothered me on my allroad as well. As part of my investigation, I put the n249 on the bench to test it out. I noticed a ~1/4 second delay in the valve closing when turning off the power. At that point I assumed I just had a sticky valve and that was the problem. I tested another valve out, and it reacted the same exact way. So either I have two sticky valves, or that's just how these n249's work, and that's what's causing the boost to spike when letting off the throttle. Because of this test and the results, I removed the n249 as it was of nearly no benefit to my application.

    That being said, in my experience with 1.8t's I have not seen this same issue with spike after letting off the throttle. I have not tested a 1.8t n249 on the bench, but I assume it will not have the same delay in closing when powered off.

  10. #90
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    Quote Originally Posted by sb_gli View Post
    I noticed a ~1/4 second delay in the valve closing when turning off the power.
    Except that the N249 routes vacuum side to DVs when energized, not when power is cut. What you describe is the N249 turning off and internal spring moving valve to switch from vacuum reservoir side to intake manifold as vacuum source, not what were discussing here.

  11. #91
    Established Member Two Rings
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    Quote Originally Posted by julex View Post
    Except that the N249 routes vacuum side to DVs when energized, not when power is cut. What you describe is the N249 turning off and internal spring moving valve to switch from vacuum reservoir side to intake manifold as vacuum source, not what were discussing here.
    Fair. Thank you for the clarification.

  12. #92
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    Quote Originally Posted by sb_gli View Post
    Fair. Thank you for the clarification.
    Sorry for terse tone. I meant to say that the spring must be pretty weak if it takes so long to return to default state. i\It must be weak so that energizing the solenoid means fast switching action. Less resistance to overcome = faster piston movement.

  13. #93
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    Quote Originally Posted by julex View Post
    Sorry for terse tone. I meant to say that the spring must be pretty weak if it takes so long to return to default state. i\It must be weak so that energizing the solenoid means fast switching action. Less resistance to overcome = faster piston movement.
    No worries. I was thinking about how the valved worked opposite of how it does. When the solenoid is energized, if that switches flow to the vacuum reservoir, then what I experienced on the bench was that valve opened immediately... closing it is what had a lag time. I thought that explained the boost spike in my logs, but it doesn't if it's the opposite of what I was thinking.

  14. #94
    Registered Member Three Rings
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    I think this was brought up earlier with no response but it makes sense to me: How about a direct acting electric solenoid valve? With the current system we're depending on the N249, vacuum and the diverter valves to bleed off the boost during throttle lift situations. Vacuum is air and has elasticity in this application. The N249 is probably as quick as any valve we'd source but the rest of the system is slow. Vacuum is air and has elasticity in this application so it's going to slow the response considerably.

    A solenoid valve is going to run about 160 bucks each but you'd get instant bleed.

    Here's a McMaster valve that needs 24vdc to switch: https://www.mcmaster.com/#2660K34

    The price is why Audi didn't go with direct acting valves. The N249 and the diverter valves probably cost them ten bucks. Similar valves like these would run 50 bucks each and provide no benefit in the stock application.

    That's my $160...

  15. #95
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    Quote Originally Posted by rdcyclist View Post
    I think this was brought up earlier with no response but it makes sense to me: How about a direct acting electric solenoid valve? With the current system we're depending on the N249, vacuum and the diverter valves to bleed off the boost during throttle lift situations. Vacuum is air and has elasticity in this application. The N249 is probably as quick as any valve we'd source but the rest of the system is slow. Vacuum is air and has elasticity in this application so it's going to slow the response considerably.

    A solenoid valve is going to run about 160 bucks each but you'd get instant bleed.

    Here's a McMaster valve that needs 24vdc to switch: https://www.mcmaster.com/#2660K34

    The price is why Audi didn't go with direct acting valves. The N249 and the diverter valves probably cost them ten bucks. Similar valves like these would run 50 bucks each and provide no benefit in the stock application.

    That's my $160...

    This is essentially what I was eluding to earlier, although the electrical requirements for a solenoid large and fast enough for this application would draw almost as much current as the engine's starter. The problem is you don't get a very strong solenoid field when only using 12VDC, so in order to compensate you have to increase the current draw. It's not an easy solution, which is why auto manufacturers use vacuum-based systems to activate the DV itself.

    If I were to design my own electric high-performance DV I would figure out a way to use small supercapacitors, but that may just be me.

  16. #96
    Veteran Member Three Rings rnagy86's Avatar
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    Quote Originally Posted by julex View Post
    Here is a graph from some old log b_ldsua as "Diverter Active". I rdrop the throttle on sample 401. I would suggest logging throttle angle as well, maybe there is some anomaly there.

    Can you please measure the vacuum at your reservoir?

    I am really courious about the readings because it seems that an A6/allroad has a different vacuum reservoir.



    while the B5 has:


  17. #97
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    Did you look at your turbo intake/charge pipes yet as I suggested above?

    Regarding me looking at my vacuum levels, that will not happen since I literally have zero time these days for such projects . FWIW I heard before about the vacuum reservoir collapsing/crumbling inside which might be a factor here. You might have a proper pressure of vacuum in such situation but very very little supply of thereof.

    If you're concerned about vacuum levels, you could always obtain vacuum pump subsystem from tiptronic B5 (it has to cost near zero for used one from junk car) and have unlimited supply of vacuum at WOT .

  18. #98
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    Did you come to solution on this one Robert?

    Here is an intresting video. Easy to test.

    https://www.youtube.com/watch?v=I0Rt...ature=youtu.be

  19. #99
    Senior Member Four Rings blitz2190's Avatar
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    Quote Originally Posted by rnagy86 View Post
    Can you please measure the vacuum at your reservoir?

    I am really courious about the readings because it seems that an A6/allroad has a different vacuum reservoir.



    while the B5 has:

    I may not get to it this week but if I can get the car out of the snow, I'll measure for you, the b6 chassis has the same reservoir(three ball looking one).
    Never argue with an idiot, they'll bring you down to their level and beat you with experience.
    2.7T Swap Wiring Guide (Psst this is a link)
    New Build In progress built 2.7 STK 2004 B6 A4- Thread and pic to come

  20. #100
    Veteran Member Three Rings rnagy86's Avatar
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    I did not really have time to move forward with this, the weather is crap, I have a newborn to take care of and I am
    still trying to gather information / data from others.

    Anyway on the RS4 pressure pipes the welded ports have definitely have a smaller ID by the looks of it, and I will
    try to ask someone to actually measure it because I don't fancy removing them just for measuring.



    There can be some porting done to that I'd say.

  21. #101
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    Id say so. That might be your issue.. Most of the big power cars Ive followed over the years dont use the Rs4 parts, usually custom ones made with thiner wall pipe stock. Probably double the flow capacity of that RS4 port if no more....

    That is a damn small hole. (ha!)

  22. #102
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    I'd say that as well. Pretty heavy gauge wall on these nipples . I also suspect that the weld protrudes out inside of the pipe creating a ridge of sorts in front of DV port entry creating yet another obstacle the air needs to turn abruptly around. I wouldn't be surprised if other craftsmanship issues won't be discovered once you peek inside from the throttle opening side.

  23. #103
    Senior Member Three Rings PwrWgn's Avatar
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    I had been meaning to post this sooner, but here is an image of the DV ports and locations on the Hannover RS4 limo. Note the valve location upstream of the coolers and the very large flow area.


  24. #104
    Veteran Member Three Rings rnagy86's Avatar
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    Just a quick update. The rs4 pipe’s ID is 15mm :) ... i am getting new ports welded on it to match the DV size and will come back with the results.

  25. #105
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    Cool, keep up updated.

  26. #106
    Veteran Member Three Rings rnagy86's Avatar
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    Well the difference is huge


  27. #107
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    It sure is. I hope this solves your particular problem.

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