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finally some proof

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by jimmcgee, Nov 29, 2013.

  1. jimmcgee
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    jimmcgee Member

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    [Nov 29, 2013]
    #1
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  3. desertstorm
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    desertstorm Well-Known Member

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  4. jimmcgee
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    jimmcgee Member

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    cool , did not know he was on this forum :cool:
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  5. adamss24
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    adamss24 Well-Known Member

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    [Nov 29, 2013]
    Without a remap the exhaust mod would do jack ! I have rs6 exhaust on my allroad with free flowing back boxes, did it make my car faster ? No...remap, turbo and nozzles did !
    Turbocharged engines have specifically tuned exhausts in order to retain certain back pressure and allow the turbo to have a transient response, by removing the "restrictions" you modify the exhaust path in a big way and the response changes accordingly ! Take all the results with a huge pinch of salt, a dyno is just a measuring tool, if you input wrong data it will output wrong results.
    #4
  6. desertstorm
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    desertstorm Well-Known Member

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    [Nov 29, 2013]
    Hello Chris, I have to say that in my experience and plenty of other peoples you do get an increase in performance by reducing flow restrictions in an exhaust system. The percentage gains are nowhere near as significant or noticeable as a remap but it will be positive. In this case a gain of 20bhp does seem excessive about an 8% increase.
    I linked to this before 195bhp Seat Leon Cupra TDI - Mufflerectomy and ECU Remap - YouTube and on this an exhaust was worth about 4.5% extra and if that improvement was translated to the V6 it would mean an 11bhp increase.As the V6 has 2 silencers each is only flowing half the gas from the engine so gains I think would be smaller than 4.5% maybe 3% , 5 - 7bhp would seem reasonable.
    The thing I can't work out with the pre and post dyno runs is the amount of increase lower down.I have grabbed stills from the video and put them together in a picture.

    [​IMG]

    You can see the shape of the torque and power curve is radically different at lower RPM. AT 2250 RPM the car was making 120bhp after the exhaust mod it was making nearly 160bhp, the whole shape of the map is completely different.
    So something is not quite right as that is a very significant difference.

    Karl.
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  7. adamss24
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    adamss24 Well-Known Member

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    Hi Karl, on my a6 tdi the previous owner did put a 3" exhaust from turbo all the way to the spare wheel well then 2.5 inches split in two, after the exhaust job he reckoned he lost a lot of top end but he gained a little midrange ! In the post above the car had one of them generic remaps, also the turbo fitted on the a6 is the bv50 which cannot flow as much as the GTB2260vk as fitted to the a4. As i said, please take the graphs with a pinch of salt...if it was a gtb2260vk it would have map to 270-280Bhp...the dyno over-reads anyway, it should show 233Bhp if it was calibrated properly...it's all in the correction factors !
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  8. jimmcgee
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    jimmcgee Member

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    [Nov 29, 2013]
    on a turbo car , back pressure after the turbo is bad mister Mackey

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  9. adamss24
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    adamss24 Well-Known Member

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    [Nov 29, 2013]
    Just remember that the factory spends millions to get the cars to what they are, it's rather hard to improve on what they do but not impossible.
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  10. jimmcgee
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    jimmcgee Member

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    [Nov 29, 2013]
    I thought I had removed that pic lol

    Adam , Audi have there hands tied when it comes to noise , and as you can see from inside that backbox , money as well , as there is not even any glasspack in there .

    anyhow , it's a **** design so , :nyah: .
    #9

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