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Old 07-16-2018, 01:09 PM   #1
exaurcism_666
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3 inch downpipe

does a 3 inch downpipe gives more power to a stock mkv gti?

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Old 07-16-2018, 06:10 PM   #2
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No because what will give you power is the amount of boost, and the boost is limited by the ECU so even if a 3" downpipe could in theory give you more boost the ECU will limit it to stock values, the only thing you could get is more throttle response but you will also probably lose some torque due to the absence of back pressure from the 3" DP vs the stock one.
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Old 07-16-2018, 06:44 PM   #3
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Backpressure myth is still going strong in 2018.
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Old 07-16-2018, 08:46 PM   #4
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Quote:
Originally Posted by gti2slow View Post
Backpressure myth is still going strong in 2018.
Turbos donít make backpressure /s
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Old 07-17-2018, 12:02 AM   #5
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No...will give no more power to a stock mk5 w/K03.

Unless you have done necessary mods to open up the throttle body, increase boost by a bunch with a much bigger turbo, and add fueling for those changes while keeping the balance correct for the compression ratio.

OEM is 60mm or 2-3/8". I run a K04 with a 2.5" Turbo-Back successfully and have done so with a tune that boosted over 26 psi. I would say do a 3" for a big turbo and fueling upgrades that make more pressure than what you could do with the oem lpfp and hpfp with internals upgraded...and custom tune for those increases.

On the other hand...the 3" DP will not hurt the power of a stock MK5. It will change the sound of the exhaust and this is likely why a number of people ride that Fanboy train.
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Old 07-17-2018, 12:24 AM   #6
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Cat-less 3" downpipes for days!
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Old 07-17-2018, 07:17 AM   #7
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Maybe back pressure is not the correct term but my understanding is that restricting the exhaust size increase the exhaust gases speed which in turn brings positive benefits, especially at low RPM. A bit similar to restricting the intake at low RPM which gives more torque.

Thanks for correcting me if it's a false belief.
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