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How-To Do A Proper Boost Leak Test on A6/S4 - 2.7T

How-To Do A Proper Boost Leak Test on A6/S4 - 2.7T

Old 06-22-2014, 06:31 PM
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Default How-To Do A Proper Boost Leak Test on A6/S4 - 2.7T

Ok, I have come across the normal boost leak test. Also not my 1st turbocharged car. Is it my 1st Audi with hoses to so many valves, tanks and twin turbo's... so yes I know how to boost leak test have on many cars.

Now the APB 2.7T engine in my car is only holding about 5/7psi. Haven't timed leak down. It's florida, it sucks to be outside. What I have been doing is removing Y-pipe a capping off 1 crab claw. And use the other for my pressure input.

Now a few people talk of the n249 valve. They say to pinch it of. Which one of 3 lines? When? Also been told to ignore wastegate control lines. I'm guessing this is why I'm doing.

Am I seeing if the n249 is my boost leak?

Also I hear air by passenger cam tensioner and either under intake manifold by driver diverter. Now the leak by DV. I don't know what's going on. I have checked anything I know it could be. Re torqued intake manifold bolts same.

My tune is NVR Stage 2++ told to be 20 - 21psi hold taper to 15psi. Taper seems off. My logs show about 18-19 maybe.

Also I just got my ebay SMIC, 3" Tiptronic Downpipes from XSpower, Torque Converter Replaced and boost gauge. TCU upgraded. SAI removed. Block off plates installed and air hoses are blocked off. Also no rear o2.

My car has no CEL at all. I have removed everything from the ecu file I custom make out of the NVR Stage 2++

Gauge is ebay, looks like a digital (with sending unit) APR style replica which maxs -15 to 30psi and a 21psi warning light...

Now at idle cold I get -8 to -9. On deceleration in 2nd gear max -11

My LTFT is 1.56% now this is via my ELM327 bluetooth to android device. Can check any blocks in VCDS if anyone wants to know if block 032 might read something else but they seem to match up.

Also blocks 15/16 show no misfires at idle.

I run BKR7E's at .028, stock airbox with pipercross filter and forged (none leaking) DV.

Any ideas or info someone please. I can post my last log. Also DazDlinger has pointed out in my logs I have a boost leak and a not so good tune with timing pull at 4k or so. Anyone. Help???

All I have is a husky 2 gallon 110psi max air compressor wit regulator.

LMK guys!
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Old 06-23-2014, 05:07 PM
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You clamp off the one going back to the turbos, be careful you will damage the engine if you boost higher than its fueled for. If it makes your desired boost than its a control problem, likely the n249. If it doesnt make enough its a mechanical problem, restricted exhaust, waste gate or turbo damage. If you dont hear it hissing and wooshing being a leak big enough to loose 21-7 psi. It would be loud. I doubt its a boost leak.

Last edited by Prospeeder; 06-23-2014 at 05:09 PM.
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