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Author Topic: B6A4 1.8t - Not hitting requested boost N75 maxed out  (Read 4388 times)
stew
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« on: October 28, 2015, 10:24:15 AM »

Hi Guys,

So my B6A4 6mt 1.8t is not hitting requested boost. The car is on an unknown chip/tune, 300k kms, otherwise stock. I have older logs of it hitting 20psi and the wastegate duty cycle functioning.

As of now it almost hits requested boost and then falls as the rev's climb, wastegate duty is 100%.

The car had a cracked head/misfire coolant burn (typical AMB) and I replaced it with a rebuilt AWP head about 3 months ago. Ever since then the car has been down on power (but no misfires/white smoke). So the problem could be related to something mechanical that was done during the head install.

What I have done so far:
- Changed the DV (new 710P)
- Checked the N75/wastegate line for leaks
- Pressure test (only up to ~8 psi, I need to build a better boost leak tester)

What I plan on doing:
- Change out cat for test pipe (could be clogged cat?)
- check wastegate action
- better boost leak test
- check turbo (see if it spins freely)
- Anything else?

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nyet
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« Reply #1 on: October 28, 2015, 10:27:25 AM »

That's the short list. Let us know of any progress you make.
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SB_GLI
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« Reply #2 on: October 28, 2015, 11:18:40 AM »

N75 could be bad.  pinch off the line going to the wastegate actuator and (carefully) see if boost changes.

Also, your fueling request is not good.  Check the low pass lamfa filters (info is in the A4 community stage I thread)
« Last Edit: October 28, 2015, 11:21:51 AM by SB_GLI » Logged
aef
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« Reply #3 on: October 29, 2015, 06:37:23 AM »

100% duty will kill any N75
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SB_GLI
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« Reply #4 on: October 29, 2015, 08:58:14 AM »

his logs show 95% DC.
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stew
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« Reply #5 on: November 01, 2015, 11:23:08 AM »

OK so I pulled out the airbox for the test pipe install and checked all the connections. The line going to the wastegate was only holding 2-4 lbs and then leaking. Pulled off the line, not leaking. So looks like I have a torn/broken wastegate actuator. The wastegate flap was a little bit loose in the exhaust housing.

Now I have a few sets of used 2.7t k03's lying around with good actuators, too bad they don't swap over. So I am looking for a wastegate actuator or waiting until frankenturbos go on sale for black friday.

I put in the test pipe while I was in there.
« Last Edit: April 18, 2017, 11:45:36 AM by stew » Logged
stew
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« Reply #6 on: April 21, 2016, 10:07:20 AM »

Went to change out the wastegate actuator last weekend, was removing the turbo and broke off a manifold-> turbo bolt in the turbo. Crap.

This turbo was making noise and had 292k kms on it, so probably not a bad thing. Found a used one (100k kms) on craigslist for $150 and put that in.

Car drives much nicer. Only mods are:
-unknown tune
-test pipe
-drop in air filter

Not sure when injectors are considered maxed out. IDC is around 120% at peak.

new logs attached.
« Last Edit: April 18, 2017, 11:45:54 AM by stew » Logged
nyet
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« Reply #7 on: April 21, 2016, 10:35:31 AM »

Not sure when injectors are considered maxed out. IDC is around 120% at peak.

90%
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ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
stew
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« Reply #8 on: September 24, 2016, 08:23:26 PM »

Turbo replaced, new logs.
« Last Edit: April 18, 2017, 11:47:01 AM by stew » Logged
316LV
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« Reply #9 on: September 25, 2016, 04:14:01 PM »

Pressure test for leaks. Chances are if your wastegate hose was bad, other hoses of the same age are going to be just as bad. I had the same issue as your log shows and it was a bad hose to the boost reservoir (Heimholz or what ever it is really called)...
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nyet
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« Reply #10 on: September 25, 2016, 04:17:24 PM »

or just need more IMAX
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ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
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