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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKV-A5 Golf/Jettas

VW MKV-A5 Golf/Jettas Discussions area for A5/MkV Jetta/Golf (2005/2006 PD and 2009 CR).

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Old May 11th, 2019, 08:23   #1
atikovi
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Join Date: Jun 2002
Location: Suburban Washington DC
Default 06 Jetta BRM, rebuilt turbo runs bad unless

the hose to the VNT actuator is disconnected. I had the turbo rebuilt by a reputable turbo rebuilder, installed it, and the car runs like crap. No power until 2200 rpm, black smoke, rapping noise, acidic smell from under the hood like the converter is overheating. It ran better BEFORE the rebuild.
If I remove the hose from the VNT actuator it's a whole different animal. Tons of smooth power, no significant smoke or noise. I assume removing the hose keeps the turbo vanes closed so it builds full boost all the time. Thats great but if not careful could damage the engine if you give it too much boost so I want it running like it should.
Ran some tests. Put vacuum to the actuator and the rod moves smoothly and holds vacuum. Checked the solenoid and it puts out good vacuum to the valve. Do have the code P0299 low boost. What to check next? Could the actuator rod be out of adjustment? Don't rebuilders bench test and adjust that?

Last edited by atikovi; May 11th, 2019 at 08:25.
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Old May 12th, 2019, 05:10   #2
JETaah
 
Join Date: Jan 2001
Location: mi 48836
Fuel Economy: 53 max, 42 min, average 46
Default

With out the vacuum hose hooked up it runs the turbo vanes wide open at the no-boost position.
Sounds like the vanes are closed down too much. Sounds like your reputable rebuilder may not have tested it before delivering it.
Try the zip tie mod test:
https://www.myturbodiesel.com/wiki/t...ne-hesitation/


Looks nice, though
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Last edited by JETaah; May 12th, 2019 at 05:12.
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Old May 15th, 2019, 17:15   #3
atikovi
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Quote:
Originally Posted by JETaah View Post
With out the vacuum hose hooked up it runs the turbo vanes wide open at the no-boost position.
Sounds like the vanes are closed down too much.
I think just the opposite. Without the hose the vanes must be closed since it has plenty of boost.
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Old May 16th, 2019, 00:59   #4
JETaah
 
Join Date: Jan 2001
Location: mi 48836
Fuel Economy: 53 max, 42 min, average 46
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On your turbo, when you apply vacuum does it draw the actuator rod inward or push it out?
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1999.5 a4 Jetta, port matched, RC2, sprint 520's, 1.5" lift kit
1996 Passat B4V, coat hanger supported exhaust system,
Visit me www.martinbergelllc.com

Last edited by JETaah; May 16th, 2019 at 01:04.
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Old May 16th, 2019, 05:01   #5
atikovi
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If I remember correctly it pushes out.
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Old May 16th, 2019, 07:52   #6
JETaah
 
Join Date: Jan 2001
Location: mi 48836
Fuel Economy: 53 max, 42 min, average 46
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It should. Just wondered if the actuator got substitued with a more typical configuration.


Is this car tuned?
On some of the BRMs that I've worked on, the turbos will boost even without the vacuum attached. I believe that it was a flaw in the manufacturing process where the vane lever was welded in the incorrect position.



No vacuum = open vanes...and should not produce significant boost unless the vanes are positioned where they can not be put in the wide open position.

Did you give a read of the link that I posted above? It would provide a better explanation of what happens when the vanes are closed down too far because of the lever stop screw is not adjusted correctly.


Here is a post by Jeff from Rocketchip tuning regarding the BRM's turbo
https://forums.tdiclub.com/showpost....45&postcount=3
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1996 Passat B4V, coat hanger supported exhaust system,
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Old May 16th, 2019, 08:04   #7
atikovi
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Yes I read that link. It goes from about 960 to 1050. Now a question about the N75 valve. Is this a solenoid, i.e. on or off, or variable vacuum? Because when I do this test with a vacuum gage in the hose to the VNT actuator it reads either 0 or 25 in. so that's expected. But outside the test, at idle, it shows 17 in. Is this normal? Shouldn't it be 0 at idle so the vanes are closed?
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Old May 16th, 2019, 09:06   #8
JETaah
 
Join Date: Jan 2001
Location: mi 48836
Fuel Economy: 53 max, 42 min, average 46
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You still don't get it.
no vacuum = open vanes = no boost in a properly functioning turbo.




17in/hg is about right for the idle vacuum...sometimes higher. 17-20 is a correct range and the lever should be on the stop screw.

The N75 valve is a pulse width modulated valve. The ECU varies the duty cycle for the N75. The valve alternates between venting and applying vacuum to the actuator to vary the position of the lever.


17in/hg = is vanes closed ready to boost until there is more boost than requested. When there is more boost than requested it drops the vacuum to start opening the vanes.


Re read the myturbodiesel link.
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1996 Passat B4V, coat hanger supported exhaust system,
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Old May 16th, 2019, 09:52   #9
atikovi
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Quote:
Originally Posted by JETaah View Post
You still don't get it.
no vacuum = open vanes = no boost in a properly functioning turbo.
I don't. If that is the case, why does it have so much more power (boost) with the vacuum line off? And with the line connected it has little power, little or no boost and black smoke?
Quote:
Originally Posted by JETaah View Post
The N75 valve is a pulse width modulated valve. The ECU varies the duty cycle for the N75. The valve alternates between venting and applying vacuum to the actuator to vary the position of the lever.
Ok thanks for clarifying, I was thinking it was either open or closed. I'll look at the zip tie mod link again.
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