Video: BRM Boost Hunting / Surge/Blip -- Activity Possible Actuator Issue?

PhunkFX

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Joined
May 19, 2011
Location
Hudson Valley, NY
TDI
2014 Audi Q5 TDI S-Line, 2005.5 Jetta TDI (BRM) 6MT (02Q)
This is a short video illustrating the weird blips and surges I experience while on a steady throttle or cruise control. The blip and surge is momentary and only noticed the instant before this weird boost spike drops off and goes down to normal expected boost.

VIDEO: https://youtu.be/Zrb4Pp39K9w -- the buzzing you hear is the boost gauge itself. (supposed to be a no-buzz fitting :( )

This is the behavior I witnessed after installing my boost gauge on 19 March 2017. The evidence via the boost gauge is very interesting. At first, I thought there was something wrong with my gauge!!

Odd boost hunting that occurs at random. No rhyme or reason. Notice my MPH and RPM do not move, as I'm set at ~80mph on cruise. During the duration of the increased boost, I notice (feel nor hear) anything different in the running. I notice a small surge of power, or blip right before the boost falls off down to ~4-5psi, as stated previously.

Crazy huh? What do you think?
 

PhunkFX

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May 19, 2011
Location
Hudson Valley, NY
TDI
2014 Audi Q5 TDI S-Line, 2005.5 Jetta TDI (BRM) 6MT (02Q)
I'll be taking some VCDS logs / graphs on the way home. That should be very telling as well. Perhaps all I may need is a new N75. We'll see. I'd rather figure this out, than throw hardware at it until it's resolved. You know, for future information.

R
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
I dealt with the same problem as you describe on a customer's car. (wonder if it is the same one).

At a steady speed of around 45 and up, the boost would work it's way up to 20-25PSI and then drop to about 6PSI and start the cycle over. At 80MPH it would cycle every 5 seconds or so. Really annoying.

The closest that I could get to resolving the surges was to stiffen up the actuator until it just started to move the lever with 9"hg vacuum and pull back on the stop screw adjustment. Anymore than that and it would throw an implausible code for the position sensor.

The customer had been through a lot expenses with the car, (transmission, clutch, camshaft, timing belt,... he had just bought the previous owner's nightmare), and did not want to shell out more for a new turbo or even remove it to see what was going on with the vane mechanism. Chances are that the vanes were distorted. Disconnecting the vacuum to the actuator produced a lag in the boost at low RPMs but otherwise gave all the boost that it needed.

This car was chipped but not above a stage1.5-2.
Try to see if the car runs fairly normal without vacuum to the actuator.
 
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PhunkFX

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May 19, 2011
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Hudson Valley, NY
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2014 Audi Q5 TDI S-Line, 2005.5 Jetta TDI (BRM) 6MT (02Q)
I'll be sure to check that... It may be a tuning issue... I'm still looking into it. As I have deleted the EGR and ASV, my custom tune may not have it corrected.

Then again, I'll grab some logs on my commute home, tonight.
 

Kalter|Tod

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Joined
Feb 23, 2012
Location
Wyoming
TDI
2006 Jetta (BRM)
research the zip tie mod..... This will fix all those problems..... I run a Stage 2 tuned car and this fixed all the above problems...... Zip tie Mod is your friend
 

DonsJetta

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Sep 27, 2015
Location
Hershey, PA
TDI
2006 Jetta Special Edition
Is the zip tie mod used as a limiter or, does it increase the spring rate at the end of the stroke? One reason I ask is because a zip tie cannot be loosened if you go to far, it must be cut and re-installed..
 

PhunkFX

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May 19, 2011
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Hudson Valley, NY
TDI
2014 Audi Q5 TDI S-Line, 2005.5 Jetta TDI (BRM) 6MT (02Q)
Is the zip tie mod used as a limiter or, does it increase the spring rate at the end of the stroke? One reason I ask is because a zip tie cannot be loosened if you go to far, it must be cut and re-installed..

Good Question!
 

DonsJetta

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Location
Hershey, PA
TDI
2006 Jetta Special Edition
OK good! I used a foot of stainless safety wire folded in half and made a small loop to just fit over the end of the actuator rod, pulled around 17 to 18 in/vac, then twisted the wires together over the vacuum port nipple. Allot easier than trying to loop a zip tie for me anyway. I did have to attach a light weight spring to keep the wire loop against the rod adjusting nut as the rod moved through it's stroke during operation. Without the spring, the wire loop would slide down the threaded rod and lock, limiting the travel and throwing a code. So far its working well.
 

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 1999.5 jettaIV,2005 BEW Beetle
A byproduct of shortening the stroke (zip tie mod) is that it requires less vacuum to reach the max boost position.
You would have to increase the actuator rod preload to maintain the original relationship of (X)"hg = max boost position.
 

PhunkFX

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2014 Audi Q5 TDI S-Line, 2005.5 Jetta TDI (BRM) 6MT (02Q)
I think the majority of my problem is tuning related. But I do have a vacuum related issue as well. I probably did not re-attach some kind of important vac line, or I plugged the wrong one, after the full EGR/ASV delete.

I'm not entirely worried about overboosting with the turbo, I am going to get a much safer tune soon. But likely sometime this summer, I am going to upgrade the turbo, just because I want better flow, possible MPG, and more power. Aka, yes I'm greedy.
 

PhunkFX

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May 19, 2011
Location
Hudson Valley, NY
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2014 Audi Q5 TDI S-Line, 2005.5 Jetta TDI (BRM) 6MT (02Q)
And then ultimately my nozzles... and I'm in need of a clutch now, and the flywheels makes so much noise as the clutch is pressed down.

Man, buying a fully stock vehicle entails a log when you want to modify it ;) I'm very happy with it however. I'll make a separate post of it's transformation.
 

legendman

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Nov 9, 2004
Location
19
TDI
2006 Jetta 5sp
PhunFX did you get this sorted out?

My boost gauge is doing the same as yours, goes up to 20lbs then drops
with cruise set to 70 mph
 

PhunkFX

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Location
Hudson Valley, NY
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2014 Audi Q5 TDI S-Line, 2005.5 Jetta TDI (BRM) 6MT (02Q)
PhunFX did you get this sorted out?

My boost gauge is doing the same as yours, goes up to 20lbs then drops
with cruise set to 70 mph
I did. It was the actuator and/or clogged or sticking VNT vanes. I upgraded my turbo, as I wanted more power. This issue completely cleared up.

For whatever reason, the boost gauge was showing the PSI, but it wasn't making power, as it would seem like the air was just not making it out.... so the ECU would be calling for certain power levels, and the car would up the PSI to try to get it, but couldn't maintain it consistently. From what I can gather.

New turbo with no smart actuator, and a new tune for the turbo sorted this all out!
 

legendman

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Joined
Nov 9, 2004
Location
19
TDI
2006 Jetta 5sp
For whatever reason, the boost gauge was showing the PSI, but it wasn't making power, as it would seem like the air was just not making it out.... so the ECU would be calling for certain power levels, and the car would up the PSI to try to get it, but couldn't maintain it consistently. From what I can gather.
Thanks for the update.

This is how mine is, it sounds like it's choking on itself when the boost goes.
If I let off or give it a good amount of throttle it will clear out only to start the cycle over again.
I am going to try the zip tie mod and cleaning the turbo as I just dumped a bunch of money on a cam and timing belt kit.
 
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PhunkFX

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Hudson Valley, NY
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2014 Audi Q5 TDI S-Line, 2005.5 Jetta TDI (BRM) 6MT (02Q)
Thanks for the update.

This is how mine is, it sounds like it's choking on itself when the boost goes.
If I let off or give it a good amount of throttle it will clear out only to start the cycle over again.
I am going to try the zip tie mod and cleaning the turbo as I just dumped a bunch of money on a cam and timing belt kit.
Yeah, I was in the same place. So rest assured, its not likely your block or head or something major. In order to figure this out, which I pretty much new it was the turbo right away, I replaced the N75 valve, the tandem pump (was having check valve issues), the valve cover, various vacuum lines, MAF, tune (twice), and even tried cleaning it with ez-off oven cleaner during the down pipe upgrade.

I did not try the zip-tie mod, which could have worked, idk. LOL But I'm all sorted now with fresh ancillary parts. So I'm happy. Not it's just a tuning game for me.

Good luck to you, sir.
 

Dbheli

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Oct 1, 2023
Location
NJ
TDI
2006 MKV BRM Jetta
sorry to add to an old thread here but I am currently experiencing the same issue. Purchased the car last year when it was 10k miles out of major service (timing belt, cam, Egr delete, single mass clutch upgrade, brand new OEM turbo) my car, on the highway is cycling from 5psi to 15psi and holding for sometimes a min before dropping to 6. This cycle repeats constantly… from what I’ve read here you had luck with a turbo replacement. My turbo has 30k miles on it so I’m kinda doubting it will fix my issue. I have access to VCDS, but I’m new to TDI’s so some help would be greatly appreciated!
 
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