BV43 on AVF surging after heavy load pull

esorense

Active member
Joined
Oct 5, 2009
Location
Oslo, Norway
TDI
A4 B6 AVF TDIQ
Hi guys, earlier this year my 1749 blew up and i replaced it with a BV43. when i installed the turbo i removed the resonator and tried cleaning out the cat as well as i was able to and put things back together. After getting a remap the power was awsome, although low end torque was way down of what the stock turbo gave me. After a few weeks i started to suspect the cat was clogging up on me, but before i had the time to check it out i had an incident under heavy load.

I was accellerating hard up a steep hill to catch up with traffic when suddenly the turbo started surging and the power dropped. Up until that point the boost had always been completely steady with absolutely no issues. Since it is surging regularly. I shortly after the incident took out the cat and removed all sign of ceramics to get rid of the restrictions, and at the same time fixed a few minor boost leaks from the system. I did at the time think the leaks was my problem, so unfortunately i did not check the exhaust turbine very well. But altough the surging did decrease it is still there and increasing in frequency again. I have done a pressure test on the system which showed no evidence of any leaks, and i have checked the cold side of the turbo for shaftplay and visible damage. All looks to be in perfect condition.

What causes are there for surging? Could the exhaust side have been damaged by excessive heat due to the clogged up cat and cause this? I have lately experienced a lot of smoke when pulling away at low rpm and at times the engine management clearly holds back on boost.

Any tips on where to start? I will do some logs as soon as i get my vcds back from a friend. First thing then i will check my n75 duty cycle and double check my vacuum lines

regards Espen
 

esorense

Active member
Joined
Oct 5, 2009
Location
Oslo, Norway
TDI
A4 B6 AVF TDIQ
I know i should have put one in but unfortunately no... I have ordered one now though but shipping from the states is not the fastest to norway. Customs will probably also take their time.....

Before it started surging all logs were fine and the spool up seemed good with boost setteling nicely at 1.7 bars as requested. Peaks were seldom but maxed out at 1,8 and setteled quicly.

Boost logs still seem good, but maf logs show sudden drops in airflow. I thought my maf was acting up but tests with a new one gives similar readings. Now i am wondering if those drops could be related to the surging even though the boost logs look fine? I am guessing the pressure fluctuations are to quick for the map to recognise them??

do btw the vanes close or open with vacuum?
 
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struikie

Veteran Member
Joined
Oct 19, 2007
Location
Netherlands
TDI
BMW 335d E91
If vcds can read the dip in the maf readings... i guess it would also be registering boost differences...

Was the map sensor upgraded ?

JW
 

esorense

Active member
Joined
Oct 5, 2009
Location
Oslo, Norway
TDI
A4 B6 AVF TDIQ
In the AVF a 3bar maf is standard so it has not been upgraded. I have concidered a 3,5 or a 4bar if possible but i have guessed i should be ok with the 3bar..

What i will have to check btw is my n75 wiring since that broke earlier this year and was repaired. There could perhaps be some corrotion there disturbing the operation since both wires were completely green before mending.. I hope checking the dutycycle will reveal some issues with the vane control.

What i don't fullt understand is why it surges when there are no pressure leaks, no (apparent that is) exessive boost and below 2K rpm boost is below 1,4.

What are the actual causes of surge?
 

esorense

Active member
Joined
Oct 5, 2009
Location
Oslo, Norway
TDI
A4 B6 AVF TDIQ
The airfilter is a Brand new oem item and has been exchanged after it started surging. At the same time i also supported the turbo inlet pipe to make sure that would not collapse due to the suction.
 

struikie

Veteran Member
Joined
Oct 19, 2007
Location
Netherlands
TDI
BMW 335d E91
I am 1250km away from you... so no way to come over and check ;)

what about going back to your tuner to see what he thinks ?


JW
 

esorense

Active member
Joined
Oct 5, 2009
Location
Oslo, Norway
TDI
A4 B6 AVF TDIQ
Ha ha, and my tuner is in the uk :p

I'll figure it out, just need to find the time to pull things apart and inspect properly. Was hoping for tips on the causes since it started surging so suddenly, and has kept on doing so afterwards.

Thank you for the pointers btw, i do think i have some mechnical skills hidden away somewhere. But it always is helpful with hints. :)
 

mk1-83

Veteran Member
Joined
Aug 14, 2010
Location
Holland
TDI
LUPO 1.9 tdi 300+ hp
clogged vnt I think, when you press te go pedal at max. with low rpm the vans go full open to allow building boost.
when you drive with a heavy load and steephill then floor it. the turbo have max boost at low rpm and overboosting youre engine because the engine don't get up the rpm's that fast.
http://forums.tdiclub.com/showthread.php?p=417913
 

esorense

Active member
Joined
Oct 5, 2009
Location
Oslo, Norway
TDI
A4 B6 AVF TDIQ
Not much progress with this yet, still searching for possible answers.

Overboosting would show in the logs but they are very similar boost control vise as before the incident. I will not rule it out yet though, I did however discover a timing error which i think might give some issues. Engine measureblock 4 value 4 shows a steady 3.3 kw at idle (861rpm) I pulled the upper timingbelt cover and discovered the cam pulley was dialed back as far as it would go. I guess the guy that did my timing belt the last time misplaced the belt and then tried to get as close to the tolerance as possible without assembling everything a second time. I have no idea how this affects performance but the coming tuesday it will be timed properly and we will see. Performance has always seemed good but i have for quite some time even before the turbo upgrade felt it was not 100%

In addition i have to pull my egr and replace some gaskets since that has shown a few signs of leaking. A good time now to replace it with a race pipe i guess.

Any recomendations for timing the AVF? 0-0,5 i read is ideal for economy on 2.0TDI?? My map is maxing out the stock pd nozzles. I guess faulty synchronisation will have a bigger effect on performance than it would with a stock or moderate tune, since SOI and duration probably are very close to the extreme limits.
 
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esorense

Active member
Joined
Oct 5, 2009
Location
Oslo, Norway
TDI
A4 B6 AVF TDIQ
I have hopes that the drive back from the garage tuesday night will be a good experience:) Atleast it should be a good step in the right direction...
 

Rub87

Top Post Dawg
Joined
Dec 10, 2006
Location
Belgium
TDI
Ibiza '99 90HP
earlier cam aids spool slightly altough the earlier the cam, the less after tdc you can inject.. I don't know what duration you're making..

I have bv43 from CR 170h on my 120hp CR and the sounds it makes is really strange, when you go off throttle it sort of wines and under 2000rpm when you floor it it also turns some heads on the streets, it's not surge and the turbo looks in perfect condition and it is working very nice now for 20.000km at 200hp, the stock turbo didn't make this sound altough when I put the 170hp bv43 on I also removed the dpf
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
If you are seeing changes in air flow rate that do not follow boost pressure, then you almost certainly still have a boost leak. The shape of the MAP curve and the MAF curve should be almost identical until over 3500 rpm where flow might taper off a bit.

This statement assumes no EGR.
 

esorense

Active member
Joined
Oct 5, 2009
Location
Oslo, Norway
TDI
A4 B6 AVF TDIQ
I had the timing adjusted yesterday, and it certainly gave results. There was a clear improvement in spoolup and low-middle end torque. Unfortunately the timing was now set to -0,5 instead of 0,5 as i asked for. I dont know how that affects things but i will try to correct it as son as i get the chance.

I also replaced all the EGR gaskets which also has reduced some of the strange noises. The vacuum is disconnected and there is a blockingplate installed with the top gasket of the exhaust pipe, just to make sure it is not leaking and keeps the stealth look.

I will get some logs done as soon as possible to verify that things are truly better functioning, and not all in my head.

BTW The problems i had with the maf readings was that it showed 0 airflow while the MAP still was indicating boost. If leaks were the problem it should be opposite.
 

p0wer

Veteran Member
Joined
May 21, 2009
Location
Jyvaskyla, Finland
TDI
Golf 3 -94 1Z 377hp, Golf 3 Cabrio 4-Motion 1.8T 620hp, Golf 3 Syncro 2.9 VR6 HX52, Bora AJM 4-Motion 2260vk +120% Firad, Passat 3B Syncro AFN 2260vk
.....
 
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