Brand new GT1749VB huge turbo-lag!

stiffy

Member
Joined
Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
Hi guys,
My car is a 2004 Bora 1.9tdi, the original engine is an ATD 74kw(pd100). I'v swapped the engine to a brand new AWX 96kw(pd130 GT1749VA) form 2005 passat b5 since 200k km. I'v remapped the ECU to 165hp/385Nm(software calculated). 'cause I can't find the dyno machine around me. so I did 0-100km acceleration test on same weather and road condition. before tune is 9.5s, after tune is 7.9s.
After the "new" engine has run 100k km, I did some upgrades for my car:
- brand new GT1749VB turbocharger form darkside
- 2" intercooler plumbing and large SMIC form darkside
- 2.5" decat downpipe form darkside
- pd150 intake manifold form darkside
- 57mm EGR delete kit form darkside
- south bend stage2 daily clutch w/ 22 lbs single mass flywheel
I just installed the upgraded hardware a few days ago, and re-tuned ECU to 190hp/410Nm. then go test drive and VCDS log. The actual driving experience is huge turbo lag. under 2000 rpm has no boost at all. especially 1200~1500 rpm, basically no reaction of the gas pedal stepping down. :mad:
According to the log file, after 3~4 seconds the actual pressure eventually reach the specified value, and no overboost. I noticed that at nearly 4000 rpm of 3gear WOT pull, the N75 duty cycle is only 60ish%. I heard that it should be 70%~80%. Does this mean that the VNT rod length is too long? But this is a brand new authentic Garett turbocharger, all the screws and nuts have color paint marks, I dare not adjust it. :p
btw, I also tested the turbo actuator by a hand pump, it starts at 2 inch and hits the stop screw at 18 inch.
and I did basic settings group 11 in VCDS, ON is 1080mbar OFF is 970mbar.
all vacuum line are new, brand new N75(unplug the line to airbox and replace it with a little airfiler), vacuum no leak(25 inch on VAC of N75). It seems no problem at all, but still got turbo lag very much! :confused:
Any suggestions? thanks!
stiffy
some logs
3gear pull MAP

3gear pull MAF

another 3gear MAP

a little "normal" drive
 

Kevinski4

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Aug 31, 2007
Location
Nebraska
TDI
.
Yours wouldn't be the first brand new Garrett VNT17 I've seen with screwed up actuator rod settings right from the factory. Shorten the rod a turn or two and take some new longs.
 

Mike_04GolfTDI

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Nov 19, 2003
Location
Richmond, BC, Canada
TDI
Mine: 2019 Golf R DSG, Wife's: 2015 Golf Comfortline TDI
What kind of MAP sensor do you have?

For example, my car came with a 2.5 bar MAP sensor originally. I upgraded to a GT1749VB turbo, and along with that I put in a 3 bar MAP sensor, which is necessary because the pressure called for by the tune exceeds what the 2.5 bar sensor can read.

If your car started out with a PD100 engine, then you probably have a 2.5 bar MAP sensor. You can see in your graphs where there are no readings very much above 2500 millibar (2.5 bar). Take away 1 bar for atmospheric pressure, and that leaves you with just under 22 PSI boost pressure (1.5 bar times 14.5 PSI = 21.75 PSI). For 190 HP tune I have a strong suspicion that you must be running higher pressure than that. My car uses 24 PSI boost for about 170 HP.

Check with your tuner to see if the MAP sensor needs to be changed, or if that has anything to do with your boost problem. Don't just change it without contacting your tuner first!
 
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stiffy

Member
Joined
Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
Yours wouldn't be the first brand new Garrett VNT17 I've seen with screwed up actuator rod settings right from the factory. Shorten the rod a turn or two and take some new longs.
it is too hard to touch that f**kin' nut onboard. :D After trying all the other ways failed, I'll do this eventually. :(
 

stiffy

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Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
Mike,
I'v replaced to a 3bar MAP sensor when I swap the engine.
 

majesty78

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Dec 7, 2007
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Austria/ Europe
TDI
Skoda Superb 3T5 CFFB
If not somebody had fiddled around with the rod or min flow setting, it is close to impossible that the setting is off.
All turbos run through a calibration unit for setting up all VNT parameters, and if it would be off chart, it simply would not be delivered.
 

diffas

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B5q A4 Avant 2.5TDi+, B7q A4 Avant 3.0TDi
Unless its a ebay 'factory refurbished unit' [emoji23]
 

stiffy

Member
Joined
Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
I've shortened the length of VNT rod by one turn, The N75 duty cycle has risen to 77.3% at 4000 rpm full throttle.
I can feel that the turbo lag seems slightly smaller than before. Maybe it's just a placebo effect. :D
'cause there is a little spike, I'm not gonna shorten it anymore.
Anyway, I still can feel noticeable turbo lag! Is the lag of GT1749VB really bigger than GT1749VA? :confused::confused:
3gear WOT form 1500rpm:

3gear WOT form 2100rpm:
 
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ryanp

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Arosa CR - 550hp - 9.7 @ 150mph 1/4 Mile, Citigo 4x4 CR TDi - 340hp, Caddy 2.0 CR 4x4 TDI - 300+hp, Golf Mk2 Van 1.9 TDI - was 290hp, Mk5 Ibiza 2.0 FR TDi - 270hp, BMW 135d - 360hp, BMW 330d - 335hp, BMW 335d - 380hp + a few more ........
It should not be much if any laggier than a PD130 unit, I would get the tuner to check thats all OK. Might be too lean there or N75 not quite perfect.

The actuator rod being too short might give you boost creep so be careful there.
 

stiffy

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Joined
Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
It should not be much if any laggier than a PD130 unit, I would get the tuner to check thats all OK. Might be too lean there or N75 not quite perfect.
The actuator rod being too short might give you boost creep so be careful there.
Thanks for reply!
The actuator rod is fine, I'm not gonna shorten it anymore.:p
There's a zip file that contents the original ecu file and the tuned one. Can you check them for me and point out where the problems are? then I'll fine tune it.
Please help me! Doing this in the past few days has driven me crazy.:(
 

dieseleux

Théoricien -TDIClub Contributor
Joined
Nov 14, 2006
Location
Pas assez loin pour vider ma tank!
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Jetta TDI 02
24-27 inmg of vaccum on pump.?
16-18 inmg of vaccum on actuator at idle on manual car?
If not, some time, vacuum pump leak on aluminium hose nipple, a gentle hammer on pump flange to crimp the nipple and silicon to seal totaly (let silicon dry for one night before test)
One way vale (black/white device) need to be clean, i clean with air compressor and WD40.
N75 also need some cleanning action if one way valve are dirty.

Another test to do.
-At idle, actuator move to stop screw (on manual car only)

-With hot engine at neutral, no accessory on (A/C, light, fan...), turbo actuator plug on full vacuum, at 2000rpm, the turbo pressure rise to 2-4 psi if stop screw are ok (dont ajust stop screw if you are not completly sure of all other thing are ok)


Dieseleux
 
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stiffy

Member
Joined
Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
24-27 inmg of vaccum on pump.?
16-18 inmg of vaccum on actuator at idle on manual car?
If not, some time, vacuum pump leak on aluminium hose nipple, a gentle hammer on pump flange to crimp the nipple and silicon to seal totaly (let silicon dry for one night before test)
One way vale (black/white device) need to be clean, i clean with air compressor and WD40.
N75 also need some cleanning action if one way valve are dirty.

Another test to do.
-At idle, actuator move to stop screw (on manual car only)

-With hot engine at neutral, no accessory on (A/C, light, fan...), turbo actuator plug on full vacuum, at 2000rpm, the turbo pressure rise to 2-4 psi if stop screw are ok (dont ajust stop screw if you are not completly sure of all other thing are ok)


Dieseleux
Thanks for reply!

All vacuum line are new w/ brand new N75 valve. I did basic settings group 11 in VCDS, ON is 1092mbar OFF is 972mbar(pressure difference is 120mbar). I also tested the actuator by a hand pump, it starts at 2 inhg and hits the stop screw at 18 inhg.

However, I did the following test according to your instructions:

on idle, vacuum source shows me about 25 inhg


on idle, actuator shows me about 19 inhg


I use handpump pulling the actuator to max travel and rev to 2000rpm, the VCDS measure block group 11 shows me around 1300mbar MAP. which means boost is 4.4psi(atmospheric pressure is 996 mbar).

so, the whole vacuum system looks OK I think.:eek: I would rather be a vacuum leak.:mad:
 
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stiffy

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Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
I lowered the N75 values at low rpm and it looks better than before. However, the low speed acceleration still feels floppy.:mad:
4gear pull:
 

Judson

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Jan 18, 2001
Location
Cheyenne, WY
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2001 Jetta
Following this thread as I have the same problem: VB in an ALH, with PD150, no egr, new N75, all new vacuum hoses, and etc. Really have problems getting her going off the line; seem like the car is flooding. Have to feather the clutch and accelerator very carefully. Most decidedly not normal, not right at all. There's no good reason for this.
 

dieseleux

Théoricien -TDIClub Contributor
Joined
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Location
Pas assez loin pour vider ma tank!
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Jetta TDI 02
I lowered the N75 values at low rpm and it looks better than before. However, the low speed acceleration still feels floppy.:mad:
4gear pull:
4.4psi at 2000rpm, hot and neutral is good, no ajustement need.
2 and 18 for start and stop is also good, no ajustement need.
15psi at 1800rpm is not bad...

You remove KP39 for 1749VB, is not a big step, KP39 is nice reactive turbo and better than VNT15 on older engine.

To test low rpm, close vane at 100% vacuum and try 1000 to 1800rpm with very carefull attention on pressure gauge.
The turbo never do better that at low rpm.

A gt1749VC or better... GTCxxxx or GTDxxxx is better choice for low rpm reactivity like KP39 and good pressure and efficiency at high rpm.


Dieseleux
 
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dieseleux

Théoricien -TDIClub Contributor
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Pas assez loin pour vider ma tank!
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Jetta TDI 02
Following this thread as I have the same problem: VB in an ALH, with PD150, no egr, new N75, all new vacuum hoses, and etc. Really have problems getting her going off the line; seem like the car is flooding. Have to feather the clutch and accelerator very carefully. Most decidedly not normal, not right at all. There's no good reason for this.

Follow thread #12.
Do some graph or number and i reply.



Dieseleux
 

stiffy

Member
Joined
Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
Following this thread as I have the same problem: VB in an ALH, with PD150, no egr, new N75, all new vacuum hoses, and etc. Really have problems getting her going off the line; seem like the car is flooding. Have to feather the clutch and accelerator very carefully. Most decidedly not normal, not right at all. There's no good reason for this.
Have you tuned the N75 duty cycle map?
 
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stiffy

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Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
4.4psi at 2000rpm, hot and neutral is good, no ajustement need.
2 and 18 for start and stop is also good, no ajustement need.
15psi at 1800rpm is not bad...

You remove KP39 for 1749VB, is not a big step, KP39 is nice reactive turbo and better than VNT15 on older engine.

To test low rpm, close vane at 100% vacuum and try 1000 to 1800rpm with very carefull attention on pressure gauge.
The turbo never do better that at low rpm.

A gt1749VC or better... GTCxxxx or GTDxxxx is better choice for low rpm reactivity like KP39 and good pressure and efficiency at high rpm.


Dieseleux
I see, thank you anyway.
But the GT1749vb is the "best" turbo I can afford. it is worthwhile to sacrifice some reactivity for 200ps I think.:)

btw, The 22.5lbs single-mass flywheel may also be a cause of slower response.

stiffy
 

loudspl

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Osakis, Minnesota
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02 ASV w/ 02J
MAP-based tune (MAF delete) might fix this if you have a bad MAF.

Had similar issue, replaced all vacuum lines, pump, actuator, N75, etc. with zero change.

Switch to MAP based tune might help
 

stiffy

Member
Joined
Jun 16, 2017
Location
China
TDI
Bora MK4 1.9 TDI
MAP-based tune (MAF delete) might fix this if you have a bad MAF.
Had similar issue, replaced all vacuum lines, pump, actuator, N75, etc. with zero change.
Switch to MAP based tune might help
Thanks for reply!
First of all, according to the VCDS readings, my MAF seems good:


Secondly, I've tried "MAP based smoke limiter":
- Turn the Switch from MAF to MAP, turn to MAP by putting 257 instead 0 on the map.
- On MAF Smoke Limiter map blanked with max value 70mg, on the IQ by MAF do he same thing.
- Do the math on IQ by MAP (Axis: x -> Boost, y -> Rpm, Z -> IQ) using following formula:
AFR = (Boost * Cylinder Capacitie * VE * AD) / IQ
AD - Refers to Air Density
VE - Volumetric efficiency (1.9PD begins 80% and near 5000rpm decreases to 75%)

Guess what? nothing changes!:p:p:p
 

named tintin

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Jan 21, 2007
Location
quebec, canada
TDI
golf tdi
You will never get the snap of a smaller turbo with a bigger turbo, avnt17VB works good, but a little bit on the laggy side, there's better turbo today than those old vnt17.

Next, you need to tune your N75 map and all it's associated parameter to have less lag down low, you may look into some PID setting too, tweak it until you run into turbo surge, then back off a little, this will be the max the turbo can do for your setup, and don't ask more boost than what the turbo can deliver at low rpm, it's untunable doing this.
 
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