ALH TDI Overboost problems

nikolay_ss

Well-known member
Joined
Sep 30, 2014
Location
Bulgaria
TDI
1.9TDI ALH
Hello guys,

I have modified ALH with 11mm pump, DE143, Bosio DLC 1019 (0.216um), GT1749VA, 3 bar map sensor, air intake and intake manifold from PD130/150 and some more minor mods.
I use stock N75 map from ASZ and boost target map till 50mg also stock from ASZ, for 60mg-65mg(near 4V pump voltage) I did set it to go at 2400mbar at 2000rpm, 2500mbar at 2250rpm till 3750rpm.
The problem is that in any other gear, but not 5th it goes to like 3000mbar and don't go back if I did not let the gas pedal. If I WOT it at 5th gear it goes for peak of 2700mbar then goes back to 2500mbar and everything is good, but if I do this in 3rd gear it goes to 3000mbar and never come back until I release the gas pedal. Any ideas?
The geometry is clean, and actuator moves free. Not sure if this problem may be caused from N75. Because I have no problems at 5th gear, everything is as it needs to be.

Thanks!
 

adamss24

Veteran Member
Joined
Nov 2, 2005
Location
Great Britain
TDI
audi a4 2.5 tdi 98 quatrro 6speed
I reckon its boost creep, gt1749va is a rater small turbo for 11mm pump and your nozzles... I suggest you go for a bigger turbo:gt1749vb, bv43, gtb1749vk,etc...
 

Yourbuddysatin

Veteran Member
Joined
Oct 28, 2016
Location
Pennsylvania
TDI
2013 Jetta tdi
I’d check the actuator setting. Myturbodiesel.com has good videos on your tube of how to check and adjust your actuator. Also check your vacuum lines and vac pump.

I made a mistake and thought I had a loose vac line and plugged it. Well my turbo was crushing over 30lbs and holding. Wasn’t a good ending. Then I tried to increase the boost by adjusting the actuator only by 1inhg and it made too too much boost in lower gears.
 

nikolay_ss

Well-known member
Joined
Sep 30, 2014
Location
Bulgaria
TDI
1.9TDI ALH
Okay, so I got all the maps from ASZ engine, because my turbo is from ASZ.
I got turbo related maps, PID maps and drivers wish from ASZ, now boost is acting way better I still have some big peaks, but it's because I'm MAP smoke limited and if I press harder it pushes a lot of unburnt fuel and turbo spins a lot.
Thanks for your help!
 

adamss24

Veteran Member
Joined
Nov 2, 2005
Location
Great Britain
TDI
audi a4 2.5 tdi 98 quatrro 6speed
As i said, you have too much fuel and turbo is not man enough for the job ! Its spiking too quick and you will kill it that way ! I do hope you know how to stop the engine in case of a runaway ! Get a larger turbo there, pushing too much fuel wont do it much good ! Get a 3 bar map sensor if you don't have one already...
 

nikolay_ss

Well-known member
Joined
Sep 30, 2014
Location
Bulgaria
TDI
1.9TDI ALH
Thanks, Adams.
Well I'm not injecting maximum fuel, everything is set correctly, just in case I smash the gas pedal then I got peaks, because of MAP smoke limiter which is not calculating the fuel I can burn. The last 2 days even if I smash it, the turbo is not going more than 1.6 peak, I did open the geometry a bit more at max mg and everything seems to work fine now. And yes I do have 3 bar map sensor :)
 
Joined
Jun 16, 2019
Location
Castlegar BC
TDI
2003 Jetta TDI
How long has it been doing this? Could be sticky veins.



I would bet the vnt is sticky i see this all the time and if its not sticky the ring on the inside could be starting to wear out. best way to check this is to remove the vnt actuator off the arm and move it by hand it should move free and not hang up at all.
 
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