VNT adjustment advice

[kilner]

boost oscillation gtb2260

im having a problem seting up the vnt on my gtb2260vk on a pd170
i had to readjust all the actuator as the stock position it was in would not fit in the engine bay as the actuator was hiting the firewall
so for intial setup i had the vnt set to full open and then set the actuator rod with no vacume to that position and locked the nuts
idle at 85.10%
but full boost vnt is droping to 12% ?
i am requesting around 27psi and my first boost logs of the current vnt rod was making 24psi and the boost is hunting see below

so after the above i set the rod 3 turns longer (pulling the rod out of the actuator?)
this then only produced 21 psi of boost and i am requesting 27psi and its still hunting for boost
so then i went back to the original position
and did around 3 turns in the other direction shorten ? mayb even lengthen

but this now produces around 30psi of boost and its not hunting as bad but the vnt is still droping down to 12% ?
as i understand it should idle around 85% and at full WOT it should be around 25-30%
so why is it that in any position i set it i am ending up with 12%vnt ?
i am doin the mapping im ok with the hybrids and stage 1 or 2 tunes but this is somthing totally new
im thinking i may have to pull some vnt out of the map ?
any advice on this please as im in deep water
Thank you

 

[Digital Corpus]

It is my understanding that the N75's Duty Cycle (The percentage you quote), should be setup to achieve anywhere from a low of 70% to a max of 80% in 3rd or 4th gear when at 4000 RPM.

 

[kilner]

It is my understanding that the N75's Duty Cycle (The percentage you quote), should be setup to achieve anywhere from a low of 70% to a max of 80% in 3rd or 4th gear when at 4000 RPM.

Thnaks for the response


on the pd 170 the ecu reads out vnt backwards compared to the other engines


85% = idle

25-30% is the range you need at WOT


but for some resson no matter the adjustment it keeps goin to 12%


to make this more simple for people 12% on my car is like 95% at WOT on the ecu that you are thinking about


i have checked for boostleaks and re done all the intercooler pipework everything is fine


the boost is still huntinng around


im goin to try without my intake pipe on make sure the intake is not causing some kind of restriction

then i will try adjusting the actuator to a point were it spikes above requested and then settle backs down see if it improves


thanks again for any help advice or tips

 

[Digital Corpus]

Sure thing. That just means that the polarity is flipped between your generation and some of ours.

 

[kilner]

im not after a direct answer just some advice to point me in the rite direction

i have seen a few of these gtb2260 converstions


and people must have run the car on a base file to see what was goin on before they can even begin to adjust anything

is the above normal or am i having a mechanical issue

checked all boost pipes sevral times and re replced some of the silicone pipes

all vacume lines checked

turbo to manifold checked

tryed without the air intake still the same

tryed the actuator in around 6 difrent positions now

and its just the same no mater the position the only change is the amount of boost it builds

i kno ther is goin to be some work needed in the ecu but i would like to get the mechanical side of things spot on and i have no idea how the actuator needs to be set on such a turbo

 

[A5INKY]

Did the turbo receive a shorter VNT arm when the vac conversion was done? Or, are you trying to use the original long electronically controlled arm?

When you moved the actuator did you mount it so that the rod was near perpendicular to the arm near the midpoint of arm travel and not in a bind?

The 12% figure is strange. I have found mine will go into single digits when my rod is too long. Keep in mind that my PD actuator pushes with vac applied, don't know about yours. If your PD170 also has a push-with-vacuum type actuator then you would need to shorten the rod to correct your N75 duty cycle at WOT.

I don't think this would be any other kind of mechanical issue. The VNT would not be trying to open so far if there was a boost leak.

Also, I am not so sure you want to get the actuator spot on prior to changing the map. I know my N75 map got adjusted in the tune with my GTB turbo. Not sure which should come first, chicken or the egg. I would speak to your tuner about it if I were you.

 

[majesty78]

In this case he would need to speak with himself ;-)

 

[kilner]

i had a good speak with myself last night and adjusted all the vnt maps the waves are still ther but at higher rpm the boost starts creeping above requested

lets just say i adjust the vnt maps to an extreme level and it did not do much i would not be happy to adjust these anymore for the backpressure


i think this is more of a problem with the mechanical side of the turbo than in teh ecu at the moment


it seems people dont like the fact i want to tune my own car


im not asking for help tuning im just asking for help to decided if its mechanical or ecu



i have the feeling its a bit of both

my turbo was bought from ryanp with the vacume conversion done



long story short the turbo would not fit into the car in its curent position due to the actuator sensore hiting the firewall so i had to adjust it to its front most position on the adjustable bracket

i remeber on the setup that was on the turbo as i recived it had the vanes slightly closed with no vacume


it seems the actuator is very sensative and goin to need a fair few fine adjustments to get me into the ball park area

also 12% on my ecu is 94% on the other ecu the vanes are as open as they can be and the turbo cannot do anything else to lower boost but why would it be trying to lower the boost if its not even hiting requested ?

i think its the actuator its just a major job to move it each time and as im not sure it was teh actuator i was asking for some help

but i think i got it coverd now

also the new actuator seems a lot more soft than the original so i was thinking its possible the actuator carnt keep control as the gasses push on the vanes

also i notice wen you apply vacume to the actuator ther is some slight movment in the bracket it seems to flex a little if the actuator is as sensative as im thinking then this flex also carnt be helping

one more thing people keep saying its in the mapping but i kno the actuator is not in the correct position if the mechanical side is out now amount of mapping is goin to solve the issue

 

[kilner]

Problem fixed

i said problem solved its 90% beter

i adjusted the rod to take up the slack on the arm so the vanes are a tiny bit closed and then asked for a little more boost in the ecu


also the boost was hiting a map limiter before it was doin as the boost map was asking so this was kicking the boost down around 20psi as it hit the map limiter


some more time tweeks and logging will be involved to get it so im happy but so far i have had a major improvment