audi2.5tdi
Registered User
ive been doing some reading about the length of the control rod for the VNT mechanism on the turbo, the turbo is a GT2052V (701s)
i found a thread on another forum about how to check if its correctly adjusted, 2000-4000 rpm in 4th the duty cycle of the N75 valve should be between 70-80% @4000 rpm
if its below 70% @4000 rpm the rod length should be shortened and if its above 80% @ 4000 rpm the rod should be lengthened
i ran a log in VCDS and accelerated from 2000-4000 in 4th and the duty cycle @4000 rpm was only 58.8%
so i shortened the rod and did the same test
now @ 4000rpm its only 35.5%
which is the opposite of what i was expecting to see!?
this is the tread i got the info from
http://uk-mkivs.net/topic/34834-vnt-tdi-turbo-how-to-adjust-actuator-cure-boost-problems/
and this is the paragraph about adjusting the rod
"How to adjust the VNT rod length
When these turbos are new straight from Garrett, the rod length and stop screws are setup professionally in accordance with their specifications. since they do not publish these specifications alot of re built, re manufactured, re furbished turbos do not have them properly set up. This includes so called "Garrett approved turbo re-builders" most of the time they will just leave them as standard and expect them to work, and they will work most of the time but obviously there is going to be times when they don't. And because the hybrid turbos are different specifications, the rod length and stop screw specifications from Garrett will no longer apply. this means the turbo must be set up either on a flow bench or on the car.
Adjusting the rod length is necessary if you are getting errattic boost problems, if your duty cycle is above 80% at 4,000rpm then it needs made longer, and if your duty cycle is below 70% at 4,000rpm it needs made shorter. between 70-80% is ok, the closer to 80% the better.
How I do it is remove the TIP and get at it from above, it is possible to do it from below but theres limited space down there too, I prefer the top way.
so once you have removed the tip, you will be able to see this-"
is the 70-80% duty cycle what i should be aiming at at 4k rpm? should i try lengthening the rod past the original point and see if it goes the other way?
is there another way of doing/checking this?
i found a thread on another forum about how to check if its correctly adjusted, 2000-4000 rpm in 4th the duty cycle of the N75 valve should be between 70-80% @4000 rpm
if its below 70% @4000 rpm the rod length should be shortened and if its above 80% @ 4000 rpm the rod should be lengthened
i ran a log in VCDS and accelerated from 2000-4000 in 4th and the duty cycle @4000 rpm was only 58.8%
so i shortened the rod and did the same test
now @ 4000rpm its only 35.5%
which is the opposite of what i was expecting to see!?
this is the tread i got the info from
http://uk-mkivs.net/topic/34834-vnt-tdi-turbo-how-to-adjust-actuator-cure-boost-problems/
and this is the paragraph about adjusting the rod
"How to adjust the VNT rod length
When these turbos are new straight from Garrett, the rod length and stop screws are setup professionally in accordance with their specifications. since they do not publish these specifications alot of re built, re manufactured, re furbished turbos do not have them properly set up. This includes so called "Garrett approved turbo re-builders" most of the time they will just leave them as standard and expect them to work, and they will work most of the time but obviously there is going to be times when they don't. And because the hybrid turbos are different specifications, the rod length and stop screw specifications from Garrett will no longer apply. this means the turbo must be set up either on a flow bench or on the car.
Adjusting the rod length is necessary if you are getting errattic boost problems, if your duty cycle is above 80% at 4,000rpm then it needs made longer, and if your duty cycle is below 70% at 4,000rpm it needs made shorter. between 70-80% is ok, the closer to 80% the better.
How I do it is remove the TIP and get at it from above, it is possible to do it from below but theres limited space down there too, I prefer the top way.
so once you have removed the tip, you will be able to see this-"
is the 70-80% duty cycle what i should be aiming at at 4k rpm? should i try lengthening the rod past the original point and see if it goes the other way?
is there another way of doing/checking this?