VNT Setup.

[andybond]

Afternoon all.

I have been fiddling off and on with my VNT for a short while now.

I can either get

a) upto 10psi @ 2000rpm with the rest following around 4000rpm ( total - 18 psi ish ) The car feels nippy at the upto 10psi but feels flat at anything over it

b) it working like a t28, nothing then bang at 18psi and 4000-4500 rpm.

Neither as you appreciate are ideal.

From what I can work out I either have the duty at below 70% or above 80% but I cant find the sweet spot.

Any ideas what to do ? For reference I have the 18psi dialled in with actuator rod length and the "stopper" ( the small grub screw ) is right at the top stopping the rod from going touching the body of the turbo

[James5]

:laugh: you still not got ot setup :laugh: get the car down here and i will get my chaffeur aka 5tevel to drive it for me and I will set it up for you properly matey:coffee:

[andybond]

I thought I did have it setup. Went it in it after the megane and it didn't seem quick. Felt kinda flat. :mad:

[James5]

I thought I did have it setup. Went it in it after the megane and it didn't seem quick. Felt kinda flat. :mad:


VNT shouldn't be flat matey, so when you first getting sign's of boost rpm wise?? and when is it at it's full boost level rpm wise??

mine was 2300rpm's started to boost and full 24psi boost @2800rpm's with 1psi max spike as soon as you hit that full boost limit it should be constant on acceleration and not differ so it may feel flat as no more boost coming but you hit full boost so quick and you should be off like a rocket.

Doesn't sound like you have the actuator set correctly, grub screw setting sounds ok aas you have boost around 2000rpms' shorten the actuator arm a tad

[andybond]

Boost is starting to come in around 2000rpm , getting to 10psi sharpish , but then not going anywhere.

I cant get the rod any shorter. Its right at the very top !

Were you boosting with a short rod , or via bleed ?

[James5]

Boost is starting to come in around 2000rpm , getting to 10psi sharpish , but then not going anywhere.

I cant get the rod any shorter. Its right at the very top !

Were you boosting with a short rod , or via bleed ?

I was using AEM electronic boost controller actuator was @18psi remainder was boost controller

Loosen the rod a couple of turn's and tell me what effect it has?

[andybond]

Will do - working this week, so will have to try thursday.

[andybond]

Couple of turns ( so around 10mm "looser" ) and I am still getting alot of spike, and not a lot of boost.

Ill upload a really crappy video in a second.

crappy (http://youtu.be/yxmAgVawUU4) video.

AFR are stable , boost goes upto 18-20psi ish ( hard to hold phone on my private road and drive )

instant upto 10, crawl to 18-20, mad spike and settle. Its just so bloody slow at pulling boost.

Lengthen the rod again ?

[James5]

Couple of turns ( so around 10mm "looser" ) and I am still getting alot of spike, and not a lot of boost.

Ill upload a really crappy video in a second.

crappy (http://youtu.be/yxmAgVawUU4) video.

AFR are stable , boost goes upto 18-20psi ish ( hard to hold phone on my private road and drive )

instant upto 10, crawl to 18-20, mad spike and settle. Its just so bloody slow at pulling boost.

Lengthen the rod again ?

What actuator you got on the VNT ?, that's a pretty pathetic build up of boost for a VNT, should be a few 100rpm's of boost build up max and then just constant full boost beyond the rev limiter. I can't see why it's rapid to 10psi and sluggish beyond unless the Vanes are sticky / stuck or it's crap actuator.

What effect did lengthening the rod make??

[andybond]

Its a standard one for that type of VNT AFAIK ?

Looks identical to this one below

https://encrypted-tbn1.google.com/images?q=tbn:ANd9GcTUl2EqEGXV3RcBao2wOesVjozO87AHY IjzeoQRqW8iHhbDdP9a

Lengthening the rod ( I havent since the post above ) didnt make a great deal of difference. Lengthen again ?

[James5]

Its a standard one for that type of VNT AFAIK ?

Looks identical to this one below

https://encrypted-tbn1.google.com/images?q=tbn:ANd9GcTUl2EqEGXV3RcBao2wOesVjozO87AHY IjzeoQRqW8iHhbDdP9a

Lengthening the rod ( I havent since the post above ) didnt make a great deal of difference. Lengthen again ?


Were does your actuator take it's ref from?? in otherwards were does the other end of the vacum line go??


Not the best vid but listen to how my VNT spools ok I haven't revved it hard or given it full beans but it's gone from no boost to not far of full boost in no time

http://i252.photobucket.com/albums/hh25/GTTJames/C12%20GTT/th_MVI_5809.jpg (http://s252.photobucket.com/albums/hh25/GTTJames/C12%20GTT/?action=view&current=MVI_5809.mp4)

[andybond]

Were does your actuator take it's ref from?? in otherwards were does the other end of the vacum line go??



Carb - usual POR as normal turbo. . . .

[DaveMayGTT]

Is it possible you got a boost leak? Weak jubilee or something so by 10psi or so it starts leaking? seems a bit unlikely I know :ashamed:

[Tony Walker]

i struggled to get over 10psi when my DV diaphragm split.

[andybond]

no DV on this - and no boost leak. Holds 20psi when it eventually gets there.

[Slammed 66]

Its a standard one for that type of VNT AFAIK ?

Looks identical to this one below

https://encrypted-tbn1.google.com/images?q=tbn:ANd9GcTUl2EqEGXV3RcBao2wOesVjozO87AHY IjzeoQRqW8iHhbDdP9a

Lengthening the rod ( I havent since the post above ) didnt make a great deal of difference. Lengthen again ?



I don't really get VNT turbos despite having a pair on my Audi S4, but shouldn't you be shortening the rod to make the actuator work harder to open the waste gate?

Ross

[andybond]

On a normal turbo yep.

[allanr5gtt]

i think the length of the rod is the (boost) pre load and the grub screw is the way the vnt kicks in ( vanes angle)

[andybond]

Allan , you are correct.

[James5]

On a normal turbo yep.



Longer actuator rod equals more boost to much length and it will overboost so its a case of fiddling and finding the sweat spot

[andybond]

From what I read its to do with duty %.

Below 70% it feels flat , above 80% and there is too much turbulence and causes mental spikes ( what I have )

[DaveMayGTT]

no DV on this - and no boost leak. Holds 20psi when it eventually gets there.

Doesn't mean the turbo isn't kicking out 35psi? On an old turbo I used to get to about 10 then struggle to get to 15 but would then hold it. Had a split intercooler.

[Brigsy]

Get a proper turbo on there lad;)

[Ashy]

Doesn't mean the turbo isn't kicking out 35psi? On an old turbo I used to get to about 10 then struggle to get to 15 but would then hold it. Had a split intercooler.

Pressure test the boost system, I bet you have more than one leak...

[DaveMayGTT]

Pressure test the boost system, I bet you have more than one leak...

I probably should have just said that :cool:

[andybond]

Can now smash and hold 18psi.

Just goes no where ...

18psi on the gauge. Just does not seem to push

[robx1r]

still no joy on this?

[andybond]

It's getting tere. I have worked out the grub screw controls when and how boost comes in.

Short thread below the housing = early boost, big spikes
Long thread below = late boost low / no spikes.

Been working 80h+ weeks so had no time to play

[robx1r]

ouch thats rough! was that the one you were offering?

[andybond]

Yep.

I want it to be more raw , as in old skool, lag then bang.

Thing I found with the VNT - although it makes the car quick it looses some of its old skool appeal. I have my r26 for cross country no nonsense turbo fun , i want hooligan style lag with my other toy.

[robx1r]

can you pm me pictures and all the stuff you've found out about it? would you be interested in a swap of a gt28r?