Adjusting a ZD30 VNT

[Fity]

I have been experiencing some of the same symptoms of over boost as described in the ZD30 reference document http://www.nissanpatrol.com.au/forums/showthread.php?89-Nissan-Patrol-Reference-Document

It details how to adjust the actuator on the turbo, but my 2000 ZD30 does not have the same looking linkage. I was wondering before I get started if they all adjust the same, ie rotation and number of turns? Has anyone adjusted one before?

[the evil twin]

Thats odd... I've never seen any ZD30's with a different VNT linkage but then again haven't fiddled with early ones.

It is a dog to get at the adjustment and when you do it is guess work but you should def not have to go more than 1 turn... I went 1/4 turn after Chip and Exhaust mods and then another 1/2 turn after EGR block but probably went a tad to far. It certainly stopped the spikes tho

Waiting for a choice between Root Canal therapy and EGR adjustment before I go and re-adjust it again.

[Fity]

Here is a pic of my linkage. The pics in the document are not the best. It looks like I can adjust it without removing the actuator. When adjusting after 3" exhaust, EGR blocking and chip, do I make the linkage longer or shorter?

15497

Hope the tooth gets better. :)

[45/70]

Howdy fity.
In my honest opinion mate, I think you would be better off leaving the VNT set as it is and fit a Dawes valve, needle valve and a boost gauge to better monitor and adjust your boost and spool up settings.

[the evil twin]

Whatever you do... DO NOT adjust that linkage.

The adjustment you need to get at is the VNT stop screw behind that linkage. It is a grub screw with a locknut. Page 62 of the reference document has the linkage pushed aside for clarity.

You can adjust them in situ but you need an 8mm socket ground down at appropriate sides and with a lever welded to it at about 60 degrees to get the locknut undone/tightened.

Mine is a ZD30 CRD and the CRD's seem to be quite happy with that adjustment and don't need Dawes. The ZD30Di's seem to like the Dawes and Needle setup better.

[Fity]

Thanks for the hot tip about the linkage. I will get out the MIG and make a tool. :) I think I will have a go at it until the Dawes turns up.

I have a 3" exhaust and EGR mod. Watching the boost gauge I think it will help the problem as the exhaust parameters have changed a great deal with the 3" exhaust and EGR mod and the ECU is expecting some recycled exhaust to enter the intake which it isn't. The Dawes will definitely stop the over boost.

[the evil twin]

No worries, cobber...

Keep a close eye on where the grub screw is set at the start as it will try and turn with the locknut initially.

EGR block had the biggest effect on mine by a long way and would top out at nearly 38 PSIA (or 23 PSIG) but the CRD's behave a tad differently. I nearly crapped meself as I was also worried about Turbo surge with those pressures... but thats the price ya pay for fooling with Mr Nissans engineering

[Fity]

Mine was hitting 26psi and I thought here come the grenade! LOL

I managed to adjust it without removing the actuator, with a ground down 8mm socket, short extension and ratchet from around behind the actuator. I used a long shaft Allen Key to rotate the grub screw. It is now at 1/2 turn and I am off for a test drive. The turbo is only 2000km old, so it was easy to turn Thanks for the help.

[Fity]

Half a turn made a noticeable difference. I only got to 80kph but I could not get it to over boost like before. Under 2000rpm pickup was a little better and the egt were higher. The boost was 2 to 3 psi lower. When it would normally hit 22psi and drop off it now only hits 17psi and keeps going. I will try it on the hwy over the weekend and report back.

[bastardo]

sounds like something i need to get done but dreading.

[the evil twin]

Half a turn made a noticeable difference. I only got to 80kph but I could not get it to over boost like before. Under 2000rpm pickup was a little better and the egt were higher. The boost was 2 to 3 psi lower. When it would normally hit 22psi and drop off it now only hits 17psi and keeps going. I will try it on the hwy over the weekend and report back.

Yeah, pretty much what I had... I will amend my post before someone has a cow as the 38 PSI I quoted was absolute not gauge which equates to about 23 PSIG

[Fity]

I have done a couple hundred Ks over the weekend. On the highway it still trips out on over boost, but does not go over 17psi. The egt is about 50deg higher probably as a result of lower boost when accelerating being compensated for with more fuel.

I will leave it where it its until I fit the dawes then have another play.

[Forest1970]

Yeah, pretty much what I had... I will amend my post before someone has a cow as the 38 PSI I quoted was absolute not gauge which equates to about 23 PSIG

What do you mean by 38PSI absolute and how/where did you measure this?
Just curious and interested , thanks

[nissannewby]

Absolute is when you add boost and atmospheric pressure. Atmospheric is around 14.5 psi. Most gauges are calibrated to give you a boost reading on top of that.

[threedogs]

Fity what are your EGTs and boost PSI at 100 kph ???? 250-300 degree C and 10 PSI ?????
Sort of rule of thumb is to have 10 psi at 2000 RPM

[Forest1970]

Absolute is when you add boost and atmospheric pressure. Atmospheric is around 14.5 psi. Most gauges are calibrated to give you a boost reading on top of that.

So Zero on a Gauge is actually 14.5 PSI being atmospheric pressure?