3.0 engine and EGR

[Barrbeast]

So I'm away for the weekend with the lass I'm currently seeing and on the way down in the train the horrendous wifi made netflix a nightmare so I settled in to have a flick through the ZD30 Patrol reference doc pdf and in particular the bits about blocking the EGR and stopping the resulting overboost.

So I know there are some Terrano owners who have blocked the EGR on the 3.0 with no issues and others who have noticed the overboost protection start to kick in when cruising due to the ECU detecting the increased EGTs (this is why it causes overboost sometimes http://www.nissan4x4ownersclub.com/forum/showpost.php?p=278851&postcount=1).

It may be that the fact the Terrano is lighter than the Trol and our coooler climate helps keep the EGTs down low enough to, in some cases, stop the EGR blocking cause overboost but generally it is not a good idea to block the 3.0 EGR without doing something to stop it overboosting.

Fitting a Dawes valve and needle valve is the usual route and what a lot of the Aussies recommend BUT the alternative method suggested in the reference doc is to simply adjust the screw on the VNT/VGT (Variable Nozzle/Geometry Turbo) actuator to limit the maximum boost. 1 and 1/4 turns anti clockwise seems to be the magic number. Apparently there is a slight loss of torque low down but you gain a serious power band at 2000 rpm.

Think I need to look at getting a blanking plate made up... :sly

 

[makeitfit]

I've not looked into this as it doesn't effect me . However, it seems that the issue is more ECU related (safety) than a real overboost. The ecu sees higher zorst temp and so goes into a limp mode , is that fair to say ?
If so what is the actual zorst temp increase ? I wouldn't have thought that much higher :nenau
EGT gauge could be handy here. Then how about an ECU remap to accommodate the higher EGTs and so avoid limp mode ?
Couple that lot up to a electronic turbo boost controler in the cab and Bob's your Fanny's uncle
maybe :lol

 

[Barrbeast]

I've not looked into this as it doesn't effect me . However, it seems that the issue is more ECU related (safety) than a real overboost. The ecu sees higher zorst temp and so goes into a limp mode , is that fair to say ?
If so what is the actual zorst temp increase ? I wouldn't have thought that much higher :nenau
EGT gauge could be handy here. Then how about an ECU remap to accommodate the higher EGTs and so avoid limp mode ?
Couple that lot up to a electronic turbo boost controler in the cab and Bob's your Fanny's uncle
maybe :lol

Well it is all the ECU's fault :doh but it does cause a real overboost unfortunately - ECU detects the higher EGTs and works to bring them down by working the VNT actuator to increase the boost.

In normal high EGT conditions ie. when the EGR is unblanked, it works and doesn't cause an issue but when the high EGTs are caused by the EGR being blanked off rather than the driving conditions the result is that the engine starts to overboost.

The ECU detects the overboost and if it goes on for too long it causes the overboost protection mode to kick in - throttle goes to a pre-determined setting and refuses to work until you take your foot off the pedal which resets things.

I'm definitely going to make up a blanking plate and adjust the VNT actuator when I get a minute (there are a few things to do when I get a minute!).

 

[Banshee]

Well it is all the ECU's fault :doh but it does cause a real overboost unfortunately - ECU detects the higher EGTs and works to bring them down by working the VNT actuator to increase the boost.

In normal high EGT conditions ie. when the EGR is unblanked, it works and doesn't cause an issue but when the high EGTs are caused by the EGR being blanked off rather than the driving conditions the result is that the engine starts to overboost.

The ECU detects the overboost and if it goes on for too long it causes the overboost protection mode to kick in - throttle goes to a pre-determined setting and refuses to work until you take your foot off the pedal which resets things.

I'm definitely going to make up a blanking plate and adjust the VNT actuator when I get a minute (there are a few things to do when I get a minute!).

Why don't we get this issue with the TD27 then?

 

[Barrbeast]

Why don't we get this issue with the TD27 then?

Older design of engine bud (that's why it runs on veg and the 3.0 doesn't) and I would imagine the 2.7 ECU doesn't monitor EGTs.

 

[Banshee]

Older design of engine bud (that's why it runs on veg and the 3.0 doesn't) and I would imagine the 2.7 ECU doesn't monitor EGTs.

:thumb2