Patrol 4x4 - Nissan Patrol Forum banner

1 - 19 of 19 Posts

·
Registered
nissan patrol gq
Joined
·
306 Posts
Discussion Starter #1
Hi guys,
I have recently purchased a 2000 GU II ZD30 intercooled.
It has a 3" exhaust, SW chip, dawes valve and needle valve setup as well as a blocked EGR.
I've set up the dawes valve tonight and took it for a spin and it'll boost up to 19-20 psi and it pulls like a freight train. The only downside is 5 seconds later car is in limp mode.
Now my question is what is the max safe boost that can be run? I know of the anti limp devices out there but wonder if they are worth it. Is running 20 psi under acceleration ok or will this be too much to handle for the engine? If that is an acceptable level of boost I'll turn my attention to such a device.
Also what is the maximum EGT one would want to see? I'm new to the whole diesel thing and with the reputation of ZD30 in the back of my mind I'd love to know what is safe and what should ring alarm bells?
Thanks in advance.
 

·
Registered
nissan patrol gq
Joined
·
306 Posts
Discussion Starter #3
So the boost should never go over 18 correct? I'm getting 20 at full throttle. It smoked before hand and this has all but fixed it so I thought I was on the right track. To adjust it down do you screw in or out and to lose 2 psi how many turns approx should I be going? I won't hold you to it just a base line to start with.
Is there a fix for the dodgy afm?
 

·
Registered
nissan
Joined
·
197 Posts
mine is setup to 15psi max. id rather run it a bit lower so i know for sure its not going to go into limp mode when im crawling up a massive hill or something. i get between 270-330 EGTs when cruising on the freeway at 100kph.
 

·
Registered
nissan patrol gq
Joined
·
306 Posts
Discussion Starter #5
I tune most of the pre CRD only to about 16-18psi tops. They still have the dodgy afm that causes problems with fuel delivery.
Do you run into limp mode problems when tuned at 18psi?
 

·
Registered
Joined
·
9,513 Posts
I run 20psi on mine and have done so for the last 120,000km with no issues other than having to constantly mess around to avoid the limp or fuel cut. Peak boost under hard acceleration is around 22 psi. I cranked it up to 24 psi and really could not get any noticeable improvement so went back to 20 max. So I think without going to extremes, as DT suggested, 16--18 psi is a good starting point. Highway at 110 km/h it is about 15 psi and EGT are 300 to 350 ish.

The problem is more that the increased boost means more air flow through the MAF sensor, then at certain points in the rev range the bloody ECU detects more air (higher MAF voltage than was set as a factory limit) so it cuts fuel.

You can run more boost but then you need to mess with MAF voltage (JCDVM) or the MAF sensor housing. It works but is a lot of messing around to get right.
 

·
Registered
Joined
·
9,513 Posts
Some of them do have limp mode issues with 18psi. Just take it on a per car basis really.
Yes I never understood why each one is different. I was helping a mate with his Di which is only one year older than mine and it seems to behave quite differently with the limp or fuel cut issues. So I can only imagine what it is like dealing with different vehicles every day.
 

·
Registered
nissan patrol gq
Joined
·
306 Posts
Discussion Starter #9
I run 20psi on mine and have done so for the last 120,000km with no issues other than having to constantly mess around to avoid the limp or fuel cut. Peak boost under hard acceleration is around 22 psi. I cranked it up to 24 psi and really could not get any noticeable improvement so went back to 20 max. So I think without going to extremes, as DT suggested, 16--18 psi is a good starting point. Highway at 110 km/h it is about 15 psi and EGT are 300 to 350 ish.

The problem is more that the increased boost means more air flow through the MAF sensor, then at certain points in the rev range the bloody ECU detects more air (higher MAF voltage than was set as a factory limit) so it cuts fuel.

You can run more boost but then you need to mess with MAF voltage (JCDVM) or the MAF sensor housing. It works but is a lot of messing around to get right.
So 20psi isn't too high for the ZD30? That's great cause I do like how it pulls. AS for the MAF voltage and/or MAf housing, what do you do to avoid limp? What's JCDVM other than Jean Claude Van Damme spelt incorrectly?:D
 

·
Registered
nissan patrol st-l gu3 4.8
Joined
·
68 Posts
Jaycar digital voltage modifier. Its hooked up between maf signal wire to decrease maf voltage so the computer thinks that its not boosting as much as it really is. What i don't understand is that wouldn't it be pointless running higher boost when maf voltage is decreased equaling less fuel. Might be good for keeping egts lower but would do nothing for power..
 

·
Y61=WIN
nissan
Joined
·
3,003 Posts
I tune most of the pre CRD only to about 16-18psi tops. They still have the dodgy afm that causes problems with fuel delivery.
This is an interesting outcome. Diesel engines, I know for a fact, wont get worried at a fair bit more than this pressure in terms of rod failure, head failure, etcetc

I find your insight quite curious - does the air flow meter wig out at higher boost pressures and that in turn stuffs up the AFRs and the fuel metering becomes dangerous? Obviously iirespective of boost pressure if the fuelling is wrong the engine could self destruct

What would make the AFM wig out at higher pressure sir?
 

·
Registered
nissan
Joined
·
2,994 Posts
When set to 18-ish psi, at times with a MAF / AFM reading > 3.95v under 3000rpm the ECM will order a fuel cut and drop back to zero throttle. I guess the AFM reading falls outside the ECM's lookup tables so it's a 'safety' thing, yet not quite a full limp. Taking your foot off the throttle and back on will reset it.

Keeping the boost under this level won't see you hitting that combination of AFM voltage and RPM.

I believe it's more of a 'computer says noooo' thing rather than the engine self destructing.

This is also why some people get what is referred to as the cold limp... Works fine at 17 or 18psi during the day but they will get the fuel cut on cold mornings... AFM readings are higher when the air is colder due to the higher air density.
 

·
Premium Member
nissan patrol
Joined
·
3,946 Posts
Well the engine timing is also determined by this air flow value.

Even though you might have 10-20psi of boost and relatively safe fueling, if the timing is advanced, the actual cylinder pressure can be dangerously high.
Its very easy to far exceed 3000psi cylinder pressure even on a mild setup if the timing is not correct.

Its not a matter of the afm wigging out under operating conditions, but more so they fail for absolutely no reason. At around 2004 they changed them over for a more reliable sensor which is of the square type rather than round.
 

·
Premium Member
2003 ZD30 Di Patrol (The rare Gold one)
Joined
·
25,657 Posts
Jaycar digital voltage modifier. Its hooked up between maf signal wire to decrease maf voltage so the computer thinks that its not boosting as much as it really is. What i don't understand is that wouldn't it be pointless running higher boost when maf voltage is decreased equaling less fuel. Might be good for keeping egts lower but would do nothing for power..
You only need to reduce the maf voltages at the load point that it occurs. (255 points)
The rest of the time you can increase fueling with it to suit your mods.
 

·
Registered
nissan patrol gq
Joined
·
306 Posts
Discussion Starter #15
OK. I think I will go down that track. Now I'm not particularly electronically minded. Can these units be purchased assembled? If not does anybody have one for sale?
I could probably do it but I think it's the 10ohms pot and the constant 12v supply that'll be extra costs for me that will be used once and never again.
 

·
Registered
Joined
·
5,326 Posts
GU2 can probably help ya out with building ya one, or chaz or Geordie. There is a few gurus on here re the zd and fancy mods!

There is also a good thread on the JCDV modifier somewhere in the zd section.
 

·
Registered
nissan patrol
Joined
·
1,823 Posts

·
Registered
nissan patrol gq
Joined
·
306 Posts
Discussion Starter #18
That would be great or else I'll have to take the plunge and build it myself. Also which is best the Jaycar unit or the Fuel Cut Defender 2?
 
  • Like
Reactions: Rex cars

·
Registered
nissan patrol gq
Joined
·
306 Posts
Discussion Starter #19
OK. I have purchased the JCDVM and hand controller. Geordie4x4 recommended another device, an Ultra Air Fuel Controller, but I think the 250 points from the JCDVM will suit me better than the 14 from the Ultra Air Fuel Controller. Though I did read up on it and it does seem like a good piece of kit especially given the fact you can run 3 "maps" on it.
All going well I'll have it on monday and then the tricky stuff begins :roll:
 
1 - 19 of 19 Posts
Top