ZD30 engine safety featre

[big_fletch]

I saw a question about power loss on the zd30 motor, so just for the people that are not aware the 3.0 motor has a boost safety feature built into the computer (I believe it was introduced into the late 2001 models after so many motors had problems in 2000-2001)..
When boost is to high for to long the computer cuts power to the motor and the accelerator pedal becomes dead, this prevents damage to the engine..
When the accelerator pedal is completely released then power is restored and vehicle runs normal again, you are free to accelerate (basically foot off and back on)

Just thought I would post this up, might save someone from replacing sensors and spending their hard earned cash on something that's not a problem..

Fletcha

[Sir Roofy]

very interesting ill keep that in mind for future reference

[ashbee37]

have a problem with my auto 3ltr. when accelerating, gets to around 3grand and then stops accelerating egts, boost stays the same, no Eng lights. lift my foot and reapply and all is fine till next time. could be maf or tps by my guess but wanted to make sure what it is as haven't got the dosh to wast, so took to local diesel mechanic to diagnose but when he hooked up his computer it could not read the CPU. anybody got a clue whats going on and why he cant talk to the comp, he said i would have to take it to Nissan to find out why
not maf, changed it and still the same, well not quite the same. now ive got more problems after reconecting battery after having it off for 24hrs, now the alternator was dead so i had to get a new one and when taking well trying to take drive belt of the tensioner was at a 45deg angle so, new one of them and while reading manual i saw that its recommended you change timing chain every 100thou so seeing its just clocked over 200thou and don't know when it was changed last well,dash lights are on, sub tank, at temp, seatbelt, handbreaK and alt lights are all light
the alternator was dead so i had to get a new one and when taking well trying to take drive belt of the tensioner was at a 45deg angle so, new one of them and while reading manual i saw that its recommended you change timing chain every 100thou so seeing its just clocked over 200thou and don't know when it was changed last well,after new alt, timing chain, tensioner, hoses ect. i also started putting catch can in but did not realize one of the fittings was blocked, well when i started motor ran for a couple of minutes then stalled, heap of white smoke. worked out it was the blow bye that built up and stalled it. fine disconnected the catch can and motor started fine and smoke went away. now runs fine but now on the idle sits on 45 instead of 24 warm or cold plus i think the running pressures are higher will note tomorrow and post. plus i think there may be more blow bye now.

so can anybody tell me what damage i may have done now. and bye the way still got the original problem just comes in different times depending on needle valve setting

[Lieney]

I have the same problem with the engine cutting out under load about 3500rpm. Release foot and re-apply, power is returned.
#A diesel place#
said it was a pinched vacuum line under the plastic cover. No fault codes appeared. cost me $90 for them to check it.
Problem occurred again today but worse. I checked it and the only possibility would be the dawes valve fitted by them. Nothing else is any where near it.
On thread stated an earth strap on engine can cause issues, but not sure if this is our problem as I haven't checked it.
Please let me know if you find out what it is as I really need to know. I'll do the same if I find out.
I had relax plans tonight but I guess I will be tinkering instead.

[threedogs]

Clean the MAF sensor just to left of aircleaner, need torx bits to remove
Is yours Di or Cr????
Really need to fit boost guages to the Z30 motors, and EGT man hasta know whats going on.

[Lieney]

Boost limited at 17psi.
Engine Di not comin rail.
Had MAF out few months back & spotless.
Have all the tools so will do that again & check it.
I want a wiring diagram with all the specs so I can test & play but cant get one off
Nissan

[the evil twin]

Ashbee... pls excuse the lack of the quote as your post is a tad big...

The reason he can't read the ECU is that prior to the CRD's the Patrols aren't full OBDII compliant. Thats why Scanguages will work on ZD30 CRDs etc but not on the ZD30 Di or TD42's. You need either Nissan Consult or "ECU talk" software.

As big fletch mentions a huge amount of the limp mode issues are boost related. There are some threads on here detailing how to check the TPS and if that is OK then I'd try dialing back the boost a tad. Altho there are some other issues in your post that need attention as well and may be confusing the symptoms and the causes so just work thru them and see how you go.

[Rumcajs]

Boost limited at 17psi.
Engine Di not comin rail.
Had MAF out few months back & spotless.
Have all the tools so will do that again & check it.
I want a wiring diagram with all the specs so I can test & play but cant get one off
Nissan

17 psi limit is too high as on GU IV Di ECU will go in to limp mode at around 18 psi and if you have Dawes set at 17 that means that there will be a spike past 18 momentarily which under right circumstances will cause limp mode.

I have set mine (Dawes) to 15 psi and have no more limp issues. There isn't really any advantage to go higher TBH. Indeed I found that fuel consumption increase particularly at cruise 100-110 km/h is especially hurting the valet. I have the second Dawes to fit so I can have 2 stage boost control, low (8 psi) for economy and high (14 psi) for power run.
Cheers

[threedogs]

Rumcajs, can you explain how lower boost will increase fuel economy, all I can see is it increasing EGTs
Got me beat this one, heard it a few times now

[Rumcajs]

Rumcajs, can you explain how lower boost will increase fuel economy, all I can see is it increasing EGTs
Got me beat this one, heard it a few times now

In simple terms; more boost = more fuel, if you restrict amount of boost the ECU's "smoke map" will restrict amount of fuel. There is a relationship between amount of boost and amount of fuel the so called AFR (air fuel ratio) which affects the whole system subject to engine load, of course EGTs will be higher but we aren't talking 500° C. I will have this system automated to work of the "loud pedal" percentage but still have manual over ride.

I have noted fuel consumption drop by lowering the Dawes limit from 17 psi down to 14 psi by as much as 1.0 L alone while EGTs only increased marginally ( I do have needle valve as well). I also noted a weird thing when first installed Dawes and went for a drive without adjusting anything (it was set to 7 psi) and the whole experience was for very smooth persistent acceleration and cruise except it didn't want to climb the hills that well.

GU IVs are funny beasts in this case. I don't think personally that high boost is really an answer for everything ZD30 performance/EGTs related.
Cheers

[Rumcajs]

Double post.

[Lieney]

I have found that nearly everyone that has a GU 3.0, other than grenade issues, can have similar faults but require different solutions.
I cleaned MAF & repaired a split vacuum hose on a switch located under the engine cover. Good for a while but once driven an hour or so,problems again.
Ive thought about bypassing the butterfly in the inlet manifold to stop it restricting air flow but not sure what exactly triggers it's operation.
I might also adjust the Dawes valve tomorrow & lower the boost a notch or two.
Does engine light come on when safe mode kicks in?
Easier with a "normal" diesel.

[Lieney]

Well I adjusted the Dawes valve down a smidge so she's running about 15psi. I also cable-tied the butterfly back. Short run in second worked a treat but a good road run should determine if it's fixed.
Don't think it was boost at 17psi as it was running quite well until recently.
The butterfly is another issue.

[threedogs]

By butterfly do you mean throttle body at back of the motor??
You may find that 1-2 psi makes a huge difference with over boost issues.
Pain in the butt but I drove around with 2 spanners and adjusted DAWES as I
drove around, frisky as now, Don't try and obtain more boost it wont work like that.
I was reading all the time 15 psi so was trying to get 18 psi as still safe, aint gunna happen.
goes better smoother quicker and boost just touches 15 psi, nipped up the Dawes, thats it.
NO TWO ARE THE SAME. Also EGTs are great now too.

[Lieney]

Cheers threedogs. I didn't seem to have an issue running 17psi until a month or two ago.
I fitted a 3" exhaust, then I had EGR blocked, Dawes installed and then Dyno fitted before Simpson desert trip.
The engine torque died after gear change but car had done this since I bought it.

The butterfly does look like it would be a throttle; however, I don't believe it is exactly that as diesel engines use fuel metering as throttle, as apposed to petrol.
Although in later diesel I have found more and more differences with computer controlled nightmares.
I discussed my issues with a bloke at the 4x4, camping & fishing show Sunday who sells all the latest and greatest power increasing products.
He said the 'throttle' is controlled by the ECU and assists in preventing overboost by restricting air flow, getting a signal from computer, amongst many other things that occur.
I checked how it operated and found it was vacuum opened, spring closed.
I cable-tied it in the open position and adjusted the boost down to about 15psi so engine would get unrestricted air, and computer would do its thing.
Engine ran real smooth, boost guage didn't push upward of about 18-19 and there was no lag in gear change as previous.
I will increase boost again a smidge and see what happens.
Happy with outcome so far.

[threedogs]

Need to block off the vacuum solenoid, block egr. Thats all I've done plus fit Dawes and needle valve under bonnet,
You need to read Chaz Yellowfoot {guru} on Z30 via search engine. don't think 18 is better 15, doen't work like that.
By doing all these things you take the thinking away from computer and controll it yourself, When you do adjustments disconnect battery for 1 hr or so
as well, Whats Dyno fitted??? Just doesn't sound right, or I'm missing something

[Rumcajs]

The butterfly does look like it would be a throttle; however, I don't believe it is exactly that as diesel engines use fuel metering as throttle, as apposed to petrol.
.......................
I discussed my issues with a bloke at the 4x4, camping & fishing show Sunday who sells all the latest and greatest power increasing products.
He said the 'throttle' is controlled by the ECU and assists in preventing overboost by restricting air flow, getting a signal from computer, amongst many other things that occur.
I checked how it operated and found it was vacuum opened, spring closed.
I cable-tied it in the open position and adjusted the boost down to about 15psi so engine would get unrestricted air, and computer would do its thing.
.................


There are two "butterflies" in there, the one closer to bulkhead is the so called swirl control valve and its precise nature is according to Nissan; to generate better airflow swirl in to cylinders and its suppose to only work at low RPM (up to 1200). I believe personally ( I have no proof but on other small Diesels it is used for that) that this valve is/can be used for additional EGR control to assist with reducing intake air pressure to allow exhaust gases to get in. This one can be safely disabled as it suppose to have no net effect. Not really there to control overboost as such! It is actually EGR which is used to some degree to deal with overboost. Some experts ay.

The other(closer to the front of the engine in the main part of the Y piece) one is an engine stop "strangler" it is activated when engine is turned off to assist the engine shutdown. Don't disable that one!

Is yours by any chance with auto tranny? On those the way to reduce chance of overboosting induced limp mode even with Dawes is to actually adjust the VNT stop screw to reduce/limit the rate of turbo spool. Apparently it is desirable to do it and the results can be very beneficial.

On manual tranny it isn't that crucial as with every gear change the revs will drop to idle so the turbo needs to pick up again whereas with auto you've already spooled the turbo with RPMs up and when gear change happens with out them really dropping off back to idle it is easier to overboost, you'll get an idea.
15 psi is plenty pushing to 18 is asking for trouble and further action is required like the VNT stop screw adjustment.
Cheers

[Lieney]

Whats Dyno fitted??? Just doesn't sound right, or I'm missing something
No, you are not missing something. I miss-typed.
I had the dawes valve fitted and then had a Dyno test done.
I could not get any decent information on exactly how the vacuum system in this engine actually worked, so was a little scaredI was going to destroy something.
LOL - typo. I do that sometimes

Rumcajs
I was unaware there was another butterfly. I might just have a little look when I get more time, and it warms up. Freezing tonight.
One causes turbulance ay? It used to stall the turbo, but now i got it held open, the stall seems minimal and engine acceleration is smooth as
I had all this apart when replacing my turbo. Would have been a good time to investigate if I wasn't in a rush.
Its a manual, until I get my hands on an LS3 and adapter kit, maybe. :)

Thanks again