limp mode mod

[Rumcajs]

I thought boost sensor was disregarded with dawes and needle valve installed?, unfortunately dont have the cash to buy the JDVM unit, so I couldnt just use one fuel cut kit for the MAF?, if the boost controller is still used then I would buy the second fuel cut unit? I purchased 1 unit last night online, when I get some extra coin will buy JDVM unit

Boost (MAP) sensor is used as engine protection only in other words it is not considered for overall AFR calculation, only MAF is used for that.
There is clearly a relationship between those too as boost pressure over 18 psi in any RPM will bring on fuel cut (limp) and MAF voltage over 3.99 bellow 3000 RPM will do the same. There is also this so called "cold" limp (engine temp bellow 70°C) which occurs when MAF voltage is over 3.75 or so and around 2500 RPM.

You could/can adapt the Jaycar fuel cut defeat unit to MAF only but you still have the boost (MAP) sensor to watch/consider if you want to allow Dawes at higher pressure where boost spike can take it past 18 psi at lower RPM (<4000).
One still needs to find out what voltage reading is MAP output at 17-18 psi. Jaycar unit seems to be preset to keep the voltage bellow 3.9 V so lets just assume that ==>

this simple Fuel Cut Defeater (FCD) to eliminate the standard factory fuel cut which typically occurs at boost levels about 16-17psi. The unit is not adjustable, so no external controls are required.

would than be sufficient to keep the boost pressure related limps from occurring.

In any case it has been proven that ZD30 Di with boost pressure over 18 psi is doing nothing beneficial from either performance or engine reliability prospective.

What JDVM unit gives you is ability to control the "holy grail" of performance especially on ZD30 that is low to mid range torque/power thanks to fooling ECU in to thinking that more air is supplied hence the fueling increase thus bypassing the smoke maps limits . The ability to tweak the loading points individually where possibly limp might occur is another bonus.

Once set right it will be another "OMFG why didn't I do this earlier!" moment. If you thought Dawes and needle valve transformed the car wait for the JDVM effect....

Cheers

[mudski]

This is what my local mechanic/turbo place does. He doesn't subscribe to any of this dawes/needle stuff. He's had 4-5 blokes come in with dawes valves and stuff, and hes ripped it out, tinkered with the MAF voltage, and the owners couldn't believe the difference when they picked the car up.
They also do this when they fit a chip. He didn't reveal specifics, but showed me some dyno sheets to prove it.

Unfortunately what Mark, the said mechanic, does, it half correct, or right. By ripping out BOTH dawes and neelde valve and only playing with the MAF voltages only gives you half of the control over the turbo. Messing with the maf voltages cannot give you spool up rate control where the needle valve does this.
So when the owners pick up there Patrols and feel the extra power, its only because of more boost and the spool up rate is still controlled by the POS ecu.
While it may be a cheaper option to mod the maf voltages you technically still have no control over it.
I myself went down the somewhat expensive track and purchased a HPD hi flow air box lid and HPD hi flow maf housing. Once fitted there was zero difference. IT was only when I raised my boost levels beyond what it could before, whilst still retaining the needle valve, I felt the difference. I went as high as 25psi and there still was no limp mode. I didn't go any higher. Currently running 20psi...
Next on the list is to modify the intake of the turbo to accommodate a larger intake pipe as the macca's straw used now is by far the biggest restriction on the motor.

In any case it has been proven that ZD30 Di with boost pressure over 18 psi is doing nothing beneficial from either performance or engine reliability prospective.



Cheers

While I don't doubt your expertise on this Rummy I'd have to disagree on this. While there is minimal performance increase from 16-20psi, when I drove mine with 25psi it was really a different car to drive. I could have gotten used to the extra ponies it had at 25psi but I was a bit worried that something was to go bang quite quick. Maybe not as the turbo is quite capable of providing this type of boost pressure, I was concerned for the motor not handling it.

Cheers.
Mark.

[Rumcajs]

..................
I myself went down the somewhat expensive track and purchased a HPD hi flow air box lid and HPD hi flow maf housing. Once fitted there was zero difference. IT was only when I raised my boost levels beyond what it could before, whilst still retaining the needle valve, I felt the difference. I went as high as 25psi and there still was no limp mode. I didn't go any higher. Currently running 20psi...
.................
While I don't doubt your expertise on this Rummy I'd have to disagree on this. While there is minimal performance increase from 16-20psi, when I drove mine with 25psi it was really a different car to drive. I could have gotten used to the extra ponies it had at 25psi but I was a bit worried that something was to go bang quite quick. Maybe not as the turbo is quite capable of providing this type of boost pressure, I was concerned for the motor not handling it.
............

While you welcome to disagree you are still confirming what I have said, the second part about engine reliability that is. Now having HPD lid and housing changes a thing or two but on stock ZD30 there is very little benefit going past 18 psi and this isn't just my observation but a few Patrol gurus too.

I have both, HPD MAF housing and airbox lid and without JDVM I would need to bump boost up past 18 psi to get extra ponies. In this case diesel chip would definitely be beneficial but I don't like to cough up that much for a bunch of resistors on a circuit board in a plastic box.

I have observed that in lower boost setting (12 psi) tractive effort of the engine is way better than at higher boost mode (18 psi)
(I have dual Dawes setup) I can really explain it. The downsize is cruising at 100 km/h at lower boost raises EGTs to the point I'm not comfortable with.

Cheers

[Rickie3]

You could/can adapt the Jaycar fuel cut defeat unit to MAF only but you still have the boost (MAP) sensor to watch/consider if you want to allow Dawes at higher pressure where boost spike can take it past 18 psi at lower RPM (<4000).
One still needs to find out what voltage reading is MAP output at 17-18 psi. Jaycar unit seems to be preset to keep the voltage bellow 3.9 V so lets just assume that ==> would than be sufficient to keep the boost pressure related limps from occurring.


Cheers

I'm more than happy running my bus at the 16psi, cant see any point pushing it any harder, after i'm not towing with it, so for the time being i will be more than happy to do the MAF mod, but when funds do improve JDVM is on the cards, I will no doubt need some advise on installing the fuel cut unit for the MAF, and I really appreciate the time you have taken to post your very helpful informative comments

[mudski]

While you welcome to disagree you are still confirming what I have said, the second part about engine reliability that is. Now having HPD lid and housing changes a thing or two but on stock ZD30 there is very little benefit going past 18 psi and this isn't just my observation but a few Patrol gurus too.

I have both, HPD MAF housing and airbox lid and without JDVM I would need to bump boost up past 18 psi to get extra ponies. In this case diesel chip would definitely be beneficial but I don't like to cough up that much for a bunch of resistors on a circuit board in a plastic box.

I have observed that in lower boost setting (12 psi) tractive effort of the engine is way better than at higher boost mode (18 psi)
(I have dual Dawes setup) I can really explain it. The downsize is cruising at 100 km/h at lower boost raises EGTs to the point I'm not comfortable with.

Cheers

Yeah I was mainly referring to the performance benefit by my rambling kinda gets in the way. At 25psi there was a massive difference to performance. But not a great deal at 18psi.
As for the dual Dawes. You think its worth it? I considered doing it. I have all the gear here to do it. But I realised I would just have it on the high setting anyway so I didn't bother.

[Rumcajs]

As for the dual Dawes. You think its worth it? I considered doing it. I have all the gear here to do it. But I realised I would just have it on the high setting anyway so I didn't bother.

For me it is, as I look for fuel eco as well. I have it both automated via accelerator pedal and manual overide with low,high,auto, in the city and when engine is cold I force low boost mode only, on open road I sometimes keep it on low to get some economy especially on flat roads subject to EGTs than I flip it over to automatic control.
Mine is set up to change over from low to high at about 20% accelerator pedal or 1.6 V.

Main reason is fuel economy as mine is atrocious when cruising in high boost mode sitting on 12 psi @100 km/h will drink over 13 L. There is something about GU4 series as earlier versions don't have that problem or so it seems. Some guys are getting around 10L or even lower. Forcing it to sit at 8-10 psi I can manage 10-11 L too.

And I can have fairly aggressive spool up (needle valve is just about closed) and I get no cold limps this way.

Cheers

[mudski]

Now what you have just said makes me think I should do this mod. As it stands, I'm running 20psi boost and 15psi at 100ks. If I go 10psi, my spool up rate is too slow and the car just won't go. Maybe I should do this and use the low boost for highway driving, which I do a lot of too. Yuo may need to start a new thread on this mate on how you set it up to work via your acc pedal. Very interesting indeed.

[Rickie3]

From what ive read a simple inline diode between the MAF and the ECU will drop the voltage caused by blanking the EGR, cheap mod just a matter of snipping the red wire and soldering in a diode if its not any good easily taken back out

[oddkid82]

Does this work

[threedogs]

@ Rickie what value diode did you use