An easy way to be rid of those annoying 3Ltr limp mode issues forever.

[mudski]

Thought this would be good for all the 3ltr owners who have had a gut full of limp mode. I know I did back in the day. Plug and pray and just clip the voltage on the maf signals using this device and enjoy your new freedom of raising your boost levels without looking the limp mode issues. I don't know much about them, I just know plenty of people have used them. Other than making your own up from Jaycar, or using the HPD maf housing, which suits the Di'd only, this is another way to go.
http://www.14point7.com/products/ultra-air-fuel-controller

[Wilburnator]

Thought this would be good for all the 3ltr owners who have had a gut full of limp mode. I know I did back in the day. Plug and pray and just clip the voltage on the maf signals using this device and enjoy your new freedom of raising your boost levels without looking the limp mode issues. I don't know much about them, I just know plenty of people have used them. Other than making your own up from Jaycar, or using the HPD maf housing, which suits the Di'd only, this is another way to go.
http://www.14point7.com/products/ultra-air-fuel-controller

Just out of curiosity mudski, what sort of max boost levels would bring on the limp mode?


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[mudski]

It varies between vehicle but its usually around 16psi for the Di motors and maybe around 18psi for the CRD's.

[Wilburnator]

It varies between vehicle but its usually around 16psi for the Di motors and maybe around 18psi for the CRD's.

Is it a fairly quick response, as in hits the high boost and goes straight into limp? or does it have be in that range of boost for a given time?


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[Turtle_au]

Downloaded manual and had quick look. Aimed at petrol engines, uses ignition coil pulse for rpm input.

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[mudski]

Is it a fairly quick response, as in hits the high boost and goes straight into limp? or does it have be in that range of boost for a given time?


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I can't remember exactly but I think its 2 second or so before it hits limp mode.

Downloaded manual and had quick look. Aimed at petrol engines, uses ignition coil pulse for rpm input.

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There must be different models as I do know that this is being used for the Patrols. I'm crap when it comes to deciphering this electrical stuff. But I dont think they are using the rpm side of it. Just accessing the maf voltage signals.

https://cdn.shopify.com/s/files/1/0189/1312/files/UAFC_User_Manual.pdf?1955
http://www.14point7.com/pages/software-and-documentation

[nissannewby]

They are also starting to do some nifty things with ecu remaps.

Be aware that at this point not all di ecus are able to be remapped.

[mudski]

Upon more searching around I see the boys on P4x4 have a thread about it...
http://www.patrol4x4.com/forum/nissan-patrol-gu-gr-10/uafc-digital-voltage-modifier-sharing-ideas-tuning-thread-335202/

Interesting stuff.

[Turtle_au]

It has its own table that takes the MAF signal and rpm then from the table sends the new MAF signal to the ECU. If the aim is to limit the MAF voltage to stop it triggering limp mode, a simple zener diode on the MAF sensor line would do the same thing.

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[mudski]

It has its own table that takes the MAF signal and rpm then from the table sends the new MAF signal to the ECU. If the aim is to limit the MAF voltage to stop it triggering limp mode, a simple zener diode on the MAF sensor line would do the same thing.

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Yeah I spoke with a chap a few weeks ago who has done this. A simple inline resistor or diode, and his limp mode issues were gone. I'm no expert though, but the MAF is there to assist control of air fuel ratio's, so just adding a diode, I don't know how it would affect the AFR's across the rev range. Might be nothing, not sure...

[Turtle_au]

A zener diode has a breakover voltage. You pick a size thats just under limp mode.
So if you picked 3.9 volts, the MAF volts will rise as normal until you get to 3.9 volts then anything over that is diverted to earth. The ECU will only see upto 3.9 volts.
Yes above that the ECU could do a couple of things, keep injjecting the amount of fuel for that air volume and try to increase the airflow by increasing boost ( which is already over what the MAF volts are telling it )
I would not add the diode without firstly having some form of boost limiter fitted and maybe even a BIG warning light to let me know I have hit the limit so I would know to back off before overboost and under fuelling killed the engine.

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[mudski]

A zener diode has a breakover voltage. You pick a size thats just under limp mode.
So if you picked 3.9 volts, the MAF volts will rise as normal until you get to 3.9 volts then anything over that is diverted to earth. The ECU will only see upto 3.9 volts.
Yes above that the ECU could do a couple of things, keep injjecting the amount of fuel for that air volume and try to increase the airflow by increasing boost ( which is already over what the MAF volts are telling it )
I would not add the diode without firstly having some form of boost limiter fitted and maybe even a BIG warning light to let me know I have hit the limit so I would know to back off before overboost and under fuelling killed the engine.

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Yeah right! That makes sense. Thanks. Over boosting isn't the killer of these motors too. Its the under boost at certain levels which creates massive cylinder temps and then the pistons give up in the end. My old Di happily spent its life at 25psi, went bloody good for what it was too.
I kind of wish I still had a 3Ltr so I could experiment more on this. Maybe I'll buy a shitter of one. Hmm....
Off topic, I did speak to a guy last week who had used the intake side of a BMW turbo, I can't remember which motor it was, on the stock turbo and he's getting over 300nm by 1800rpm. Seems pretty impressive.

Its good to see more people thinking outside the square with the motors now.

[nissannewby]

A zener diode has a breakover voltage. You pick a size thats just under limp mode.
So if you picked 3.9 volts, the MAF volts will rise as normal until you get to 3.9 volts then anything over that is diverted to earth. The ECU will only see upto 3.9 volts.
Yes above that the ECU could do a couple of things, keep injjecting the amount of fuel for that air volume and try to increase the airflow by increasing boost ( which is already over what the MAF volts are telling it )
I would not add the diode without firstly having some form of boost limiter fitted and maybe even a BIG warning light to let me know I have hit the limit so I would know to back off before overboost and under fuelling killed the engine.

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Doesnt quite work like this. The ecu has a map so if it sees a abnormally high maf voltage for a given parameter it will go into limp. For example if the maf voltage goes over 2.5v at 2000rpm with a tps under 60% and the map sensor is only seeing 5 psi it will go into limp.

The good thing about what mudski has linked is it can be tabled like an ecu so you can program for a setpoint so maf voltages between certain rpm say in 100rpm increments. So this allows you to control the output maf voltage to the ecu and basically tune limp out.

Also diesels work the other way to petrol. The leaner the afr the better. Rich afrs can and will kill a diesel engine. Only thing high boost will do to the standard turbo is kill it.
mudski

[mudski]

Also diesels work the other way to petrol. The leaner the afr the better. Rich afrs can and will kill a diesel engine. Only thing high boost will do to the standard turbo is kill it.
mudski

Never killed my old turbo.:icon_driving:Haha It was still like new when we pulled the motor out. Just the rest was failing around it. This makes me wanna get a 3ltr now and do some mucking around.

[Hodge]

Never killed my old turbo.:icon_driving:Haha It was still like new when we pulled the motor out. Just the rest was failing around it. This makes me wanna get a 3ltr now and do some mucking around.

Now now ...

[mudski]

Now now ...

Thanks Eric. I need to be brought back to reality... Haha!

[Turtle_au]

Doesnt quite work like this. The ecu has a map so if it sees a abnormally high maf voltage for a given parameter it will go into limp. For example if the maf voltage goes over 2.5v at 2000rpm with a tps under 60% and the map sensor is only seeing 5 psi it will go into limp.

The good thing about what mudski has linked is it can be tabled like an ecu so you can program for a setpoint so maf voltages between certain rpm say in 100rpm increments. So this allows you to control the output maf voltage to the ecu and basically tune limp out.

Also diesels work the other way to petrol. The leaner the afr the better. Rich afrs can and will kill a diesel engine. Only thing high boost will do to the standard turbo is kill it.
mudski
Ok I follow that.
What about early non-crds that only have MAF sensor and no MAP sensor.
Also that unit uses the low side of ignition coil for rpm sensing.

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[mudski]

Ok I follow that.
What about early non-crds that only have MAF sensor and no MAP sensor.
Also that unit uses the low side of ignition coil for rpm sensing.

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The Direct injection motors, pre CRD, also used a map sensor. Its found mounted on the intercooler....

[nissannewby]

Ok I follow that.
What about early non-crds that only have MAF sensor and no MAP sensor.
Also that unit uses the low side of ignition coil for rpm sensing.

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You can use the tachometer or the low side of an ignition coil. The rpm for the module is as simple as splicing into the correct wire that goes to the ecu in a zd 30. You dont have to use the rpm either but it gives you only 16 setpoints rather than a nice table when using the rpm.

And there is a map sensor on the earlier di motors.

[nissannewby]

Never killed my old turbo.:icon_driving:Haha It was still like new when we pulled the motor out. Just the rest was failing around it. This makes me wanna get a 3ltr now and do some mucking around.

Push it beyond 25 and you may find its limit pretty quick.

[mudski]

Push it beyond 25 and you may find its limit pretty quick.

Yes. From my research when I owned the 3ltr, the stock turbo is quite capable of anywhere up to 25psi. Anything above this your running a high risk of damage to the turbo.

[Turtle_au]

You can use the tachometer or the low side of an ignition coil. The rpm for the module is as simple as splicing into the correct wire that goes to the ecu in a zd 30. You dont have to use the rpm either but it gives you only 16 setpoints rather than a nice table when using the rpm.

And there is a map sensor on the earlier di motors.
Where would I look for the MAP sensor?

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[Turtle_au]

The Direct injection motors, pre CRD, also used a map sensor. Its found mounted on the intercooler....
This motor is in a 2002 4x4 Elgrand. Had all the inlet pipework and intercooler off on monday and cleaned it out.
Nothing on the intercooler. Only has the MAF sensor between the air filter and turbo.
Just had flick through of workshop manual, engine control section. No mention of any MAP or pressure related sensor. Also NDS1 doesn't show anything either.

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[mudski]

This motor is in a 2002 4x4 Elgrand. Had all the inlet pipework and intercooler off on monday and cleaned it out.
Nothing on the intercooler. Only has the MAF sensor between the air filter and turbo.
Just had flick through of workshop manual, engine control section. No mention of any MAP or pressure related sensor. Also NDS1 doesn't show anything either.

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Imported motors are different then. Australian built motors all have a MAP sensor.

[Turtle_au]

I thought the MAP sensor and shorter dipstick ( more oil in sump ) were nissan's initial response to the grenading. BTW which vehicle out here had the ZD30 first, the patrol or the navarra?

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[Turtle_au]

The Elgrand is a bit of a mix and match. Engine from patrol/navarra, drivetrain from terrano/pathfinder.

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[mudski]

I thought the MAP sensor and shorter dipstick ( more oil in sump ) were nissan's initial response to the grenading. BTW which vehicle out here had the ZD30 first, the patrol or the navarra?

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Patrol came out in 2000 with the ZD30.... I think the D22 came out with the ZD30 in the same year.