limp mode??

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14th March 2014, 08:28 AM
threedogs

not doubting just needed some clarification, I run 19psi max boost and mine never goes into limp mode.
The longer we have these motors seems the more we find out about them.
Whats a voltage modifier look like out of interest and is it a big mod or fairly simply.
I have my ECU-Talk in view when I drive I'll see what readings the MAF says
14th March 2014, 08:37 AM
Mud Gecko

Mate if you don't get limp mode that's great! I wouldn't worry about it then. But for those that do you'll need this-

http://www.jaycar.com.au/productView.asp?ID=KC5490

and this-

http://www.jaycar.com.au/productView.asp?ID=KC5386

and a degree in electronics to put it all together lol

or check out this thread- http://www.patrol4x4.com/forum/zd30-...difier-102192/
14th March 2014, 10:31 AM
Rickie3

I just went out and removed the blanking plate and put back in the original gasket, and test drove it has stopped the limp mode issue and appears to be running spot on
14th March 2014, 11:16 AM
threedogs

Quote:

Originally Posted by Mud Gecko

I have a Di, according to the Nissan manual, MAF voltage should be 1.6v-2.0v. With a blocked EGR and no modifier, MAF voltage at idle is 2.2v-2.3v. Without my modifier and running 18psi of boost I will get limp mode at 2500rpm and just under 3000rpm @ WOT in 3rd and 4th. Limp mode is a combination of high boost and high MAF voltage. Usually if you go over 3.98v under 3000rpm you'll get limp.

With my modifier, I have tuned my MAFv at idle to 1.7v-1.8v. I no longer have that "fuely" smell at idle and I can tune out limp mode by raising or lowering the MAF voltage around those limp points.

If you don't believe me there is plenty of info on the "other" site, lots of guys doing it now.

My MAF reads up to 3.9 and a bit driving along normally, with no limp
14th March 2014, 11:57 AM
BillsGU

Quote:

Originally Posted by Mud Gecko

Mate if you don't get limp mode that's great! I wouldn't worry about it then. But for those that do you'll need this-

http://www.jaycar.com.au/productView.asp?ID=KC5490

and this-

http://www.jaycar.com.au/productView.asp?ID=KC5386

and a degree in electronics to put it all together lol

or check out this thread- http://www.patrol4x4.com/forum/zd30-...difier-102192/

Sounds good. Never knew it existed.
14th March 2014, 12:20 PM
the evil twin

Well, I bow to popular opinion but something doesn't gel to me.
I think you are effectively detuning the engine by reducing fuel

If a MAF is serviceable and its temperature and airflow output voltages are "in spec" then they are proportional to the airflow.

If you "reduce" the voltage then the ECU is being told "you are getting less air".

Anyway, no biggee. I'm guess I'm lucky mine runs fine with out the need for a modifier
14th March 2014, 12:47 PM
Lemo79

Quote:

Originally Posted by the evil twin

Well, I bow to popular opinion but something doesn't gel to me.
I think you are effectively detuning the engine by reducing fuel

If a MAF is serviceable and its temperature and airflow output voltages are "in spec" then they are proportional to the airflow.

If you "reduce" the voltage then the ECU is being told "you are getting less air".

Anyway, no biggee. I'm guess I'm lucky mine runs fine with out the need for a modifier

And I think that is where the problem is, when we block EGR more air is dragged past the MAF increasing the the voltage hence increasing the fuel. Restoring the correct voltage ensures the correct amount of fuel and not an increased amount of fuel.
It would also make wonder though if the ECU has two fuel maps, EGR open and EGR closed. In which case by modifying the voltage it upsets the fuel mapping at times when the EGR is supposed to be closed, eg off idle and not at cruise.

Just my thoughts?

Lemo.
14th March 2014, 01:29 PM
the evil twin

Quote:

Originally Posted by Lemo79

And I think that is where the problem is, when we block EGR more air is dragged past the MAF increasing the the voltage hence increasing the fuel. Restoring the correct voltage ensures the correct amount of fuel and not an increased amount of fuel.
It would also make wonder though if the ECU has two fuel maps, EGR open and EGR closed. In which case by modifying the voltage it upsets the fuel mapping at times when the EGR is supposed to be closed, eg off idle and not at cruise.

Just my thoughts?

Lemo.

That is where it doesn't quite work with me as well.
I think it is a hide the symptom versus cure the problem but Pffft, both will stop a limp mode.
I guess it is only needed for MAF's that have a 'higher' output for a given airflow.

I want more air so my ECU and Chip can feed more fuel so I get more herbs.
The MAF sensor is saying you are now getting more air so have more fuel.
I modify the signal to say you are getting less air.
The ECU then takes fuel so I get less grunt.

... and to make it more complicated the EGR valve control is different between the Di and CRD
AFAIK CRD's aren't an "open/close" valve, they are a stepper motor.

Anyway, the OP has a Di so I'll bow out and stop confusing the issue with my CRD gibberish. :clownredpuff:
14th March 2014, 02:04 PM
BillsGU

ET - Just kicking around some thoughts. With the ERG unblocked the engine would be getting air from two sources (the normal air intake and the air supplied via the EGR). The ECU would supply fuel proportional to this amount of air. The only metered portion is via the normal air intake, where the MAF senses the amount of fresh air supplied. I would imagine that the ECU would compensate for the air that is also supplied via the EGR.

When the EGR is blocked the ECU would not know that this amount of air is now shut off and the engine would be getting less air than it should have for the amount of fuel supplied. This device would allow the adjustment of the correct air / fuel ratio by making the ECU think there is less air entering the engine than there actually is.

Does this makes sense ...................................... ?
14th March 2014, 02:07 PM
Mud Gecko

Quote:

Originally Posted by the evil twin

That is where it doesn't quite work with me as well.
I think it is a hide the symptom versus cure the problem but Pffft, both will stop a limp mode.
I guess it is only needed for MAF's that have a 'higher' output for a given airflow.

I want more air so my ECU and Chip can feed more fuel so I get more herbs.
The MAF sensor is saying you are now getting more air so have more fuel.
I modify the signal to say you are getting less air.
The ECU then takes fuel so I get less grunt.

You are correct. I don't have a chip. I only reduce MAF voltage at idle, above idle I actually increase the voltage thus increasing fuel (sort of a poor mans chip :) ). I only need to reduce the voltage at particular points in the upper rev range when I get limp, it can be a surprisingly small amount that makes all the difference.

If you don't have issues with limp mode then I wouldn't worry about it. It seems these cars each have their own idiosyncrasies...

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