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Discussion Starter #1
Hey guys !

First things first - this is something i have done to my troll for about....40km or so. No long term testing, i admit, but results can be observed right away. And not to forget, my appologies for my bad English.

Considerations:
Perhaps you (or at least many of you) are aware of the fact that after blocking EGR, MAF voltage rises to from 1.6V - 2.0V (as it should be by default) to 2.2V - 2.3V. You can tell that by the way it smells like unburnt diesel at idle. Talking to my friend Chaz, i tried to solve this issues, but with a small amount of cash and effort. So, after bugging Chaz for a while, he told me to use a resistance. And so i did.

Previous attempts
In this summer, i bought a Donatorstore black box. I thought that was the solution. Nothing far from the truth. After fitting that box, lack of power occured. BIG TIME. A very light hill i used to make it to the top using 5th gear, after fitting the DonatorStore thing i had to use 3rd gear. Adjusted and readjusted, no improovment at all. So, obviously i took it off. But i kept in mind where it connects....



First shot

I tried to use a 10ohms resistance, and put it in-line with the wire that goes from the MAF to ECU. No change. Then i remembered how DonatorStore thing altered the signal. The wire that carries 5V. Still no change. What to do next ?

Second shot

After an unsuccessfull attempt, i tried a bigger resistance. 100ohms. Same steps followed...no improovement. I started to get a little angry, because the weather got very cold, and i had no result. My back started to send signals (i have been diagnosed with hernia), freezing and the damn thing wont work.

....and STRIKE

Going back into my office, my eyes stopped on a malfunctioning PC power supply. I torn it apart, and found there a variable resistance of 1000Ohms, or 1KOhm. At first, i thought this thing is too big, but since i had nothing to loose, i gave it a shot.....AND STRIKE !

Set to minimum value no change....but when you start to turn the knob, EcuTalk starts to read different values....

Here is a shot of EcuTalk at idle before



And here is a shot of EcuTalk at idle after



So...it works. Took the car for a ride to test the new setup. I admit it is a bit lazy (just a bit) than before, but no ECU reset performed and i did 5000+km (wait.....about 10.000km) with the MAF showing a higher voltage than normal. But, what is more important....no more limp mode. No matter how hard i pushed it, no limp mode occured.

So .... short story:
- locate the 5V wire.
- insert in-line a 1KOhmn variable resistance
- tune it until you get a 1.8V - 1.9V reading.

I did not measure the resistance in order to find the exact value, for the moment i'd like to keep it variable. Did not take any picture with the resistance mounted, as, just like explained to Chaz it is a "gipsy thing"....

PS. I noticed here is full of skilled people and what an amazing work did they to their trolls, so i thought my pictures will be an insult. Advised by Chaz i considered this would be a mod to help the Patrol perform even better.
 

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nissan
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Hello Daemonus,
Good work!
That sound like a quick and easy fix to the dreaded limp mode. My Patrol has been suffering this since I increased the boost from 14 to 16 psi.
Just for interest, what are your MAF voltage readings through out the RPM range?
Cheers,
B&B
 

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Discussion Starter #3
After doing this "mod", the readings show a linear trend.

Before the "mod", i could not establish any link between the RPM and MAF voltage. I got different readings at the same speed, boost and RPM. Limp mode occured at very different speeds, boost and rpm - and became very annoying.

Anyway, all the credit goes to Chaz, he is the one that pointed me to that direction....
 

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Hello again,
So the MAF voltage reads 1.9 vdc at idle. What is the MAF voltage at 4,000 rpm?
Cheers,
B&B
 

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Hi,

When you get the right value resistance, make sure you replace the variable resistor with a fixed one. ( or network of them to get the right value ) It will be far more stable and reliable.

Regards B M
 

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Discussion Starter #6
Hello again,
So the MAF voltage reads 1.9 vdc at idle. What is the MAF voltage at 4,000 rpm?
Cheers,
B&B
Did not reach 4.000 (no need to). The day after tomorrow will start the car again and bring it up to 4000 and take some pics.

I have a short video i shot while driving, at 80km/h, 2.000 rpm the MAF delivers ECU a vaue or 2.76V. Dont know if that is relevant...

@Bidgee Man - i'll consider that. Thank you for your intervention.
 

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Discussion Starter #7
Updates:

Today was cold here, a real late autumn day. Took the troll out of the parking spot, for a short neighborhood run. Outside temp....around 12oC, or at least the inside thermometer showed. I started the engine. Something was odd though....even the engine started without any problems, the RPM stayed at 750. I remember that a temperature like that the RPM would increase to at least 800RPM....but i might be wrong. Anyway, back to problem....MAF reports a value of 2.2V....just as it would before fitting the resistance.

Nobody drove the car since yesterday, the resistance is pressumed to work (otherwise i would expect a Check Engine and an error code thrown). The car drove all right, and even with the short periods of "pedal-to-metal" - no limp mode occured.

Tomorrow will check the resistance, as my meassuring device is somewhere well hidden from my eyes right now. Anyway a few questions appear:

a) if the resistance has an issue and stop working, how come the troll still runs ?
b) if the resistance is working just fine, how come the value reported by the MAF to ECU is unchanged ?
c) when i turned off the engine, the water temp was 70oC. The MAF voltage was the same...2.2V. It was supposed that when the engine becomes warmer, the voltage should go down, right ?
d) i dont know if the MAF i own is the original one that comes with the car, but with the Donator store thing i had pretty much the same experience. When i set-up a value of 1.8V (just an example), the very second day it changed to something bigger, some like 2V. Who to blame for all these ? MAF ? ECU ? The Black Dwarf ??

I started this little thing, hoping that there would be a simple solution to a common problem. Next Q is : did someone here tried to alter DIRECTLY the voltage send by the MAF to ECU, by inserting some sort of device directly into that particular wire ???

I will keep you posted.
 

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Hello Daemonus,
Interesting stuff indeed!
The voltage reading may be higher because of the cooler temps.
Cooler air is more dense or has more mass. Perhaps the Mass Air Flow sensor is sensitive enough to measure this and so it's output voltage is higher.
The other thought that occurs to me is that you may need a new MAF sensor. Your current one may be on the way out, and giving inconsistent readings.
Cheers,
B&B.
 

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I started this little thing, hoping that there would be a simple solution to a common problem. Next Q is : did someone here tried to alter DIRECTLY the voltage send by the MAF to ECU, by inserting some sort of device directly into that particular wire ???

I will keep you posted.
I have not tried it but I wonder if placing a germanium diode in that wire will produce the desired effect that daemonus is after (reduce voltage by around .3V across the entire range)?
 

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Y2KGUII ZD Wgn
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Updates:

Today was cold here, a real late autumn day. Took the troll out of the parking spot, for a short neighborhood run. Outside temp....around 12oC, or at least the inside thermometer showed. I started the engine. Something was odd though....even the engine started without any problems, the RPM stayed at 750. I remember that a temperature like that the RPM would increase to at least 800RPM....but i might be wrong. Anyway, back to problem....MAF reports a value of 2.2V....just as it would before fitting the resistance.

Nobody drove the car since yesterday, the resistance is pressumed to work (otherwise i would expect a Check Engine and an error code thrown). The car drove all right, and even with the short periods of "pedal-to-metal" - no limp mode occured.

Tomorrow will check the resistance, as my meassuring device is somewhere well hidden from my eyes right now. Anyway a few questions appear:

a) if the resistance has an issue and stop working, how come the troll still runs ?
b) if the resistance is working just fine, how come the value reported by the MAF to ECU is unchanged ?
c) when i turned off the engine, the water temp was 70oC. The MAF voltage was the same...2.2V. It was supposed that when the engine becomes warmer, the voltage should go down, right ?
d) i dont know if the MAF i own is the original one that comes with the car, but with the Donator store thing i had pretty much the same experience. When i set-up a value of 1.8V (just an example), the very second day it changed to something bigger, some like 2V. Who to blame for all these ? MAF ? ECU ? The Black Dwarf ??

I started this little thing, hoping that there would be a simple solution to a common problem. Next Q is : did someone here tried to alter DIRECTLY the voltage send by the MAF to ECU, by inserting some sort of device directly into that particular wire ???

I will keep you posted.
Just a few comments:
My idle revs are 750 +/- 10 without aircon and 825 +/- 10 with aircon, this has not changed in 12 years.
My idle MAF voltage now, post EGR failure, is 2.2v and this never changes either.

Chaz had a device he bought and assembled from JayCar some time back and he could individually change something like 240 setpoints in the MAF range. Not sure how it finished up though, we were attacking the same problem from different perspectives at the time.

I have a TurboSmart FCD2 fuel cut defender fitted into the MAF wiring, but that only clips and unclips the high end, you cannot change the low end.
 

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Hey guys !

First things first - this is something i have done to my troll for about....40km or so. No long term testing, i admit, but results can be observed right away. And not to forget, my appologies for my bad English.

Considerations:
Perhaps you (or at least many of you) are aware of the fact that after blocking EGR, MAF voltage rises to from 1.6V - 2.0V (as it should be by default) to 2.2V - 2.3V. You can tell that by the way it smells like unburnt diesel at idle. Talking to my friend Chaz, i tried to solve this issues, but with a small amount of cash and effort. So, after bugging Chaz for a while, he told me to use a resistance. And so i did.

.....................

Hi daemonus,

very interesting and this is an observation i was not aware of.

sorry to take a step back here, but i'm first trying to understand what is happening here and what issue we are trying to resolve.

Am i right here:

-At idle with an operational EGR was the engine recycling exhaust therefore the less air was being inducted.
-Now with a blocked EGR all induction gas must be clean air, so more air is passing the MAF, hence a higher MAF voltage.
-Consequently the ECU is injecting more fuel.

So why is the fuel not simply being burnt and the idle subsequnetly running high?
Does the increase in voltage remain across the rev range or only when the egr valve is supposed to be open?

Regarding readjusting the MAF voltage, are you trying to prevent limp; improve fuel consumption, performance or both; or simply resolve the unburnt fuel issue.

Cheers,

Grogey
 

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Y2KGUII ZD Wgn
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Grogey, have you seen the comparison between std MAF voltages and blocked EGR MAF voltages (at idle, pre 1.8v, post 2.2v in my case), if you haven't I will find them, mine is increased across the rev range but it is not totally linear.
There have been a few anecdotal observations re extra "soot" on the back door from idling and traffic driving after a EGR block.

Something I forgot to say to Daemonus in earlier post was that I notice no difference in MAF voltages hot or cold as he seems to suggest should happen.
 

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I have no idea why the resistance would change. Sure cooler air may increase the MAF voltage, but as the resistor warms up, its resistance should increase slightly also, possibly reducing the voltage. I think whitie is on the money using a germanium diode because that will drop the voltage by only 0.3v rather than 0.6 with a silicon diode, but I haven’t seen a germanium in a long time so not sure how easy they are to obtain.

To work out the correct resistance needed to drop the MAF voltage by 0.4v, we need to know the current that flows through the circuit, if not it will be trial and error until someone cracks it. Daemonus, perhaps your variable resistor has a faulty contact on its brush causing the voltage to increase. Anyway, it’s worth investigating because I heard that a workshop in Perth were fitting resistors the MAF sensors to eliminate limp mode issues.

Ideally we need 1.8v at idle so the only problem I see in doing this is that dropping the voltage at idle will also decrease it throughout the rpm and load range which may produce a noticeable drop in performance, albeit improved fuel economy, so it may be a compromise.
 

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I might have abit of a go at this. I think i'll try putting a decade resistance box in the loop and slowly up the ohms till i get what i want. Then i can order the closest precision resister to optium i can.

Any comment on this method?

Would be interesting to know if this did actually drop overall power but?
 

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This is what my dyno tuner is doing. I don't yet know the exact resistance used but I can say that it has not gone into limp mode since fitment.

I have noticed a drop in low down power and the need for more throttle input since the mod.

The dyno tuner would normally use the chip settings to overcome the lost power but I have a chip which they aren't set up to program.

At idle, I had 1.9v post egr and this has dropped to 1.75 with the resister mod. It used to limp at 3.8v but now only reaches 3.6v at 4000rpm.

Sent from my iPhone using Tapatalk
 

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I've had a couple of beers tonight, so, probably shouldn't be replying but, I have been there and 3.98v under 3000rpm resulted in limp, my FCD2 has cured this problem by clipping the voltage below this point and then unclipping above 3000rpm to resume normal operation. With no low speed performance lost.
 

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I've had a couple of beers tonight, so, probably shouldn't be replying but, I have been there and 3.98v under 3000rpm resulted in limp, my FCD2 has cured this problem by clipping the voltage below this point and then unclipping above 3000rpm to resume normal operation. With no low speed performance lost.
I’m still at work, so probably shouldn’t be replying either, but (whoops, nearly caused a railcar collision) it sounds like the FCD-II would be the answer if adjusted correctly.

I’ve also managed to eliminate fuel cut occurring by bumping my low boost limit up to 12psi to cope with my higher mid range MAF voltages. I now have 1.85v at idle, up to 3.8v to 3000rpm and up to 3.9v at 4000rpm. I do sometimes see the alarm go off (set to 4.0v) with sudden hard acceleration, but still no limp.
 

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Discussion Starter #18
Hey guys !

Thank you for your input. Today will try out a brand new resistor too see what happens.
Why do i want this mod ? Main reason is to avoid limp mode as much as possible. Had a very bad period regarding finance and buying a FCD2 is out of the question. Taxes would double the price :(

Second reason would be fuel economy. When urban driving, i dont need much power, so a lower MAF voltage could help me save some fuel. If the new resistor holds up and does the job, i will think to a way to use it only when i am onroad and have no requirements for full power.

I'll keep you informed, any advise is apreciated.

PS. I regret i wasnt the son of a millionaire. :)
 

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I’m still at work, so probably shouldn’t be replying either, but (whoops, nearly caused a railcar collision) it sounds like the FCD-II would be the answer if adjusted correctly.

I’ve also managed to eliminate fuel cut occurring by bumping my low boost limit up to 12psi to cope with my higher mid range MAF voltages. I now have 1.85v at idle, up to 3.8v to 3000rpm and up to 3.9v at 4000rpm. I do sometimes see the alarm go off (set to 4.0v) with sudden hard acceleration, but still no limp.
I've seen as high as 4.27v at 4000 after the unclip (from 3.95v from memory, would need to confirm) at 3100. I have no problem there, BUT, my 2400rpm limp still catches me out from time to time, hadn't seen it for months and it got me last weekend on a climb?????????? manual transmission though.
 

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I've seen as high as 4.27v at 4000 after the unclip (from 3.95v from memory, would need to confirm) at 3100. I have no problem there, BUT, my 2400rpm limp still catches me out from time to time, hadn't seen it for months and it got me last weekend on a climb?????????? manual transmission though.
Hi mate,
I tend to forget that even though the MAP sensor doesn’t assist in mixture control, boost does have an influence toward MAF voltages, so I need to try a few new maps to get the best out of it.

I’ve also seen it in the 4.3v range and no fuel cut, but at high rpm. Like you I had the problem at lower revs. I need to do another log after changing the settings again since fitting the W/M, but overall it’s been good for the last few weeks since raising the boost slightly at lower rpm.

I think if daemonus was mainly concerned with higher rpm limp mode, a resistor or diode that reduced the MAF voltage by say 0.3-0.4v would most likely work without losing too much bottom end. Reducing it by more will improve fuel consumption and give a leaner idle, but also reduce performance. I can’t think of any other way to have both scenarios unless there was a way to “switch” the resistor in and out, say with a throttle position sensor switch, boost activated switch or rpm switch which may be worth a try, but again it starts to get complicated.
 
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