[daemonus]

@geeyoutoo - your thread was the first i have read, in fact it was like some kind of reference for me. Some issues i found there and served as base starting point in my discussion with Chaz.

But the running rich thing and unburnt diesel smell from the exhaust seems really strange. Surely if the ECU at idle is squirting in more fuel because it is getting a higher MAF reading, this should simply mean a faster idle. Isn't their oodles of air in an unthrottle diesel to combust all fuel injected. I not saying this isn't happening. I even think mine is doing this.

@groogey
As for the smell of unburnt Diesel i know just one thing....it suddenly dissapears when MAF voltage is adjusted.

4 years ago, Tweak'e said that he thinks swirl control valve has to do with the EGR valve. As Gu Workshop manual sais (long story short) that the swirl control valve when idle and low speed, it closes so it increases the air velocity, increases fuel burning speed. (fact)

Now, we blocked the EGR, so, at least i think so, the gas that used to intoxicate our engines now is pumped in the exhaust manifold, increasing turbocharger speed at idle (not significant for us to feel). By that, a little vacuum builds up in the intake (between the air box and turbocharger), so...sucking more air.

These are my thoughts. At least, if technicaly is full of errors, i hope you get a good laugh.

 

[geeyoutoo]

Daemonus,
You raise a good point. It will be interesting to note changes (if any) in soot levels in mine now that the Swirl valve is open permanently. After around 2 weeks of driving I still think the low end (under 1250 rpm) is smoother.

As said in my swirl valve thread it takes off easier in 2nd so maybe there is a better burn going on :smile:. Playing around today I took it down to 1200 in 4th and feathered the throttle and away it went, no vibration, so I have picked up another 100 vibration free rpm over and above what I picked up following the lift pump install..

 

[daemonus]

I am at work now, so i am full of ideas....So, time for stupid questions. Here i go...
We all blocked our EGR using blocking plates. But did anybody tried to redirect the gas directly into the exhaust pipe ?

Assuming what i said earlier is correct and the gas that was supossed to intoxicate our engine does alter the normal regime of the turbocharger, that precise quantity could be fed directly into the exhaust pipe, and the default regime of the turbocharger at idle would be restored, and so the MAF voltage would be correct. Very difficult for me to test this, as i dont have a garrage to work, but i am pretty confident there would be positive results.

Just some thoughts, based upon what i assumed it is correct. Same words go for this too....faulty tech info, but a healthy laugh .

 

[geeyoutoo]

I am at work now, so i am full of ideas....So, time for stupid questions. Here i go...
We all blocked our EGR using blocking plates. But did anybody tried to redirect the gas directly into the exhaust pipe ?

Assuming what i said earlier is correct and the gas that was supossed to intoxicate our engine does alter the normal regime of the turbocharger, that precise quantity could be fed directly into the exhaust pipe, and the default regime of the turbocharger at idle would be restored, and so the MAF voltage would be correct. Very difficult for me to test this, as i dont have a garrage to work, but i am pretty confident there would be positive results.

Just some thoughts, based upon what i assumed it is correct. Same words go for this too....faulty tech info, but a healthy laugh .

I've been going over the question for 20 minutes and I can't get a handle on it. The gas is coming from the exhaust manifold beside pot #4, then being fed into the inlet manifold via the EGR at very low speed and cruise at no/low load, so, where are you thinking of feeding it back into?

 

[Chaz]

There are quite a few sensors used in fuel control eg; the MAF, coolant temp, fuel temp, barometric pressure, TPS, engine and IP rpm. In our case, boost isn’t used because a MAF is much a more precise way of measuring intake air volume unlike on the Navara. The ECU uses a 3 dimensional map to control fuel delivery and engine speed based on the sensor inputs and it controls the IP accordingly, so by altering one of the sensor inputs – “the MAF voltage” - won’t necessarily change the speed of the engine, just the way the ECU manages it. We know the Patrol doesn’t use an oxygen sensor, so the ECU can’t adjust fuel delivery to correct mixture from the output like a closed loop petrol injection system. It only uses the air volume it sees coming in.

Personally, I’m convinced that reducing the MAF voltage has made a difference to the tailpipe smell and perhaps even the amount of smoke that it emits at idle. I can increase my MAF voltage at idle and the engine rpm doesn’t increase. Increasing it over the mid range makes the car feel much crisper with improved throttle response. I suspect that some of cheaper performance chips simply re-map the MAF voltage that the ECU reads.
I guess the main objective here is to eliminate fuel cut issues when they shouldn’t be happening, but a leaner idle won’t do any harm.

I have to wonder if the improvements found after blocking the EGR are partly a result of the MAF voltage increase, and lost when the resistor is fitted and the voltage reduced.

 

[Chaz]

I am at work now, so i am full of ideas....So, time for stupid questions. Here i go...
We all blocked our EGR using blocking plates. But did anybody tried to redirect the gas directly into the exhaust pipe ?

Assuming what i said earlier is correct and the gas that was supossed to intoxicate our engine does alter the normal regime of the turbocharger, that precise quantity could be fed directly into the exhaust pipe, and the default regime of the turbocharger at idle would be restored, and so the MAF voltage would be correct. Very difficult for me to test this, as i dont have a garrage to work, but i am pretty confident there would be positive results.

Just some thoughts, based upon what i assumed it is correct. Same words go for this too....faulty tech info, but a healthy laugh .

Take into consideration that the EGR valve is adjustable (by the ECU), so at some stage it will be closed. Releasing some exhaust manifold gas and pressure out through the exhaust pipe will only make the turbo less efficient unless you had similar control over it, like a waste gate.

 

[daemonus]

Google translation cannot provide a decent translation for POT. So i only can assume that pot means. Look at the picture attached.

 

[daemonus]

@Chaz - i thought the point of blocking the EGR valve was to keep the junk getting back into the engine. That thing is a gain IMO and cannot be lost if adjusting MAF voltage. Other bonuses like a more sensitive and powerfull engine at low rpm are altered, indeed. But they were bonuses...not the trophee itself. My thoughts.

I know ECu controlls the EGR, that is why i did not touch the control part. It's just a matter of pipe relocation. EGR functioning mode remains the same.


PS1. I am here to learn so i am open to mistakes . But i strongly belive that from stupid ideeas the great inventions were made....
PS2. So i take it that the question 'Why MAF voltage increases after EGR block?' remains still without a well argumented anwser.....

 

[whitie]

PS2. So i take it that the question 'Why MAF voltage increases after EGR block?' remains still without a well argumented anwser.....

What is going on is that a working EGR feeds spent exhaust gas into the intake system at idle which takes the place of healthy fresh air coming from the air filter and being measured by the MAF.

The same volume of air is ingested by the engine however it is now a mixture of fresh air and spent exhaust gas, the MAF is measuring the fresh air only. With a blocked EGR all air has to come from the air filter and the MAF will show an increase in fresh air intake.

Re the smell, as a diesel engine is already at its maximum "lean" state at idle and any "richening" of the mixture under the same condition will produce an increase in rpms, my best guess at what causes the smell is that the ECU is probably changing the injection timing due to the higher MAF reading which requires an associated change in the amount of fuel injected to keep the rpms stable at idle?

As Chaz mentioned, the main improvement in power / torque when the EGR is blocked are a result of the ECU seeing more air in the intake (higher MAF voltage) so it is free to add more fuel according to its 3D fuel mapping. Don't forget that the burn is also happening quicker now as well as there are no exhaust gasses in the combustion chamber so there would be a possible increase in torque due to the increased efficiency of the burn.

:cheers:

 

[JFF45]

Could an electronic load adjuster be used to get your MAF voltages back to where they should be after blocking the EGR?

The Jaycar Digital Fuel Adjuster accepts the MAF voltage signal at 128 load points between 0 & 5 volt and can adjust in 0.01v increments at any chosen load point.

Pics of mine for sale:

They cost ~$70 each in kit form. I'm looking for $70 the pair already assembled.

I now have an Xede processor that does ignition timing as well so no longer need these..

 

[geeyoutoo]

This is what Chaz Has/Had, I'm not electronically smart enough to build one so I went the FCD2 route. I can clip and unclip the voltage whereas Chaz can alter right through the range.

 

[Grogey]

What is going on is that a working EGR feeds spent exhaust gas into the intake system at idle which takes the place of healthy fresh air coming from the air filter and being measured by the MAF.

The same volume of air is ingested by the engine however it is now a mixture of fresh air and spent exhaust gas, the MAF is measuring the fresh air only. With a blocked EGR all air has to come from the air filter and the MAF will show an increase in fresh air intake.

This makes sense and daemonus's comment regarding a little extra exhaust through the turbo drawing in a little more air if at significnant volume would only add to this.

Re the smell, as a diesel engine is already at its maximum "lean" state at idle and any "richening" of the mixture under the same condition will produce an increase in rpms, makes sence

my best guess at what causes the smell is that the ECU is probably changing the injection timing due to the higher MAF reading which requires an associated change in the amount of fuel injected to keep the rpms stable at idle?
Can you expand a bit on how timing changes may cause a failure to burn all the diesel?

As Chaz mentioned, the main improvement in power / torque when the EGR is blocked are a result of the ECU seeing more air in the intake (higher MAF voltage) so it is free to add more fuel according to its 3D fuel mapping. Don't forget that the burn is also happening quicker now as well as there are no exhaust gasses in the combustion chamber so there would be a possible increase in torque due to the increased efficiency of the burn.

:cheers:

Hi Whitie,

in red as above.

Cheers Grogey

 

[JFF45]

The Jaycar items have been sold..

 

[whitie]

Hi Whitie,

"my best guess at what causes the smell is that the ECU is probably changing the injection timing due to the higher MAF reading which requires an associated change in the amount of fuel injected to keep the rpms stable at idle?"
Can you expand a bit on how timing changes may cause a failure to burn all the diesel?

in red as above.

Cheers Grogey

Hi Grogey, I still believe that all the diesel is being burnt but it may have a different smell to it due to when it is being injected and the quantity of fuel that is injected at that point to keep the idle rpm constant.

At the moment, I am finding it hard to think of any other plausible explanations hence my question to the forum

Cheers,
Whitie

 

[Grogey]

Hi Grogey, I still believe that all the diesel is being burnt but it may have a different smell to it due to when it is being injected and the quantity of fuel that is injected at that point to keep the idle rpm constant.

At the moment, I am finding it hard to think of any other plausible explanations hence my question to the forum

Cheers,
Whitie

A recent thread regarding a later model ZD30 Di piston failure included a post from the owner who mentioned a strange smell in the months prior to failure. He’d done over 240,000km from memory with no NADs. I’m wondering had his EGR system blocked with sludge and the blocked EGR was in effect creating the same changes we get with a blanking plate with respect to the MAF voltage.

If he had that much sludge it likely had also built up significantly in the induction manifold, the air/fuel ratio to the cyclinders was compromised, thus leading to a grenade type failure.

Speculation again but it’s a possible scenario.

Cheers

Grogey

PS - for the record i think my exhaust at idle smells funny. I've had the EGR blocked for about 10 to 11 months so i'm trying to remember how long i've noticed. I do think it would be over the same period.

 

[heyhey]

I believe smell of diesel has something to do with injection, either pattern, pressure, air-fuel ratio. You can smell signficant difference between older deisel engines, DIs, CRDs, Piezo injectors, etc. They are all diesel and some even turbo diesels, but even at idle they smell different. It could also be attributed to the CAT too.

I haven't ever noticed a change in smell to one particular vehicle and I've never had an engine faliure, so I can't expand into that area. I have changed exhausts, put on a bigger intercooler, NADS, had stuffed MAFs, etc and I've never noticed a change in smell. If there was a change attributed with the MAF, unpluggin it would soon give you a confirmation.

 

[daemonus]

Hey Groogey !

Interesting scenario and very possible one, i'd say. But i do have a clean intake manifold (water/meth injection), and the smell came up right in the second i first started the car after i blocked up the EGR. So it definately has something to do with it. The same smell i have it on my Hyundai Santa Fe 2007 CRDi, cold mornings. When i presume the EGR vave is ....closed. Could the smell be the result of "pure" burning ? (by that meaning only diesel and air is burnt, not junk exhaust gas). Unfortunately, i dont have a way to measure MAF readings (or what normal values would be), to see what happens.

:cheers:

 

[geeyoutoo]

A recent thread regarding a later model ZD30 Di piston failure included a post from the owner who mentioned a strange smell in the months prior to failure. He’d done over 240,000km from memory with no NADs. I’m wondering had his EGR system blocked with sludge and the blocked EGR was in effect creating the same changes we get with a blanking plate with respect to the MAF voltage.

If he had that much sludge it likely had also built up significantly in the induction manifold, the air/fuel ratio to the cyclinders was compromised, thus leading to a grenade type failure.

Speculation again but it’s a possible scenario.

Cheers

Grogey

PS - for the record i think my exhaust at idle smells funny. I've had the EGR blocked for about 10 to 11 months so i'm trying to remember how long i've noticed. I do think it would be over the same period.

I don't think there is too much speculation there mate, I have believed this been one of the contributing factors for quite some time. particularly on the #3 and #4 pot failures, of which mine was one. But I'm not sure of any link to smell, mine hasn't changed over the years and I have a very keen sense of smell (natures way of making up for being deaf).

Deamonus, "Pot" is old slang for cylinder here in Australia, not the herb you may have been thinking of .

 

[heyhey]

Also at first start in the morning, your turbo is not hot, so the air entering the engine is denser and would cause a leaner burn.

 

[daemonus]

@geeyoutoo - sorry to hear about your hearing impediment.
To be honest i did not think about the herb you mentioned - here weed is a more popular termn to refer to that plant, i have friends who "study" this plant, i prefer a good home made wine, or my friend Jack Daniel's or some good Palinka (Chaz can explain what palinka is).

And speaking of Chaz, i think his motto "Keepin' it clean!" in conjuction to the story that Groogey told us earlier makes A LOT OF SENSE.