Closing the EGR Valve *check first post for links*

[sierra]

Please excuse me if I seem blunt at times but I don't mean to be and I actually enjoy chatting about this stuff.

Are you are saying that when the manifold is at atmospheric[ambient] pressure or slightly above, 1psi, the flow will be reversed back through the EGR valve?
If so why? Are you assuming the exhaust will be less than that, negative relative to the manifold?
If there is more than 0-1psi of boost to cause flow from the modified source to the EGR valve then there would have been about twice that pressure from the exhaust in the same circumstances and not less than the manifold pressure as you speculate.

LR mentioned that feeding clean air instead of cooled exhaust will lower the EGT but surely that is part of the purpose of the EGR in the first place, to lower the combustion temperature by adding relatively inert gas? Also therefore, lowering the emissions in those circumstances.

[srb]

I love this thread!

[srb]

LR mentioned that feeding clean air instead of cooled exhaust will lower the EGT but surely that is part of the purpose of the EGR in the first place, to lower the combustion temperature by adding relatively inert gas? Also therefore, lowering the emissions in those circumstances.[/quote]

Yep this is what I understand to be true... But at the cost of carbon build!

[fraz91]

I've actually got my bluetooth OBDII adapter set to give me a readout on when the EGR is actually in operation (only what's commanded, not the actual). The EGR is closed under full open throttle (so full acceleration and full engine braking), but is open the rest of the time. How far it's open depends upon the boost pressure, and the more the boost goes up, the more the EGR closes.

There's no possible way for the EGR to push clean air through the exhaust to give better emissions. If this was the case, then the exhaust would have a breather on it at the start that sucked cold and clean air through to make the emissions look better.

[sierra]

I've actually got my bluetooth OBDII adapter set to give me a readout on when the EGR is actually in operation (only what's commanded, not the actual). The EGR is closed under full open throttle (so full acceleration and full engine braking), but is open the rest of the time. How far it's open depends upon the boost pressure, and the more the boost goes up, the more the EGR closes.

There's no possible way for the EGR to push clean air through the exhaust to give better emissions. If this was the case, then the exhaust would have a breather on it at the start that sucked cold and clean air through to make the emissions look better.

When you say the EGR is open do you mean the EGR valve or the throttle valve?

[coxy47]

All good mate i didnt take it that way. I think i was becoming unclear and that my comments were getting to the point where they would only create confusion.

The best way i can think of explaining it is that the air flow will try to reach a point of equilibrium. Air and all gases for that matter will expand to occupy the space that is available. In a closed air system this will either raise or lower the pressure to a certain absolute pressure regardless of the atmospheric pressure. In an open system (i.e. a system that is open to the atmosphere) the air will expand indefinitely until it is at an equal pressure with the atmosphere.

So in a perfect system where there is no resistance in either the egr or the exhaust, the exhaust flow will first equalise (each cycle it will go into a slight vacuum) the inlet manifold and then remain at atmospheric pressure as the exhaust pipe is an open system.

However in the actual system since there is resistance in the piping and exhaust. In my experience there appears that there is slightly more resistance in the standard exhaust then in the egr piping so the pressure equalises slightly above atmospheric. While the exhaust is still technically open, the flow rate of the gasses wont be high enough for this to behave as an ideal system.

Its not so much that the exhaust flow is reversed back through the egr valve its more that there is a point of equilibrium. Think of it like holding your finger over the end of a hose. When you partially cover, it causes the water to spray out at a higher velocity and there is a sudden jump of pressure in the hose. But this doesnt continue to get larger it reaches a point of equilibrium where the pressure builds up to a point where it forces the fluid out at the same rate as the hose can provide it to the end. This the point of equilibrium.

EDIT:This is the same principle as the egr only raising the manifold to slightly above atmospheric pressure except that the inlet manifold and associated egr piping acts as another cavity that must be filled and pressurised to equilibrium. It is also necessary to note that pressure is not constant through the system. It does vary at each point in an open system with respect to restriction points and pressure losses.

Long story short from the air intake to the end of the exhaust is one big system. Unfortunately the way in which the system reaches equilbrium is reasonably complex under egr operation as there is a portion of the system that recirculates through which makes the equilibrium pressures harder to represent at any point in the system. So the equilibrium pressure will be constant but different at each point. (i.e. the egr port will always be at the same pressure under equilibrium but the pressure post turbo will be lower but still constant)

With LRs mod in place it effectively makes the system behave as if the egr was always closed and the throttle is permanently open.

LR's point about the cool clean air lowering the egts is simply due to two reasons. First is that the exhaust gas will be a couple of hundred degrees hotter then the intake air regardless, though this will change depending on how hard your pushing, and secondly because the the clean air allows the diesel to burn more efficiently. Clean air will always burn more efficiently then air that has already been through one combustion cycle as some of the checmical bonds in the oxygen (which in air is in the form of O2) and have formed new compounds which arent broken down as easily such as CO2 etc. This means causes the engine to run in a more lean state which produces lower egts.

With regards to lowering emissions. The EGR system is designed to help reduce carbon monoxide in the exhaust (someone correct me if im wrong) by burning it a second time which is effective. However this also increases the concentration of other gases such as carbon dioxide. So with LRs mod the theory is that the clean air will reduce the concentration of the majority of emissions but it does slightly raise CO levels. Not sure if hes actually tested this but the theory is sound and in my opinion better overall.

Hope ive explained what im trying to get across more clearly and not made things worse with my long winded explanation

[coxy47]

Wow that took me a long time to write. Fraz is right about how the egr operates but it was never intended to push clean air through the system so that the exhaust gases are leaner. See my previous post

Well mostly right, the egr will open at idle at least in the ML . As the egr valve opens the throttle closes mostly so that exhaust gases are not pushed back through the intake system.

[sierra]

Wow that took me a long time to write. Fraz is right about how the egr operates but it was never intended to push clean air through the system so that the exhaust gases are leaner. See my previous post

Well mostly right, the egr will open at idle at least in the ML . As the egr valve opens the throttle closes mostly so that exhaust gases are not pushed back through the intake system.

I'll answer this one first and read the other one in the morning.
The throttle valve is there to cause lower pressure in the intake manifold so as to increase the flow of cooled exhaust gasses. Also to aid a clean shutdown.

It is not there to stop exhaust gas getting pushed back through the intake system. The engine at idle is flowing over 14L of air per second and nothing that flows through that piddly little EGR valve is going anywhere but straight down the manifold to the cylinders with that air.

[coxy47]

Fair point. I'm definitely wrong on that one. My apologies.

I do apologise if I've said anything else wrong as well in my previous few posts. It's not exactly unlikely I'd much rather be corrected then continue to be wrong while thinking I'm right.

[srb]

Yep clear as mud coxy!

Nar I see what your saying mate and I agree with most of it. I think?.... Can you run through that one last time?

[odie602r]

... and all that was going through my mind was 'is 16% increase in fuel usage a fair trade for no carbon in the manifold' ...

(BTW, I have now successfully tee-ed in a one way valve on MAP sensor line, thanks srb. Road trip tomorrow, so see if that restores the economy).

[srb]

... and all that was going through my mind was 'is 16% increase in fuel usage a fair trade for no carbon in the manifold' ...

(BTW, I have now successfully tee-ed in a one way valve on MAP sensor line, thanks srb. Road trip tomorrow, so see if that restores the economy).

Good luck mate and fingers crossed for ya!

[Tony]

Lets remind our selves why the EGR system is in place.

Basically the idea is to feed lower oxygen exhaust gas into the intake.

Our diesel EGR systems are designed to lower combustion temperature resulting in reducing emissions of NOx. This makes combustion less efficient and compromising economy and power. Diesel EGR as we are all aware increases soot production, this has been overcome in some cases with diesel particulate filters. (Has me buggered why the smaller diesels haven't adopted the idea) The EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine life.

FACT.......Engine manufacturers have refused to release real details of the effect of EGR on fuel economy, the EPA regulations of 2002 that led to the introduction of cooled EGR were associated with a 3% drop in engine efficiency.

What we see is lower Nox production with lower combustion temps, more fuel, more soot and higher EGTs

I find it fascinating some of us see higher fuel usage due to the EGR removal. More a tuning issue no doubt.

[srb]

I've actually got my bluetooth OBDII adapter set to give me a readout on when the EGR is actually in operation (only what's commanded, not the actual). The EGR is closed under full open throttle (so full acceleration and full engine braking), but is open the rest of the time. How far it's open depends upon the boost pressure, and the more the boost goes up, the more the EGR closes.

There's no possible way for the EGR to push clean air through the exhaust to give better emissions. If this was the case, then the exhaust would have a breather on it at the start that sucked cold and clean air through to make the emissions look better.

Nobody said the EGR would let clean air back through to the exhaust fraz? Did they? If so yes they are wrong.

I think you may be confused with LR's bypass? Have a read a page or two back mate.

I also have my Ultra gauge setup to see the EGR open and shut percentages. Mine is usually 100% open when I first start up in the mornings, then slowly shuts to around 45 - 69% driving around town. It does fluctuate with stop start driving and like you said it closes completely under full acceleration and engine braking. And it also opens up 100% at highway speeds. It's interesting to see it work under different conditions ay.

[srb]

Lets remind our selves why the EGR system in in place.

Basically the idea is to feed lower oxygen exhaust gas into the intake.

Our diesel EGR systems are designed to lower combustion temperature resulting in reducing emissions of NOx. This makes combustion less efficient and compromising economy and power. Diesel EGR as we are all aware increases soot production, this has been overcome in some cases with diesel particulate filters. (Has me buggered why the smaller diesels haven't adopted the idea) The EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine life.

FACT.......Engine manufacturers have refused to release real details of the effect of EGR on fuel economy, the EPA regulations of 2002 that led to the introduction of cooled EGR were associated with a 3% drop in engine efficiency.

What we see is lower Nox production with lower combustion temps, more fuel, more soot and higher EGTs

I find it fascinating some of us see higher fuel usage due to the EGR removal. More a tuning issue no doubt.

Tony, yeah I find it almost comical that the EPA go to all this effort to place higher emission standards and force car manufactures to come up with cheap crap ideas like our EGR systems that at the end of the day cause the vehicle to run less efficient and end up polluting the environment worse that if we didn't have the EGR system in the first place! I mean you just have to wonder why they don't think of that?

[Longranger1]

Tony has nailed it. The main purpose of the EGR system is to lower NOx emissions - that's it.

By adding exhaust gas into the intake charge air only serves to lower combustion temperature which has the effect of reducing NOx produced.

It also has the effect of increasing other emissions such as CO, HC and particulates. This is dealt with to a degree by adding a catalytic converter and in a lot of modern diesels, a particulate filter.

I think there some confusion that by lowering combustion temperature it also lowers the EGT as well. This is an incorrect assumption, as the burn is delayed to the point that the process is continuing when the exhaust valve opens.

A cleaner, more complete burn means more of the heat energy produced in the combustion process is utilised in pushing that piston down the bore. As a result, there is less residual heat remaining to be blown out through the exhaust valve (despite the actual combustion temperature being higher). This is why (at least to a point) increasing boost pressure will lower EGT's.

Steve is spot on with engines becoming less efficient as they become congested with crud building up in the intake. When the engine is new all is well, but when the miles pile up, well, we all know what happens. From a NOx perspective, it would probably reduce emissions over time as the engine became less efficient,at the expense of greatly increased other pollutants and fuel efficiency loss.

I'm no engineer, but that's my take on it. Happy to be corrected.

[coxy47]

Damnit. I knew it wasn't CO I meant. Thanks for that Tony and LR. I'm sorry if I've confused anyone worse. My explanation got a little out of hand and was wrong in parts.

I agree with your take on it LR. I can't see how the increased fuel usage and smoke over time caused by having an egr system in a diesel is better for the environment the slightly higher NOx levels.

[coxy47]

... and all that was going through my mind was 'is 16% increase in fuel usage a fair trade for no carbon in the manifold' ...

(BTW, I have now successfully tee-ed in a one way valve on MAP sensor line, thanks srb. Road trip tomorrow, so see if that restores the economy).

sorry mate we made it a little hard for you. I hope the map tee in the MAP line works for you. I think overall it is a reasonable trade as that's what I got and am still running the egr blank.

[sierra]

... and all that was going through my mind was 'is 16% increase in fuel usage a fair trade for no carbon in the manifold' ...

(BTW, I have now successfully tee-ed in a one way valve on MAP sensor line, thanks srb. Road trip tomorrow, so see if that restores the economy).

No, 16% higher fuel consumption isn't a fair trade, especially since most of us seem to have gained better economy and earlier boost.
I'm pleased you're trying the one way valve mod and looking forward to hearing how it works out. I'm sure srb made it clear which way around it goes, which is critical.

If you still have lousy fuel consumption you could try disconnecting the throttle valve for a tank to see what effect that has?
You can use the scanguage to remove the CEL if it irritates you but it shouldn't do any more than that and give you a lumpy shut down, less engine braking too.

[sierra]

Fair point. I'm definitely wrong on that one. My apologies.

I do apologise if I've said anything else wrong as well in my previous few posts. It's not exactly unlikely I'd much rather be corrected then continue to be wrong while thinking I'm right.

No need to apologise. I'm surprised you haven't got the squits from being contradicted.
I didn't appreciate that the lower combustion temps from introducing cooled exhaust would actually increase the exhaust temp but what LR said made sense, as did higher boost lowering them and too much fuel raising them.
That can't be good for the valves.

[sierra]

I also have my Ultra gauge setup to see the EGR open and shut percentages. Mine is usually 100% open when I first start up in the mornings, then slowly shuts to around 45 - 69% driving around town. It does fluctuate with stop start driving and like you said it closes completely under full acceleration and engine braking. And it also opens up 100% at highway speeds. It's interesting to see it work under different conditions ay.

Srb,
I asked Fraz91 the same question.
When you say the EGR being open or closed and the % do you mean the EGR valve that lets the cooled exhaust in or the throttle valve that limits the air?

[Longranger1]

I also have my Ultra gauge setup to see the EGR open and shut percentages. Mine is usually 100% open when I first start up in the mornings, then slowly shuts to around 45 - 69% driving around town. It does fluctuate with stop start driving and like you said it closes completely under full acceleration and engine braking. And it also opens up 100% at highway speeds. It's interesting to see it work under different conditions ay.

Srb,
I asked Fraz91 the same question.
When you say the EGR being open or closed and the % do you mean the EGR valve that lets the cooled exhaust in or the throttle valve that limits the air?

Sierra, if you have an Ultraguage you can see in real time what the EGR valve opening percentages are. Yes, it is exactly as you say - the EGR valve opening percentages and consequent gas flow. There is also an Ultraguage function which shows the percentage of error in relation to the throttle valve. The throttle valve and the EGR valve work together and if one is out of step with the other then this will show as a percentage of error.

[odie602r]

... and all that was going through my mind was 'is 16% increase in fuel usage a fair trade for no carbon in the manifold' ...

(BTW, I have now successfully tee-ed in a one way valve on MAP sensor line, thanks srb. Road trip tomorrow, so see if that restores the economy).

No, 16% higher fuel consumption isn't a fair trade, especially since most of us seem to have gained better economy and earlier boost.
I'm pleased you're trying the one way valve mod and looking forward to hearing how it works out. I'm sure srb made it clear which way around it goes, which is critical.

If you still have lousy fuel consumption you could try disconnecting the throttle valve for a tank to see what effect that has?
You can use the scanguage to remove the CEL if it irritates you but it shouldn't do any more than that and give you a lumpy shut down, less engine braking too.

Man, that's frustrating, that's for sure. Most people put in the blank and get an improvement - I put it in and it goes the other way. Still can't understand why it would do different things with different Triton's. I fill up the tank tomorrow and will see true economy again then, but it hasn't brought a smile to my face yet. Is there any logical reason why it isn't constant on every vehicle?

Yeah, I'm pretty sure the one way valve is the right way around - so that the direction of air is into the vacuum hose.

If fuel economy is still around 11L/100kms I'll slide the EGR blank out for the return trip and directly compare. Won't pull the throttle valve yet for two reasons 1. Don't know where it is 2. The scan gauge hasn't arrived yet

Do I need to block the one way valve in MAP line if I slide out the EGR blank fornthe return trip?

Ben

[coxy47]

Man, that's frustrating, that's for sure. Most people put in the blank and get an improvement - I put it in and it goes the other way. Still can't understand why it would do different things with different Triton's. I fill up the tank tomorrow and will see true economy again then, but it hasn't brought a smile to my face yet. Is there any logical reason why it isn't constant on every vehicle?

Yeah, I'm pretty sure the one way valve is the right way around - so that the direction of air is into the vacuum hose.

If fuel economy is still around 11L/100kms I'll slide the EGR blank out for the return trip and directly compare. Won't pull the throttle valve yet for two reasons 1. Don't know where it is 2. The scan gauge hasn't arrived yet

Do I need to block the one way valve in MAP line if I slide out the EGR blank for the return trip?

Ben

No you shouldnt need to block the one way valve but I would still take it out to be sure.

Im sorry to hear your having the same troubles that i was. I still think its worth it, just need to go down one of the other paths to rectify the problem . There are a few theories as to why some tritons are worse then others but i dont think there is a definite answer.

[odie602r]

Hey another question - sorry guys! If it works out that the EGR blank increases fuel economy as it has done initially, will a catch can in isolation provide enough protection to eliminate carbon buildup?

One more, and Tony may be able to best answer this - will a ChipIT chip restore whatever the blank has done to my bus?