Diesel Engine Design Fault?

[Thermal]

I own a petrol Avensis, but am I right in concluding that there is a design problem in modern diesel engines?

I can see the need for exhaust gas to be re-circulated back into the inlet in order to re-burn what's left in it, to comply with emission regulations.

However, since the valve is placed into the exhaust path, a diesel engine designer can expect that unburned fuel, soot and carbon pass through this EGR valve.

Shouldn't this EGR valve have been designed in such a way that these waste products do not clog up this valve?

I've owned diesel cars before, in times when particle filters or catalytic converters didn't exist yet, did 100's of thousands of Kms with them, and I never ever needed to clean any parts of the exhaust.

OK, you can blame me for the climate change then, but I find it amazing how many EGR valve related problems are mentioned on the various forums, with a device that is supposed to improve emissions.

Why on earth should deposits now pick the EGR valve and clog it?

Can anyone explain that?

[t-spiritpete]

I own a petrol Avensis, but am I right in concluding that there is a design problem in modern diesel engines?

I can see the need for exhaust gas to be re-circulated back into the inlet in order to re-burn what's left in it, to comply with emission regulations.

However, since the valve is placed into the exhaust path, a diesel engine designer can expect that unburned fuel, soot and carbon pass through this EGR valve.

Shouldn't this EGR valve have been designed in such a way that these waste products do not clog up this valve?

I've owned diesel cars before, in times when particle filters or catalytic converters didn't exist yet, did 100's of thousands of Kms with them, and I never ever needed to clean any parts of the exhaust.

OK, you can blame me for the climate change then, but I find it amazing how many EGR valve related problems are mentioned on the various forums, with a device that is supposed to improve emissions.

Why on earth should deposits now pick the EGR valve and clog it?

Can anyone explain that?

Hi Thermal, i made a comment about this a few weeks ago and I can only speak about the Toyota 2.2d4d EGR valve, when the valve is removed and stripped down you will find that the internals of the casting is very rough inside. It is in my humble opinion that if this was a polished surface and the route to the valve seating was made better then I doubt that the carbon build up would occur so soon, the soot and carbon would have a fast and unrestricted route through. This goes back to my days of port polishing on cylinder heads on Minis and Ford Escorts Rs etc, ..... in worked in them days so why would the theory not apply now, anyway now my car is out of warranty I shall see what I can do about polishing inside the EGR valve later this year.

Best regards Pete.

[igormus]

I own a petrol Avensis, but am I right in concluding that there is a design problem in modern diesel engines?

I can see the need for exhaust gas to be re-circulated back into the inlet in order to re-burn what's left in it, to comply with emission regulations.

However, since the valve is placed into the exhaust path, a diesel engine designer can expect that unburned fuel, soot and carbon pass through this EGR valve.

Shouldn't this EGR valve have been designed in such a way that these waste products do not clog up this valve?

I've owned diesel cars before, in times when particle filters or catalytic converters didn't exist yet, did 100's of thousands of Kms with them, and I never ever needed to clean any parts of the exhaust.

OK, you can blame me for the climate change then, but I find it amazing how many EGR valve related problems are mentioned on the various forums, with a device that is supposed to improve emissions.

Why on earth should deposits now pick the EGR valve and clog it?

Can anyone explain that?

hi mate

1. each mordern diesel engine good performance is subject to regular and time maintenance + all consumables change; this demands money, as we know; But in order to save money and own a mordern car (!!!) the human starts to ignore this maintenance schedule leading to many issues criating etc ;

2. Yes the EGR is a part of an exhaust system and responsible for emmission. The statistics shows the more issues with burning process the more issues with EGR valve (the reason is as per item No1);

3. Yes the cast iron or Al after foundry have a rough surface that accumulates all deposits after burning process giving lack of power; etc etc ---the gas passing canals (on recirculation) can not be made widely cos this leads to the recirculation gas pressure dropping giving more deposits originating due to poor burning process -- so the only one remedy is to suct this gas under the pressure (designed) with all carbons into the cyliinder + regulary clean these iinternal canals.

Cheers/Igor

[Thermal]

...the casting is very rough inside.

Hi Pete,

If it's that simple, the roughness of the inside of the valve and restrictions in the inlet path, it is a design flaw, and it's amazing that after all these years Toyota have not come up with a better part.

It must be a time consuming and very dirty job to clean that valve and intake again and again, let alone the costs of it when done by a garage, and I also wonder what is given back to the environment by those who do the job themselves.

I had to take the exhaust manifold off of my Mercedes 220D (560.000 Km) once, because of a snapped bolt.

It was black inside, smooth but just black.

I had a Peugeot 405 diesel (>360.000 Km) that blew a head gasket twice during its life.

The exhaust was black inside, just black.

Must be a design fault, and Toyota should do something about it.

Not just replace the EGR's under warranty until that ends.

[Parts-King]

You cannot say it is a design fault as such, when cars didnt have EGR valves, the emissions they put out were much higher, then came along EURO 1V compliance and things had to change. The EGR valves basic function is to reduce NOX emissions, this is done by introducing CO2 to cool the exhaust gas. The EGR valve is designed to open and close at appropriate moments but it can get sticky or even stuck! If it is stuck open, you'd find the engine will have a rough idle or stall. If closed the combustion chamber temperatures will rise under load and you will get a knocking or pinking type noise. Add to all this a turbo, and if the EGR valve sticks closed and you have very high exhaust gas temperatures, then you could be in for turbo trouble too! Having a smooth surfaced EGR valve would have very little effect, if it was a "Cure all" then everbody would have them, they don't, EGR valves are a way to get emissions and NOx levels down, if they didnt have to fit them, they would'nt. Just look at any diesel engine in third world countries, you dont have any emission regulations so the manufacturers provide just basic diesel engines, many still have mechanical fuel pumps!

Good quality oils and fuels help, as does regular maintenance, so use the correct grade oil for your car, use a quality brand, this will help reduce wear AND lower engine temperatures

Kingo

EDIT Anyone thinking of cleaning their EGR valve should take adequate precautions, wear suitable gloves and mask, avoid breathing any dust/fumes when cleaning it or blowing any dust out. Some nasty things happen to carbon at very high temperatures and you should take extra care

[t-spiritpete]

You cannot say it is a design fault as such, when cars didnt have EGR valves, the emissions they put out were much higher, then came along EURO 1V compliance and things had to change. The EGR valves basic function is to reduce NOX emissions, this is done by introducing CO2 to cool the exhaust gas. The EGR valve is designed to open and close at appropriate moments but it can get sticky or even stuck! If it is stuck open, you'd find the engine will have a rough idle or stall. If closed the combustion chamber temperatures will rise under load and you will get a knocking or pinking type noise. Add to all this a turbo, and if the EGR valve sticks closed and you have very high exhaust gas temperatures, then you could be in for turbo trouble too! Having a smooth surfaced EGR valve would have very little effect, if it was a "Cure all" then everbody would have them, they don't, EGR valves are a way to get emissions and NOx levels down, if they didnt have to fit them, they would'nt. Just look at any diesel engine in third world countries, you dont have any emission regulations so the manufacturers provide just basic diesel engines, many still have mechanical fuel pumps!

Good quality oils and fuels help, as does regular maintenance, so use the correct grade oil for your car, use a quality brand, this will help reduce wear AND lower engine temperatures

Kingo

EDIT Anyone thinking of cleaning their EGR valve should take adequate precautions, wear suitable gloves and mask, avoid breathing any dust/fumes when cleaning it or blowing any dust out. Some nasty things happen to carbon at very high temperatures and you should take extra care

With all due respect to you Kingo, how do know if it would have little effect if it hasn't been tried, polishing may have little effect on the performance of the EGR valve but I believe it would help in the reduction of carbon build up and so lead to less attention being req'd. As to the comment about "3rd world" engines .... any engine built in the Eurozone has to meet at least euro 5 standards not matter where in the world it is being supplied to and that is causing the "3rd world" a big headache if you talk to engineers from Perkins engine to name just one company.

Best regards Pete.

[Parts-King]

What I'm saying Pete is that the EGR valve and its various issues have been around for a long time, if it was as simple as making a polished version, then that would have been done and any new valves would be the polished variety. They are not because it has little effect. I am well aware of the various engine standards, the point I was trying to make is that from EURO 1V onwards, EGR valves have to be used to lower NOx emissions, if the manufacturer didnt have to fit them, they would'nt, hence the earlier comments about older model cars only having a little soot in them. The UK has some of the better fuel in Europe, some of our European friends have had really bad problems, specifically related to poor fuel quality, and if you use the higher quality diesel available in this country, top quality oil, regular servicing etc, then you can reduce some of the effects of EGR soot build up. The vast majority of customers dont suffer badly with EGR issues, but it certainly does cause a problem for a minority of people

Kingo

[t-spiritpete]

What I'm saying Pete is that the EGR valve and its various issues have been around for a long time, if it was as simple as making a polished version, then that would have been done and any new valves would be the polished variety. They are not because it has little effect. I am well aware of the various engine standards, the point I was trying to make is that from EURO 1V onwards, EGR valves have to be used to lower NOx emissions, if the manufacturer didnt have to fit them, they would'nt, hence the earlier comments about older model cars only having a little soot in them. The UK has some of the better fuel in Europe, some of our European friends have had really bad problems, specifically related to poor fuel quality, and if you use the higher quality diesel available in this country, top quality oil, regular servicing etc, then you can reduce some of the effects of EGR soot build up. The vast majority of customers dont suffer badly with EGR issues, but it certainly does cause a problem for a minority of people

Kingo

Hi Kingo,

I never disagree with a man who knows what he is talking about and after reading a lot of your replies you are in that bracket mate but ...... I would like to wait and see if my idea does really work on my engine type, the 2.2 D4D. It certainly can't do any harm and I don't think Toyota have actually tried it as yet. Sometimes the simple things are overlooked and I have modified many engines in my career to great effect to prove that point.

Thanks again for the informed reply, best regards as always, Pete.

[Parts-King]

Just take care when cleaning it Pete, cheers

Kingo

[Thermal]

Co2 ---> NoX ...

@Kingo

I know what the EGR valve is supposed to do, but I have to agree with Pete that from an aerodynamics point of view it is not an advantage for an air flow to pass over rough surfaces.

Roughness causes turbulence, which causes drag.

And in an EGR housing, where the airflow is highly contaminated with nasty substances and particles, such particles will stick to the roughness easily, build up over time and clogging it entirely in the end and lead to the dreaded performance problems and cleaning job.

That's just a matter of time.

If it were perfectly smooth inside... maybe not.

It seems so obvious.

[t-spiritpete]

Just take care when cleaning it Pete, cheers

Kingo

Cheers mate will do!

Now if I could just get hold of an old one from someone in the trade, ;) .... I could experiment on the old casting!!:D

Pete.

[Parts-King]

Co2 ---> NoX ...

@Kingo

I know what the EGR valve is supposed to do, but I have to agree with Pete that from an aerodynamics point of view it is not an advantage for an air flow to pass over rough surfaces.

Roughness causes turbulence, which causes drag.

And in an EGR housing, where the airflow is highly contaminated with nasty substances and particles, such particles will stick to the roughness easily, build up over time and clogging it entirely in the end and lead to the dreaded performance problems and cleaning job.

That's just a matter of time.

If it were perfectly smooth inside... maybe not.

It seems so obvious.

I hear what you are saying, I am no expert in EGR technology, I just know a little of the theory on how they work. In some instances in engineering, a rough airflow is desirable, like the dimples on a golf ball (I'm not sure its a good example but lets go with it for now) Golf balls have dimples to reduce drag and create a thinner wake when the ball is going through the air. If it was a simple case of say chroming the EGR valve, would that affect the way the EGR valve worked? I don't know is the honest answer, but I'm sure that if that was the case, then EGR valves would be made like that from the factory. There are far greater minds than mine making these design decisions :D:

Kingo

[Thermal]

...the dimples on a golf ball ...

Nice one. :) You could have tried "shark skin" as well.

I think discussing aerodynamics is far beyond the scope of this forum, but allow me to say that airflow manipulation of surfaces is really high-tech business.

See for instance laminar flow manipulation on aircraft wings.

Applied on the EGR case, that would mean a very carefully crafted "roughness" of a specific pattern and on specific points of the EGR's interior, where the shape and size would not obstruct the airflow and have a self-cleaning effect.

Such a design would probably make an EGR valve extremely expensive.

From the pictures I've seen, it's just a rough cheap casting.

In aviation, the use of such a sub-standard device would be prohibited.

[caveman_si]

...the dimples on a golf ball ...

Nice one. :) You could have tried "shark skin" as well.

I think discussing aerodynamics is far beyond the scope of this forum, but allow me to say that airflow manipulation of surfaces is really high-tech business.

See for instance laminar flow manipulation on aircraft wings.

Applied on the EGR case, that would mean a very carefully crafted "roughness" of a specific pattern and on specific points of the EGR's interior, where the shape and size would not obstruct the airflow and have a self-cleaning effect.

Such a design would probably make an EGR valve extremely expensive.

From the pictures I've seen, it's just a rough cheap casting.

In aviation, the use of such a sub-standard device would be prohibited.

Thermal if you are talking about manipulation of boundary layer flow depending on the exact flow you want as long as there is an even average roughness this can provide exactlly the same benifit as an ordered roughess.

Or it can give you the same or better cost benefit taking into account the extra cost involved in the higher manufacturing costs.

If you want to know more about boundary layer flow maninpulation have a look for "ribblets" this surface finish have been banned on some classes of high performance yatch racing (americas cup i think) and most recently has been banned from being on swim suits for competitons so we might never see michael phelps world records broken as he wore a fast suit.

AS for the use of "sub standard" parts in aviation, i think you;ll find the aero industry gets away with much finer tolerances on if stuff works for a while or not due to the regimented service schedules. Concorde is a prime example, Im lead to believe if it had to meet a standard car or even standard for the aero industy service shedule it would have ceased to be in service long before it did due to major malfunction.But it had a very rigorus service shedule that kept it flying safetly for years. But thats going off topic.

Personally I think a smoothed surface may help in the egr. Not because of the improved airflows, but because a smoother surface presents less spikes/ rough bits for soot to condense on and start to form layers of carbon so would slow down the rate of initial carbon formation. Once a layer starts to form no surface finish would have much of an effect.

As ive mentioned on another thread I think to improve the air flow in the manifold you need to insert directly under the valve a curved piece to make the bit below the valve flow better instead of being square. This is of course assumeing that the designers of the manifold didnt leave the bit of the engine under the egr square to induce a higly tubulent mixing regime when the valve is open so there is an even spread of the exhaust gas into the inlet manifold and even distribution to all of the cylinders.

If I had access to metal work tools I would have had a piece done and be testing it in the car by now.

[Thermal]

... the regimented service schedules.

True, and inspection cycles.

But even then, I could provide a link here to an official site that lists malfunctions and design faults in modern passenger aircraft, which Concorde was not, but I won't.

If you're familiar with aeronautics you'll probably know which one I mean.

And if you happen to own an airplane, you certainly will.

But back OT, wait what t-spiritpete can achieve, modifying an EGR.

P.S.

As said in my 1st. post, I own a petrol AV, because of all this.

I hope that this topic contributes to a smooth- and non-clogging EGR, should my next car be a Toyota diesel again.

[acetip]

... the regimented service schedules.

True, and inspection cycles.

But even then, I could provide a link here to an official site that lists malfunctions and design faults in modern passenger aircraft, which Concorde was not, but I won't.

If you're familiar with aeronautics you'll probably know which one I mean.

And if you happen to own an airplane, you certainly will.

But back OT, wait what t-spiritpete can achieve, modifying an EGR.

P.S.

As said in my 1st. post, I own a petrol AV, because of all this.

I hope that this topic contributes to a smooth- and non-clogging EGR, should my next car be a Toyota diesel again.

has anyone tried BG44K & BG2441, there are favorable reports on these two additives for cleanig carboned up diesels & petrol engines.