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Why EGR valve got so popular even if it create more harm than good?

Why EGR valve got so popular even if it create more harm than good?

Why EGR valve got so popular even if it create more harm than good?

(OP)
Everything is in the title. It seem that in almost all diesel engine, the EGR valve is clogging the intake until there's so much restriction that the engine begin to smoke a lot, starving for air. Next thing you learn, your engine is creating even more pollution than it would've create without any EGR valve. Why every constructors are still using such a crude system?

RE: Why EGR valve got so popular even if it create more harm than good?

Huh?

What Diesels have EGR?

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Why EGR valve got so popular even if it create more harm than good?

To meet emission standards.
See the link below for some information.
http://www.myturbodiesel.com/1000q/egr.htm

On my VW diesel, I used a vag-com to minimize the EGR flow.  I have never had a problem with intake goo; however, I only have 110,000 miles on the car.  In addition, I suspect that I am pumping a little more pollution out than a unmodified computer controlled TDI VW; however probably much less pollution than a TDI with a fouled manifold.

      

RE: Why EGR valve got so popular even if it create more harm than good?

Heavy duty diesels (except Caterpillar) have used cooled EGR since 2002, in order to meet emission regulations.
Light duty European & Asian diesels have used cooled EGR since the late 90's, also to meet emission regulations.  Any light duty diesels sold in the US since ~2002 have also used cooled EGR to meet emission regulations.
I'm sure there are better informed experts on diesel combustion in this forum than myself, but I'll do my best to explain.
The main purpose of EGR is to dilute the mixture in the zone where combustion is occuring (of course it dilutes the mixture everywhere, but the zone of combustion is where it matters).  The purpose of dilution is to reduce peak temperature, by adding inert matter mixed with the reactants, that absorbs heat without adding to the heat release.  NOx formation is a strong function of peak temperature, which is why this strategy is very effective.
The purpose of cooling the EGR is to increase the density of the inert matter, so the manifold and cylinder pressures can be reduced for given EGR mass flow rate.  Also, this not only reduces the peak gas temperatures, thereby helping with NOx reduction vs non-cooled EGR, it also reduces the peak temperatures and thermal loading on critical components like pistons and exhaust valves.
EGR is now a fact of life for diesel engines in tightly emission regulated markets.  Increasingly, it will also become the norm for high power density (i.e. boosted) spark ignited engines in these markets also.

RE: Why EGR valve got so popular even if it create more harm than good?

(OP)
Zapster, I have a VW diesel too, I had to reprogram the ECU to deactivate the EGR because my intake was completely clogged. I used the vag-com adaptation like you did on your car, for a while, but I learned later that it almost doesn't change anything if you only use vag-com to tamper with the EGR. You need to reprogram the ECU, if you want to make sure you won't get any intake clogging. This is usually done when you add a performance chip to the car.

I know it is there to reduce NOx emission but the point is that it's doing more harm than good. Why is it still necessary? Every modern diesel use urea aftertreatment to remove NOx so it seem that the EGR valve is redundant.

RE: Why EGR valve got so popular even if it create more harm than good?

What Diesels have EGR?

Pretty much all of them made now. Well for automotive applications anyway.
EGR is a great way to ruin HP and fuel economy. It is counter to anything that is done to increase power in a reciprocating internal combustion engine.
It is done to remove oxygen and cool the combustion process. To reduce Nitrous oxides. I guess I better stop here.  

RE: Why EGR valve got so popular even if it create more harm than good?

"Every modern diesel use urea aftertreatment to remove NOx"

Not true.  For heavy duty diesels, there are two NOx reduction strategies: urea or EGR.  Broadly speaking, USA companies favour urea; Europeans favour EGR.

Diesel engine manufacturers are bound by legislation.

- Steve

RE: Why EGR valve got so popular even if it create more harm than good?

"USA companies favour urea; Europeans favour EGR."
Hmmn, last time I checked, it was the other way around.  Have things changed since 2007?

 

RE: Why EGR valve got so popular even if it create more harm than good?

Maybe I got it the wrong way around (?).  But there are two competing approaches to the same legislative problem.

- Steve

RE: Why EGR valve got so popular even if it create more harm than good?

... or maybe I'm thinking of the future rather than the present (?).

- Steve

RE: Why EGR valve got so popular even if it create more harm than good?

(OP)
Nobody ever tried water/methanol injection to reduce combustion temperature? It should be simple enough, just use a bigger windshield washer fluid reservoir and inject the washer fluid in the intake. Washer fluid is composed of methanol and water... The water would also help the intercooler as its evaporation would cool down the airstream. The methanol would probably help create a more complete combustion, reducing black smoke.

RE: Why EGR valve got so popular even if it create more harm than good?

at this moment most european truck manufacturers use urea to reduce emissions (since it is cheaper and less technically complicated), but when more stringent emission regulations are introduced EGR and DPF will be unavoidable. EGR nowadays is restricted to areas (city centres)where extra emission regulations sometimes are called for.

RE: Why EGR valve got so popular even if it create more harm than good?

Nico3d3

How will adding more fuel reduce black smoke.

You obviously live in a cold climate and presume everyone else does.

Water injection may help to remove carbon deposits, depending on where they are.

A small siphoning problem or excessive flow can cause hydraulic lock in a diesel a lot easier than it does with a spark ignition engine.

It sounds like a decoke of the EGR area should be a regular service item like changing oil and filters. My car (not diesel) actually has a fine mesh filter on the EGR supply.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Why EGR valve got so popular even if it create more harm than good?

(OP)
What makes you believe I live in a cold climate? Maybe the addition of methanol to the water will prevent it from freezing but that was not the main goal. I thought methanol would act as an accelerant promoting a more complete combustion. Kind of like some people are doing with propane injection on their diesel.

RE: Why EGR valve got so popular even if it create more harm than good?

If you can catch it before the EGR valve and/or passages become compleatly clogged, water injection is an effective way to remove deposits. Principle of operation is the same for SI and CI engines. --------Phil

RE: Why EGR valve got so popular even if it create more harm than good?

Smokey44211, I thought that the way water effectively removed carbon deposits was when it flashes on the deposits.  I can't picture adding so much water that it flashes downstream of the EGR valve.        

RE: Why EGR valve got so popular even if it create more harm than good?

In warm climates we simply use water and detergent in windscreen washers so your presumption of the normal content was in fact presumptuous.

Adding extra fuel to a diesel at full throttle will overfuel and result in black smoke. Alcohol is a fuel and consumes oxygen as it burns.

Alcohol in the water of a water injection system is useful to prevent the growth of algae which can block nozzles.

Water injection is very effective at removing coke from the chamber, but not from upstream of the inlet valve.

 

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Why EGR valve got so popular even if it create more harm than good?

On the latest-generation diesel engines (example: North American specification 2009 VW Jetta TDI) they are using a low-pressure EGR that takes the exhaust from after the particulate filter, which ought to solve the clogging issue.

RE: Why EGR valve got so popular even if it create more harm than good?

...possibly with the downside of a sulphuric/nitric acid ingestion issue, depending on how the dpf is catalyzed.
 

RE: Why EGR valve got so popular even if it create more harm than good?

With ultra-low-sulfur diesel fuel, the amount of sulfur oxides in the exhaust ought to be extremely low. The temperature in the DPF is high enough to be well beyond the temperature that any of this stuff can condense into an acid.

RE: Why EGR valve got so popular even if it create more harm than good?

Yes, having ULSD is critical.  A bad batch of fuel (one tank) might be enough to destroy an engine.  The acid  doesn't condense in the DPF necessarily, but rather in the turbocharger itself (if temperature&pressure reach the right points) and in the aftercooler, from where it blows into the cylinders.  Even with ULSD some amount of acid will be formed.

RE: Why EGR valve got so popular even if it create more harm than good?

EGR provides a handy low-oxygen stream on the engine to reduce NOx. In a modern engine, EGR will not cause buildup, and even if something is not working correctly and there is buildup on the EGR valve, it may choke EGR flow but will not choke the intake. It seems that you are talking about systems that are old or that require maintenance.

Even Caterpillar added EGR to their engines beginning in 2007. In the future, it's likely that everyone will have both EGR and aftertreatment, although there are more aftertreatment schemes than just the urea-based ones.

RE: Why EGR valve got so popular even if it create more harm than good?

I work in the heavy truck industry.  The 2010 EPA regs are creating a major stir, with most manufacturers of heavy diesels electing to use Selective Catalytic Reduction (urea injection) to meet the stringent NOx regs.  These engines will also use cooled EGR, along with diesel particulate filters required since 2007.

Truck stops all across the US are gearing up for the urea infrastructure.

Once manufacturer (Navistar) will use only cooled EGR to meet the regs, based on techniques developed by MAN in Germany.

Regarding the comment about Caterpillar, the poster may not realize that they announced last year they are ceasing production of on-road diesel engines beginning in 2010....  They were the last to hold out using cooled EGR, and attempted to meet the 2007 regs using adaptations to their ACERT technology, but fell behind other manufacturers (e.g. Cummins) and lost market share as a result.

RE: Why EGR valve got so popular even if it create more harm than good?

You can add the TWC to the list of expensive, anti-engineering nasties that our governments have legislated in.

- Steve

RE: Why EGR valve got so popular even if it create more harm than good?

It's true that Cat lost market share and announced that they would stop selling on-hwy engines in the US in 2010... but it was not a technological problem that caused the decision.  The decision was based on their assessment of the truck engine market and how well a "high tech" engine would fit into truck OEM's plans in the future.  With consolidation and vertical integration in the truck industry, the pie was not big enough anymore.
 

RE: Why EGR valve got so popular even if it create more harm than good?

I do not see how water will eliminate intake carbon problems.

I recall spending two hours scraping about a half liter of carbon from my TDI intake manifold.  The port passages could barely flow any air and the plenum was likewise nearly solid with carbon.

In the combustion chamber, I could see water helping.  That is not where the problem is occurring, though.

 

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