Why EGR valve got so popular even if it create more harm than good? 1

[Nico3d3]

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?

 

[BrianPetersen]

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.

 

[ivymike]

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.

 

[JSteve2]

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.

 

[JWaterstreet]

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.

 

[SomptingGuy]

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

- Steve

 

[ivymike]

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.

 

[izzmus]

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.