SCR vs EGR

Both of em to reduce NOx pollution to save our glory California.
here is some theory of combustion.
To increase power of combustion from same amount of fuel used you need to increase temperature of combustion by inducing more oxygen . But it will increase NOx in exhaust gases.
EGR designed to reroute some exhaust gases to replace O2 and decrease combustion temperature in cylinder to decrease NOx pollution.
#####!!!!
Now engine starts smoking because not enough O2 to burn fuel completely . Californians not happy.
OK here solution, readjust EGR to put less exhaust in intake and attach SCR to reduce NOx.
We don't care about life cycle of powertrain. We need healty ppl in California.

 

SCR.......is installed after engine so no effect on the engine.
EGR......installed on the engine and thus has a direct effect on the engine.

 

There are no filters for SCR systems. The DPF (diesel particulate filter) is part of the EGR system and will regenerate periodically (either automatically while running down the road or manually by the driver if/when the system promts them too), think of it as an equivalent to a gas engine's catalytic converter, only it cleans itself (regenerates) with diesel fuel. It does have to be removed and "baked" (cleaned at an extreme temperature) every couple of years.

DEF is part of the SCR system, it is injected into the exhaust after the DPF has done it's job. Most of the engine manufacturers except International went with SCR initially. International tried and failed to meet the pollution standards with just EGR (with the dreaded Maxxforce engine), but eventually gave up on that plan. Now all modern, complaint engines use both EGR and SCR.

 

I think you mean the DPF has to cleaned out.
Diesel Particle FILTER.

 

If only they could make a dpf that spits out charcoal brickettes when it accumulates carbon.

The dpf is the major problem. It creates a lot of back pressure. Egr is also a problem recirculating exhaust gas with soot in it right back to the intake. I'd rather have no egr and use more def.

 

Not just Maxxforce, but Cummins as well. We had many engine and DPF related failures, but fortunately all my trucks were rentals.

 

Kind of a moot point. All diesels, even with SCR units, have EGR systems on them. It is a team thing. One either has EGR only, or EGR/SCR. There is no SCR only system. DPF is another thing altogether. That is for soot. EGR and SCR are for NOx reduction. At least the SCR systems allow for greatly reduced EGR function.

 

Cowpie you are right but wrong too.
In the USA all SCR have a EGR system.
In the EU some went back to SCR only but that has lead to a very high rate off DEF usage.
The jury is still out on which way is best.