Alright, I'm laying on my favorite couch, and full off of Costco pizza, so it's time to type this out.
So for diesels, emissions started being mandated by the epa in 2002 to reduce NOx, which stands for nitrogen oxide, which is by definition, gases-nitric oxide (NO), which is a colourless, odourless gas and nitrogen dioxide (NO2), which is a reddish-brown gas with a pungent odour.
NOx is bad, because even in small quantities, it is harmful to your upper respiratory tract and can lead to asthma and other lung diseases. It also attaches to Ozone molecules, thus breaking it down even further.
So in 2002 for diesels to reduce NOx, they introduced Exhaust Gas Recirculation (EGR) which introduces inert gasses to the combustion cycle, which in turn lowers combustion temperatures, which lowered NOx. Took care of a majority of it and it ran that way until 2007. It is designed that EGR only operates typically under motoring, cruising, or idling conditions. Power demand like accelerating or pulling loads, it's supposed to be closed. So the old rumor of 'it lowers power output' is for the most part a half cop out from those who don't understand it.
In 2007 the EPA, being the big brother they are, said NO MORE BLACK SMOKE. So thus the Diesel Particulate Filter (DPF) Was designed. It works in conjunction with the Diesel Oxydation Catalyst (DOC) which is essentially a giant catalytic converter right before the DPF.
This device does have the potential to reduce fuel economy, and in more cases than not, does. The DPF and DOC work by all of the airborne soot particles coming out of the exhaust are caught in the DPF. The DPF is essentially a wall flow-through trap design of ceramic material. Think of a catalytic converter, except it looks like a checker board. Each pinhole is a soot trap.
So what happens when it gets full? That's when the engine has to do a regeneration. There's two kind of regens, passive and active. Passive occurs when the exhaust is able to get hot and maintain it's temperature based off of just it's operating condition. Driving for miles at a steady speed on the freeway is a good way to achieve this.
Active regeneration is when the engine computer has to take over and force hotter exhaust. How that work? Well, during the exhaust stroke, raw fuel is injected into the exhaust stream, either via the fuel injectors, or an extra fuel injector that exists just after the turbo before the down pipe.
This raw fuel goes through the DOC, which creates a chemical reaction called Plasma gasification, where the exhaust jumps up from about 600-700F, to anywhere between 1100-1300F. This hot exhaust literally bakes the soot caught in the DPF until it cooks it down to ash and releases gasses. I forget what gasses it releases. I think it's oxygen and nitrogen molecules.
Early in it's developments, DPF and regen systems sucked butt. They did slowly get better over the years, and not rarely have issues. As long as you don't idle your truck. Seriously, even without emission controlled engines, idle is the killer of engines.
So anyways, it ran this way until EPA was like oh hey these guys let's mess with them and make things more strict. So in 2010 diesels had to lower their NOx even more, because EGR just wasn't cutting it. Thus came along the Selective Catalyst Reductor (SCR) system and everyone's favorite, diesel exhaust fluid (DEF)
So these are actually a little neat to me, just because of the science that went into it. So the DEF is injected into the exhaust stream right after the DPF into a swirling type device to really mix it up, then it enters the SCR, where the vaporized Def fluid reacts with the SCR material and literally rips the molecules of NOx apart, until you have individual nitrogen molecules, and oxygen molecules. They also have NOx sensors at the turbo outlet and SCR outlet, to determine the efficiency of them.
Sure, over the years they've had their own fair share of issues, leaky lines, quality sensor issues, all sorts of stuff. But as things progress, they've gotten way better as well. I now see trucks pushing 700k miles with all original emission parts on them. Sure, maybe a replacement sensor here or there but that's it.
Mind you, this is all industrial diesel stuff, not Ford or Chevy's stuff. And don't get me started with Cat, and how they decided they wanted to run a giant glow plug to get their super heat... Part of the reason they pulled out of the over the road market.
Anyways, my thumbs hurt. Time for a drink.
So for diesels, emissions started being mandated by the epa in 2002 to reduce NOx, which stands for nitrogen oxide, which is by definition, gases-nitric oxide (NO), which is a colourless, odourless gas and nitrogen dioxide (NO2), which is a reddish-brown gas with a pungent odour.
NOx is bad, because even in small quantities, it is harmful to your upper respiratory tract and can lead to asthma and other lung diseases. It also attaches to Ozone molecules, thus breaking it down even further.
So in 2002 for diesels to reduce NOx, they introduced Exhaust Gas Recirculation (EGR) which introduces inert gasses to the combustion cycle, which in turn lowers combustion temperatures, which lowered NOx. Took care of a majority of it and it ran that way until 2007. It is designed that EGR only operates typically under motoring, cruising, or idling conditions. Power demand like accelerating or pulling loads, it's supposed to be closed. So the old rumor of 'it lowers power output' is for the most part a half cop out from those who don't understand it.
In 2007 the EPA, being the big brother they are, said NO MORE BLACK SMOKE. So thus the Diesel Particulate Filter (DPF) Was designed. It works in conjunction with the Diesel Oxydation Catalyst (DOC) which is essentially a giant catalytic converter right before the DPF.
This device does have the potential to reduce fuel economy, and in more cases than not, does. The DPF and DOC work by all of the airborne soot particles coming out of the exhaust are caught in the DPF. The DPF is essentially a wall flow-through trap design of ceramic material. Think of a catalytic converter, except it looks like a checker board. Each pinhole is a soot trap.
So what happens when it gets full? That's when the engine has to do a regeneration. There's two kind of regens, passive and active. Passive occurs when the exhaust is able to get hot and maintain it's temperature based off of just it's operating condition. Driving for miles at a steady speed on the freeway is a good way to achieve this.
Active regeneration is when the engine computer has to take over and force hotter exhaust. How that work? Well, during the exhaust stroke, raw fuel is injected into the exhaust stream, either via the fuel injectors, or an extra fuel injector that exists just after the turbo before the down pipe.
This raw fuel goes through the DOC, which creates a chemical reaction called Plasma gasification, where the exhaust jumps up from about 600-700F, to anywhere between 1100-1300F. This hot exhaust literally bakes the soot caught in the DPF until it cooks it down to ash and releases gasses. I forget what gasses it releases. I think it's oxygen and nitrogen molecules.
Early in it's developments, DPF and regen systems sucked butt. They did slowly get better over the years, and not rarely have issues. As long as you don't idle your truck. Seriously, even without emission controlled engines, idle is the killer of engines.
So anyways, it ran this way until EPA was like oh hey these guys let's mess with them and make things more strict. So in 2010 diesels had to lower their NOx even more, because EGR just wasn't cutting it. Thus came along the Selective Catalyst Reductor (SCR) system and everyone's favorite, diesel exhaust fluid (DEF)
So these are actually a little neat to me, just because of the science that went into it. So the DEF is injected into the exhaust stream right after the DPF into a swirling type device to really mix it up, then it enters the SCR, where the vaporized Def fluid reacts with the SCR material and literally rips the molecules of NOx apart, until you have individual nitrogen molecules, and oxygen molecules. They also have NOx sensors at the turbo outlet and SCR outlet, to determine the efficiency of them.
Sure, over the years they've had their own fair share of issues, leaky lines, quality sensor issues, all sorts of stuff. But as things progress, they've gotten way better as well. I now see trucks pushing 700k miles with all original emission parts on them. Sure, maybe a replacement sensor here or there but that's it.
Mind you, this is all industrial diesel stuff, not Ford or Chevy's stuff. And don't get me started with Cat, and how they decided they wanted to run a giant glow plug to get their super heat... Part of the reason they pulled out of the over the road market.
Anyways, my thumbs hurt. Time for a drink.
