DEF doesnt replace DPF. The new trucks will have both the emissions devices installed. Its just that with the DEF, the impact of the EGR is minimized on the engine's internals and regens are curtailed to an extent.

 

Agree with above that being said if you are planing on just having a stock truck you're better off with the def


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DEF improves fuel economy and emissions, but at the cost of price and reliability. Pick your poison.

DEF is the better way to go on a stock truck, on a modded truck... Getting rid of them both is the best!


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+1 to that.

Wouldn't the meth injection be even better than DEF since it gets sprayed before as opposed to after combustion?

Those would be totally different things. Meth injection cools the intake charge to help produce more power.

DEF is injected into the exhaust to help reduce NOx emissions when reacting with the SCR catalyst.

 

DEF is the better way to go on a stock truck, on a modded truck... Getting rid of them both is the best!


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My dad has a 2012 6.7 stroke that is completely stock. Except, leveling kit. All in all, the DEF fluid doesn't seem to be that big of a PITA. He gets it refilled when he gets an oil change. He does pull trailers, but nothing extreme. For a stock truck, I think it'll be good and we may have to get use to that with the way things are going.


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DEF(diesel exhaust fluid) is a fluid that sprays into the DPF(diesel particulate filter), 2 completely different things

 

DEF has helped increase the mileage of the Powerstroke and Duramax trucks. It has helped reduce regens and is really not that bad, the only problem we have seen is that some guys have issue with it freezing up. But that has only been in extremely cold weather.

 

Wouldn't the meth injection be even better than DEF since it gets sprayed before as opposed to after combustion?

 

Thanks for the answers. Pretty much what I suspected, better for stock vehicles but still sux for modded diesels.

 

I read a writeup from John Deere on EGRs, DEF, and DPFs. In summary, EGR helps reduce NOX but EGR creates excess soot which requires the DPF to regen more frequently. The original deleters back in 2007 figured this out when they did dpf deletes with sims but did nothing about the egrs. They got more smoke than they expected.

DEF is injected to reduce NOX so that the system isn't as sooty as it was with the Non-DEF systems with the EGR. Less soot equals fewer regens equals better economy. Another problem with the Dodge design is that the fuel for DPF burnoff is injected in the cylinder and that heat has to radiate all the way down the pipe to the DPF. It's very inefficient compared to systems that inject right in front of the dpf or that have the dpf mounted near the exhaust manifold. If I build a big bonfire and stand 50 feet away the temperatures are far lower than if I stand five feet away. Same concept.

 

anyone...?

 

No, meth is injected and acts like nitrous while the water cools the charger ultimately creating lower temps. The DEF is injected in tithe DPF to burn soot more effectively. 2 totally different set ups and purposes


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Just to clear something up-

DEF is typically injected post DPF, before the SCR. It does not control soot whatsoever. It's purpose is to react with the NOx within the SCR and reduce NOx emissions.

 

I know this is an ancient thread but unless my training was wrong. DEF is injected post cat pre DPF. the DPF is sorta like a cat it collects soot when drive and towing the exhaust heat is hot enough that the DPF can "regen"(passive regen) which is the process of breaking the soot into ash so more space is available in the DPF to elongate times between getting it cleaned. the DEF (urea) is use while city driving or parked when the exhaust is to cold to passive regen its sprayed to "piss off" the DPF this is called active Regen again to break the soot to ash. If im wrong then I guess i need to go re read that section but im pretty sure thats what i read( that was not said in a smartass tone i was being honest)

 

Just a correction-

The DPF and the DEF/SCR system are separate.

The DPF collects soot, that is correct. When the exhaust is nice and hot, it burns off the soot. When it is insufficiently hot, it regens. To artificially create heat, the engine dumps fuel into the exhaust, either late in the exhaust stroke or with a dedicated injector.

The DEF/SCR system is after the DPF and doesn't work with it. It's purpose is to decrease tailpipe emissions like CO and NOx. It does this by injecting the DEF into the exhaust before the SCR with a doser. This DEF fosters the chemical reaction for breaking down harmful emissions, along with the SCR.

It's quite confusing, especially when you throw in the fact there's a third element, the DOC, the diesel oxidation catalyst, which is often packaged with the DPF, and is just your regular passive oxidizing catalyst.

Whew.

Remember when it just went from the turbo through a straight pipe?

 

Just to clarify. The use of water/meth is generally to increase mpg and power but it does have the side effect of reducing emissions across the board including particulate matter and nox. Some university tested it on a 5.9 cr cummins and diesel power did a write up of their procedure and results

 

My guess is soon we won't see an EGR on these trucks in the future. We will still need a filter, but if they can make it so the DEF will do the work just as efficient as the EGR, that might make these trucks more reliable. Who knows...

 

Lots of good info on here... hopefully I can add a little more and tie it all up with a nice bow:

DEF does not in and of itself improve gas mileage.
What it does do is allow the truck to be tuned to run leaner vs a non DEF truck. Running lean leads to higher engine temperatures and pressures, which is good for power and efficiency, but produces NOX. DEF is used to break down the NOX in the exhaust. Another benefit of running lean is that virtually all injected fuel is burnt, so there is little soot remaining. This means that what would have ended up as soot in the DPF requiring regens, is instead burnt in the cylinder allowing you to go down the road.


On a non DEF cummins the engine runs rich, especially when the EGR activates. This is to slow down combustion and reduce the amount of NOX produced. Because combustion is slowed more soot is produced.

Water methanol injection can also be used to reduce nox. Water methanol injection is primarily used to increase the performance of an engine, by cooling the charge and allowing more aggressive timing (injection and/or ignition depending if we are talking gas or diesel). The added bonus of cooling the intake are charge, other than causing the engine to go leaner, is that a portion of the heat produced by the burning diesel is absorbed transforming the water mixture into steam. This means that combustion takes place just as violently (good for power), more completely due to the leaning of the fuel air mixture due to increases in density of the intake charge (good for power and reducing soot production) and at lower temperatures (reduces NOX output).

SO... if you have DEF, your engine can run leaner, which means you are not going to be relying on your egr as much to richen the mixture. Because you are not running an artificially rich mixture your engine burns all the fuel, leading it to turn this fuel into power to spin your wheels instead ofsoot clogging up your DPF, where it will need to be burnt out wasting more fuel. Running water meth theoretically reduces the workload of the DEF (depending how the monitoring sensors are hooked up), further reducing the need for the EGR, and consequently the DPF.

Unfortunately there are no factory installed water meth systems that I am aware of. Talk to Snow or AEM. They appear to be the big dogs ATM.

 

Umm... how can it run leaner or more rich??? A diesel only uses what it needs to stay running. But if your saying with and with out the egr it uses more fuel or less to stay running then I understand.

 

Leaner simply means less fuel being injected per stroke

 

Close... It means that there is less than 14.5 parts fuel to each part air by weight. If you start running egr, you are putting in less air, so the same amount of fuel is going to make you richer. If you run meth, you get effectively more air so you are leaner, again if the same amount if fuel is injected.

In response to smoked: if you are rolling coal you are rich. If you have an oversized turbo and you are on stock settings, to where turning up your tune still does not make you smoke you are lean.