How does the Adblue SCR DEF system work? Explained Diesel Exhaust Fluid Selective Catalyst Reduction

The Adblue or Selective Catalyst Reduction (SCR) system is a solution for the exhaust gas aftertreatment used to reduce the NOx within the exhaust gas emissions.
For this purpose a specified amount of (Adblue) or Diesel Exhaust Fluid (DEF) is injected into the gas inlets of the Diesel Particulate Filter (DPF) and the SCR catalytic converter. The injected DEF into the exhaust system is converted to ammonia (NH3) and carbon dioxide (CO2). The resulting ammonia (NH3) is used within a special catalyst in the exhaust stream. The resulting reaction converts the unwanted NOx into harmless nitrogen (N2) and water (H2O) vapor.
The SCR system is equipped with LNT catalytic converter and DPF assembly is located in the downpipe from the turbocharger. An additional SCR catalytic converter is located in the exhaust center section.
The DEF is a pure, odorless, colorless, synthetically manufactured, aqueous solution. The DEF is used for the aftertreatment of exhaust gases in the DPF and the SCR catalytic converter.
The SCR catalytic converter can be contaminated by low quantities of metals and thus the quality of the DEF is held to closely controlled standards. The DEF cannot be substituted or diluted with any other fluid.
The diesel exhaust fluid is not categorized as a dangerous substance, because
· The DEF is non-flammable
· The DEF is non-toxic
· There is no danger in the event of spills.
The DEF can be stored on board vehicles, despite the limitation that it crystallizes at temperatures below -11°C (12°F).
In Europe, DEF is also known as AdBlue®, the fluid is specified by ISO22241.
The DEF tank is blow moulded from High Density Polyethylene (HDPE). The DEF tank unit contains the DEF module. The DEF tank includes a 12% unusable volume to protect the internal components because of fluid expansion under freezing conditions.
If the ambient temperature falls below -11°C (12°F), the DEF will freeze in the DEF tank and this will provide difficulty with the refill procedure. In order to thaw the DEF in the DEF tank, place the vehicle in a warm place for 2 hours before refilling the DEF.
The DEF level sensor is an ultrasonic device, which sends the DEF level value to the Powertrain Control Module (PCM) through Pulse Width Modulated (PWM) signals. The ultrasonic cone angle is 10° and the readings are most accurate when the vehicle is stationary and on level ground.
The heater element is a Positive Temperature Coefficient (PTC) type heater, which provides safe operation to the system. Increased heater element temperature results in decreased current drawn from the DEF heater control module, which actuates the power supply of the heater element. Under normal operation the maximum current is 6A.
The DEF injection pump is an assembly of 2 solenoid pumps, located in the DEF tank module. The pressure pump provides 6.5 bar (94.3 psi) operating pressure. The 6.5 bar (94.3 psi) pressure is required to maintain the complete DEF atomization in the exhaust gas. The purge pump purges the DEF from the DEF line at engine shutdown to prevent freezing in the DEF injector at low temperatures. The PCM controls the ground connection of the pumps individually.
The DEF line provides hydraulic connection between the DEF injection pump and the DEF injector. The DEF line is manufactured from a plastic material, which is specifically designed for use with DEF. A copper based resistor wire is installed within the DEF line with an electrical connector. The resistor wire enables electrical heating of the DEF at low-ambient temperatures.
A pre DPF DEF injector is located on the top of the DPF. The DEF is injected vertically to the exhaust gas flow direction. The mixer plate and the high exhaust gas speed provide the DEF is mixed well and distributed evenly within the exhaust gas. The DEF injector consists of an injector and a liquid cooled housing. The liquid cooled housing connects to the engine cooling system to protects the injector from overheating.
The DEF injectors works at high pressures to obtain the complete atomization of the injected DEF. This provides the SCR catalytic converter is working to its optimum performance. The PCM controls the DEF injector with PWM signals.
The DEF heater control module has hardwired connections to the DEF tank module and the DEF line heater element. If the ambient air temperature is below -7°C (19.4°F) the PCM switches on the DEF heater control module through the private CAN bus.
#Adblue
#DEF
#SCR
#engine
#howitworks
#GarageTech
#cars
#Animation
#diesel
#emissions
#exhaust
#gas
#garagetech
#auto
#automotive
#motor
#motors
#internalcombustionengine
#dieselengine
#trucks
#HGV
#p20e8
#p20e800

[@sinegra30]

This is so far the most clear explanation I've found on the internet, thank you!

[@djbravo8124]

TO THIS DAYYYY

[@balndek7967]

I agree, I'm doing a term paper on the scr system and this recording will make my work much easier.

[@bonusnudges]

Ad blue works really well when it works ! , But unfortunately the sensors, pump and other associated equipment are horribly unreliable. Those components just last until the warranty runs out . When one of the components fucks up the vehicle usually won’t run without it ! . Due to government regulations it’s against the law not to have that system working , especially in hgv vehicles . Because it’s government legislation , manufactures can charge what they want for spare parts . The parts for that system are mostly made by the same manufacturer and the same shite . As a result , the end user is ransomed to pay extortionate amounts of money for components that probably cost next to nothing to produce. The whole system is a big fuck off conn

[@jaggass]

Cars are deliberately not built to last so you go out and buy another one.

[@Kit_Bear]

Just another unnecessary expense to run a car. Why the hell do I need to use that crap when my previous car never needed it. Now, if the government wanted all the diesel cars off the road all they have to do is ban the use of Adblue. Absolute con.

[@foppo100]

Thanks we are conned from morning to night.

[@Deontjie]

I wonder what the next stupid thing is the government will enforce on cars. Meanwhile Scotland cut down 150,000 trees to make place for wind turbines.

[@garreysellars5525]

​@@jaggass You are right Not only parts but labour ad well Cheaper to replace not fix same with house hold stuff I think the greenwashed avangelist trying to save the planet Need to talk to the engineers WHO ARE MAKING EVERYTHING DISPOSABLE

[@xjonasxv]

Best video on the FULL explanation of adblue. Thank you so much. Inwas wondering if the adblue tank was crystallised because the line was empty. Now i know that it is pumped back in the tank.

[@peteyourdoom]

Really good explanation. Have a new (old) Diesel car and the Adblue is the new thing for me, as well as the NOX sensor (which I've just had replaced). Found the filler for it in the back of the car and wondered what AdBlue was and how it works.

[@YouDoNotKnowMe99]

How much was it to get it replaced mate

[@Deontjie]

Meanwhile my 1965 Land-rover series 2 is still going. And cheap to fix.

[@ronaldlloyd9189]

Excellent video. Your video describes more of the components that make the def system rather than a lot of colorful dots changing colours.

[@sophiegreen2802]

Hi I have just got a Citroen ds3 and hass not got a ad blue tank do I have to put in in the diesel tank .

[@bossdog1480]

@@sophiegreen2802 If it's old and doesn't have the ad-blue tank, no, probably not.

[@littlewilly1922]

@@sophiegreen2802 I hope you didn't put the adblue into the diesel as your whole fuel system will be ruined immediately and the car scrapped

[@Legolize23]

Well done, that’s a great explanation!

[@noelf3127]

Good video. This is the most informative I've found on Adblue and how it works, including the actual reactions that happen.

[@Mal_Outdoors]

Thank you for such a thorough explanation. It's even more complicated than I thought!

[@swarajjoye]

Jesus, that was heavy but very interesting. Will have to watch this over and over with many cups of coffee

[@garreysellars5525]

Might need rum on the coffee

[@EddieDaOnly1]

Thanks for explaining I just filled up adblue in my Audi TDI I can't wait to delete.

[@markhurst8425]

Spot on made it sound so simple

[@fastlanetuningschweiz6632]

Excellent video, well prepared and very clear. Thankyou.

[@nickayivor8432]

KNOWLEDGEABLE GarageTech Thank you very helpful information video start to finish loved it From Nick Ayivor from London England UK 🇬🇧

[@antohosm43]

Great video! So clear and of much help to me with regards to my TDi A4. I hold a Chemistry Ph.D. but my automotive knowledge needs much improvement.

[@1allan2]

Imagine the power the engine could make with a strait through system !

[@markm49]

Excellent video- just bought a car with this system. Always good to know how these things work.

[@um02122]

Yeah, you've bought a car running on piss.

[@chuckmaddison2924]

The best thing with Adblue is the amount of damage it can do if you put in the fuel. It's also good for making crystals

[@foppo100]

My son in laws car broke down the other day Ad Blue problem.It was repaired by Peugeot he had problems before.The AA man said to him I can't do anything with this car has to go back to the dealership.Drove him and the car to a garage.He just paid over a thousand pounds for repairs.So another thing to go horrible wrong with a modern diesel arn't we happy.

[@charletonzimmerman4205]

GO EV.

[@eladarye9817]

You are a real pro!!! Love it

[@csengo70]

Excellent excellent explanation. This system ads so much complexity to diesel engines. Don't think electric cars are not complex. Their complexity is different, but still overly complex. Petrol is still the best way to go.

[@brettymike]

I warn people to avoid the diesels like the plague, and buy a petrol these days.

[@derektaylor6713]

Absolutely unbelieveable. Why would it have to be so complicated? Just how clean are the exhaust gases? If they're practically clean as a whistle why are these engines being banned. And how does a diesel engine running with ad blue complare with a modern petrol engined car? Which is cleanest. No wonder some hapless motorhome owners have had to pay thousands out for new ad blue tanks. This ad blue just isn't good enough. It's got a very short shelf life and starts to chrystalise and knacker the tank up. For this reason I wouldn't buy a diesel car that runs on ad blue. But what a good video. It's really opened my eyes to just how complicated and these things are. I've seen inside modern televisions and they aren't this convoluted.

[@abhic4u]

Excellent video

[@jamalamarir6525]

this is great video thank you for all your efforts

[@pasindurathnayake4260]

great video

[@joseantonioyereguiurmeneta8543]

I see that the passage from the catalyst to the particulate filter does not have direct access because it has gas flow deflectors. I was thinking of cleaning my dpf through the Addblue inlet, going down to the particulate filter, but thanks to your video I see that I won't be able to do it.

[@alethephobe7586]

Epic explanation, great animations, instant subscription!

[@luckystrike656]

thank you for your video. Peugeot, on his 308 Bluehdi models has problems with the Adblue tank. Every car, at around 50000-60 000km has to replace the tank. It arrives suddenly as Check Engine+Adblue+Service it is almost 1000€ cost They say the tank is deforming because of wrong pressure

[@luckystrike656]

@Little Reptilian i dont know. The "new" tank has the same part number so probably no modification has been done. For now I am filling the tank every month, not letting the urea form cristals

[@luis0martins]

I have a Peugeot 308 with 67000 km and I had a problema with the adblue injector… it really seems that it is a faulty system. However, I only had to replace the injector. In your case did the dealer covered the costs of repairment?

[@partfoltatlan371]

i think you've found the reason this system was invented for! If they've wanted cleaner exhaust air, they've could put a physical filter to the rear with a filter that needs to be replaced every week or so...

[@bb21again.67]

You state that 30% urea is used for its freezing point,does that mean if cold was not a concern would a higher % mean less adblue volume needed to be injected for the same results?

[@iCrackPro]

Thanks for helping.

[@EJAZenarosa]

Thank you

[@shafrazshaifdeen9455]

Very good explanation. great video. Than you.

[@leocheckup6645]

Parabéns pelo conteúdo !

[@AugustineAAmaniampong-po7cj]

What are the electrical components and it’s functions and also how they operate.

[@joemengler1666]

Very informative. Thank you

[@akshayjagtap3747]

nice,very informative.Thank you.

[@eddywaluva6820]

Informative video. Good work.

[@sleelakrishnan]

Thank You Very Much...

[@MrLeeKnees]

great video, very informative

[@subhanansari8489]

Very good video sir thanks

[@FluidTekPH]

expalain very well, thank's you

[@clivebenjamin3452]

Great stuff

[@kapilramanujancbse]

Great job

[@bardslee]

so add blue could be piss but isn't?

[@mohindersembi7647]

Hi very interesting video you are professional engineer just question I have audi A6 ....2016 year its only done 40000 miles from new and its coming up with p20e800 code low pressure and the adblue tank is full now when the engine is cold does the adblue injector spray the adblue?? Or the engine have to be at normal temperature ie 90° Celsius and then the adblue injector works ? Please kindly help me on this on this issue waiting for your reply Thankyou 🙏

[@GarageTechAutomotive]

Hey thanks for the comments, I’ve worked in the automotive trade many years. Could be a couple of things, this is a bit of a generic fault code so the system needs to be checked, yes it will work from cold if needed, depends on how much Nox emissions are produced. This Fault code could relate to an issue with the pump, it’s common for the AdBlue system to become blocked. As it’s full, that rules out low fluid. There’s also been software updates, which could be needed if there’s no other obvious faults

[@terrygoyan]

No wonder new vehicles are expensive. That's a complex system added to an exhaust! Is the exhaust fluid added before or after the headlight and taillight fluids?

[@GarageTechAutomotive]

It’s added right before the blinker fluid 🤣

[@terrygoyan]

@@GarageTechAutomotive Ha! That's what I thought....thanks for a great explanation of the SCR system!

[@candrevajonathan-matic6604]

Keep it up thank u very much

[@murateyi]

QUESTION: I've got a new Nercedes GLC Coupe 300. There is an intermittent throbbing noise coming from the engine. My local Merce dealer said it is from AdBlue injector and it is normal. The car is brand new and I found it very loud as my previous Mercedes's did not have this issue despite all having AdBlue? How can I find out whether or not they are lying?

[@karim_a.]

Murat Taner Eyi I drove several cars of different brands (no mercedes) but never I have heard specific noise due to adblue system

[@foppo100]

He is taking the piss give the care back not fit for purpose.

[@MFDOOMgr]

So the Diesel Oxydation catalyst is now a Diesel oxydation catalyst with NOX catalyst? and then the remaining Nox are converted with the scr?

[@xyzchannel4269]

Good thanks 😊👍👍👍😊😊

[@mauriceupton1474]

Every diesel car owner with adblue needs to read their owners' manual or risk destroying your exhaust filter system. It is important to go on a high-speed, sustained journey for at least 30 minutes every month, to clean out the particle filter. Short trips will not get the system hot enough, and the filters will block. At great cost.

[@sen5908]

Does a car with adblu leave less soot in the DPF, than a car without adblu ??

[@Nothing-g7e]

It's made with carbon dioxide and it still comes out the exhaust, what good is it doing please tell me.

[@mohanraut3232]

Dear Sir, Can we use catalytic converter for following flue gases.1) Carbon Monoxide 2) Nitrogen oxide 3) Sulphur Oxide 4) Hydrogen chloride gas 5) Hydrogen fluoride 6) Mercury vapours

[@comfortablynumb8832]

So the add blue dosnt go into the fuel tank? The other question what impact would it have on a vans engine if I were to gut the dpf and software delete it, would this be ok? Thanks

[@SirRodericSpode]

Excellent video, liked and subscribed!

[@XISAV]

Hey! I have question about valve in exhaust pipe after ammonia trap (can see at 6:58 in video)? What it is called? I can't find any information in google about that valve, but i want read something about it. Thanks!

[@joseantonioyereguiurmeneta8543]

What happens if I mix this product with one for cleaning the particle filter in the Adblue tank?

[@GarageTechAutomotive]

Good question, but I’m not sure to be honest but it will likely cause an issue, the system will detect that the AdBlue fluid is not doing what it’s supposed to do and then put the warning light on and stop working. That might mean you’ll need to flush the system out.

[@joseantonioyereguiurmeneta8543]

Thank you very much for your quick and sincere response.

[@sumpleA]

I've heard fuel consumption increases with this system, but why, technically speaking, would it?

[@GarageTechAutomotive]

I don’t have any data to suggest it does, you normally find the engines get more fuel efficient. The DPF system will use additional fuel in the burn off phase where it uses heat to burn off the soot.

[@nelly365]

My question is where is the adblue made? Can the manufacturer shut down production and therefore cripple a country’s fleet of diesel machines

[@busby905]

Does this make the car slower?

[@1allan2]

I admire the science, but the amount of systems and complexity on an internal combustion engine these days is making the electric car more feasible.

[@zephyrdrake_]

@@zee7931 This ^^

[@baileydbenson1]

@@zee7931 that is EXACTLY the goal! Class warefare...only the rich will be allowed the freedom of easy travel. The rest of us need to buy a public transport card.

[@scaracci24]

@@baileydbenson1 EVs r expensive to manufacture and the production of them emit more green house emissions that I.C.E equipped vehicles

[@LuMaxQFPV]

Electric cars are NOT environmentally friendly or as useful as compared to an ICE vehicle. There exists WAAAY too much fanboi-ism for electric vehicles... and it's cringe! Massive environmental impacts from battery production, vehicle weight and it's effects on tire wear and road damage, lack of realistic range, inability to tow just about anything a useful distance.... it's a fanboi utopia. FYI, I am all about any future, much-improved energy storage scheme that works on the order of what an ICE engine delivers. We are FAR from that, however, and it seems stupid to me that people aren't simply willing to admit that. Furthermore, our government should NOT have any agenda to promote our current uneconomical, expensive electric vehicle technology upon us. That is stupid and short-sighted. Most of the people who are cheering g on electric vehicles with our current immature technology have no tech credentials... and are ignorant of scientific facts.

[@bertjedekat]

@@LuMaxQFPV you are delusional

[@terryyouth]

is this an ongoing thing? I mean i had diesel car 2ltre and never heard of this

[@a.p.3167]

How to explain where the carbon particles gose?

[@bekas2739]

Hellow I got trouble on my truck Mitsubishi fuso adblue light come on and truck went off since July I read code with my diagnosis I found : P20EE and P111C. Any help?

[@GarageTechAutomotive]

P20EE would indicate an issue with the adblue system, first check the quality of the adblue fluid. If its been filled with water for example. The other common issue is the injector can become blocked. you could try taking it off and soaking the end in hot water to try and clear it.

[@garreysellars5525]

What thaws the fluid in the lines

[@GarageTechAutomotive]

The lines have a heating element through them so are heated as well.

[@garreysellars5525]

@@GarageTechAutomotive seously

[@onw123]

Any chance you can tell me the side effects of somebody using adblue instead of eolys? my mechanic has just done this and i'm concerned it's causing issues.

[@bananarsle]

Like it's said in the video. Adblue is water based. Eolys however is oil based.

[@willdatsun]

@@bananarsle really bad news, i think eolys is injected into the fuel, whereas adblue is injected after combustion, very different systems. i am astonished anyone could mix them up as eolys requires specialist equipment - connectors and tubes and such to refill the tank. thankfully only needs doing every 90,000 miles or so

[@prasadreddy5421]

I have VOLKSWAGEN POLO 1.2 L Diesel Engine Car Do this version has Adblue System. Thank you. - Prasad reddy

[@GarageTechAutomotive]

prasad reddy, no I don’t think so.

[@terryyouth]

I guess you will be getting more views nowadays

[@mancheetah5610]

These things increase fuel consumption. My 18 plate transit is way thirstier

[@jackd5089]

I found the same with our 2017 transit she was way heavier on juice, but then in our new 2019 crafter she is very economic

[@steveguest8028]

Jack d I work for a Ford dealer and we get loads of complaints about these new transits drinking fuel and adblue

[@jackd5089]

@@steveguest8028 then tge timing blet Snaped after 200 000km in January 2019 they replaced it with new engine but put on a timing chain we trader her after another 20 000km

[@steveguest8028]

Jack d Modern vehicles are all junk,too much electronics and stuff you don’t really need then when it goes wrong it costs an arm and a leg to fix that’s if you can actually find where the fault lies

[@jackd5089]

@@steveguest8028 ford to be fair was very helpful and service and repairs were always cheap

[@jamescarter26]

Can i pee in my tank ?

[@hamish2202]

back when an exhaust was just some pipe and things were simple

[@jacoblee739]

great video for turning people off buying diesel cars.

[@pragmaticapproach1590]

Remove temporary NOx sensor! Fill the hole using a bolt! Life will much easier!

[@garreysellars5525]

I thought we were trying to reduce the amount of carbon dioxide emitted ad well All sounds like a joke How can such a small amount of fluid sprayed intermittently saturated all the exhaust gas😢

[@syrymyeskenderuly340]

If Addluw low if added full add blue engine starting sprinter w907

[@mjames2117]

Working EGR must have a larger effect on NOx by reducing combustion temperature and by effectively reducing cylinder capacity by introducing exhaust gases into the cylinder. Why not introduce higher volume but better filtered EGR exhaust gas into cylinders at cruise?

[@garreysellars5525]

Use water methanol injected into the air intake to reduce combustion temp and the trade off is MOREPOWER😅

[@matrasimca6192]

Those who bought such technology vehicles for use inside airports cry for their money as the DPF filters often clog and there is necessary down time. Those vehicles are useful only for long trips. For short trips they are disaster

[@mysongs1803]

over complicating what should have been a great invention

[@brettymike]

Diesels used to be the greatest engine in the world for land based transport, now money men and bean counters have turned them into unreliable and bloody expensive piles of junk.

[@olarubogdan46]

I would love to somehow fit this on my euro 4 non dpf diesel. Even though this causes trouble on the long run... at least the car does not polute that much...

[@xdygmnyrdf]

Lots of people pay big bucks just to remove all these emission systems from their car. lol

[@shivaprasadgv8622]

Any one let me know the cost price of the ADBLUE fluid?

[@mehulparmar80]

R you individual user or commercial ? connect if commercial volume supply - [e-mail]

[@stephenmellentine]

ADBLUE is simply common DEF (Diesel Exhaust Fluid), sold under a variety of names. There is literally no harm in using other manufacturers' brands of DEF as a replacement to Volkswagen's ADBLUE-branded fluid. Usually, 2.5 gallons of DEF goes for around $17-22, which should fill your DEF tank for at least 8,000 to 12,000 miles, depending on how aggressively you drive the TDi.

[@astryker5931]

www.walmart.com/ip/Sinopec-DEF-Diesel-Exhaust-Fluid-2-2-5-Gallon-Jugs/297544828

[@shueibdahir]

This adds WAY too much complexity to the engine. I can't imagine how expensive this gets in the long term

[@wag0NE]

Piss and water, thanks no need to buy adblue anymore!

[@baltukur3368]

Too much technology to go wrong avoid expensive bills do not buy these cars

[@Hunguerilla87]

well all this complicated thing should unnecessary if using hemp oil based fuel. not the same as methanol. check about hemp oil 100 percent pure and onlny 2x strained put into a modern diesel engine. the resoult was no or mutch less NO2 THAN WITH ADBLUE

[@andypreston1524]

Emissions Tax..........

[@vainamoinen007]

Vojage

[@vainamoinen007]

Vojage anny

[@vainamoinen007]

Vojage

[@vainamoinen007]

Annie lennox

[@vainamoinen007]

Vojage

when germans doesn't have a petrol

[@paolotoscano1328]

The little bit I did watch of this clip was very informative and I would have watch the entire clip if it was not for the annoying throat / swallowing noises.

[@ameenleqyanya8352]

لو بالعربي

[@wickedleeloopy2115]

This is truely the beginning of the end of diesel. This is a complete waste of investing money into this. Just start building electric cars... it just seems easier. 😕 this is a sad day in the history of combustion engines.....its just getting worse. Time to cut your losses & start again.

[@74kimbo]

Should listen to guy martin he's explain it its a money spinner and costly badly

[@DC_p220]

Volkswagen das auto

[@felixalbion]

Cars were so much better before all this emissions rubbish. They were more reliable and didn't cost a fortune every time the emissions system failed. So many cars get scrapped because of the cost of replacing dpf etc.

[@drhhodge8243]

Absolutely amazing what a Democrat can fuck up

[@rigamortice]

So the answer is, DON'T BUY A CAR THAT NEEDS ADBLUE

[@AugustineAAmaniampong-po7cj]

What are the electrical components and it’s functions and also how they operate