A Euro 6 truck carries an emissions system that runs on AdBlue, a urea fluid injected into the exhaust to turn nitrogen oxides into nitrogen and water. That system, the SCR, sits alongside the EGR and the particulate filter, and it is what lets the truck meet the standard and pass inspection. When someone asks about remapping a Euro 6, the first thing we make clear is this: remapping the performance and touching the AdBlue are two different things. You can tune the engine's torque and fuel use without going near the emissions system, and that is legal and passes the roadworthiness test. Disabling the AdBlue or the EGR, on the other hand, is illegal, it gets detected and it puts the truck outside the law. We do the first and not the second.
AdBlue is urea dissolved in water that an injector sprays into the exhaust gases before the SCR catalyst. There it reacts with the nitrogen oxides, the NOx, and turns them into nitrogen and water vapour, which are harmless. It is what lets a modern diesel engine meet Euro 6 without being choked. The system controls itself: a control unit measures the NOx at the outlet and adjusts how much AdBlue it injects. Disabling it brings three problems. It is illegal and finable, because the truck no longer meets the standard it is type approved for. It gets detected at inspection and on the road, with more equipment every year. And it strands the haulier if a customer or a site demands emissions in order. That is why we leave it alone: a working truck has to be able to run anywhere without nasty surprises.
A stage 1 on a Euro 6 works on the engine, not on the emissions. We tune the turbo boost pressure, the injection and the torque maps so the engine delivers more pull at the revs a loaded truck really runs at, between 1,000 and 1,500 rpm. On a long-haul tractor unit that is usually in the order of 10 to 15% more torque, which is not used to go faster but to hold speed on a climb without dropping so many gears. The speed limiter stays as it is, because it is legal and mandatory. We do not touch the SCR, the EGR or the particulate filter: they keep working as standard, with their AdBlue and their regenerations. We save the original map to put it back before a main-dealer service or if the truck is under warranty or on finance.
A Euro 6 uses AdBlue in proportion to the diesel, roughly between 3 and 6% of fuel use depending on the engine and the job. A well-done stage 1 does not send that use up: because the engine works more easily to move the same load, it burns a little less diesel on the road, and the AdBlue drops in the same proportion. The percentage can creep up slightly if more sustained torque is asked for, because more combustion means more NOx to neutralise, but we are talking tenths, not doubling the use. What we do not do is touch the dosing to save AdBlue: that would be tampering with the emissions. In a fleet, the figure that matters is the diesel, which is the big cost, and there a long-haul stage 1 comes in around 5 to 8% less.
Yes, if only the engine performance is touched and not the emissions system. Tuning torque, boost and injection without disabling the AdBlue, the EGR or the particulate filter is legal and passes inspection. What is illegal is disabling or tampering with the emissions. We do the first and save the original map in case it needs putting back before a service or under warranty.
No, and we do not do it. Disabling the AdBlue is illegal, it gets detected at inspection and on the road, and it puts the truck outside the standard it is type approved for. On top of that, the real saving is in the diesel, not the AdBlue, which is a small cost next to fuel. A legal stage 1 lowers diesel use without touching the emissions.
A Euro 6 uses AdBlue at around 3 to 6% of the diesel. After a well-done stage 1 that percentage holds or rises very little, because the engine moves the same load with less effort and burns a bit less diesel. The dosing is not tampered with: the AdBlue keeps doing its job to meet the standard.
On long haul, a legal stage 1 comes in around 5 to 8% less diesel, because the engine delivers more torque low down and does not have to be thrashed or drop so many gears on a climb. The saving depends on the route, the load and the driver. In a fleet that covers a lot of miles, that percentage of the diesel bill is real money a month.