I’ve recently inherited a 61 plate Actros which has an eco roll facility. Basically (for anyone who hasn’t heard of or used this) the vehicle default overrun setting is +6kph over your set cruise speed, once you exceed that the exhaust brake comes on, but before reaching 6kph over the eco roll kicks in which basically knocks it into neutral on tickover until your speed drops.
I actually set my cruise to 86kph and alter the overrun to +2kph which saves me constantly using the brakes on long hills, and at this setting the eco roll never kicks in.
My question is; I was always told that an engine on the overrun uses no fuel whatsoever, but surely in neutral and ticking over (eco roll) it MUST be using fuel, so how can this be more economical?
I’m not particularly mechanically minded so was wondering if someone in the know could explain the benefits to me.
cissa:
Because you roll longer. That makes up for the fuel use.
Then when it kicks back into gear it uses more fuel to get it back up to your set speed because at the end of it’s eco roll the speed dips to slightly below what you originally had it set to if you know what i mean, i don’t like it by the way either.
Strange system as you are always taught never to freewheel as you loose any engine breaking etc …I drove a Euro 6 XF with it ,I personally was impressed ,it was seemlees without looking at the dash you never felt or noticed it coming in or out…It is programmed to work on certain gradients and if it builds up too much speed the gear is re engaged.It is part of manufacturers ways of improving fuel consumption…Since all manufacturers are using it ,I can only assume it works.Though obviously it is on available on autos
You raise a pertinent point there Norb, I always thought that to coast in neutral was against the law (don’t know how true that is) but if so it could raise some interesting issues methinks.
It should be legal as it will be in the construction and use .But like you I have been told it also wasted fuel to freewheel …But it appears everything was taught all those moons ago is obsolete ,a bit how I feel at times …But it will only work when certain parameters are met …Am looking forward to learning more about it myself ,
the minimal amount of fuel the engine uses by freewheeling more than makes up the distance it wins by not braking with the engine. for example when coming to a stoplight you don’t freewheel but when you’re in a fully loaded artic on a straight road and you want to stop in the layby 1 mile ahead, then you freewheel.
the maoster:
I’ve recently inherited a 61 plate Actros which has an eco roll facility. Basically (for anyone who hasn’t heard of or used this) the vehicle default overrun setting is +6kph over your set cruise speed, once you exceed that the exhaust brake comes on, but before reaching 6kph over the eco roll kicks in which basically knocks it into neutral on tickover until your speed drops.
I actually set my cruise to 86kph and alter the overrun to +2kph which saves me constantly using the brakes on long hills, and at this setting the eco roll never kicks in.
My question is; I was always told that an engine on the overrun uses no fuel whatsoever, but surely in neutral and ticking over (eco roll) it MUST be using fuel, so how can this be more economical?
I’m not particularly mechanically minded so was wondering if someone in the know could explain the benefits to me.
If you go into the settings and change the fuel consumption from mpg to l/100km you will notice in eco roll it uses 0, on overrun/engine brake it uses about 3-5 and in neutral it uses similar. I set my eco roll at +6mph minimum sometimes 9mph, the more eco roll the better mpg I can assure you that. I don’t know how it works but it’s something to do with the motion of the wheels and the cutting off the fuel supply that keeps the engine going and the mpgs up.
