Most cruise control systems use engine braking to slow vehicles and keep them at or near the set speed.
Where Mick and I live (and you too from what you have said on this forum) they cant keep you close to the set speed, engine braking is pretty futile on many of our hills. That is before people like me knock it into neutral to prevent the engine braking from happening.
Yes, engine braking. CC and Speed Limiters don't change gear, neither do they put the brakes on.
The fuel is cut off at the set speed. Engine braking is there because there is no fuel getting through, so the vehicle is speed limited.
Come to a hill, engine braking comes in, but if the hill is long and steep, the engine can't hold the vehicle back. If you wanted manual engine braking, you'd change down. CC and Speed Limiters don't do anything but shut off the fuel supply.
Try it on the A30 in West Devon and over Bodmin Moor in Cornwall. If you are in a car at 70mph, it's ok ish. There's a stretch near Bolventor/Temple heading west or down Highgate Hill near Indian Queens heading west where the CC won't work properly.
As for a heavy vehicle, it's even worse. One, you're going slower, and two, the extra weight works with gravity very well indeed.
Most cruise control systems use engine braking to slow vehicles and keep them at or near the set speed.
Where Mick and I live (and you too from what you have said on this forum) they cant keep you close to the set speed, engine braking is pretty futile on many of our hills. That is before people like me knock it into neutral to prevent the engine braking from happening.
I thought good practice was not to coast on neutral, what are new drivers taught? Coasting in top gear would be fast enough
Entertainer, juvenile, curmudgeon, PoB, 30120 Cycling-of course, but it is far better on a Gillott We love safety cameras, we hate bullies
You're considered "not in control" if selecting neutral in a moving vehicle. And you're not, you have no immediate control over the propulsion.
MIAS L5.1 instructor - advanded road and off road skills, FAST aid and casualty care, defensive tactics, SAR skills, nav, group riding, maintenance, ride and group leader qual'd. Cytec 2 - exponent of hammer applied brute force.
meic wrote:On the other hand it reduces pollution quite considerably. Who cares about the environment though?
I might have the wrong end of the stick here, but taking your foot off the throttle and using engine braking (on modern fuel injected vehicles) cuts the fuel completely to the engine. Therefore engine braking is excellent for pollution.
Hybrids and electric cars really win out here with regenerative braking.
Any savings from cutting off the fuel compared to fueling an idling engine are dwarfed by the energy needed to replace the momentum, potential energy or kinetic energy lost to the engine braking.
Planning your journey to reach each peak at just moving and each trough at the speed limit minimises fuel usage. Rather like riding a bike.
meic wrote:Any savings from cutting off the fuel compared to fueling an idling engine are dwarfed by the energy needed to replace the momentum, potential energy or kinetic energy lost to the engine braking.
Planning your journey to reach each peak at just moving and each trough at the speed limit minimises fuel usage. Rather like riding a bike.
I guess if you're familiar with the road and its actually possible to do that then yeah. But for most people engine braking is usually replace by a foot on the brakes. Often because it never seems to occur to them to change down rather than sit in top watching the speedo go up!
But for most people engine braking is usually replace by a foot on the brakes. Often because it never seems to occur to them to change down rather than sit in top watching the speedo go up!
Both of those scenarios have no effect on fuel economy or pollution (except possibly some engine oil v brake liner dust). That is just a matter of the balance between brakes and engine braking restricting your speed, neither way is consuming any fuel. My brakes need the exercise.
meic wrote:On the other hand it reduces pollution quite considerably. Who cares about the environment though?
I might have the wrong end of the stick here, but taking your foot off the throttle and using engine braking (on modern fuel injected vehicles) cuts the fuel completely to the engine. Therefore engine braking is excellent for pollution.
Hybrids and electric cars really win out here with regenerative braking.
Yep! Plus the brakes aren't used as much so there's less pollution coming off them. Plus, the front wheels stay remarkably clean due to the absence of brake dust.
This last little nugget I only noticed after we'd had ours a few weeks when I realised the alloys stayed clean and didn't need Wheel Cleaner or a scrubbing brush.
meic wrote:Both of those scenarios have no effect on fuel economy or pollution (except possibly some engine oil v brake liner dust). That is just a matter of the balance between brakes and engine braking restricting your speed, neither way is consuming any fuel. My brakes need the exercise.
I thought you were "coasting in neutral"?
In which case your engine is running, so engine braking must be more efficient since it isn't...
Coasting in neutral when you dont wish to lose speed. The scenarios that you mentioned and we had moved on to talking about, is the different case where you are seeking to lose speed so are not coasting anymore but using engine braking or brakes. It would be rare to be using brakes in neutral the engine would be engaged before brakes were applied to save idling fuel and to have more control as there is no need to sacrifice it any more. The issue of changing down a gear only alters the ratio of brakes to engine.
meic wrote:On the other hand it reduces pollution quite considerably. Who cares about the environment though?
I love the environnent, but safety trumps it for me.
MIAS L5.1 instructor - advanded road and off road skills, FAST aid and casualty care, defensive tactics, SAR skills, nav, group riding, maintenance, ride and group leader qual'd. Cytec 2 - exponent of hammer applied brute force.
We need lorries to have food in our supermarkets etc which I am quite keen on, food that is, and I've always found lorry drivers to be amongst the most skilled and considerate of drivers, as a group, although I guess there is always the odd one. Watching a lorry driver reverse into a small street gets my admiration.
However, that is in the context of their vehicles being huge, towering, terrifying, road shaking, leviathans. I'm scared of them, when they pass me - the draft that sucks at me as I pedal along and that terrifying sight of all those massive wheels right next to me and what will happen if I wobble on a dodgy bit of tarmac - and the noise! Shock and awe.
Sometimes, it seems to be forgotten that the roads are for everyone, not just cars and lorries. They were there long before cars and lorries and aren't really designed for them for the most part - no matter how much tarmac and paint you put on them. They were made for much slower traffic. Being a bit frustrated because you can't go fast enough - well if I'm honest I've done it, but really, well, you know - people live alongside those roads, their kids walk alongside it and the notion that motor traffic should just blast along and its for anything else to just get out of the way - well no.
Being fast is what motorways and rail freight is for. Country road traffic is far too fast as it is - places without pavements and terrifyingly fast traffic going past you for anyone not in a vehicle.
