1 hour ago, DaveMiller said:

If you took an hour longer to get home, your average speed was much (25%) lower. That’s likely to make consumption notably better, in its own right.

 

My average until the traffic cleared was still in the mid-high 40s, it was only in the last 50miles or so that it climbed above 50mpg and that was back up to doing 70

Edited 26 April, 20197 yr by PoloGaz

I find there are many other variables that have a significant effect on economy, and make it difficult to compare just a single journey. 

 

For example, colder ambient temperature in the morning compared to higher for the return journey helps a lot; especially if the engine doesn’t completely cool down; prevailing wind direction can make a massive difference in a big SUV like the Kodiaq at motorway speeds; average speed alone is unhelpful unless traffic conditions were identical - stop start traffic brings down the average but harms economy whereas a long stretch of easy flowing 50mph roadworks brings down the average speed put massively improves the average economy. 

All true. It’s a journey I do regularly and I’ll keep monitoring, particularly when I switch to the kodiaq in a few weeks.

On 26/04/2019 at 23:11, PoloGaz said:

Old thread, but interesting topic!

 

Does anyone know if the new 1.5s fully shut down in the kodiaq?

 

I currently have a BMW 320i which has an 8 speed auto box. It coasts (engine on) in 'eco pro' mode but most of the time it seems to do it when I actually want the car to slow down!

 

I regularly drive from Manchester to London in the car, 400 or so mile round trip. My best run in eco pro mode I managed around 47-48mpg

 

This week I drove down one evening and I did the trip in around 3 hrs, sticking religiously to 70mph (using speed limiter) average mpg was 46.something according to the computer.

 

I found the option to disable coasting for the return leg, and even though I hit traffic and it took 1 hour longer to get home, my average mpg was 50.5mpg.

 

I expect it makes more of a benefit on diesels or cars with short gearing. The BMW has a very high top gear, 1600rpm at 70mph and there is very little engine braking from this engine. So i am convinced that I am using more fuel with coasting.

 

having the engine completely shut down for coasting makes a lot more sense!

 

Coasting CAN be more economical but it will really depend on the driving environment and how good a driver you are at anticipating traffic behaviour.

A simple rule of thumb is how much you use the brakes when in a coasting capable mode compared to a mode providing engine braking.

If you find you use the brakes far less in engine braking capable mode then during the time the engine is on overrun then no fuel is being used for the distance travelled compared to coasting mode.

For instance, travelling on a busy motorway you have to make a lot of small variations to speed to maintain a safe distance to the car in front. In coasting mode you would have to constantly use the brakes and accelerator which is less economical than utilising engine braking and acceleration.

I have seen cars travelling too close to the vehicle in front and their brakes are constantly flickering, but I am not sure if that is the driver behaviour of whether they have the ACC set incorrectly and the system is driving so badly it must almost be like having binding brakes.

 

I have a manual box so I just flick into neutral when I want or select the most suitable gear for the level of engine braking needed. If I had an auto then I would be flicking between modes.

The idea of an engine switching off when coasting is tantalising and reminiscent of the American hypermiler's 'kill switches' for use in pulse and glide driving which can give remarkable results but would be highly anti-social on UK roads.

 

As you can gather I am a bit OCD about fuel consumption, but I still travel at speed limits, or whatever the traffic dictates and if at the front at traffic lights then I gun the engine to give as many cars behind the opportunity to get through on the green...And I do use the brakes when necessary.

 

Edited 27 April, 20197 yr by Gerrycan

Good reply Gerrycan! I am finding very few scenarios where I wouldn’t have to hit the brakes when coasting or pull the downshift to get some engine braking.

 

The only scenario I can see where it’d benefit is a long downhill that’s not quite steep enough to overcome engine braking on top gear. There is a hill like that on the m40 near Princes Risborough  but in the bm even that hill was overcoming the weak engine braking it has so I disabled the limiter and let it speed up to 75. I’m sure in a diesel the coasting function would have helped here.

 

I’m wondering if diesels should have an air cut-off to reduce engine braking, but I’m sure they would have such a thing if they were easy to implement (some industrial engines have them to stop runaway)

My RS coasts as well in Normal and Comfort modes.

Which means if it`s software related it maybe could be activated with VCDS?

On 28/04/2019 at 04:11, PoloGaz said:

Good reply Gerrycan! I am finding very few scenarios where I wouldn’t have to hit the brakes when coasting or pull the downshift to get some engine braking.

 

The only scenario I can see where it’d benefit is a long downhill that’s not quite steep enough to overcome engine braking on top gear. There is a hill like that on the m40 near Princes Risborough  but in the bm even that hill was overcoming the weak engine braking it has so I disabled the limiter and let it speed up to 75. I’m sure in a diesel the coasting function would have helped here.

 

I’m wondering if diesels should have an air cut-off to reduce engine braking, but I’m sure they would have such a thing if they were easy to implement (some industrial engines have them to stop runaway)

 

Where I live the terrain is mostly flat and urban traffic generally flows more smoothly than UK urban environments and even though my 1.4tsi provides very little engine braking it is still enough to avoid a lot of unnecessary brake use and I can get really good mpg as a result, even without coasting.

However a recent motoring holiday via the ferry to Tasmania took me into a quite mountainous terrain and to be quite honest I really missed not having decent engine braking available. I probably put more wear on the brakes in 1,000km there than I did on the previous 30,000 km.

If I lived in a mountainous or very hilly area I'd seriously be considering the merits of hybrid or phev vehicle with regenerative braking options.

 

You have probably worked out that I regard standard brakes as very primitive, albeit effective, method of reducing momentum. Probably predate cart springs.

Edited 29 April, 20197 yr by Gerrycan

I wonder, Gerrycan, quite how steep the hills were.  My own 1.4TSi is a DSAG, and as soon as I touch the brakes when going downhill, it "knows" to change down and give me engine braking.  It goes rather lower than I would expect to do in previous manual cars (it typically changes down as low as  3rd for a town-type hill), but it certainly gives decent control and I don't need further braking unless I'm going down something like a 1-in-5.

8 hours ago, DaveMiller said:

I wonder, Gerrycan, quite how steep the hills were.  My own 1.4TSi is a DSAG, and as soon as I touch the brakes when going downhill, it "knows" to change down and give me engine braking.  It goes rather lower than I would expect to do in previous manual cars (it typically changes down as low as  3rd for a town-type hill), but it certainly gives decent control and I don't need further braking unless I'm going down something like a 1-in-5.

The parts we went through were pretty steep, similar terrain to the Lake District and we were fully loaded with 4 adults and accompanying luggage.

I've used the following story before on this forum but I live in Adelaide, South Australia which is bounded to the south and East by the Adelaide Hills, not real tall but the main freeway approach from the South East has a relatively long 3 km downhill with 1:8 to 1:10 gradients terminating suddenly at traffic lights on the City edge.

All other vehicles I have driven on this road whether diesel/petrol/auto/manual have been able to provide sufficient engine braking in 3rd gear or so to remain comfortably within the 90kph speed limits without having to make supplementary use of the brakes.

My manual 1.4tsi in 2nd gear, revving its nuts off cannot cope with these gradients  and to avoid it overrevving I have to use the brakes a lot or use 3rd gear and even more braking. And that is in a lightly loaded car.

Commercial vehicles are compelled to restrict their speeds to around 40kph or less on this descent with engine braking only and if they are seen to be using their brakes too much by police they may be stopped and fined. This rule came in after a series of truck drivers, descended too quickly, reliant on their brakes which rapidly became overheated and ineffective and failed to use the provided run off points with disastrous and tragic consequences.

Brake pads and discs are easier and cheaper to replace than engines and gearboxes. 

On 01/05/2019 at 05:14, silver1011 said:

Brake pads and discs are easier and cheaper to replace than engines and gearboxes. 

You are right of course and when you have GOT to use the brakes then only a fool chooses not too.

I probably just have a number of personal problems,

A childhood in crappy drum-braked cars where holidaying in more mountainous British areas meant engine braked descents were mandatory, it influences your driving for life.

A personal mix (justifications?) of frugality, concern for the environment and enjoying the challenges of daily economical driving.

I have never liked the concept of having to depend entirely on the brakes, I try to make them 'Option B' where possible and I never regarded simply taking your foot off the accelerator as really putting much stress on the engine. I thought that good anticipation of traffic conditions was essentially a characteristic of safe driving.

As I said before, if I lived in a more hilly environment I'd probably be looking at hybrid/PHEV alternatives with regenerative braking options, but I don't and I'm happy if I never have to replace brake disks or pads due to wear and I have never knowingly caused damage to an engine or gearbox over decades of driving from my (eccentric) driving habits.

After almost 15 years I know every inch of my 124 mile daily commute.

 

I've got not braking down to a fine art, knowing at which points to ease off the accelerator and when to down change is a skill that offsets the otherwise monotonous journey 

 

I've recently changed to an auto which is proving to be much more of a challenge though!

On 28/04/2019 at 19:42, linni said:

My RS coasts as well in Normal and Comfort modes.

Which means if it`s software related it maybe could be activated with VCDS?

 

I wondered why my car would only occasionally coast in normal drive and discovered that when if you release the  accelerator quickly, the car remains in gear, if you release slowly, the car will coast

23 hours ago, Matt3 said:

 

I wondered why my car would only occasionally coast in normal drive and discovered that when if you release the  accelerator quickly, the car remains in gear, if you release slowly, the car will coast

That makes sense, and depending on your driving style it is not something that would necessarily be obvious. 

Manufacturers sometimes put in 'features' that you only discover at odd, maybe inopportune moments, like when radar emergency braking  activates unexpectedly on a bend or adjacent to another vehicle. At least the coast feature is relatively harmless.

 

 

On ‎04‎/‎05‎/‎2019 at 08:31, silver1011 said:

After almost 15 years I know every inch of my 124 mile daily commute.

 

I've got not braking down to a fine art, knowing at which points to ease off the accelerator and when to down change is a skill that offsets the otherwise monotonous journey 

 

I've recently changed to an auto which is proving to be much more of a challenge though!

Likewise .. I know every poor manhole cover and pothole and miss accordingly! Appreciate that might seem sad to some ..

Mine coasts in normal and sport. I went for flappy paddles and can override coasting by pressing one of the paddles. It doesn’t kill the engine

 

The engine braking is fairly strong on the 1.5tsi, so I can see the advantage of the feature in this car, when it’s doing it at the right time!

Edited 6 June, 20196 yr by PoloGaz