I have a different car, an old 1.4tsi manual Octavia, and of course I can choose when to coast where and when I want.

 

I have experimented with coasting and there are pros and cons.

An example of 'pro' I have cited before is a long descent on a 110kph limit highway where the gradient allows the car to coast at a constant 110 kph (aero drag matches gravity), the (my) engine is idling and consuming 0.5L/hour. If it is in top gear, then some extra throttle has to be applied for the engine to maintain 2700rpm to avoid engine braking and slowing the car below 110kph and that shows consumption near 2L/100, which is nearly four times as much.

If the gradient was more then I would be better off with car in gear using engine braking and zero fuel to keep the car below the speed limit.

 

In an urban environment, coasting will get better consumption than having to maintain revs in a lower gear for a low speed.

If lessening of speed is required, then you are better off using engine braking than coasting the distance and then applying the brakes.

 

While I know what works I cannot be bothered to utilise that knowledge all the time and just do what is easiest, which is read the road and anticipate traffic movements to avoid unnecessary use of brakes.

 

Mad keen hypermilers in the US have a kill switch in the car so that when they are free coasting then can turn the engine off, the semi-sensible ones have pumps supplying air pressure for the brakes. And continually accelerate and coast (engine off), getting up everyone's' nose. 

 

Remember the time when they built tiny vehicles with specialised engines that achieved 1000mpg? IF they ran the engine all the time then they would 'only' get consumption in the hundreds, but by accelerating to speed and then coasting with engine off they managed multiples better consumption. It also utilised the factor that an ICE engine is at its most efficient at revs and under load. 

It is somewhat confusing for some that an ICE car running at its most economical speed (let's say top gear at 65 to 70 kph) is actually operating below best efficiency because a high percentage of the fuel consumed is just to get the engine to the required revs and the rest in propelling the car. A formula one car at full throttle is one of the most efficient engines in the world despite the huge amount of fuel consumed.

Edited 11 June, 20241 yr by Gerrycan

'Urban'  as in Town / City very much depends what type of town or city roads those are. 

 

As to a manual put into Neutral that is one thing that many might never do when moving where the 'Coasting Mode' is part of the Type Approval of the vehicle and something anyone might activate and feel totally comfortable doing. 

21 hours ago, Ootohere said:

'Urban'  as in Town / City very much depends what type of town or city roads those are. 

'Urban' and 'highway' are generic but non-specific terms, the former usually has more interrupted flow patterns and slower speed limits than the latter. Still useful terms to distinguish between the driving environments, I think.

21 hours ago, Ootohere said:

As to a manual put into Neutral that is one thing that many might never do when moving where the 'Coasting Mode' is part of the Type Approval of the vehicle and something anyone might activate and feel totally comfortable doing. 

You don't have to be in neutral, you can also coast just by disengaging the clutch on a manual  .

 

The point is that I can coast more freely than some seem to be able to with their DSG box and associated programming.

It had never occurred to me that there would be so much variation between similar models with DSG.

If I ever make the transition to DSG (but probably more likely an EV) then I'd like to have the option to coast where I think conditions will promote lower consumption of fuel or electricity.

 

Edited 12 June, 20241 yr by Gerrycan

On 11/06/2024 at 11:51, Ootohere said:

@Gabbo  What messes up your theory is that the Test Conditions with the NEDC and then WLTP does favour 'Coasting'  and the cheats that VW had with DSG,s / S-tronics and cars during and after the Emissions Scandal. 

 

This is exactly my point. 

The test cycles are "lab conditions" driven by a trained driver or robot. 

Stop Start was created just to win some emissions on the cycle because there was a long "idling phase".

Coasting of the gearbox is quite likely developed for exactly the same thing. 

 

All manufacturers have coating so it clearly gives some benefit on the test cycle.

 

 

I don't say that in some conditions coasting wont have a benefit but in the real world, like stop Start, it will be worse in some conditions/better in others.

 

Overall, In 1000km driving on a tank, the difference between coasting for 50km or ingear for 40km will hardly register & I'd say that wind, temperature or wet conditions for a few kms will have much more significant impact on the fuel economy.

It was & is Lab Conditions and to the regime on the screen.  The European Kidology.  

The USA,s EPA is nearer real world.

 

As to Stop / Start, Cylinder Deactivation, Coasting being worse in some conditions, i doubt very much because they engineered in that at the low temperatures and the likes they are disabled. 

 

I would say the Emissions Control Systems, DPF / SCR & GPF are more fuel wasters.  but then VW dealt with that in the past by cheating with Defeat Devices, Software, 

and cheated testing with the likes of diesel in the engine oil.

 

For the WLTP that had gone to 0w 20 FS IV to help matters.   Now others are at it with 0w-8 engine oil. 

 

......................

In 1,000 km / 621 miles driven on a tank of fuel, or maybe the 721 miles i might get when keeping the toe off the accelerator & making the most of coasting being enabled that would be a lot more than just 31 miles of coasting.

But true, the difference of doing 25 miles or 31 miles might make a difference not to be noticed.

 

Lots of turbos happen to be better performing in a bit of wet weather / damp,  and then there might be losses with tyres in the rain.

Swings and roundabouts.

But then colder denser air in winter or just colder temps and the summer tyres on dry cold roads with less grip / traction / friction is also small differences.

 

Back to Many a mickle maks a muckle.   As Hypermilers know.  

Edited 12 June, 20241 yr by Ootohere

On 03/06/2024 at 09:39, CJXA said:

This morning hooked up obd11 to my IV octavia, unfortunately very few gateway coding bits were labeled, none of which were related to coasting, have to check it with vcds sometime later.

Did manage to find it in Octavia IV, FPA coding bits are under adaptation Driver profile selection (which makes sense). None of the freewheel related bits were active, but the car still coasts. I expect the FPA config work only in case you have an actual drive mode selection, which I don't.