Engine braking

[Voodoo_Ray]

Question 2:

 

I am trying to driving on ECO mode and like the slip into Neutral the gearbox makes when I am coasting on the motorway.  However, I've noticed that when going downhill the auto gear box uses the engine to break and slips down a gear or two resulting in the RPM going over 2500 to slow the car down.  It's a grating noise with the RPM runs that high and is spoiling my fuel economy whilst feeling completely unnecessary on the road gradients I am using.    

 

Is there a way to turn this off?

 

Cheers

Steve

 

[WaterMelonMan]

......when descending, feather the accelerator very slightly and for a very brief moment, this will kick gearbox back to coasting, as soon as you touch the brake the gear box will kick back into a gear to invoke engine breaking.

• Brake touched last = engage gear
• Accelerator last touched = coast

[RicardoM]

@Voodoo_Ray

You bought the 190 HP edition and you need to drive it in ECO mode? On top of that with an automatic gearbox? That is hilarious. All conditions are met to burn a LOT of fuel and to fight the gearbox that has its own mind. If you had the money to buy the car, you can open the kitty wider for fuel too...

[MrTrilby]

1 hour ago, Voodoo_Ray said:

Question 2:

 

I am trying to driving on ECO mode and like the slip into Neutral the gearbox makes when I am coasting on the motorway.  However, I've noticed that when going downhill the auto gear box uses the engine to break and slips down a gear or two resulting in the RPM going over 2500 to slow the car down.  It's a grating noise with the RPM runs that high and is spoiling my fuel economy whilst feeling completely unnecessary on the road gradients I am using.    

 

Is there a way to turn this off?

 

Cheers

Steve

 

 

Are you using cruise control at the time? The car will use engine braking to prevent the speed increasing. As WaterMelonMan mentioned, it will also automatically use the gears to assist the brakes on some hills. 

 

And glad to amuse Ricardo too - I use eco mode a lot to reduce fuel consumption too. Although I don’t find it makes any real difference on the motorway as you’re mostly travelling at near constant speed for long periods. Biggest improvement to economy by far on the motorway is to keep the speed at or below the legal maximum.

[WaterMelonMan]

I've copy and pasted snippet by someone else from another forum which I found interesting:

 

Quote

In the olden days, when we had simple carburettors, coasting definitely saved fuel: releasing the accelerator left the throttle open just enough to provide at idle speed sufficient fuel for the engine to idle. When going downhill still in gear, though, much more air would be sucked through the carb than at idle, and hence more fuel consumed.

With modern fuel injection, the amount of fuel supplied is electronically programmed to match the power demand, rather than just the revs. A small amount will be provided at idle (so it doesn't stall), but on the overrun, as when going downhill with the accelerator released, the power demand is nil, and the supply of fuel is essentially turned completely off. Going downhill in neutral will use MORE fuel than in gear, as the engine tries not to stall.

There are no doubt slight benefits in that, with the transmission out of action (especially if 4-wheel drive), there will be less frictional resistance to the car's movement. I'd happily take those benefits via the DSG, but not by putting the transmission into neutral (for the reasons of sudden need, described above).

 

[Ootohere]

There are circumstances where vehicles that have the option of putting into ECO Mode can suit.  Nothing to actually do with fuel saving, maybe just the driving in traffic jams, commuting traffic etc, different weather / seasons, drivers or trips.  Like all Modes and driver options you can try, use or not use as suits. They are not compulsory and might be suitable for some drivers needs and use. 

Edited 10 August, 2019 by Roottootemoot

[MrTrilby]

I disagree with that snippet, particularly with respect to turbo diesels. There's a reason why the term engine braking uses the word "braking".

 

(1) Turbodiesels can run very lean, so when warm at idle with no load they really don't burn very much load. Particularly if ancillaries such as the alternator and A/C are also disengaged.

(2) When coasting in gear, the engine is effectively being asked to compress air, which takes energy. Modern turbodiesels run fairly high compression ratios.

(3) When coasting in gear, the momentum of the car is being used to overcome the full drag of the drive train

 

Coasting with the engine in neutral reduces those energy losses: the car slows down less than if it were in gear. That's a pointless saving if you're heading towards traffic lights and about to hit the brakes but a useful saving if you're just backing off the throttle a bit as the traffic in front sorts itself out; or you're wanting to lose speed gently before a corner; or you're heading down a hill steep enough to maintain speed etc.

 

In my experience, on some journeys (particularly gentle A road commutes in traffic), it can save a noticeable amount of fuel. On other journeys (motorway trips or in a rush) it makes no difference at all.

 

The nice thing with Eco Mode as well is that you can you decide when it coasts and when it does not - a light tap to the brakes or a paddle shift switches off coasting. A light tap on the throttle switches it back on.

[Voodoo_Ray]

I'm glad this post has provoked lively debate thus far.

 

I'd worked out the accelerator tap to go back into coast.  It just seems a bit unnecessary which is probably just me being a bit lazy.

 

I can't quite say the engine is screaming at 2500-3000RPM when the gearbox goes down a notch or two on a hill but it disturbs an otherwise smooth ride.  Guess I will have to invoke the above manoeuvre or live with it.

 

And Ricardo, I take your point; however, buying the car damn near made me broke and no point in using fuel unnecessarily.  Most of my drive is on the M1 during rush hour, so even on Sport mode, it's not going to be as enthralling as a lap at the Nurburgring.

[ZacDaMan72]

Why would you buy a car that damn near makes you broke? 

[WaterMelonMan]

1 hour ago, ZacDaMan72 said:

Why would you buy a car that damn near makes you broke? 

 

....it's quicker than walking and can carry heavy items easier?

[Ootohere]

Go to the Octavia / Superb section and you will find some that did it to make their fortune as Taxi drivers.....

[RicardoM]

16 hours ago, Voodoo_Ray said:

And Ricardo, I take your point; however, buying the car damn near made me broke and no point in using fuel unnecessarily.  Most of my drive is on the M1 during rush hour, so even on Sport mode, it's not going to be as enthralling as a lap at the Nurburgring.

Yeah, but you made all your neighbours jealous🤑 Including Daisy at14B that still drives a 10 years old Japanese car. "Yeah her car has exceptional fuel economy, yeah it is reliable, yeah it has a manual gearbox that she can shift when she wants, but let's face it, mine is bigger and shinier, and most importantly I look rich although I had to sell a kidney to buy it and for the next 15 years I will have to eat yogurt and bread."

Enjoy.

[DaveMiller]

Wow. Two of my favourite foods: yoghurt, and bread.

[TheRobinK]

Wow. One of my favourite girls: Daisy at 14B, who shagged me cos I drive a Kodiaq.

[ZacDaMan72]

8 hours ago, WaterMelonMan said:

 

....it's quicker than walking and can carry heavy items easier?

 

Sorry, didn’t realise that you could do that with a more affordable car. 

[RicardoM]

8 hours ago, TheRobinK said:

Wow. One of my favourite girls: Daisy at 14B, who shagged me cos I drive a Kodiaq.

Just to be clear. This is Daisy.

[Sabertooth]

She is by no means unattractive. I guess as the saying goes; beauty is in the eyes of the beholder. 

[WaterMelonMan]

10 hours ago, ZacDaMan72 said:

 

Sorry, didn’t realise that you could do that with a more affordable car. 

 

........glad to be of service