danny_f,

I disagree with your disagreement... By definition, fuel CUT OFF would be engine no longer running.. DANGEROUS!

The fuel MAY well be restricted to a tickover but you would notice a "Bump start" Every time you touched the gas again, in a similar manner, Motorcyclists often used to do what was refered to as a "Plug chop", Where you would ride, hit the cut off switch (Or turn off ignition) And then switch back on after a brief wait, the engine then re-fires up, often with a loud detonation/flames out of the exhaust. This was a method of checking the igniton and/or plug.

On cars, the engine is still powered, even if only at a very low volume, whilst removing pressure from the accelerator, in order to maintain function.

As for power steering... You refere to electric, which I believe is only part of the system (Combined hydro-electric) And even if soley electric, would NOT apply to ALL cars. My Yaris has hydraulic, my old driving schol Yaris had combined!

In addition, the electric system would fail very quickly indeed, if the engine was not running, hence the electric rear window only coming on after switching the engine on, along with many other, limited electrical functions, on almost (If not all) Modern vehicles.

Mrgf

I do not think you have looked at the AA link?

They say and I quote " Modern car with electronic engine management - fuel and ignition systems are effectively combined and controlled by one Electronic Control Unit (ECU). Take your foot off the accelerator and the ECU cuts the fuel supply to the injectors anyway so there's nothing to be gained by coasting.

Modern diesel engines - these also have the ability to shut off the fuel when you take your foot off the accelerator."

All other functions work due to the engine being turned mechanically by momentum.

Edited 21 May, 201115 yr by Dempsek

Mrgf

I do not think you have looked at the AA link?

They say and I quote " Modern car with electronic engine management - fuel and ignition systems are effectively combined and controlled by one Electronic Control Unit (ECU). Take your foot off the accelerator and the ECU cuts the fuel supply to the injectors anyway so there's nothing to

be gained by coasting.

Modern diesel engines - these also have the ability to shut off the fuel when you take your foot off the accelerator."

All other functions work due to the engine being turned

mechanically by momentum.

I coast and will do so for years to come, I however never ever switch the ignition off, I know the ECU shuts down fuel to the engine if your not on pedal and coasting , but by leaving it in gear the kinetic energy is stopped in gear and the engine is in breaking mode so you will not travel as far so will be forced to put foot on gas much sooner

On the PD engine you can actually hear the injectors come to life again as you slow down......the ecu recommencing injection to maintain idle. Its also noticeable on steeper downhill sections when with light pedal pressure the injectors cut out as the car overruns. The exception on my car is when its regenerating, the cut off system doesnt engage which makes the car 'run on' and freewheel (in gear) much more readily. Its very noticeable and one of the signs a regen has started

I think there is some confusion here between switching off the engine and switching off the fuel supply during pedal release when moving forward. On some 'sportier ' models you can reprogram this to maintain fuel flow even when not applying power, this gives faster pickup at the expense of economy.

Makes absolutely no difference whether its fuel burning making the engine rotate or if its the wheels driving the engine. Its still turning and everything works, your just saving fuel. Provided you are in gear on a petrol car you will still have manifold vacuum for the brake servo assist. On a diesel you usually have a vacuum pump driven by the engine for servo vacuum so makes no difference if fuel is flowing or not.

Seems like a lot of fuss on here for something so trivial. Diesels and petrol cars with injection that has electronic control cut the fuel off when in gear going downhill etc. Hard to change the habits of those die hard car drivers that get all nostalgic about carburretors and coasting

danny_f,

I disagree with your disagreement... By definition, fuel CUT OFF would be engine no longer running.. DANGEROUS!

The fuel MAY well be restricted to a tickover but you would notice a "Bump start" Every time you touched the gas again, in a similar manner, Motorcyclists often used to do what was refered to as a "Plug chop", Where you would ride, hit the cut off switch (Or turn off ignition) And then switch back on after a brief wait, the engine then re-fires up, often with a loud detonation/flames out of the exhaust. This was a method of checking the igniton and/or plug.

On cars, the engine is still powered, even if only at a very low volume, whilst removing pressure from the accelerator, in order to maintain function.

As for power steering... You refere to electric, which I believe is only part of the system (Combined hydro-electric) And even if soley electric, would NOT apply to ALL cars. My Yaris has hydraulic, my old driving schol Yaris had combined!

In addition, the electric system would fail very quickly indeed, if the engine was not running, hence the electric rear window only coming on after switching the engine on, along with many other, limited electrical functions, on almost (If not all) Modern vehicles.

lol, you couldn't be more wrong. The fuel feed is NOT restricted to a tickover. Fuel cut off does not mean the engine is no longer running at all, simply that it is 'running' on the kinetic motion of the wheels etc. Instant economy indicator on the CItroen C4 shows 999mpg (ie: unlimited mpg) as it is not using any fuel whatsoever when driving downhill as the ECU cuts the injectors when it senses the engine needs no fuel. If I was driving on the same road but knocked the car out of gear the indicator shows 125mpg, which is the basic tickover mpg - in this instance there is no kinetic energy coming through the gearbox so the ECU supplies fuel accordingly. All this bump-start nonsense is back in the last decade mate, modern ECUs are simply too clever.

The rest of your post, referring to electric systems etc is also moot, as the engine is still running, just not being supplied with petrol, so other systems on the car which rely on the engine running are not affecting.

Edited 22 May, 201115 yr by Didescharlie

danny_f,

I disagree with your disagreement... By definition, fuel CUT OFF would be engine no longer running.. DANGEROUS!

The fuel MAY well be restricted to a tickover but you would notice a "Bump start" Every time you touched the gas again, in a similar manner, Motorcyclists often used to do what was refered to as a "Plug chop", Where you would ride, hit the cut off switch (Or turn off ignition) And then switch back on after a brief wait, the engine then re-fires up, often with a loud detonation/flames out of the exhaust. This was a method of checking the igniton and/or plug.

On cars, the engine is still powered, even if only at a very low volume, whilst removing pressure from the accelerator, in order to maintain function.

As for power steering... You refere to electric, which I believe is only part of the system (Combined hydro-electric) And even if soley electric, would NOT apply to ALL cars. My Yaris has hydraulic, my old driving schol Yaris had combined!

In addition, the electric system would fail very quickly indeed, if the engine was not running, hence the electric rear window only coming on after switching the engine on, along with many other, limited electrical functions, on almost (If not all) Modern vehicles.

In you motorcycle example you are switching off the ignition but continuing to fuel so you end up with a lot of unburnt fuel when the spark is switched back on hence your bang.

When you lift off the throttle, when in gear, on modern engines the fuel is switched off totally, the engine continues to rotate as it's physically connected to the wheels so you do not loose any electrical or hydraulic systems as they are still being driven by the rotating engine

Anyone with the slightest knowledge of engine maps will confrim this too you as the programming is easy to see. When the engine revs drop to near tickover or the clutch is dipped the fueling is reintroduced.

Sometimes coasting will be more benificial to fuel economy as it doesn't scrub off speed. The 7 speed DSG will coast in certain situations but as soon as you touch the brakes it will engage gear to maintain engine rotation and cut the fuel.

Cheers

Lee

Edited 22 May, 201115 yr by logiclee

http://youtu.be/ZsdiEc80vKs

I bet the director had a nightmare making this video look and sound exciting - obviously he failed.

Just found out a greenline in dealers here 10 weeks they are lost to know only getting 30 mpg 10 plate with 3k on the clock

The way its driven perhaps? (Mechanics' hack?!).

Just found out a greenline in dealers here 10 weeks they are lost to know only getting 30 mpg 10 plate with 3k on the clock

That'd be a Greenline I wouldn't it? Don't think the advances were that great in terms of fuel consumption though...

That'd be a Greenline I wouldn't it? Don't think the advances were that great in terms of fuel consumption though...

should be nearer 70 than 30 mpg

I coast and will do so for years to come,

Although this is only one example; I am amazed, from reading this thread, at how many cars may not actually be under full control of the driver in certain road conditions.

I was taught to abide by the Highway Code and although I am no saint on the road, have always followed the general safety requirements and recommendations for controlling a vehicle.

Tony

Although this is only one example; I am amazed, from reading this thread, at how many cars may not actually be under full control of the driver in certain road conditions.

I was taught to abide by the Highway Code and although I am no saint on the road, have always followed the general safety requirements and recommendations for controlling a vehicle.

Tony

Hi tonyvrs

down your way in july,bassingbourne atr may bump into you

Edited 26 May, 201115 yr by seboni121

I've never coasted - I just let my foot off the gas if going downhill, hence car is still in-gear, and keeping my right foot over the brake pedal in case I need to slow it down...

The swiss got it right with their mountain steam railways, the engine unit acted as an air brake on the downhills, no steam was directed to the pistons and the compression of air in the pistons kept the speed at a steady rate all the way down.

Not exactly a new concept in engine design now is it?

Anyway, back on topic, I notice the drivers average speed was 85Km/h (around 50mph), he must have been on fairly flat roads nearly all the way and 'coasted' where possible!

Edited 26 May, 201115 yr by Guest

Hi tonyvrs

down your way in july,bassingbourne atr may bump into you

Smashing; I'll bring this thread to the court room.

Tony

I've never coasted - I just let my foot off the gas if going downhill, hence car is still in-gear, and keeping my right foot over the brake pedal in case I need to slow it down...

That's the way to do it.

Would be glad to meet you on the road any time.

Regards

Tony :yes:

That's the way to do it.

Would be glad to meet you on the road any time.

Regards

Tony :yes:

Likewise, sir! /tips hat

Dave :yes:

Ooooooh all those VRS owners who've never coasted?

Do you actually realise the 7 speed DSG does it all the time?

Ease off the power in Drive and the clutches disengage and you coast along without the engine being connected to the wheels. As soon as you brake or go back on the throttle the clutches reengage.

Cheers

Lee

Ooooooh all those VRS owners who've never coasted?

Do you actually realise the 7 speed DSG does it all the time?

Ease off the power in Drive and the clutches disengage and you coast along without the engine being connected to the wheels. As soon as you brake or go back on the throttle the clutches reengage.

Cheers

Lee

1-0 to the coasters, that will be an own goal then chaps/ tips his hat

I've just had 78.2mpg out of mine at an average of 50mph over a 1.5 hour 75 mile route!

Ooooooh all those VRS owners who've never coasted?

Do you actually realise the 7 speed DSG does it all the time?

Ease off the power in Drive and the clutches disengage and you coast along without the engine being connected to the wheels. As soon as you brake or go back on the throttle the clutches reengage.

Cheers

Lee

So how do account for the 'apparent' engine braking you get off throttle down hill that you won't get in N?

Also if you are correct why coast in N at all?

Confused.

Continuation: Just extracted this from the manual "When driving downhill, it is possible to shift down into the Tiptronic

position, in order to exploit the engine brake torque". This would support the clutch disengaging theory. I have not noticed this as I generally snick it down a gear or two on the paddles to obtain extra engine braking.

Also: "If the selector lever position N is selected by accident while driving it is first necessary

to release pressure on the accelerator pedal and wait for idling speed of the engine to

be reached before engaging a drive position in the selector lever". This seems to imply that the selection of 'N' whilst under way is not normal.

So that makes it 1 all and time to close this issue.

Tony

So how do account for the 'apparent' engine braking you get off throttle down hill that you won't get in N?

Also if you are correct why coast in N at all?

Confused.

Continuation: Just extracted this from the manual "When driving downhill, it is possible to shift down into the Tiptronic

position, in order to exploit the engine brake torque". This would support the clutch disengaging theory. I have not noticed this as I generally snick it down a gear or two on the paddles to obtain extra engine braking.

Also: "If the selector lever position N is selected by accident while driving it is first necessary

to release pressure on the accelerator pedal and wait for idling speed of the engine to

be reached before engaging a drive position in the selector lever". This seems to imply that the selection of 'N' whilst under way is not normal.

So that makes it 1 all and time to close this issue.

Tony

You should never select N while moving in a DSG, on the wet clutch DSG especially as this causes starves the clutch pack of lubrication. Even on the dry clutch models there is potential to cause damage when engaging Drive at high speed.

The 7 speed dry clutch has to meet certain paremeters to disengage the clutches and coast, the box must be in Drive, the accelerator and brake pedals must not be depressed and the vehicle speed must not be increasing ie going downhill.

If I can find the technical information online I'll post it up.

Cheers

Lee

I've just had 78.2mpg out of mine at an average of 50mph over a 1.5 hour 75 mile route!

Very good MPG what gear did you use to trundle on 4th or 5th?

Very good MPG what gear did you use to trundle on 4th or 5th?

Most of it was in 5th at 60mph on motorways and dual carriageways, it's the country lanes at both ends of the journey that bring the average speed down to 50mph.

Edited 1 June, 201115 yr by Guest