[sheppards1984]

Hi all

Not absolutely sure it's a problem, but I'm experiencing the following behaviour:

When coasting around 40-50 kmh, in whichever gear with the clutch depressed ,  the car revs fine, reacts quick.
BUT
When coasting around 40-50 kmh, shift into neutral, then both feet on the floor, and I rev the engine, it revs really sluggish, delayed, and drops RPMs fairly slowly. Depress the clutch, and it's reacting as it should

Did anyone experience the same? I'm more inclined that this has something to do with emissions, but I don't really know. It's funky 

[Phil №❶]

When coasting around 40-50 kmh, shift into neutral, then both feet on the floor, and I rev the engine, it revs really sluggish, delayed, and drops RPMs fairly slowly. Depress the clutch, and it's reacting as it should

You shouldn't be driving in this way, it's a dangerous practice IMO. 

[sheppards1984]

Yea, we all know highway code (or what's its name in english).

In the city, and in a lot of cases out of the city, I can glide and coast for km-s depending on the conditions. I've been doing this for 10+ years   

Anyway, any thoughts on the topic? This is not why I posted here, you know 

[Surferdude]

Fair question IMO. I don't know the answer but it would be good to know what factors are causing this.

[Dazzler]

I think it has been discussed/revealed on here before by someone (Alan maybe?) That apart from being dangerous, that coasting in neutral(due to ECU management and other factors) does not result in better economy than coasting in a high gear. 

SO, in my opinion, as modern cars are not designed to do this, the ECU does not manage the engine well in these situations. 

[crayman]

Yes something with an ecu is a totally different animal to diesels of old.
The ecu programmer can do anything and I'd hazard once the ecu detects the neutral signal, it switches to a different map for best emissions.
Car thinks it's sitting in traffic or such.   
But it would still have a speed signal and this is when ecus often get confused, so strange things happen.
A clever programmer might foresee this situation and build in another correction, but as it's such a rare occurrence, they'd probably ignore it.

[sheppards1984]

Yup, I was thinking it had to something with the programming of the ECU.

Engine braking (letting it slow down and coasting in gear) in most cars equals zero fuel consumption. However in modern (diesel) cars I've heard that it in fact has some consumption due to the mapping of the ECU.

On the other hand, coasting in neutral is constantly eating up 0,3-0,4 litres/hour ~ nothing, at for example 80-90 kmh speeds.

So if you compare the 2 hypermiling methods, the results are roughly the same in consumption, however when coasting in neutral, you can actually cover a much larger distance, because engine braking slows you down.

In reality it depends on the situation. You can use engine braking to approach a red light, and for example there are slight slopes, where you actually need to give a little throttle to keep the speed up, whereas gliding in neutral would yield you constant speed because of the slight slope.

Just a few thoughts. I'm using both techniques on a daily basis (I've been travelling the same route for 5 years constant), and I've calculated that I glide/engine brake 10 % of the whole trip 

But back to topic, thanks for the answers,   

[crayman]

You raise some interesting points.
An ecu equipped vehicle will have zero % duty cycle on the injectors on overrun (fuel cut on deceleration) where as your coasting will have the engine running at idle settings.
But you're going to cover a greater distance in neutral than the vehicle in gear.
Might be one for Mythbusters ???
Haven't done any "Angel" gear driving since the 60's and 70's when our underpowered trucks would need all the assistance available to run at hills.
Modern huge hp trucks will come downhill with the engine brake maintaining cruise control setting then power up the other side like there was no hill at all.

[diablo]

I think it has been discussed/revealed on here before by someone (Alan maybe?) That apart from being dangerous, that coasting in neutral(due to ECU management and other factors) does not result in better economy than coasting in a high gear. 

SO, in my opinion, as modern cars are not designed to do this, the ECU does not manage the engine well in these situations. 

Yes, I and some others have mentioned that if the engine is in gear and your foot off the throttle then fuel consumption will be zero.  If it is in neutral then the ECU has to supply fuel to keep the engine going.

[sheppards1984]

Agreed 

Where I live,there are crapload of hills, climbs and descends,so bot can be used quite randomly.

Even on highways,we have special "climb lanes" where there are bigger inclines.


Not sure about GB,but aussie guys are usually living in flat terrains?

[Phil №❶]

Oz is pretty flat, unless you live in the eastern states were 80% of the population live, so not so flat actually.

[Dazzler]

Oz is pretty flat, unless you live in the eastern states were 80% of the population live, so not so flat actually.

And Tasmania is one of the hilliest islands in the world!

[Phil №❶]

Tas is considered easterly, by me at least.

[sheppards1984]

Ah,no worry guys, I only know about Australia's terrain ftm mad max

[CraigB]

Ah,no worry guys, I only know about Australia's terrain ftm mad max

Which one? the last film Fury Road was filmed in Namibia

[sheppards1984]

The first loe budget ones 

[CraigB]

They were the best one's, the first two anyway...Beyond Thunderdome was crap

[Lakes]

Hey Sheppard, can't help with your problem, but the fuel controlled with software not the old way.
But forty years ago they called what your doing, " using Angel gear "
Diesel's use a full bore of air and control engine speed with fuel, petrol control engine speed with air & the ECU just works out afr. thats why diesels have a low speed flat spot off idle, but the new ones do a good job hard to feel it now, but still there!
good luck