Eco-driving in practice: Tips that work!

[Christophe]

An article on eco-driving published in an HS de Science et Avenir of 2008.

We go from 5.6 L / 100 to 4.2 L / 100 by adopting eco-driving ... much better than any magnet or other magnetizer

25% savings that still means 1 full in 4 "free" ...

Other tips fromeco-driving on the road: saving fuel




ps: I still hope that the drop is constant ...

[Christophe]

A quick reminder on the standardized European consumption cycle and the evolution of consumption



Source: same issue of S&A - 154 H - May / June 2008

[Remundo]

Hmm, there are some questionable little things ...

In particular the "longest and low speed" report places the engine on a specific bad consumption.

For vehicles with carburetor (old and increasingly rare), especially not to put in engine brake, that siphons the gasoline direction the muffler. On the other hand, for vehicles with electronic injection, it is favorable because in general, there is a cut in the injection in this case.

But this is only correction at the margin.

If there is something fundamental, it is to remember that the energy to be supplied on a path is proportional to the square of the imposed speed... Power, on the other hand, is the cube of speed.

Therefore, between the one traveling at 50 and the other at 100 km / h, one of the two will go 4 times less with the same volume of fuel, and will need 8 times more power during the whole trip...

I'll let you guess which one?

[Christophe]

Sacred Remundo!

I do not know whether to take your message in the tone of irony or not ... but it seems to me that you contradict yourself

Firstly :

a)

In particular the "longest and low speed" report places the engine on a specific bad consumption.

Absolutely, the performance depends on the engine power (therefore RPM) (although with recent diesel it is less and less sensitive) ...

...And on the other hand:

b)

is to remember that the energy to be supplied on a path is proportional to the square of the imposed speed

From a physical point of view yes but from a motorist point of view no since the specific consumption is precisely better at more sustained speed (= at greater engine power) ... see your point a)

There is a good chance that driving 20h at 5km / h will consume more than driving 2h at 50km / h ...

ps:

Therefore, between the one traveling at 50 and the other at 100 km / h, one of the two will go 4 times less with the same volume of fuel, and will need 8 times more power during the whole trip ...

Physically yes but in practice, this turn is 1 deceptive hair, with a vehicle with thermal engine, we do not consume 4 times more at 100 than at 50 km / h ... see a)

In practice, there is an ideal speed of "specific vehicle consumption", currently given the average powers, it is probably between 50 and 100 ... I would say more precisely between 70 and 90km / h ...

The more powerful and aerodynamic the vehicle, the higher this minimum consumption speed ... With a Ferrari, it surely exceeds 100 km / h ...

This remark is no longer valid with an electric vehicle.

[chatelot16]

it happened to me a long time ago with my citroen gs making the trip besancon angouleme at night, a long weekend not finding a gas station open to refuel ... did not have enough gas to finish the journey with normal consumption ... I did not want to spend the winter night waiting for it to open ... so I continued my journey in great economy, engine cut downhill .. very low speed in the mounted and no more flat ... I arrived in Angouleme without dry breakdown by spraying all the low consumption records

Another remark, I laugh when I see the drop in consumption of cars ... my gs without any mechanical modification also decreased consumption ... 20 years ago when I was making a lot and I was not afraid of cops, it consumed 12l / 100 ... now it consumes rather 6l / 100 ... of course the speed is not the same ...

[sspid14]

I hope that the course was not carried out one in positive elevation and the other in negative elevation, neither one with strong wind in the back and the other from the front ... otherwise it distorts not badly the data.

However, when I see some people in my family who consume 6,1 to 6,3 l per 100km and I reach 5,5 l per 100km with the same car, I confirm that it is possible to reduce not bad consumption !! 10 to 13% savings just by driving at 100 - 110 km / h on the highway and by anticipating the places where it will be necessary to brake (turning, giving way, stop, light, ...).

[elephant]

Say, Chatelot, you were flying too low!

In 1981, with a GS 1300 petrol station wagon, 3 people + luggage, Charleroi Carcassonne half highway, half national, 6,5 liters!

[Remundo]

Sacred Remundo!

I do not know whether to take your message in the tone of irony or not ... but it seems to me that you contradict yourself

Firstly :

a)

In particular the "longest and low speed" report places the engine on a specific bad consumption.

Absolutely, the performance depends on the engine power (therefore RPM) (although with recent diesel it is less and less sensitive) ...

...And on the other hand:

b)

is to remember that the energy to be supplied on a path is proportional to the square of the imposed speed

From a physical point of view yes but from a motorist point of view no since the specific consumption is precisely better at more sustained speed (= at greater engine power) ... see your point a)

There is a good chance that driving 20h at 5km / h will consume more than driving 2h at 50km / h ...

ps:

Therefore, between the one traveling at 50 and the other at 100 km / h, one of the two will go 4 times less with the same volume of fuel, and will need 8 times more power during the whole trip ...

Physically yes but in practice, this turn is 1 deceptive hair, with a vehicle with thermal engine, we do not consume 4 times more at 100 than at 50 km / h ... see a)

In practice, there is an ideal speed of "specific vehicle consumption", currently given the average powers, it is probably between 50 and 100 ... I would say more precisely between 70 and 90km / h ...

The more powerful and aerodynamic the vehicle, the higher this minimum consumption speed ... With a Ferrari, it surely exceeds 100 km / h ...

This remark is no longer valid with an electric vehicle.

But no, I don't contradict myself ...

The problem is complex: since you can't turn off your heat engine at 5 km / h, here's the rub.

In addition: the systematic engine brake is not the most economical. You have to let the car go while disengaging and leaving the gear engaged.

Why ? Do not forget that an engine brake is dissipative in a thermal. So the only possible regeneration is to recover its potential gravity energy by freewheeling downhill.

Again, because you cannot turn off the engine (much too dangerous), it idles, but consumes very little compared to the energy recovered through the work of gravity. What we would have gained in fuel by cutting the injection is more than recovered on the kinetic energy at the bottom of the hill ...

It's all an art

Etc ....

[dirk pitt]

some additional info:

on minimum consumption speeds:



and an example of a specific consumption diagram for a diesel engine: the mini consumption is good for large loads at low speed:

[Remundo]

very good these links and images, Dirk;

it will allow the reader to understand what I say about the specific cons