Renault's car 2300 €

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Christophe
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by Christophe » 22/06/07, 12:08

Toutafé it depends especially on the engine power and the SCx (aerodynamic friction) I wanted to specify it but not made not to confuse, but for an "average" car (which is not the case of a porsche or a ferrari ..) that's pretty accurate.
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by Targol » 22/06/07, 12:38

Well, it must also depend on the gearbox reports, right?

Between 2 identical cars, one with "short gearbox", the other with "long gearbox" (they did that on the previous generation of Laguna), the best speed for less consumption must change.
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by Christophe » 22/06/07, 12:41

Yes actually it depends a bit on everything but the 2 biggest parameters are the ones I gave above.

After all, if we put a rally box in an everyday car ... necessarily .. :|
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by Woodcutter » 22/06/07, 13:26

Christophe wrote:
Woodcutter wrote:I find completely stupid the speech which says: "We can very well consume more by driving slower...
Well for sure : roll: on peut, but you really should be very stupid to do it ...


Not necessarily my dear Bucheron, because of the performance curve of an engine (which you also know, if not better than me) and especially the race with always more power.

However as the performance of an engine is better when it is loaded, I am convinced that by running optimally (no under nor over speed) an average car will consume more when driving at 30 km / h than at 70 km / h ... to obviously make the same distance.
[...]
Except that there was no question of 30 km / h, but a government speech to encourage people to drive slower ...

And whether at 130km / h, 110 km / h or 90 km / h, driving 10 to 20 km / h slower will always consume less ... (except maybe between 90 and 70 km / h but it depends circumstances).

Regarding the performance, it is especially valid if there is a real need for power demand from the engine ... To run a car at 70 km / h on flat, 10 horses are enough. And to make a sedan engine spit 10 horses, you just have to look at the accelerator pedal ...
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by bamboo » 22/06/07, 14:42

There is something else to take into account in the case of dense traffic:
When the speed is reduced, the circulation is much smoother (ie more constant speed): no big brakes, nor furious accelerations, which implies a reduced consumption.

This was verified in practice on the Paris ring road, at the _beginning_ of the installation of speed cameras: the places where there were these speed cameras had fewer traffic jams than before. This is explained by several things, including the following example: when someone enters the device, the guy on it no longer needs to brake because the incoming is almost at the same speed as those who are on the device.
(this is a little less true now because motorists give big brakes before the radar and quickly re-accelerate right after, which is no longer very fluid ...

However, if people drive slower (including when there is no radar), traffic is smoother, and the car consumes less.
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by ThierrySan » 23/06/07, 09:20

I see that the debate about speed limits works quite well, in fact !! : Mrgreen:

In fact, I wanted to talk about that, because at the time we went from 60km / h to 50km / h in town, for pollution issues. However, the design of the gearboxes is based on the available engine torque, and now we also integrate limited speeds in order to have so-called "economic" consumption.
To explain myself, if we take my little Ford Fiesta, when I drive at 50km / h, I am constantly in 3rd gear and I cannot pass the 4th gear at the risk of causing the car to graze: engine accoups, callage limit. Whereas, if I drive at 60km / h, it is then possible for me to drive in 4th gear, at a much lower engine speed.
However, the design of the new engines makes them very flexible, as much for V-shaped engines (the most flexible) as in-line engines. Indeed, I've happened to drive vehicles since the years 98/00, and I noticed that you could drive at 50km / h in 5th !! I find it fabulous ... Therefore, this discussion may not be more valid, but for old vehicles, it is amply !!

Then, for high-speed motorways and highways, I don't really know if the advantage of lowering the speed from 10 to 20km / h is just as valid, for the reasons mentioned by Christophe: journeys where the gearbox is constantly in 5th; this can be questionable for speeds between 90km / h and 110km / h. There is also to add aerodynamic resistance, which plays, I believe, significantly only after speeds of 140 / 150km / h ...

A little more serious study would be interesting and I look forward to it Chris! : Wink:
Still waiting for your feedback! : Mrgreen:
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by stef5555 » 23/06/07, 10:29

ThierrySan wrote:There is also to add aerodynamic resistance, which plays, I believe, significantly only after speeds of 140 / 150km / h ...



:? I would rather lean up to 70/80 km / h

good at the time the cx was quite important for some cars so I do not know if this indicated speed is still valid
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by Flytox » 23/06/07, 12:56

Bonjour à tous

ThierrySan wrote:In fact, I wanted to talk about that, because at the time we had gone from 60km / h to 50km / h in town, for pollution issues.
:


For my part I bought the explanation for a security story
pedestrians who are broke by a car in town.

The 10km / h less would statistically have a big impact on injuries and death. The braking distance at 50 km / h being significantly shorter the impacts are less violent.

ThierrySan wrote:However, the design of the new engines makes them very flexible, as much for V-shaped engines (the most flexible) as in-line engines.
:


In the automotive literature, flexibility is found to be proportional to the number of cylinders rather than the arrangement of these same cylinders.

For this story of 4 ° or 5 ° in town I often dreamed of having an overdrive that is 1/2 speed to easily adapt to this use in town at the limit of chatter.

ThierrySan wrote:Then, for high-speed motorways and highways, I don't really know if the advantage of lowering the speed from 10 to 20km / h is just as valid, for the reasons mentioned by Christophe: journeys where the gearbox is constantly in 5th; this can be questionable for speeds between 90km / h and 110km / h. There is also to add aerodynamic resistance, which plays, I believe, significantly only after speeds of 140 / 150km / h ...


The fact that one can consume less at higher speed than at lower speed is the proof of a big mismatch of the vehicle to normal use.

The saddest thing is that the marketing of this kind of vehicle is not slowed down, but promoted by the manufacturers who sell you dreams (it consumes almost nothing at 150 km / h)

There is also the state which would do better to adapt the taxation of vehicles according to the real nuisances produced and not the money to be withdrawn.

A+
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by Woodcutter » 23/06/07, 16:40

ThierrySan wrote:[...] Indeed, I happened to drive vehicles since the years 98/00, and I noticed that one could roll at 50km / h in 5th !! I find it fabulous ... Therefore, this discussion may not be more valid, but for old vehicles, it is amply !!
I don't know if my vehicle is "old" (1991) but I can drive very well in town at 50 km / h in 5th gear, or even at 40 km / h, as I have already explained many times ...
In fact, I can drive at idle speed on 5th gear ...
but:
- it's a Diesel,
- it is a 2,1 l engine
therefore which has much more facilities to run at very low speed than a small petrol engine from Fiesta (especially with oil, which improves the "roundness" of the engine at low speeds).

However, your 3rd and 4th year story surprises me a bit, because although I have been driving "fuel oil" for over 12 years, I have still driven a number of small gasoline vehicles ...

ThierrySan wrote:[...] Then, for motorways and high-speed lanes, I don't really know if the advantage of lowering the speed from 10 to 20km / h is just as valid, for the reasons mentioned by Christophe: journeys where the box is constantly in 5th gear; this can be questionable for speeds between 90km / h and 110km / h. There is also to add aerodynamic resistance, which plays, I believe, significantly only after speeds of 140 / 150km / h ...
No.
The influence of aerodynamics is really felt from 60 km / h.

Mon experience (which is therefore not not necessarily generalizable) makes me say that, whatever the road conditions encountered (except the extremes of course: mountain, tight turns, etc ...), it is at 90 km / h that I consume the least ...
Knowing moreover that I have never tried to drive for a very long time at a lower speed (70 for example), considering that, by design, my car cannot answer all the situations which one meets on the road under 90 km / h in 5th gear, because the turbo does not really bring power under 2000 rpm ...

In any case, under "ideal" conditions (in the laboratory for example) the consumption of my car would be the lowest at 40 km / h! (still in 5th)

I am therefore extremely wary of speeches that proclaim "my car consumes the least at 150 km / h!"
I'm like Saint Thomas, a well-known poker player: I ask to see!

(By cons, I have some strengths in my sleeves ... 8) : Mrgreen: )
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by Targol » 23/06/07, 23:20

Flytox wrote:The fact that one can consume less at higher speed than at lower speed is the proof of a big mismatch of the vehicle to normal use.

The saddest thing is that the marketing of this kind of vehicle is not slowed down, but promoted by the manufacturers who sell you dreams (it consumes almost nothing at 150 km / h)

There is also the state which would do better to adapt the taxation of vehicles according to the real nuisances produced and not the money to be withdrawn.

A+


Completely agree with all of this, Flytox 8)

Woodcutter wrote:Mon experience (which is therefore not not necessarily generalizable) makes me say that, whatever the road conditions encountered (except the extremes of course: mountain, tight turns, etc ...), it is at 90 km / h that I consume the least ...
Knowing moreover that I have never tried to drive for a very long time at a lower speed (70 for example), considering that, by design, my car cannot answer all the situations which one meets on the road under 90 km / h in 5th gear, because the turbo does not really bring power under 2000 rpm ...

In any case, under "ideal" conditions (in the laboratory for example) the consumption of my car would be the lowest at 40 km / h! (still in 5th)

I am therefore extremely wary of speeches that proclaim "my car consumes the least at 150 km / h!"
I'm like Saint Thomas, a well-known poker player: I ask to see!

(By cons, I have some strengths in my sleeves ... 8) : Mrgreen: )


I knew you sharp, I find you player, Bucheron : Lol:
Nevertheless the challenge interests me and I add 50F in the pot Image to have arguments encrypted on this drop in consumption when the speed increases.
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