And aerodynamics?

Tips, advice and tips to lower your consumption, processes or inventions as unconventional engines: the Stirling engine, for example. Patents improving combustion: water injection plasma treatment, ionization of the fuel or oxidizer.
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Did67
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by Did67 » 28/01/11, 12:04

I do not think you're talking about the same thing:

1) cars a little old: at the end of the hood, there is a part of bodywork more or less horizontal, then windshield with wipers plated on ...

There, in this lower part, one is in overpressure, with generally gills for the entry of air ... which works without fan

2) more recent models, with the hood which ends up a bit like a "spoiler" and which hides a space "sheltered" from the air flow, in which the wipers actually fold ...

There, I think that we are in depression in the central part hidden by the lip of the hood in "spoiler" ... I did not blow under all the hoods, but on my C5, there is no plug between ; there is just a flow of water ...

The gills are then poiséed more on the side, where the spacing of the air flows, with a leak on the side at the height of the retro, near the amounts, will generate a slight overpressure or at least a turbulence ... So at this level, I think we are rather overpressured ...

I agree that the natural ventilation is less good, but it exists (eg on my C5, which has this niche and this spoiler effect)


I get the feeling that Citrox is talking about 1) and that storm is talking about 2) ... No?

NB: the internal ventilation, in addition to the effect of overpressure to the air intake, can also be linked to the extraction effect at the level of the exhaust openings in a zone of depression at the back (sometimes behind the uprights). tailgate and / or trunk)
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oby
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Registration: 29/10/08, 11:29




by oby » 28/01/11, 13:56

Hello,

of course, engine manufacturers and car designers study the Cx of the vehicles they design. The question is not simply "with a lower Cx we will consume less", but also "what should be put aside to have a lower Cx?".

You talk about the vents, actually it is a friction of the air (at least a downstream grid turbulence, so the energy dissipation), but a poorly cooled engine consumes more (we are not in the same place on the Carnot cycle) ...

Simplistic answers of this type are therefore perfectly incomplete.

I allow myself this remark because, as in many energy fields, when a "detail" disturbs, the solutions provided are currently generally worse than the previous causes (catalytic converters, E10 etc.).

Sincerely,
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Macro
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by Macro » 28/01/11, 14:15

If I can allow myself ...

The E10 do not have a solution brought..It is a response gifts of our thinking heads to the sugar beet sugar cerealiers lobby .....

To such a point a doll in the zieuzieu that says it to incorporate 10% and that one incorporates barely 7.5 ... Because we are not able to say if the cars will be able to burn it without problem in our latitudes. ..

This product has not diminished the dependence of our country in oil ... On the contrary ... The people who thought they were doing well by renewing their old trolleys by a capable of swallowing this patent ... See their fuel budget increase...
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oby
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by oby » 28/01/11, 14:52

perfectly
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I Citro
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by I Citro » 29/01/11, 00:48

Macro wrote:The E10 is not a solution brought..It is a response gifts of our thinking heads to the lobby of cereal sugar beet growers .....
...
This product has not diminished the dependence of our country in oil ... On the contrary ... The people who thought they were doing well by renewing their old trolleys by a capable of swallowing this patent ... See their fuel budget increase...
+2
Sugar lobbies lobbied the government for a new financial windfall (our taxes) to compensate for the announced loss of EU subsidies they were receiving under the Common Agricultural Policy (CAP)

I remind you that among the first beneficiaries of the CAP, there were big "farmers" like Prince Charles of Great Britain or Prince Albert of Monaco ...

For the energy efficiency of ethanol, experts agree that producing 1 liter of beet-based ethanol consumes more than one liter of oil (fuel for agricultural machinery, transportation, fertilizers and other inputs ...), the opposite of the desired effect ...
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oiseautempete
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by oiseautempete » 29/01/11, 09:49

Did67 wrote:I do not think you're talking about the same thing:

1) cars a little old: at the end of the hood, there is a part of bodywork more or less horizontal, then windshield with wipers plated on ...

There, in this lower part, one is in overpressure, with generally gills for the entry of air ... which works without fan

2) more recent models, with the hood which ends up a bit like a "spoiler" and which hides a space "sheltered" from the air flow, in which the wipers actually fold ...

I agree that the natural ventilation is less good, but it exists (eg on my C5, which has this niche and this spoiler effect)


I get the feeling that Citrox is talking about 1) and that storm is talking about 2) ... No?


Indeed ... on an R12 for example. the air intake is even slightly rising, but this type of car is still "a little" obsolete, the proof, the SM was designed in 1969 and already has a relatively modern configuration ... the first car that I had and which had not the slightest ventilation without fan motor (the one or this one broke down) was a VW Scirocco series 2 and the air inlet was however horizontal in front of the windshield (there is no had no deflector for windshield wipers) like what we do not necessarily have overpressure at this place (depends on the shape of the body) ... there was also an accessory, a scoop, which we could install to improve ventilation, it was a very common gadget at the time (we could find it even in supermarkets ...) ...
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Ca
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by Ca » 30/01/11, 11:41

Wao, since time : Cheesy:

Finally, a chemist should have told me that the resin was eating polystyrene : Cry:
In short I ordered the vortex generators directly in the United States, with customs fees at the same time (band of swelling).

If we ever have openings at the end of the hood just before the windshield rises, and we have no natural ventilation (and we want one), is an air intake (as on the subaru on the middle of the hood for example) that forces the air to enter the gills is it possible?
Since the air speed "horizontally" on the hood is high, and therefore the pressure small, if the air necessarily enters the gills,
after the speed will be low and vice versa for the pressure.

If not on a few recent vehicles, I noticed at the end of the bonnet, just before the wiper compartment, a kind of jump wind, a small recovery of the hood followed by a clean cut, or even a small flat horizontal (I do not know anymore).
Is this the kind of spoiler you mentioned Did?
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oiseautempete
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by oiseautempete » 30/01/11, 11:50

Your questions already have an answer in previous posts ... and on the Subaru, the hood air intakes are for the air / air exchanger ...
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eco_mobile
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by eco_mobile » 11/12/11, 18:53

basis of a quality system => you have to know the initial state.
So we have to measure

To measure your consumption under aerodynamic stress, as long as we do not have access to wind tunnels : Mrgreen:
There is now for an 40ene of euros the kits ELM323 or elm327 + software obdII which dialogues in dynamics with the management of the engine (ECU).

With this you can memorize at steady speed
throttle butterfly opening (throttle pedal electric control)
-instant consumption
-speed
-charging engine

Since aerodynamics is predominant at high speeds, it is advantageous to measure at 130 KM / h steady speed.
Change an aerodynamic element of the car
redo a measurement

I will try to improve the aero AR of a Twingo 2 (raw and straight cut ass, by a spoiler with the famous 14 ° // airflow on the bodywork.

Have others already tried?
I just acquired an ELM327 and I tested some inconclusive free software.
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dedeleco
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by dedeleco » 11/12/11, 19:54

Simpler method of measuring wind force (square of wind speed):
In the mistral you measure the force on the vehicle hung at the end of a cable under a large gantry or crane, by measuring the angle deviation due to the wind (and an anemometer for the wind speed) !!
More simple with a model of the same shape as the car, with the changes, not too small!
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