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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vttdechaine
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And aerodynamics?




by vttdechaine » 07/04/06, 17:38

Hello everybody

By quickly going around the current topics, I have not yet seen any topic dealing with aerodynamics. I am, perhaps, off topic (in this case I will not be bothered that I change creamery ). But as it is noted "Tips to consume less", I think I have found my home port.

I have a Saxo oil 122 000 km that rolls today with a mixture of oil and diesel (between 15 and 30% depending on the mood). The goal is to move it to medium-term G +. But there will be work is sure!

In the meantime, I intend to modify a few points of the Saxo to improve the flow of air and graze ... 0.2 liter to one hundred (this is the stated goal!). The current conso is always lower than 5 liters except on highway (speed stabilized between 120 and 130). I own a notebook where are noted all full with mileage since the first kilometer of the car. It will be easier to measure the gain.

In terms of aerodynamics, I am told, properly documented since I am interested in this since the end of the 80 years (I was 15 years still it was a long time ago ... :? ). I have signed some articles in the car press but I know that I still have a lot of things to learn and understand.

I had already made some changes (aero and weight) on my previous car: Citroën AX diesel. The conso was down to 3.95 liters in normal use (80 km / h alone on the road - 90 km / h when I was followed + a little city). But the changes were rather poorly made and I hope to improve my achievement now on this project.

So I will try to transcribe in the coming months the changes on my car with some photos, difficulties encountered and measured gains.

If other people have made similar experiences I will be happy to have their advice.

Finally, if some have questions about aerodynamics in general, and to the extent of my abilities far from being exhaustive, I can answer them.

Econologically to all
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by Former Oceano » 07/04/06, 17:47

Years ago, I had put hubcaps on a 5CV tax company R6. The wheels were fitted with old rims and it was both ugly and very wavy :P .

With the hubcaps, the wheel was smooth and we won 0,3 at 0,5 L / 100 km.
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by vttdechaine » 07/04/06, 17:48

I forgot the main : Lol: !

Modifications expected to date are:

- flat bottom on the back part of the car (supported by the spare wheel basket)
- rear wheel arch partly carinated
- small blade under the front shield
- fairing on part of the radiator
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by Christophe » 07/04/06, 18:19

1) The aerodynamics is obviously very important but its importane remains rather negligible at low speed (below 60 km / h) beside the other forces.

After (> 100 km / h) the aero friction obviously becomes the majority.

It seems to me that I had calculated this in the 1ere part of this report:

https://www.econologie.com/les-transport ... es-27.html

2.2) The energy need far too satisfied in the city.

2.2.1) The computational approach.

2.2.2) Results and conclusions.


2) What is the G +?

3) I think you know the citroën Eco2000?

4) And the technique of shark skins? Will not it be applicable to cars by accident? : Idea:
Last edited by Christophe the 14 / 08 / 06, 10: 34, 1 edited once.
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by vttdechaine » 07/04/06, 18:38

Econology wrote:1) The aerodynamics is obviously very important but its importane remains rather negligible at low speed (below 60 km / h) beside the other forces.
Yes. Below 60 km / h the mechanical friction forces (tires, bearings ...) are more important than the aeros losses.

After (> 100 km / h) the aero friction obviously becomes the majority.
Widely! Especially since this force evolves to the square of the speed and that the friction evolves just with the speed.

It seems to me that I had calculated this in the 1ere part of this report: https://www.econologie.com/les-transport ... es-27.html

I'll go see!

2) What is the G +?
The Pantone version of Michel and André on a diesel 205. Unless I'm miserably stuffed ... :|

3) I think you know the citroën Eco2000?
Yes ... But all the others too! Vera, Vesta, Ford, VW versions ... I also worked on an Eco Marathon a few years ago without having the possibility to concretize by the track ... I was the team to me all alone and very little support from teachers.

4) And the technique of shark skins? Will not it be applicable to cars by accident? : Idea:
If I'm not mistaken about what is shark skin I think no. We must actually separate the drag force (which interests us to consume less) in several components: the shape drag, the internal flows, the friction of the air on the bodywork ...
The drag is a big part of the drag. It is on her that you have to work when you want to win big!
The internal flows are small disturbances: engine cooling, ventilation of the passenger compartment. There is gain to be made but it is very rarely a priority.
The friction of the air which licks the bodywork is negligible compared to the two previous parameters. If this friction can be important in the water, in the air (and on a car!) It is better to work the shape than the coating.


Last edited by vttdechaine the 07 / 04 / 06, 18: 44, 1 edited once.
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by vttdechaine » 07/04/06, 18:42

Ah ... I can not download the linked document. He does not recognize me as a member ... :|
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by Former Oceano » 07/04/06, 19:18

Go see the home page of the site and request to receive the Letter.
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by Other » 07/04/06, 19:20

Hello Vttdechaine

A place where the Aerodynamics is often neglected is the underside of the car, just put a sheet under the engine and provide a parralelle exit to the floor, the rear of the vehicle would be a good place to work but difficult to achieve without getting into problems with the big changes.
A rounded gulf shape forward is preferable to the pointed form
supersonic aircraft. all the small asperities antenna, door handle, gutter ect .. that damaging
But to ride at speeds of 80kmh 100kmh gains are minimal, when you exceed the 160kmh it starts to feel, around 230kmh it becomes very hard,

For your information

We made some small changes on an Aeronca champion 7AC that looks like a J3 piper
This model does not exceed 145 kmh at the factory

Changes by importance of gain

Seal the joints in the fins with a sticky tape in the seam (the biggest gain)

Modify the air outlet under the hood (extend the air outlet under the floor so that the air must remain glued to the floor)

Laying wheel fairings

Butcher the joints of the elevator and drift governors

Install bosses in all shrouds against the wing and against the fuselage.

It's now crunching at 170 kmh and more fuel-efficient.

I may be out of focus but when you get into aerodynamics you have to start with the most strident things and you end up with the trinkets
The more you go, the more the effect is felt, the gain must be measured in% speed.
We made all the changes one after the other and the way to measure is full power and GPS speed measurement Measurements must be made the same day same atmospheric condition. it took us a whole summer to do these tests
and we have not finished ...
Often the most important gain is not where we believe it when we say it to others they are well septic, yet this old cuckoo with a 85hp engine far exceeds a 150hp cessna 100hp recent model in all configurations of flight

Good modification and patient

Andre
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by vttdechaine » 08/04/06, 17:36

Hello André,

Andre wrote:Hello Vttdechaine

A place where the Aerodynamics is often neglected is the underside of the car, just put a sheet under the engine and provide a parralelle exit to the floor, the rear of the vehicle would be a good place to work but difficult to achieve without getting into problems with the big changes.
I prefer not to touch the underside of the engine that can also ventilate. The F 355 for example (but also the Porsche Carrera 2 1991 with an almost flat bottom), despite a profiled bottom that ran on all the car, kept the underside of the engine in the open air ... and I think that there must be a reason ... (must be hot if you careen everything!). If I wanted to do this very well I would need measurements of the temperature of the engine compartment and then I arrange for this temperature remains the same, as you say, putting a "clean" air outlet which avoids some of the turbulence. Regarding my thin equipment I prefer not to engage in this study and book my time (and my nerves) for changes that will want to blow.

A rounded gulf shape forward is preferable to the pointed form
supersonic aircraft. all the small asperities antenna, door handle, gutter ect .. that hurt.
It would indeed be tempting to lengthen a little car to earn him a little Cx but I refuse. Knowing also that one of the directives and to be able to mount and remove this equipment quickly and thus not to have drilling on the bodywork. At most, in the wheel arches, I planned to stick the supports that will allow me to fill some of the arches of the rear wheels.

But to drive at speeds of 80kmh 100kmh gains are minimal, when you exceed the 160kmh it starts to feel, around 230kmh it becomes very hard.
Indeed, considering the "gargantuan conso" of the Saxo highway (I exceed 5 liters!!) I hope that this is where I would have my maximum gain (in logic it will be there). The only problem is that I rarely take the highway (there is 1 year it was weekly ... it's terrible to be late like that ...) and the measures will be so slow.
In addition the effects of the aero stand out all the faster than the car is ... big (S.Cx important). For my little Citroën so I really did not take the right model ... Does anyone have a C6 to sacrifice for my happiness in the audience? : Lol:


For your information

We made some small changes on an Aeronca champion 7AC that looks like a J3 piper
This model does not exceed 145 kmh at the factory

Changes by importance of gain

Seal the joints in the fins with a sticky tape in the seam (the biggest gain)
I thought about it but I fear that my companion does not appreciate that I condemn her door for the cause ...

Modify the air outlet under the hood (extend the air outlet under the floor so that the air must remain glued to the floor)

Laying wheel fairings

Butcher the joints of the elevator and drift governors

Install bosses in all shrouds against the wing and against the fuselage.

It's now crunching at 170 kmh and more fuel-efficient.

I may be out of focus, but when you get into aerodynamics you have to start with the most shooting things and you end up with the trinkets.
Not out of topic in my opinion. Auto aerodynamics and aviation have always been closely linked. Airplane experiments often remain references.

The more you go, the more the effect is felt, the gain must be measured in% speed.
Excellent idea !

We made all the changes one after the other and the way to measure is full power and GPS speed measurement Measurements must be made the same day same atmospheric condition. it took us a whole summer to do these tests
and we have not finished ...
For my part I will make all my changes the same day for two reasons:
I am "sure" of my modifs (I do not have the infuse science but they were for one part experimented on prototypes so I have little risk of error).
Take one by one, I do not know if I can find a gain. But all together, I think it will be significant enough to find a conso gap. By the way, you have to do a few hundred miles to get enough trial and I do not know if I want to roast 500 kms / week-end during 2 months to measure the gains of each modification :frown: .
But I realize that, technically and scientifically, it is a questionable attitude.


Often the most important gain is not where we believe it when we say it to others they are well septic, yet this old cuckoo with a 85hp engine far exceeds a 150hp cessna 100hp recent model in all configurations of flight

Good modification and patient

Andre
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by Christophe » 08/04/06, 17:42

vttdechaine wrote:Ah ... I can not download the linked document. He does not recognize me as a member ... :|


Ah yes ... it's for the "members".

Everything is indicated (it is free of course): https://www.econologie.com/devenir-membr ... s-452.html
Last edited by Christophe the 14 / 08 / 06, 10: 33, 1 edited once.
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