Aerodynamics
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DZLguy
Veteran Member
<font size="2" face="Verdana, Helvetica, sans-serif">If you lower it & brace it enough, it could become a real nice snow plow!
gdr703
Veteran Member
TurbeinDeizle, thanks for the encouragement. You said above a certain speed an airdam looses effectiveness for economy. Any idea, (ballpark) of what speed that might be?
cheers.
cheers.
Ya know, if you put a strip of them vortex inducer thingies just a little ahead of where the flow separates across the roof, you might be able to get the flow to come down the back nicely.
This will help hwy MPGs, and help the flow intercept that wing thingy.
Really, I'm not kidding.
This will help hwy MPGs, and help the flow intercept that wing thingy.
Really, I'm not kidding.
For itsmejerry-I don't know about imperial gallons or what ever,- all I know is that I have gotten 60mpg twice on my daughters 2001 5 speed TDI Jetta here in Calif. checked the filling, Odometed etc. Was driving at abour 70mph on the 2nd test with some 25-35 through a few small towns
(hers is stock as a rock)
She thinks that a trunk spoiler is cool-I think it looks like SH##, What are the opinions about its messing with her aerodynamics (milage)?
[ October 24, 2002, 13:20: Message edited by: skier013 ]
(hers is stock as a rock)
She thinks that a trunk spoiler is cool-I think it looks like SH##, What are the opinions about its messing with her aerodynamics (milage)?
[ October 24, 2002, 13:20: Message edited by: skier013 ]
Dorado
Veteran Member
If you want to keep your bug clean, you need to add an extra coat of wax to where the red arrows are swirling. Otherwise, the reduced airflow will allow dust to settle very quickly on your bug's behind. Good waxing helps to slow that process down.
gdr703
Veteran Member
I've been digging around and it seems that the ground clearance has an effect. That is the ground clearance at the rear of the car should be greater than that at the front so that whatever air gets under the car can readily get out the back.
There are several ways to encourage this nose down - rear up attitude:
Air pressure in the tires should be greater at the rear than at the front. Anyone any idea what that effect might be? that is the tire diameter at 30 psi or 40psi? Is it the same, or by how much does it differ? Even if its the same the higher pressure tires will be stiffer.
Weight distribution of anything carried in the car should be as far forward as is reasonable. Anyone any idea of the effect of putting say 100lb over the axle, front or rear, on ground clearance? ie how stiff is the suspension?
There are several ways to encourage this nose down - rear up attitude:
Air pressure in the tires should be greater at the rear than at the front. Anyone any idea what that effect might be? that is the tire diameter at 30 psi or 40psi? Is it the same, or by how much does it differ? Even if its the same the higher pressure tires will be stiffer.
Weight distribution of anything carried in the car should be as far forward as is reasonable. Anyone any idea of the effect of putting say 100lb over the axle, front or rear, on ground clearance? ie how stiff is the suspension?
Rammstein
Top Post Dawg
Deep, the Jetta sedan has the best aerodynamics at 0.30.
The Jetta wagon gets 0.32.
Now, anybody know what is the Cx of the B4 (sedan and wagon).
I have an old brochure (1997) which include all the VW line at that time.
It doesn't say anything about the Cx of these first TDI's.
Rammstein.
The Jetta wagon gets 0.32.
Now, anybody know what is the Cx of the B4 (sedan and wagon).
I have an old brochure (1997) which include all the VW line at that time.
It doesn't say anything about the Cx of these first TDI's.
Rammstein.
Aero-TDI
Well-known member
Has anyone done any mods to their cars such as smooth out bottom?
Ed's TDI
Top Post Dawg
With these numbers, are the German ones geared taller? I'm wondering how they get 53-54 for highway when they're rated 49 on the window sticker here in N. America.
itsmejerry,
It's probably because they don't have 90hp like we do and their highway cycle for mileage testing is done at higher speeds than here in N.America.
Studying these figure after the conversion, I note that the automatic wagon achives better fuel economy than the automatic sedan. Why? Did I mess up doing the conversion?
WVWSP61,
No you didn't make a mistake in the conversion. I noticed the same thing in the original post of these figures.
itsmejerry,
It's probably because they don't have 90hp like we do and their highway cycle for mileage testing is done at higher speeds than here in N.America.
Studying these figure after the conversion, I note that the automatic wagon achives better fuel economy than the automatic sedan. Why? Did I mess up doing the conversion?
WVWSP61,
No you didn't make a mistake in the conversion. I noticed the same thing in the original post of these figures.
gdr703
Veteran Member
rated 49.
Its to do with the test method. The mpg figures are calcualted on a non urban cycle run on a dynamometer. The results are then downgraded by 22% to allow for real world situations of the average driver. That's how they get 49.
In Europe they have a similar test but with different parameters.
hth
Its to do with the test method. The mpg figures are calcualted on a non urban cycle run on a dynamometer. The results are then downgraded by 22% to allow for real world situations of the average driver. That's how they get 49.
In Europe they have a similar test but with different parameters.
hth
jackbombay
Top Post Dawg
that jetta with the wedge looks like it's right out of death race 2000.
-Jack
-Jack
santacll
Veteran Member
Dang; i was just thinking that a wing on the back of the beetle might cleanup the flow, and generate some downforce at speed... now the picture makes it clear, definitely a no go...
Pressurized
Well-known member
Some comments:
Lowering the car, figure about 0.010 Cd for each inch.
Altering the ride attitude (front/rear ride height relationship) with the nose down, some vehicles such as the Jetta sedan would probably be better since the rear deck height would be effectively be higher. Would help the Bug recover some pressure on the back end. Might hurt the station wagons though.
The current mirrors look pretty good, they have more wind noise issues than aero concerns.
The underbody already has a flat front panel and is relatively flat in the mid-body floorpans. There is some smoothing or add-ons on the rear axle already. The rear axle and backend probably has the most opportunity for improvement. Hopefully in the next reinCARnation of this chassis, VW will bless it with an independent rear that tucked up more. The underbody does not have to be completely flat, there will be turbulence from the engine compartment no matter what, relatively flat with no cross-wise protuberances is OK. But then on my car I stuck on the stupid Draw-Tite hitch, what a piece of $hit.
The VW aero engineers are not idiots, they have a state of the art open jet rotating wheel tunnel. You might get a little bit more from a small front airdam, under 1" max. Airdam's do not lose effectiveness at high speeds unless they are deflecting under pressure loading.
Big tires with square shoulder will hurt you.
Flush wheel covers are good, the cheapy ones on the base models ones look decent for aero.
The snow plow front end on the old VW would work better on that car than the current models. The older ones had separation problems on the hood and fenders and grille porosity. The latest have attached flow on the front, the deer catcher would'nt be worth the effort except hurt stability and add a lot of weight were you don't want it.
Remember when comparing Cd's that the frontal area is a factor, isn't the Jetta larger than the Golf?
Those are cool pictures of the Bug rear airflow. I'm very surprised that the flow is still attached that far back.
Good books:
Hucho "The Aerodynamics of Road Vehicles" latest edition available through SAE and the old standbyes - the aircraft books by Hoerner, two volumes, very intitutive. All are $ pricey.
Lowering the car, figure about 0.010 Cd for each inch.
Altering the ride attitude (front/rear ride height relationship) with the nose down, some vehicles such as the Jetta sedan would probably be better since the rear deck height would be effectively be higher. Would help the Bug recover some pressure on the back end. Might hurt the station wagons though.
The current mirrors look pretty good, they have more wind noise issues than aero concerns.
The underbody already has a flat front panel and is relatively flat in the mid-body floorpans. There is some smoothing or add-ons on the rear axle already. The rear axle and backend probably has the most opportunity for improvement. Hopefully in the next reinCARnation of this chassis, VW will bless it with an independent rear that tucked up more. The underbody does not have to be completely flat, there will be turbulence from the engine compartment no matter what, relatively flat with no cross-wise protuberances is OK. But then on my car I stuck on the stupid Draw-Tite hitch, what a piece of $hit.
The VW aero engineers are not idiots, they have a state of the art open jet rotating wheel tunnel. You might get a little bit more from a small front airdam, under 1" max. Airdam's do not lose effectiveness at high speeds unless they are deflecting under pressure loading.
Big tires with square shoulder will hurt you.
Flush wheel covers are good, the cheapy ones on the base models ones look decent for aero.
The snow plow front end on the old VW would work better on that car than the current models. The older ones had separation problems on the hood and fenders and grille porosity. The latest have attached flow on the front, the deer catcher would'nt be worth the effort except hurt stability and add a lot of weight were you don't want it.
Remember when comparing Cd's that the frontal area is a factor, isn't the Jetta larger than the Golf?
Those are cool pictures of the Bug rear airflow. I'm very surprised that the flow is still attached that far back.
Good books:
Hucho "The Aerodynamics of Road Vehicles" latest edition available through SAE and the old standbyes - the aircraft books by Hoerner, two volumes, very intitutive. All are $ pricey.
gdr703
Veteran Member
Pressurised, good information, thank you.
I am trying out a small air dam, chin spoiler, call it what you will. Its made from 2.5 inch black rubber base board and attached with sticky back velcro, so reduces the front air space by an inch and a half. Too early to tell what the results are as I have to factor in the winter fuel effect, but its holding up.
Do you have any comment on the rear wheel arch covers as seen on the Insight. I wouldn't want anything like that on my Golf, but are they effective, and to what extent? I had thought of using the above material and method from the airdam to create a small "eyelid" over the top of the rear wheel arches, or is that a silly idea? What do you think? Any point to it?
I am trying out a small air dam, chin spoiler, call it what you will. Its made from 2.5 inch black rubber base board and attached with sticky back velcro, so reduces the front air space by an inch and a half. Too early to tell what the results are as I have to factor in the winter fuel effect, but its holding up.
Do you have any comment on the rear wheel arch covers as seen on the Insight. I wouldn't want anything like that on my Golf, but are they effective, and to what extent? I had thought of using the above material and method from the airdam to create a small "eyelid" over the top of the rear wheel arches, or is that a silly idea? What do you think? Any point to it?
SnakeOil
New member
- Joined
- Dec 30, 2001
- Location
- California
the "eyelid" that you are talking about wouldn't make much of a difference as the fenders of the golf are heavy at the top and stick out quite a bit. but thats just vw styling. i would explore more with a wheel skirt that "rides" up and down with the suspension. very much like the ones used on the ford ka "step 1" the trick here is to get tangency with the transitions of the fenders. the fender and wheel skirts all have to flow to work.
another idea that was used on the first generation lupo 1L was the "tail cone". the bumper of the lupo extended a few inches rearward at around 30 mph. not sure if the current versions do the same. although the prototype had all sorts of cool fences and gizmos. hope this helps
another idea that was used on the first generation lupo 1L was the "tail cone". the bumper of the lupo extended a few inches rearward at around 30 mph. not sure if the current versions do the same. although the prototype had all sorts of cool fences and gizmos. hope this helps