Effects Of Air Dam (Ford F350 pickup)

[So_SiMpLe_]

Sorry this question, but if you fit a spoiler like this:

http://www.caradvice.com.au/wp-conte...age41494_b.jpg

Won't work better too by avoiding more air to get under the car?

The raise of frontal area by that strip will decrease the mpg?

I'm talking about the black strip under the front bumper that says Karcher and has the license plate.

[Big Dave]

To answer some questions:

I haven't really done anything under the hood that helped much. A 203 degree stat did yield a 0.5 MPG improvement. A 4" exhaust didn't help at all. Using a Baldwin PA2818 air filter with all under hood intake didn't help a bit. Going from split-shot to single shot injectors did not improve MPG one iota.

I use all synthetic lubricants. Didn't improve MPG at all.

Gearing and aero are the big enchiladas if you want MPG from a pickup.

I don't see how my air dam is much different than the one on the race car.

BTW, my air dam is currently on the garage floor. It snows in Nap-town this time of year, and bulldozing snow is not conducive to high MPG.

I will probably trim it back a little this spring before I put it back on. One does get tired of the scraping.

[aerohead]

Originally Posted by So_SiMpLe_

Sorry this question, but if you fit a spoiler like this:

http://www.caradvice.com.au/wp-conte...age41494_b.jpg

Won't work better too by avoiding more air to get under the car?

The raise of frontal area by that strip will decrease the mpg?

I'm talking about the black strip under the front bumper that says Karcher and has the license plate.

Maybe every vehicle should be considered on a case by case basis.
The car shown is a rally car.Past Ford rally cars suffered higher drag as a compromise to cornering downforce from induced-lift.
Front airdams,as reported in industry literature typically reduce drag on non-bellypan cars,then at some point,begin to increase drag as their frontal area grows beyond some point.
Bondo found this to be true on his F-150.
Some writers discourage the use of "rules-of-thumb" and advocate that every vehicle be investigated on a case by case basis.
It IS MY OPINION the the airdam pictured WOULD increase drag and degrade mpg.JMO.

[cfg83]

aerohead -

Originally Posted by aerohead

Maybe every vehicle should be considered on a case by case basis.
The car shown is a rally car.Past Ford rally cars suffered higher drag as a compromise to cornering downforce from induced-lift.
Front airdams,as reported in industry literature typically reduce drag on non-bellypan cars,then at some point,begin to increase drag as their frontal area grows beyond some point. Bondo found this to be true on his F-150.
Some writers discourage the use of "rules-of-thumb" and advocate that every vehicle be investigated on a case by case basis.
It IS MY OPINION the the airdam pictured WOULD increase drag and degrade mpg.JMO.

Yup. I was reading about the Opel Calibra, a car famous (among us) in the early '90's for having a Cd of 0.26 . When they were designing the front air dam, they came across this very issue. They found that if it was too low, the drag from the air dam overcame it's benefits. It's job is to get the air past all the messy engine and front suspension components. Once it has done that, it doesn't need to be any bigger. If we did a detailed analysis of the Opel Calibra, we would probably be able to come up with a simple rule-of-thumb equation.

I read this in Car Styling issue #192, which has a continuing series on car aerodynamics :



CarloSW2

[aerohead]

Originally Posted by cfg83

aerohead -



Yup. I was reading about the Opel Calibra, a car famous (among us) in the early '90's for having a Cd of 0.26 . When they were designing the front air dam, they came across this very issue. They found that if it was too low, the drag from the air dam overcame it's benefits. It's job is to get the air past all the messy engine and front suspension components. Once it has done that, it doesn't need to be any bigger. If we did a detailed analysis of the Opel Calibra, we would probably be able to come up with a simple rule-of-thumb equation.

I read this in Car Styling issue #192, which has a continuing series on car aerodynamics :



CarloSW2

CarloSW2,is that mag available at newstands? I've never seen it,but I'd look for it if available to mere mortals.I'm not a student at Art Center or CALTI,or the others,hope we don't have to be.Thanks!

[cfg83]

aerohead -

Originally Posted by aerohead

CarloSW2,is that mag available at newstands? I've never seen it,but I'd look for it if available to mere mortals.I'm not a student at Art Center or CALTI,or the others,hope we don't have to be.Thanks!

I found it at Swains, an artist/stationaries supply store. They're about $30 per copy. You need to find stores tailored for artists/designers.

EDIT: A university art/design department library may have a subscription copy you can oggle.

But forget about that issue. My wife ordered this holy-grail issue for me as my XMas present :

Car Styling - $35 - From year 2001

Automotive Wind Tunnels, Applied Aerodynamics, Aerodynamics on Concept Cars/Racing Cars/Passenger Cars/Trucks/Buses/Motorcycles, Toyota, Nissan, Mazda, Mitsubishi, BMW, Fiat, Pinifarina, Volvo, GM, Chrysler

*The Automotive Wind Tunnels: Dome, Toyota, Nissan, Mazda, Mitsubishi, Nippon Soken, JARI, BIA, Daimler-Benz, FoE, BMW, VW, Stuttgart University, Fiat, Pinifarina, MIRA, St. Cyr, Volvo, GM, Chrysler *The Basic - Why Is Aerodynamics Necessary? *The Relationship Between Drag and Fundamental Dimensions *The Wind Tunnel and Its Testing *Applied Aerodynamics - Aerodynamic Characteristics by Vehicle Type *Aerodynamics for Passenger Cars *Aerodynamics on Concept Cars *What Os Computation Fluid Dynamics? *Measures Being Taken on Recent Low-drag Cars * Aerodynamics for Electric Vehicles *Aerodynamics of Car Accessories *Aerodynamics for Racing Cars *Optimizing the Aerodynamic Characteristics of GT Prototype *Aerodynamics Measures for CART Machines *Aerodynamics for Solar Racing Cars *Aerodynamics for Trucks and Busses *Aerodynamics for Motorcycles *For The Specialist - Data Analysis and Application *Pressure Distribution and Cd *Wind Observation - Flow Visualization Methods *Nature of Vehicle Wake *Aerodynamic Characteristics of Engine Compartment Area *Aerodynamics and Improving Visibility

CarloSW2

[So_SiMpLe_]

So it means that at until some size, the spoiler will bring benefits, once you don't have a belly pan, making the air avoid that engine "troubled" area.

But you might notice more drag at certain speed.

It means that the very best solution is to keep the front as it is and add a bellypan right?

[cfg83]

So_SiMpLe_ -

Originally Posted by So_SiMpLe_

So it means that at until some size, the spoiler will bring benefits, once you don't have a belly pan, making the air avoid that engine "troubled" area.

But you might notice more drag at certain speed.

It means that the very best solution is to keep the front as it is and add a bellypan right?

Yes, but bellypans can be a PITA. Also, they can have their own troubles if not done right :

belly pan thrash 2008

Originally Posted by lovemysan

The main problem with my belly pan is not the rear exit angle. But the lack of front airdam. The problem is too much air is taken under the car and as it works its way to the rear it piles up, till it touches the ground and then tumbles. This problem is exaggerated when the car is loaded because the ride height in the rear can be reduced a further 3". I've found that a belly pan requires more design than I originally anticipated. I know what I need to change but lack real motivation now.

Because I go to a mechanic for regular maintenance I am not willing to install a bellypan that will only make things hard for repairs. It already takes me about an hour to "de-prep" my car for the mechanic, so I need to be able to get the stuff off fast.

lovemysan also had trouble with his airdam, which would be an example of being too big ... Ahhhhhh, here is a little bit on the Opel Calibra that I was talking about :

The airdam that didn't work

Originally Posted by fabrio.

I am not surprised from your results.
with your airdam, you have added more frontal area, and because your car (with many aero mods) it is very efficient, your have gotten worse the things.
If I just remember, your car is equipped with full bellypan.
You can try to reduce central height of airdam, this, reduce the FA, and permit to pass the air under your car.
Look, the example opel calibra.
Calibra equiped with engine undercover, use an airdam tested in windtunnel.
After many tests, Opel are deliveryd an airdam shaped with raised central area, and high at the side.

look the image below:



It permit to deviate the air from wheels and the suspension arm.
I do not have any report, but in my car, I am insirated me to Opel for my front deviator
if you try it, tell us the change.

CarloSW2

[So_SiMpLe_]

So it means that anyway it is not that easy to fit that aero stuff!

My car is allready lowered, the front has about 15 centimeter from the ground.

What would you recomend me?

What you think if I put a bellypan under the engine zone mainly and test it?

Thanks!

[cfg83]

So_SiMpLe_ -

Originally Posted by So_SiMpLe_

So it means that anyway it is not that easy to fit that aero stuff!

My car is allready lowered, the front has about 15 centimeter from the ground.

What would you recomend me?

What you think if I put a bellypan under the engine zone mainly and test it?

Thanks!

I like that option because it's a step-wise investment (it could complement a full bellypan later on). But me cavemen, me no expert, so let others chime in. If you look at MetroMPG's aeromod threads, you will see that he does extensive verification, mostly tuft testing with external mounted computer video cameras. That would be hard to do with belly pans, but not impossible.

CarloSW2