Any benefit to making magnetically attached hood & roof covers with Dimples?

[Josh8loop]

Fellas,

Lately traffic patterns, my driving style and a few expensive maintenance needs that I cannot afford right now are affecting my MPG's. I am moving towards doing some aero mods since they will gain quite a bit from what I understand and don't have to be high cost to be effective. So far I have started blocking the upper radiator opening and started filling in gaps between body panels to reduce turbulence. This is just a start but I want to look forward and get my mind going and try to come up with some ideas.

I am contemplating creating two magnetically affixed shells. One will go over the top of the existing hood, and one that will go over the roof. I am expecting the shell will raise the existing hood & roof protrusion by about 2 inches. After watching MythBusters show on the clay covered dimpled car it seems like it might be good to use dimples on the shells. I've not settled on a material choice that will be light, easily worked with at home tools, and one that will be rigid enough for the task. Harbor freight has some 93lb pull force cup magnets that would be perfect for non-permanent attachment. Am I crazy here or what?

[wmjinman]

Since you cite expenses you "can't afford" (trust me, I know how that is!!!), I'm not too sure that experimenting with an unknown like dimpled surfaces would give you very high odds for return on investment. Seems that most of what I read about the dimpled surface experiments come up with no gains, or gains too small to be statistically significant.

If cost (money savings) is your primary concern, maybe perfecting hypermiling driving style, and other things such as air dams, maxxed-out tire pressure, etc, etc. (unless you're already doing all of that, of course)

Now, if you're just dying to experiment with this dimpled surface idea for the sake of the experiment to see if you get results (believe me, I'm familiar with these types of obsessions, too), then I say "go for it" and let us know what happens.

[Josh8loop]

Originally Posted by wmjinman

Since you cite expenses you "can't afford" (trust me, I know how that is!!!), I'm not too sure that experimenting with an unknown like dimpled surfaces would give you very high odds for return on investment. Seems that most of what I read about the dimpled surface experiments come up with no gains, or gains too small to be statistically significant.

If cost (money savings) is your primary concern, maybe perfecting hypermiling driving style, and other things such as air dams, maxxed-out tire pressure, etc, etc. (unless you're already doing all of that, of course)

Now, if you're just dying to experiment with this dimpled surface idea for the sake of the experiment to see if you get results (believe me, I'm familiar with these types of obsessions, too), then I say "go for it" and let us know what happens.

The maintenance item I need to do is to have the injector nozzles replaced and set up properly. That's about 450 smackers and a weeks worth down time on the car! As far as tire pressure and hypermiling techniques I am already a student and in training Have been using those techniques for a couple years now and still learn every day! The front air dam I may look into shortly along with flat covers for my wheels. Did you get a chance to see the Mythbusters dirty car vs clean car MPG(which also includes dimples in the experimentation)? They received quite a large difference in fact so much so that Jamie and Adam were speechless!

[ksa8907]

i like that episode and id love to take it for fact, but considering it was only one test and fairly small sample(distance driven), i have to understand that there may be a benefit, but this test can't quantify that.

[mcrews]

ask yourself....how much better will my mpg get?
5 more miles?
then do the math with your price per gallon.

imho, your not going to see a payback or a dramatic enough increase.
See if you can bring in the parts and only pay the labor.
Most shops double the retail price of the part AND charge the labor.

[dean_park]

I'd think about using foam insulation panels. They come in 4'x8' sheets and are very light weight and easy to shape. You could even use them to shape parts and then make a mold for fiberglass or carbon fiber later.
I saw the episode and I was also intrigued. When I bought my VW Golf and looked under it, I was even more intrigued since my stock belly pans are all dimples (big golf ball sized ones like what the Mythbusters did). Honestly, I wonder if Mythbusters got the idea from what the auto industry was already doing (and had proven), making their mythbusting easy.
Keep this thread going if you ever start the project.

[Frank Lee]

Ya know there's plenty of discussion here on dimples already.

[ChazInMT]

The long and short of it is this.

You're not gonna believe us and want to argue that it's got to be worth it because you saw it on TV.

It won't do a darn thing for you to put dimples on your car/truck.

I started up here in Ecomodder 3 years ago with this exact idea "Magnetic Stick-on Dimples" and have since learned a huge amount regarding aerodynamics.

Read this for starters. There's a statement about dimples in there for you.

HotRod Mag Aero Article

Search the site for A LOT of info.

My part in this discussion is over.

[wmjinman]

Originally Posted by Josh8loop

The maintenance item I need to do is to have the injector nozzles replaced and set up properly. That's about 450 smackers and a weeks worth down time on the car! As far as tire pressure and hypermiling techniques I am already a student and in training Have been using those techniques for a couple years now and still learn every day! The front air dam I may look into shortly along with flat covers for my wheels. Did you get a chance to see the Mythbusters dirty car vs clean car MPG(which also includes dimples in the experimentation)? They received quite a large difference in fact so much so that Jamie and Adam were speechless!

I don't think I saw that particular episode of Mythbusters, but I've seen a few, and as has already been mentioned here, their test methodology is not always rigorous enough to truly determine certain things. Since I didn't see it, obviously I can't comment on it in any meanignful way.

But getting your injectors running right has the potential of SUBSTANTIALLY improving things for you. Case in point, my own Suzuki "White Gnat". I bought it for good MPG, but it started detriorating as I owned it. My best highway MPG was 51-something, and I hit 50-something a couple other times. Recently I had a much newer engine installed and a couple other things fixed. Then I went out & tested it with the ScanGauge last night and got OVER 50 mpg at every speed from 50 mph down, topping out at 62 mpg at 35 mph. Just driving around town, not even in top gear, the ScanGauge was routinely showing 40's.

Lesson learned; just having the car running right would probably be a really good "first priority".

Oh - I currently have NO aero mods or anything else on it. Tires not even over-pressure at the moment. I didn't test it at 55, but probably would have hit 50 mpg at that speed, too. (60 was 46 mpg)

[Josh8loop]

Originally Posted by ChazInMT

The long and short of it is this.

You're not gonna believe us and want to argue that it's got to be worth it because you saw it on TV.

It won't do a darn thing for you to put dimples on your car/truck.

I started up here in Ecomodder 3 years ago with this exact idea "Magnetic Stick-on Dimples" and have since learned a huge amount regarding aerodynamics.

Read this for starters. There's a statement about dimples in there for you.

HotRod Mag Aero Article

Search the site for A LOT of info.

My part in this discussion is over.

I actually will most likely believe you all. Especially after looking through and reading some information from members who have tried similar ideas on their cars and have some data to report. I guess the good thing is that even if it doesn't reduce drag it may help reduce engine noise, help keep a bit more heat in the engine compartment, and keep heat from penetrating through the roof into the interior of the car in hot Florida summers. So I guess there might be other benefits from this Thanks for the input guys!