Just made these. feedback required... (Miata/MX-5 front tire deflectors)
 

Hi Guys/Girls...

Fuels finaly hit £1.30/litre. A*se.

My MX5 (Miata) has really exposed front tyres, so yesterday I made a pair of these (see before and after photos...)

I would like to tidy the fixings up a bit ie, make them smaller/lighter.

Before...

http://i519.photobucket.com/albums/u...IMAG0698-1.jpg

After...

http://i519.photobucket.com/albums/u.../deflector.jpg


I used a store bought clear material labelled as 'polystyrene'. It was certainly flexible enough, but produced tiny cracks when cutting. It was 2mm thick.

What other products/materials would suit this application?

Have I made something worthwile?

Thanks in advance, Ian

i'll give you an "A" for the concept of deflecting the air around the front tires and a "C" for execution of concept. I've dealt with polystyrene alot (i built tons of plastic model cars growing up) and i have to say it is likely too flimsy to suit your needs in this case. i would suggest finding some 1/16"(1.5mm) Plexiglass to use instead of the styrene. I'm sure the guys on here know of a few other materials you could use. it's a good start for what your looking for and it's a good thing to look at (i'm going to put something similar on the side of the airdam on my Jeep) since it should reduce drag caused by the tires

you may want to have a look at (what toyota calls) 'aero corners'

they have recently appeared on a lot of aerodynamics cars like the new prius, iq, citroen ds3, and some others.

basically the corners before the wheels are squared off, sometimes by agresively styled daytime light, what looks like air scoops or just add-on like bumps in case of the IQ.

but all designs seem to create a sharper corner and a more flush pannel leading up to the wheels.

this aero corner thing seems fairly new and appart from a general description i don't have much info on it, but the fact it's on cars like the prius sugests there's something good about the design.

it may also explain why some olders cars managed to get a very good Cd with relatively square fronts... perhaps 'making the front as smooth as possible' is not always the best strategy

I think the material you are looking for is polycarbonate. It doen't crack like an addict when bent or machined.

^^That's one of the one's i couldn't think of^^

What you've done reminds me a little bit of NASCAR air dams. There is a lot that can be learned from racecar aerodynamics. Smooth contours, diverting airflow away from dirty parts of car (like undercarriage), not making the airflow to bend any more than necessary and eliminating extremes in pressure gradient distributions, etc. However there are things that do not pertain to those of us on the street doing under 150 MPH.

First racecars are obsessed with down-force to create high cornering loads. Many rules today are there just to eliminate that technology thereby slowing down the cars. Most racecars are so overpowered that just getting the power to the pavement is a real problem. One that we don't have. Also racecars (that resemble street cars) have quite a few restrictions on what they can and cannot do as far as changing vehicle profile and airflow around the car. Again that's mostly not a problem for us.

For us it's all about eliminating drag. Drag comes from changes in flow, both directional and pressure distributions. Anything we can do to create equilibrium and smooth contours only helps us. Anytime the airflow has to work through changes in direction, slowing down or speeding up, it extracts energy from the airstream. That energy (often called drag) has to be made up through our propulsion system. That in turn requires fuel which we all know is something we are trying to avoid.

perpendicular impact
 

Ian,you're doing a good thing.Ideally,as in solar race cars for example,complete shielding of the tires from the airflow cuts drag.
--------------------------------------------------------------------------
At say,100 km/h,the forward face of the front tires are travelling downward at 100 km/h and impacting the air perpendicularly at 100 km/h.It's a situation which makes it impossible for attached flow.
Your shields will kick the air out and around the tires where it can flow to the rear.
If you were to do likewise for the entire sides of the Miata you'd gain even more.GM measured improvements this way with its Trans AM Firebird.

Thanks all for the replies and info.

Think I'm gonna make a more polished version from better materials.

Will have a think what I can do with the rear wheels? Not sure I fancy fully faired in. But something similar to the front?

Great Idea. I was wondering is Lexan a trade name? I saw some Lexan on sale at Lowes and it says it 10 times stronger than plexaglass.

Does anyone have experience with using Lexan?

Lexan is a trademarked name for polycarbonate sheet. It's softer & scratches more easily than Plexiglas (a trademarked name for acrylic sheet), but it has much better impact resistance than plexi.

On a different note, I'll be interested to see how the Miata project goes. I think there's some real potential for hypermiling the Miata.

I'm planning to put a grill block and belly pan on mine, and maybe some removable fairings around the wheel openings. Maybe I could justify buying a Speedster tonneau cover on fuel efficiency grounds.

There are so many options for body kits, it might be possible to find some that are aerodynamically good, or that could be used as foundation for good shaping.

i would paint it so that i wouldn't have to worry about scratches. if you make a template to use when cutting it you can just cut a new piece if on breaks, try to attach it in such a way that you can remove it relatively easily

caferacer51 -

I like it. The C-Thru look is also cool. It may muddy-up over time, but "time will tell", so to speak.

I think you should look into a plastic other than polystyrene, which is where you are already going. Very good "v1.0".

CarloSW2

Yes. The new version Civic Hybrid (mid-cycle restyle) has the same change. The front corners are sharper and the side is flatter in front of the wheels.

Also note the little spoiler in front of the front and rear wheels. You might try copying that bit as well.
http://jalopnik.com/assets/resources...vic-Hybrid.jpg

Thanks all for the feedback!

I'm just starting a new tank on the Mazda/Miata. I'm not expecting anything major or even noticable, but I can at least drive knowing that they could be working...

I have a little material left over and will make a simple grill block for the car. There are x2 towing eyes in the front grill of the Mazda (why 2...?) so leaving them uncovered should allow enough air to pass in. I can always 'add holes' so to speak later if needed.

http://i519.photobucket.com/albums/u...grillblock.jpg

Further more, here in the UK we were blessed/cursed with a car called the FIAT Brava/Bravo. I saw one of these beside me at the lights yesterday and noticed some rather tasty looking wind deflectors on the sills. Might see if I can find something in the scrap-yard...

http://i519.photobucket.com/albums/u...olvo/brava.jpg

I made a similar air dam using carbon fiber last fall. Made a wire frame from some scrap 9ga wire. It was easily bent to match the shape of the front bumper cover. Covered the wire with polyester cloth and hand sewed it in place. Used heat to make sure it was shrunk tight. Sprayed some 3m super77 glue on the fabric. Layed some heavy carbon fiber cloth on the fabric then painted on epoxy. Once cured I peeled the carbon off the wire fabric frame. Put some photos here: http://ecomodder.com/forum/showthrea...ing-14670.html

Seeing it head-on, and seeing the deflectors are set away from the front spoiler, I'm fearing they may be guiding the air that's flowing towards the sides, directly onto the tyres.

They look a bit like the kind of wind deflectors you see on the front corners of trucks with a cab-over-engine design.


How about disguising it as a low mounted licence plate ?
That way you could get rid of the one on the bonnet.

I'm inclined to agree with euromodder about the offset design. It looks cool but may actually add drag. If the leading edge was touching the bodywork then it's more likely to reduce drag.

couple of thoughts.
The BMW sites (mainly 3 series) have an aftermarket-hamman- foglamp/air slot part. the air slot has a hose that leads to the front brakes. This gives some extra cooling for the brakes. I think I have also seen a part that is mounted exactly where you have your circles.
Think about the law of uninttended consequences. most cars have 2 openings. yours has 1. in other words, the mfg has already decided to 'block' the top. meaning that the bottom opening is more crucial to the car than a car with 2.
maybe you warp your rotors six months down the road.
maybe you need to install a higher capacity electric fan to force the air that is blocked
or a larger radiator, or a different themostate.

just my thoughts

I think airflow generally goes out through the wheel, so a complete air dam would reduce brake cooling (by reducing pressure under the car), but a flare pushing air out around a tire shouldn't make much difference.

I first noticed this on one of my cars when I was cleaning the wheels and found grasshopper splats on the inside of the wheel.

Depends a lot on how you're using the brakes, too. If you're hypermiling, you're probably not braking much. On the track, with repeated max-effort braking, opposite situation.

And also, those hooks are tie-down hooks for transport on the ship from Japan. They're not supposed to be used for towing, and can be removed without ill effect. (Unless you're racing in a stock class that prohibits you from removing extraneous stuff like that.)

Hi Guys,

Thanks for your comments so far!

I had a go at making the grill block I pictured in post #14, I tried to use the same materials as the wind deflectors, but I found that that material would accept a bend across one plane, but when I tried to bend it across another plane it cracked (is it 'plane' or 'plain'...?)

So back to my materials research...

Also looking at some of the feedback on the wind deflectors, especially #16 from euromodder, there may be a question as to whether they are simply trapping air and pushing them onto the rotating tyre itself...?

So there could be a much smaller/simpler/lighter version in the pipeline...

http://i519.photobucket.com/albums/u...deflector3.jpg

http://i519.photobucket.com/albums/u...deflector2.jpg

On the plus side, all the holes I'm drilling in my front bumper will soon be adding up to a serious weight loss...

Try mounting a flat piece (similar to a mud flap) on the inside of the wheel well but in front of the tire. As the air hits the flat piece, it will spill outwards and away from the tires. If you need more aero performance...you can use this as a support base/platform to work off of. ;)

Your green line is suspiciously familiar.
http://www.veloliner.com/minivan/DSCN1759.JPG

Hoping for better weather so my projects can continue.

Did you spot any gains in fuel efficiency with the deflectors ?

Not able to say I'm affraid, financialy I'm only putting fuel in the car to commute. Which means there are just too many 'variables' to get a credible comparison.
The motorway I use is very busy/undulating making an A-B-A test impossible.

The modifications are more based on looking at other peoples designs (Thanks Varn...) and semi-educated guesses. Bit of a shame really, I'd love to have the time/space/money/flat roads to do some proper testing!

I'd also love a scan guage, but my car being 1990 doesn't help and MPGuino seems to be near mythical nowadays...

So for the time being I'm just relying on your feedback and opinions!

Cheers!

Good call this one, the material will be just what I need and easy to trim.
Will need to get a subtle colour and brace myself for all the comments....

"Eh mate, you know you got your mud-flaps on the wrong way round...?"

Think they're fairly cheap on fleabay too?

i just figured out how to do the air dam on my Jeep.

It's only a 1-time effort to fill it up completely.
Which is unlikely to become much cheaper anytime soon.
After that, you can be filling up as you burn fuel.

It gives you an opportunity to properly keep track of your fuel use, which is essential if you want to see your improvements over time.

I purposely don't test modifications (nothing beyond a short functional check, that is).

The testing is in the regular driving, and the fuel economy it returns.
If you keep track of your fuel use, you'll spot the effects over time if they're there.

Don't feel bad because you can't attribute X % better fuel economy to mod Y.
That doesn't really matter.

i know this is an old post but the differance with polycarbonate and plexiglass is ,polycab is used for military bullet proof wind screens (tuff stuff), plexi is the lid for your soda

caferacer51, I understand not wanting to drive any more than necessary, but that makes this project difficult. You mentioned A-B-A testing, but the other tenet of ecomodding is tuft testing, with its own complications, but at least you would be able to see at a glance if it is working.