My new hopefully more aero Metro front bumper

[Coyote X]

With the bracing I have on it I am hoping if I did hit a deer it doesn't do much damage to it. But my car is still not quite that smooth so there is a lot of solid stuff to hit.

I have decided these colored rolls of plastic are the best thing ever made for mods. Way easier and nicer to work with than coroplast. A small amount of heat will let you form it to just about any shape you could imagine.

I was going to do a writeup on putting the kammback on but after starting on it I was done about an hour later with a really nice looking setup.

It was a matter of attaching a 1 inch wide strip of 1/8 thick aluminum to the lip so it would hold its shape then clamping it into place and drilling/riveting it on.

[California98Civic]

Nice work on the kamm back and I like the miniskirts for the wheels. You know, the "speed holes" in your rear bumper would be good for ventilation of exhaust system heat after you build your undertray. They'd be ideal then, as vents for the rear diffuser. Are you planning an undertray?

[Frank Lee]

Agreed- I think the airdam and kamm are nicely done and I expect them to provide positive gains. The mini-skirts... mmmm... I'd like to see them go down to at least axle level... can't say if they're effective as is although as a general rule mini-skirts are very effective! And you know what I think about rear bumper holes, although cal is right, with a full pan they ought to keep temps in check.

[serialk11r]

Originally Posted by Coyote X

I have decided these colored rolls of plastic are the best thing ever made for mods. Way easier and nicer to work with than coroplast. A small amount of heat will let you form it to just about any shape you could imagine.

What is it called? What's the material? Are you using a heat gun to soften them?

Looks like good stuff.

[deejaaa]

it's in the first post.
Colored Plastic Rolls, 25 Ft. - Speedway Motors, America's Oldest Speed Shop

[Coyote X]

The back bumper is not really anything great I already had it from the convertible project so I stuck it on this car. I can't remember the exact numbers but on my coastdown hill I think I went from a peak speed of 75mph to 78. About the same difference in speed as rolling down a window without the wing windows open. So it isn't much really. Cutting the section of the bumper that hangs below the rest of the underside would be much better but swapping covers was much easier and quicker and leaves me a good cover to put on it when I sell it. Next time I get the car in the air I will take a picture of the underside so you guys can see how far down the bumper hangs into the wind. I figure most cars have a decent shape to their bumpers and ventilating it won't help but not every car is the same. Now if I was drilling holes in the bumper of my Volt you guys could rightly call me goofy

The mini skirts are an afterthought. I had a strip of plastic from cutting the back and was only that thick. So I figured why not and slapped them on. If they don't work I can always make a larger set. I am not out any material since it was just scrap pieces anyway. One day in I will be driving in the rain and stick a camera out the window and see if they work, if not I will make bigger ones.

I just took the car out for a quick drive and it seems like it coasts much better than before. If they were not patrolling heavy where I normally do my coast down test I would probably go out and try it this week. I don't think they will buy my excuse doing over 80mph in a 65 of just testing my car out

[Frank Lee]

http://ecomodder.com/forum/283151-post54.html

http://ecomodder.com/forum/280092-post5.html

I suppose it's something like tailgate up for pickups- capture a rolling wave.

[freebeard]

Good result so far. I'm curious about your coastdown hill. I found one that has good turnarounds top and bottom, but the run-out area is too short.

What drop in elevation over what distance? How long is the run-out? How many runs are possible in, say, a half hour?

[California98Civic]

You really need to study the MetroMPG cars and basjoos's aerocivic threads on this forum. Many cars of the 1990s have that parachute back bumper cover, mine included. But although cars vary, in three and a half years of heavy use of this site, I never remember any of the best experts here suggesting anything other than a belly pan and diffuser as the cure for the bumper-cover parachute. Did you look at the chart of stagnation point and drag changes I post in this thread earlier? If you find your results disappointing on your nose (if) you might want to consider changes that would lift the stagnation point higher, since the ideal point on that chart is significantly higher than your current build. But yours might work wonderfully... as you rightly say... cars vary.

[Coyote X]

I am thinking of folding the bottom half back inward to get the stagnation point a bit higher. Right now it has a huge amount of down force on the front end of the car and I am sure that is not helping the mileage. I am thinking that where I put that brace, as seen by the rivets in the middle, is probably a good place to heat and bend it back. I can then use a small lip under the radiator to direct air through it and solve the fan cycling all the time while driving. On that chart it is hard to find an exact number where to make the fold but I figure anywhere is going to be better than all the way at the bottom.

My coastdown hill I normally use is Bing Maps - Driving Directions, Traffic and Road Conditions It shows 2.2 miles and from ~4000ft to 650ft elevation. At the top of the hill just over the peak there is a sign that I can get up to 50mph when I pass. I pull the car into neutral and use the engine kill button. I then just roll down the hill and get my peak mph right at that sharp curve near the bottom. If there is no traffic and I can take the curve at full speed then to be much more accurate I can let the car continue to coast back down to 55mph. That happens around the B marker. I have tried different things to measure the accuracy and on back to back runs I have seen a difference with just the wing windows open when coasting back down to 55. I usually watch for some reference at the bottom that I pass right when the speedometer hits 55. There are usually white reflectors every so often so those are the best to use. I thought I posted a video of doing a coast down testing on here a few years ago but I searched and can't find it.

I am sure a belly pan would be much better than the back bumper the way it is now, but this was quick and easy and slightly better than stock. If I wanted to put the time and effort into it I could put a belly pan on it but for now this car is good enough till I get some mileage numbers out of it. I will probably fix the front bumper a bit more then drive it for a few weeks and see if I can get some mileage numbers that are good or at least better than I was getting.