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robertwb70 08-15-2009 12:42 AM

Another Metro goes aero
 
Finally started on some aerodynamic mods to my 1991 Metro, pics at the link below. Comments welcomed.

Robertwb70

SVOboy 08-15-2009 12:47 AM

Very red :D

Nice work :thumbup:

robertwb70 08-15-2009 01:10 AM

Thanks-I don't like red so this car wasn't really what I would choose but for $150 I couldn't pass it up...even if it is red. I would rather have a gen3 5 speed but all my cars for the last 7 yrs have been manual trans cars so it's nice to have an auto for a change.

What's the record for auto trans 1.0 MPG?

I see most people claim 36-38 MPG is good for an auto but I've been getting 42 with no aero mods and only a few engine mods.

Christ 08-15-2009 01:10 AM

Nice.

Welcome, as well.

robchalmers 08-15-2009 06:05 AM

Nice :)

MadisonMPG 08-15-2009 03:10 PM

Quote:

Originally Posted by robertwb70 (Post 121407)
Thanks-I don't like red so this car wasn't really what I would choose but for $150 I couldn't pass it up...even if it is red. I would rather have a gen3 5 speed but all my cars for the last 7 yrs have been manual trans cars so it's nice to have an auto for a change.

What's the record for auto trans 1.0 MPG?

I see most people claim 36-38 MPG is good for an auto but I've been getting 42 with no aero mods and only a few engine mods.

Depends on how you drive, if you stay off the highway, it'll be good.

aerohead 08-15-2009 03:27 PM

Metro
 
The work looks great! I do think you might consider restoring the rear valance panel.It may not catch the air as you suspect but rather create an inverted pool of stagnant air that the air flowing below just skips over,as an upright "bird-bath" spoiler would do on a Mustang's trunklid.

robertwb70 08-15-2009 06:11 PM

Added some updates- Front tire deflectors, rear appearance panels and the upper part of rear fender skirts.

MadisonMPG- I drive mostly on rural roads to and from school and you can tell it doesn't like to go over about 60 MPH. I don't have a tach but I did the math and the RPMs are ridiculous at anything over 60 anyway so I just try to avoid the interstate; I do that regardless of the vehicle I'm driving so it's not a big deal for me.

aerohead- That thought did cross my mind but I can always get a better rear fascia from the salvage yard if it turns out to be an issue (this one is pretty rough so I think I did it a favor). The airdam on the front will probably make it a non-issue either way since there will be so much less air under there to begin with.

NeilBlanchard 08-15-2009 07:04 PM

Wow Robert -- you're quick and good! The front wheel deflectors are exactly what I was going to suggest, and before I can post it -- you've got them made.

You should start a fuel log!

It looks like you'd benefit from some lens polish -- I saw some stuff recently that turns clouded headlight lenses clear again...

Christ 08-15-2009 09:52 PM

I love the way your front bumper cover is turning out, but maybe you should make a 'glass copy of it when you're done, and use that instead? So you don't have 10 seams and rivets everywhere, I mean. Unless you're like me, and you like that sort of thing... LOL.

robertwb70 08-15-2009 10:05 PM

I must be like you then because I like it the way it is, fiberglass is such a PITA to work with. I even thought about leaving it all bare metal looking for even more of a "race car" feel but in the interest of less people asking silly questions I've decided to paint it so it blends in more.

If I was going to make a fiberglass cover I'd have to do the whole thing, factory part included and at that point I would want to change even more stuff to make it better. A guy has got to draw a line somewhere, it is just a Metro after all.

Christ 08-15-2009 10:28 PM

LOL. I understand.

I personally love a clean line of connective rivets, especially when they're left metal tone after the rest of the part has been painted, and just clear coat put over them.

aerohead 08-17-2009 06:15 PM

non-issue
 
Quote:

Originally Posted by robertwb70 (Post 121488)
Added some updates- Front tire deflectors, rear appearance panels and the upper part of rear fender skirts.

MadisonMPG- I drive mostly on rural roads to and from school and you can tell it doesn't like to go over about 60 MPH. I don't have a tach but I did the math and the RPMs are ridiculous at anything over 60 anyway so I just try to avoid the interstate; I do that regardless of the vehicle I'm driving so it's not a big deal for me.

aerohead- That thought did cross my mind but I can always get a better rear fascia from the salvage yard if it turns out to be an issue (this one is pretty rough so I think I did it a favor). The airdam on the front will probably make it a non-issue either way since there will be so much less air under there to begin with.

lost mpg with my CRX because of lifted valance is the reason I make the issue.

robertwb70 08-17-2009 11:49 PM

Thanks aerohead I'll keep that in mind I'm going to run it like it is for a while and later I'll probably swap a 92-94 style fascia on since I like that style better and it appears to be more aero too.

Spent most of the day today working on a bead/ flange roller/ shear tool from harbor freight trying to make it work right. Tomorrow I am going to weld some reinforcements on it and then I'll be ready to finish the fender skirts.

wagonman76 08-18-2009 12:19 PM

Looks good, should help FE too!

robertwb70 08-20-2009 09:14 PM

I've posted a couple of pics of an interesting method (to me) to figure out how to cut the sheet metal I'm adding to my car to match up with the complex curves with the minimum hassle.
I'm still working on the rear fender skirts and it's been slow going mostly due to me trying to get a little over ambitious with the design. School starts back Monday so I'm going to simplify some of the design to hopefully get it done before next week.

Also, and it might be my imagination, but it seems I have to brake longer/ harder to get the car to stop now, can't wait to see what the MPGs look like now.

MetroMPG 08-20-2009 11:32 PM

Nice to see another aeromodded Metro coming along!

Do the new deflectors ahead of the front tires actually stick out farther than the tire edge? I ask because I saw you wrote:

Quote:

I made some extensions. This increases the frontal area slightly
If the tire sidewall is just visible looking straight on, that likely would have been fine, and wouldn't have increased A at all. The airflow coming off the bumper likely isn't flowing straight aft, so completely hiding the tires behind the plastic (or metal) isn't strictly required. (It's the same reason cars with front tire "spats" don't line them up with the edge of the sidewall.)

robertwb70 08-21-2009 04:19 PM

I don't think I was looking at it from the right perspective when I made them. I see what you're saying since the air has some momentum coming off the front of the car, makes me think maybe Suzuki did it right to start with?

Well modifications are always susceptible to further modification. Sooner or later I will have to remove the front treatments and when I do I'll scoot those in about an inch, trim 2 inches off the height of the air-dam and lower the front 1 inch, but for now I'm going top leave it and see what it does.

robertwb70 08-23-2009 11:03 PM

Got the rear wheel skirts mostly finished today and posted some pictures, they still need a few adjustments but you can see what I have now.

Christ 08-23-2009 11:08 PM

Instead of putting tire spats in the rear, why not make some side skirts and use the part that you've got there for a support/mounting location?

That will also allow you another area that you can add to your rear wheel covers, however many inches lower than it is now.

Just a thought.

robertwb70 08-24-2009 12:27 AM

Do you think side skirts are worth the work? I've been thinking about them but I haven't seen anything on how effective they might be.

2000mc 08-24-2009 12:33 AM

Testing grille blocking & wheel skirts: +5.7% improvement - MetroMPG.com

...der side skirts not wheel skits

Christ 08-24-2009 12:36 AM

They will prevent potential cross flow from under to outer, and from outer to under - remember, the under belly of your car has several low pressure sections that might actually be pulling in air from the outer area.

You can also add inner and outer skirts which prevent air from getting to the tire faces at all, and help streamline the underbelly of the car after getting a belly pan.

robertwb70 08-24-2009 12:44 AM

I was just looking at the aerocivics catamaran style skirts and that looks interesting.

I was thinking maybe the outside skirt angled from the inside back of the front tire and flaring out to both sides of the rear tire (long triangle like), enclosed in the center.

Crono 08-30-2009 04:42 AM

The autos aren't too bad, and the 36mpg is the sort of mileage my mom gets in hers, and she is, by no means, an ecomodder. If you really want to go for the mpgs eventually going to standard would be better...though I'm not sure if it would be worth the work involved. (Though if you did you could always put the 4 cyl transmission and change other stuff while you were at it).

robertwb70 09-01-2009 11:29 PM

I'm not much of a hyper-miler myself, Florida and an automatic trans don't present much of an opportunity for P&G or coasting so I mostly DWL and bear it. I'll probably get a MT car eventually but I want to see how far I can get this one first, would be nice to get to 50 but that's a ways off.

Last tank (most of a tank, 300 miles) came out to 40.88 MPG so I don't know if it was a bad tank or some of the mods are actually hurting FE. There were other changes at the same time as well though, I replaced a fuel tank that was full of rust which might have been creating some kind of lean burn condition due to it clogging up the fuel pump "sock/filter".

I'm going to put another tank through and then tape the part I cut off the rear back on and see what that does for a few tanks. Then maybe I'll remove the front air-dam and see what that does for a few tanks-at that point all the mods on the car will be ones that can't possibly be having any negative effect (wheel skirts, partial grill block and mirror delete).

robertwb70 09-02-2009 12:25 AM

Added what I have written down to the fuel log here. I didn't do a very good job keeping track in the beginning but I'm getting better.

solarguy 09-03-2009 06:07 PM

Hey, nifty trick with the laser. I'll remember that one.

Keep us posted on your progress.

Finest regards,

troy

robertwb70 10-05-2009 05:05 PM

Finally added some new pictures- cardboard Kammback, Frankensteined rear bumper cover and the latest battle scars.

robertwb70 03-11-2010 02:10 AM

Just a little update (new pics soon)

I've installed Intax lowering springs and new struts all the way around, shortened the front air dam and the rear skirt parts that used to hang down so now I can drive anywhere normal cars do without scraping anything off.

Working on a permanent Kammback right now, trying to make something that works better than the cardboard prototype by making it as long as practical.

robertwb70 03-13-2010 12:39 AM

No progress due to rain for the last 2 days, I'm at the point where I need to remove the glass from the hatch to continue and I have to work outside so hopefully tomorrow I can get it (mostly) finished.

The shorter cardboard version got me around 2 mpg so I'm hoping to get 3 mpg out of this one.

Couple of rough pictures

robertwb70 03-13-2010 10:46 PM

Didn't get it finished but got a good chunk of it done, new pics on my blog and in the garage here. Also updated pics of what the front looks like now.

Somehow the angle on the Kammback changed to 17 degrees, too late to change it now so I'm hoping it will be OK. The roof directly in front of the hatch is 10 degrees already so it should allow the air to stay attached at the steeper angle I'm hoping, but we'll see. Also the rear tires are smaller than the fronts and due for replacement anytime, the new tires will likely be the same as the fronts so that will decrease the angle some.

Robertwb70

RobertSmalls 03-14-2010 10:28 AM

It looks good, and it makes you wonder why Suzuki didn't give the Metro a CRX-style upper/lower glass arrangement.

You should probably tuft test it before you cut the sides to see if flow remains attached. No sense putting all this effort into something that won't work.

How well can you see through plexiglass at 73°?

If you leave the original glass in place, then your cabin is still enclosed with approved safety glazing.

robertwb70 03-14-2010 08:12 PM

Too late, I've already removed the factory glass. I could always put it back in if necessary.

As far as seeing I'm not sure since I haven't driven the car yet but I'll find out tomorrow. I did move the car a few feet today and now the angle finder says 15 degrees so apparently my slab isn't level.

I'll put some tufts on it when I find some appropriate string/yarn.

Christ 03-14-2010 09:11 PM

Quote:

Originally Posted by robertwb70 (Post 166101)
Too late, I've already removed the factory glass. I could always put it back in if necessary.

As far as seeing I'm not sure since I haven't driven the car yet but I'll find out tomorrow. I did move the car a few feet today and now the angle finder says 15 degrees so apparently my slab isn't level.

I'll put some tufts on it when I find some appropriate string/yarn.

I'd definitely take a 16" 2x4 and lay it across the slab on the 2" face, then lay a level on it to make sure.

Also, don't forget now that when you load down the car (if you do), it will probably change the angle enough that you can't keep attached flow at highway speeds (45+), since the angle is already 15*. The roof slope might help you out a bit, though.

robertwb70 03-14-2010 09:29 PM

Don't know why I've never checked the slab before now but I'll definitely have to put it on the list.

I'm hoping some tuft testing will tell me if the angle is acceptable or not. I figure I'm in the car alone / no load about 95% of the time so I'm not too concerned with the other 5% of the time.

I've been searching and found that there are variations with what is considered the "optimal" angle from 10 to 15 to 22 degrees, depending on the source and the rest of the cars shape/ angles.

Christ 03-14-2010 09:37 PM

I can tell you how to level the slab very easily if it needs to be done, but you'll need a cement pump.

PM me if you need to.

RobertSmalls 03-14-2010 09:44 PM

Quote:

Originally Posted by Christ (Post 166106)
Also, don't forget now that when you load down the car (if you do), it will probably change the angle enough that you can't keep attached flow at highway speeds (45+), since the angle is already 15*. The roof slope might help you out a bit, though.

How much does the rear suspension compress when you throw a few hundred lbs on it? I don't know, but for each inch you compress the rear of a car with a 95" wheelbase (e.g. Insight), you change the angles by 0.6°.

Christ 03-14-2010 10:49 PM

Quote:

Originally Posted by RobertSmalls (Post 166121)
How much does the rear suspension compress when you throw a few hundred lbs on it? I don't know, but for each inch you compress the rear of a car with a 95" wheelbase (e.g. Insight), you change the angles by 0.6°.

There's something like 7" of compression from idle state, and it only takes something like 400 LBS or so to bottom out the rear suspension, IIRC.

I don't think it's the wheelbase that matters in that calculation, so much as the distance between the pivot point (front wheels) and the opposite end of the car.

The front wheels act as the fulcrum, the rear wheels are just providing resistance to movement (if you add weight to the back), so the final angle would be determined by the tail end of the car, if it makes a difference.

COcyclist 03-15-2010 02:04 PM

robert, It's good that your Kammback is clear. You can easily tuft test it with a quick look in the rearview mirror in real time, real world conditions, real driver in driver's seat. I made a coroplast prototype Kammback but couldn't see the tufts by myself and haven't had time to get back to the project.


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