Geo Metro XFI Convertible Project Finished

[MetroMPG]

Originally Posted by Coyote X

The question is how high should the car be off the ground with a flat underside?

I have read: between 1.5 to 3 inches, with 3 being quoted more often (besides 1.5 isn't quite practical for a road car, is it?). But I can't find the $*&$ sources at the moment.

Knowing the underside of the car, your largest source of underbody drag (with a smooth belly in place) is going to be the control arms. So if you can lower the suspension enough to get the belly pan at least level with, or slightly below the bottoms of the control arms, I'd say that's where you've probably achieved the most drag reduction.

How high would that have you off the ground, and what would it do to your suspension geometry?

[MetroMPG]

Also - if possible, try to taper the belly pan upwards after the rear suspension, at no more than about a 10 degree angle.

[Coyote X]

I was thinking of making it totally flat from the bumper lip in the front to the bumper lip in the rear. If I did that I could lower it maybe 1/2 inch lower than stock to make the control arms sit level with the pan. I would like it lower so if you think that going lower than that won't affect anything I will probably just use my chopped XFi springs.

I could angle the rear upwards some and just cut that rounded lower section off the bumper and just make it like a smooth roll pan on the back.



From that pic you can see the rounded part of the bottom of the bumper, if I cut that off that would give me a slight upwards angle on the rear of it.

[MetroMPG]

Know what else would be cool - stretch some rubber over the rear control arms, so you can still have full travel, but a clean aero membrane when riding flat & level. I was thinking the same membrane connecting the pan ahead & behind the front control arms would be good... and then rememebered the wheels have to steer too.

[Coyote X]

If I drop it to the bump stops I can just go over the control arms with the cover since they will be up higher

I could cut away part of the pan where the wheels turn and leave the rest alone. That would get most of the control arm covered.

On the rear I could build basically a sealed system that gave the tread 1/8" clearance and the back side could be near form fitting and let the wheel shape it precisely for me. That could join with the wheel skirts to keep all air out of the rear wheel well.

I will get it on it's side again this week and get some pictures and try and illustrate what I have planned so you can see it better. School starts back tomorrow so I will be busy with registration and junk this week probably unless I can get out of it again

[metroschultz]

Originally Posted by Coyote X

The question is how high should the car be off the ground with a flat underside?

I would believe your minimum under body ground clearance should be 5.5" . When i worked for the corner gas stations, I saw more than one slammed ricer get stuck on our speed bumps. Damn that was funny.
Here in the great Commonwealth of Va. dot regs say they (speed bumps) are not to exceed four(4) inches in height. Real world speed bumps can be as tall as six inches.
However with a light enough car you just pick up the backend and push it the rest of the way over.
Happy motoring. S.

[Fuzzy]

Originally Posted by MetroMPG

I was thinking the same membrane connecting the pan ahead & behind the front control arms would be good... and then rememebered the wheels have to steer too.

Why not have a piece that's attached to the upright, and turns with the wheel?

Originally Posted by metroschultz

Here in the great Commonwealth of Va. dot regs say they (speed bumps) are not to exceed four(4) inches in height. Real world speed bumps can be as tall as six inches.

Than why not go for 5", and if you find anything over 4" make them shave them down to the VDOT specs?

Another thing to consider is your approach angle. So, with 5" ride height, and fully compressed suspension what's the maximum angle you can approach; "the steep driveway conundrum."

As for ducting. Just think "P-51". I'd have to find/unpack some books to try and estimate opening size . But <generalizations>you'll get lower drag with a duct from the opening to the radiator and from the radiator to the exit. The exit should be "variable", so that changing the exit size will increase the low pressure zone at the exit and promote flow at lower speed (the fan does the same thing). But you'd want it in a location of low pressure to begin with. Water cooled engines still benefit from air cooling, but you could probably figure that out after getting it running again, and just pop some variable vents in the hood (in it's low pressure zone) that can be tweaked open based on OAT, ECU closed/open loop, under-hood temp and mph (or just use your brain and a lever).</generalizations>

[eta]

Good question on the ground clearance. I was going to build it with 5", and so have about 4" loaded? My car will have no overhang front or back and that helps a little on the clearance issue. To build my frame I was going to do the floor panel flat on the garage floor. The sides would be roughed out on the garage floor separately, and then just stand them upright on the floor panel and welded on? Then add the roof? Yes this light a frame shouldn't be that hard to move around.
Good luck!
Mark.

[evedder]

I like it so far I used to have a Geo Metro back in the day. Everyone used to make fun of me for it lol.

[Coyote X]

Didn't do much today to the car other than cut some holes in it with a plasma cutter

I did stick a fence post inside the rocker to see if the tube would actually work.


The plan I have for the chassis seems like it will work good. I can just mount the main tube on the passenger side the way the car is sitting now then lay it on the other side and do the same thing to the drivers side. Once those bars are in place and locating the inner control arm mounting points. I can start cutting away the rest of the structure and building the chassis one part at a time. I still think once I get those main tubes installed I should lay a sheet of metal on the floor and weld the jackstands to it and also to the control arms so the car can't shift or move in any way as I cut the unibody away.

The rear will be easy.

I can leave that center piece alone and notch it to run a tube through and weld it onto the tube. Then the spare tire area can be cut away from it. Once that is done the rear is basically done, I just need a shock tower and spring perch. Then a U shaped pipe to replace the rear bumper. None of that will have to be really much precision though so that makes it much easier.

[MetroMPG]

Well, stating the obvious, but it's amazing how much rust you can uncover once you start poking. And pressure washing. I was convinced the blue ForkenSwift Metro was a solid host car with "one or two" tiny holes in the floor. No way. I opened up some pretty big holes. It wasn't as swiss cheesy as this vert, but still a bit of a shocker.

Next topic: I'm assuming you're either friendly with your local garage, or you don't have to do state inspections to get your plates? (Wondering if they'd give you trouble for a massively modified unibody/frame.

[Coyote X]

There is a state inspection to make sure the car is road worthy. Mainly checking the lights and junk like that. They don't check the car for much of anything really. Pretty much if the car is within the uniform vehicle code specs they can't fail it. The car doesn't have to be anything resembling stock though

There are no emissions tests or any actual tests for a car unless you are trying to license a salvage title. Those have to be inspected a bit more carefully. If you have a picture of the damaged area they usually just look at it to make sure it was actually fixed then give you a clear title for it.

Really the car isn't as rusted out as my xfi. I have more or less found every bit of rust on this thing and it is in the pictures. I bet when the xfi shell is down to the bare metal it looks way worse. I think they made these cars with super cheap metal. I have cars that have been sitting outside unprotected for 20 years that have less rust on them than these cars all seem to get.

The good thing about the vert is the frame is still square and the suspension points are all in the right place so I don't have to try and re square the car. I should be able to have it sitting on it's new chassis in a few weeks if I can get the tubing in quickly and school stays easy.

[Coyote X]

Went to the steel shop today and ordered the stuff I needed. I ended up with 1.9" .130 tube for the main frame rails, 1.5 for the roll bar and some 1" for random suspension mounts and brackets. I also got about 40ft of 3/4" square to use for the body mounts and other random junk. Metal is getting expensive, it was $380 for everything. More than double what it cost for the kit car's frame.

I guess even if you add up all the costs of everything it is still cheaper to build your own chassis than have one built. $750 for a plasma cutter, $200 for a tubing bender, $600 for a mig welder, and the 380 for the metal still works out cheaper than ~$2100 the shop told me it would cost for them to build me a chassis. I had all of the tools already so it wasn't that expensive for me to just do it all myself.

Now I just need to find a few sheets of abs plastic so I can make plastic inner fenders and a few other things to keep the weight down.

[Coyote X]

I cut away all the extra metal on the passenger side inner suspension mounts. I have it pretty well figured out now. I got some of the metal for it today, they dropped off what they had in stock but the rest will be in either tomorrow or next friday.

After I cut away some of the unibody I was kind of surprised how they made these cars. There are so many layers that are 1/4 inch apart with no way for water or dirt to run out of it there is no wonder that these cars rust out as fast as they do. I see some things that would probably help keep the cars from rusting out as bad but really I would say anyone who owns one of these cars should put about a gallon of oil into the front and rear suspension mounts every year to help control rust.

[MetroMPG]

Originally Posted by Coyote X

I would say anyone who owns one of these cars should put about a gallon of oil into the front and rear suspension mounts every year to help control rust.

I noticed exactly the same thing when working on the blue ForkenSwift car. There's a drain hole in the unibody "floor" directly behind the front tire that receives spray into one of those bizarre voids between layers. If I wanted my car to rust out catastrophically, it's pretty much exactly how I would have designed it!

[Coyote X]

I was sitting here thinking of how I can repair the curve on the rocker panels when I thought about it and having the rocker not curve seems like it would be better.

So how about instead of the curved rockers like the car has stock I run it straight down and have a 90 degree angle and the floor sits flush with the bottom of it? I could extend the rocker down below the floor easily that way. Kind of like having a built in side skirt. It would make the rear wheel covers much easier to install and keep a bit more air off the front of the back tire.

[Coyote X]

moving right along, passenger side frame is almost done. It is spot welded in place for now. I will weld it right tomorrow and cut away the last of the unibody holding it in place. I will also add a few more temporary braces to attach the new tube to the old unibody panels for now.


There are a few more images plus the larger versions on my site like always. I think we need an html mode here so I can just copy and paste my entire post from my site without having to do it in bb code.