Update

Wow, it's been a while. The Geo is still my daily driver, had an issue with rust/corrosion in the fuel lines, made them impassable, took a while to figure that one out (thought it was the fuel pump). Ran some steel cable into the lines and cleaned them out good, no issues since then other than a leaky radiator hose. Got an alignment a while back, was hoping it was way off and I'd see improvements in FE, but it wasn't and I didn't. Wheel skirts have been off since the alignment. Driving only 6 miles each way to work was getting me tank averages in the 38 mpg range in winter and low 40s the rest of the year. Now I'm driving 22 miles each way in heavy to medium traffic and averaging low to mid 40s. Probably going to put a Subaru style roof scoop on soon so I can get the air to come into the front of the car better. Slow work takes time...

New tailpipe for the Metro

I was driving through a construction site where they left a rather large step in the pavement from a milling operation and the jolt knocked my tailpipe right off the car. It was only welded on to the thin sheet metal case of the stock (but gutted) muffler and the thin metal just broke around the weld. The original muffler tailpipe extended into the muffler and had several more support points so the end cap of the muffler was not designed for the stress the way I modified it. I found the tailpipe that came off and thought about just re-welding it but since the new hole was larger now and the car seemed to like it (better MPG without it) I decided to use a larger pipe. I found some 2.5" pipe in the scrap pile and this is what it looks like now.


The old pipe that fell off 1-7/8" OD I think it was.


The old pipe slid inside the new pipe.




Watch out ricers!

Roof scoop installed

I was able to mount the scoop to the 3 rivets holding each side of the vent with an "L" bracket so if I decide to get a different one there are no extra holes to fill. I couldn't decide between cutting the front the way you see it or doing a sawtooth type edge but in the end simplicity won (though I could still add the saw teeth). This scoop fits fairly close to the vent when open so I'm a little concerned about getting airflow around it and to the backside but I think it will be OK. I'm interested to see if it has the desired effect.


Front 3/4 view with vent open to the rear.


Front view with vent open to the rear.


Side view.


Rear view, you can clearly see the "24" logo from the lawnmower emblem. The gap at the rear is intentional to allow some flow through relief when the vent is closed.


Front view with the vent closed.

Possible roof scoop and mockup

This is a plastic piece that came from a 24 volt lawnmower, but it looks like a scoop to me. I don't know if I'll keep it or just use it until I decide to pony up for the Subaru type roof scoop but it was free and I'll make the mounting brackets use holes I've already made.


Top view after some trimming on the sides and back.


Bottom view.


Roughly where it will go on the car.


From the front, it's a pretty close fit when the vent is open.

Geo Metro line drawing

Roof vent for my Metro

It's summer again and I'm tired of sweating so I'm putting a vent in the roof. I got the idea from member "Badbent" at Geometroforum.com, here's the thread showing his vent with a scoop- . I'm going to try it with out the scoop first, if needed I'll add the scoop later (the scoop pressurizes the vent even when it's opened facing the rear which directs the air down to the drivers feet which might be nice). Here are some pictures of my install, it's not finished yet but I had to get it in so I could drive the car tomorrow.

A back saving cart for sheet goods

When you need to move sheets of plywood, glass table tops or 100+ lb table tops this cart is a real back saver. The cart is 24" by 40" with a 15 degree incline. It cost about $50 and took around 6 hours to make. It's made from scrap 2x4s with harbor freight 5" wheels. It has some 1" dowels with rubber tips to keep stuff on the cart, one on the side ( to keep stuff from sliding off when it's too big to rest on the angled part) and one on each end (for round table tops/ glass).I used it to move about 15 heavy table tops and it worked splendidly. I traded it to the owner of a thrift store for some metal filing cabinets.

Fuel Tank Problems

I replaced the badly rusted fuel tank that was in the Geo with a much less rusty specimen from the salvage yard on 8/11/09. The car started sputtering and pinging more and more lately so I decided to drop the tank again to investigate. Here's what I found, you can expect similar issues if your car has a steel fuel tank and you use gasohol (otherwise known as ethanol "enhanced" gas, E10, E85).

There was rust crud built up about 1/8" deep in the sump.




A white rag that I wiped the bottom of the tank with...




This (and the fuel filter) are the real problem because they make the pump work much harder and starve the engine for fuel. I used compressed air to blow this pre filter clean and re-installed it. I also replaced the fuel filter, relocated it for better serviceability and cut the old filter apart but my camera has died so pics will have to wait.

Fuel Efficiency Tracking Update

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• Lifetime Fuel Economy: 42.6
• 90-day Fuel Economy: 47.07
• 3-tank Fuel Economy: 47.69
• EPA Rating (% over): 33 (42.6364%)
• Total fills: 39
• Average cost per gallon: $2.59
• Average cost per fill: $20.03
• Average cost per mile: $0.06
• Total gallons used: 298.03
• Total miles traveled: 12697.3
• Total cost: $771.9
• Total saved: 86.74 gallons
• Total saved: $224.66
• Average tank distance: 325.57

Fianl version of Kammback extension

Finally got the Kammback redesigned, attached with all its rivets and sealed against the weather. I raised the trailing edge up 1" and tapered each side 3" from the prototype design. I gave it a quick rattle can paint job just to keep it from rusting, a full paint job is coming later so no use making it perfect now.

Here's the new profile view.


A couple of views from the rear.




This is the view from the inside. The black stuff is urethane (3M window weld) used for windshield installation and was used to seal the seams and dampen any oil can / resonances in the sheet metal.

Stock Exhaust

This is turning out to be something of a reverse order listing of what I've done but I found the pics from when I originally discovered the stock double wall exhaust configuration. I believe the inside pipe was 1.33" ID so the 1" I've replaced it with should lower the efficient range of exhaust tuning/ engine operating RPM. I believe that if the entire engine's intake and exhaust passage ways could be resized for below 4,000 RPM operation it would yield significant FE gains. Unfortunately this would be quite difficult to do so maybe the next best idea would be to take an engine that was made in different displacements and swap the heads with the smallest ports onto a larger displacement block, this isn't possible with the 1.0 metro engine though. Most engines made today can rev to and produce peak power at 6,000 plus RPMs which means all the ports/ intake/ exhaust passages and cam profiles are sized much too large for low RPM operation, which is where the motor operates for the vast majority of the time. I'm rambling now...

Exhaust size

I used the calculator here to evaluate not only what the engine might need but what the pipe I had would like. The first box is optimized for engine size and RPM while the second box is more generalized and considers engine HP.

First is what the engine would like @3600 RPMs which is 60MPH in the car and the upper end of speeds I routinely travel. As you can see the 1" ID conduit I chose is still over sized because it recommends 1" OD with 0.0625 wall thickness (16 Ga), which would be 7/8" ID.

Second is what RPM level the 1.75" ID pipe would support with the same size engine. This is about 10,000 RPMs higher than I ever get to.

Third is the HP level that the 1.75" ID pipe would support. This is about 100 HP more than I have.

Finally the engine displacement that the 1.75" pipe would be optimized for at 3600 RPMs. The engine is a 1.0 liter 3 cylinder, I could run 4 of them through that size pipe for what I am doing.

So you can see I've been running a pipe that was 3 to 4+ times too large for my engine and operating conditions. I don't have any numbers yet but the Instantaneous FE reading on my MPGuino are at least as good as or slightly better with the smaller pipe, so I certainly haven't lost anything.

Smaller Exhaust Tubing

One of the first modifications I made to the metro was removing the inner part of its stock double wall exhaust pipe that was stock from the manifold to the catalytic converter (about 13" long). I wasn't really intending to focus on MPGs at the time so I thought it would be good to have a very low restriction exhaust for better power. In hindsight it was a mistake, a 1.0 liter engine just doesn't need a 1-3/4" exhaust pipe (that's the size the remaining stock outer tubing was). Driving the car with the large exhaust I could feel how the sweet spot (when the motor really ran best) was way above the normal operating RPM range so I decided to put some smaller tubing back in place. After a doing some research on several websites I settled on 1" ID tubing which worked out well since I had some 1" EMT (conduit) laying around and a bender to bend it with too. Here are some pics comparing the difference between the old and new pipes.

Kammback progress

Didn't get it quite done but made a lot of progress. Somehow the angle is now 17 degrees, not sure what happened but I think it will be OK since the roof in front of the hatch is 10 degrees already. Still have the trickiest part left, the corners, should be able to finish it up tomorrow. The sides were left long until the corners are completed then they will be trimmed. The sides are aluminum so I think I'm going to polish them instead of painting, I'll paint all the steel parts though.

Updated pics of front airdam

It scraped too much and since I lowered the car it was going to be even worse so I had to shorten it up some. Paint doesn't stick well to galvanized metal so I just took it off, I'll get some self etching primer and re paint it eventually...if I don't make a complete new front for it before then.

Kammback begins

The beginnings of a Kamm back extension for my Metro, this is going to be a (hopefully) bigger and better permanent version of the cardboard prototype. The angle is 15 degrees and as shown here it's 36" wide. It will have smoked plexiglass for the flat sections seen here and sheet-metal will enclose the rest. The original glass will be removed before construction progresses much further. It's been raining for the last 2 days so hopefully tomorrow I can get this finished.

The scrap masonite panel on the bottom is just for mock-up, it will be plexiglass when finished.

Cold weather hurts fuel mileage

Tower 2 results

Tower 2 weighed 4.905 lbs and withstood 19,867 lbs of force before it succumbed to the pressure. This results in a strength to weight ratio of 4,050.36 lbs/lb. It was the heaviest tower and withstood the most force of all the towers tested however it did not have the highest strength to weight ratio, but it was the second highest.

Finishing touches on tower 2

It just didn't look like a tower...