The Miata of the Month from

December 2011

Jim Dowd and his three-cylinder Miata
fujioko on Miataforum

Congratulations to Jim on the selection of his Miata as the December Miata of the Month!

What if you could merge the Geo Metro fuel economy with the classic lines of the Miata?

Replacing the DOHC 1.6 engine with a little 1.0 three cylinder engine should be a snap…right? Well, not exactly. The little three cylinder is a tight fit in the engine bay of my 90 Miata. About the only thing that lines up is the throttle cable. The project took seven months to complete however I did spend about six months prior collecting the parts.

The Geo Metro engine is mated to a Suzuki Samurai transmission. I used a Suzuki Samurai clutch, flywheel and starter. The Metro oil pan was tossed in the scrap pile and I used a four cylinder Geo Tracker pan. I had to cut and weld the Tracker pan to fit the three cylinder engine.

The basic drive train slipped into the engine bay but there was no room for the distributor. I went ahead and moved the distributor to the front of the engine with some custom brackets.

The cooling hoses were all in the wrong direction and I had to mount the thermostat in a remote location. The stock Miata radiator is twice the size I needed but I elected to keep it because it was new and it fit so well.

About the only thing I regret was the way I modified the clutch system. I had to cut up the firewall and do a lot of unnecessary work. I later realized I could have replaced the clutch master cylinder with a rocker arm linkage and the whole clutch cable system would have been a bolt in. Next time….

The car was built as light as possible. The finished weight is 1960 lbs with a full tank of gas. I deleted a lot of interior parts and comfort items..

The car was finally finished in July and I began driving it. The average MPG is 45+. The car never dips below 45 MPG. I have gotten over 50 MPG and once I recorded a figure of mid 60’s. I discount the higher fuel economy figures because it wasn’t practical to drive the car that way.

One of my experiments was to add 100 lbs of ballast to the car and monitor the performance and mileage. The extra weight had no effect on the performance and the mileage did not suffer. Realistically I think I could put the full interior back in the car.

Reality is sometimes hard to accept. The car is capable of 70+ miles per hour on the expressway but it sucks down the gas too. Highway driving is where the car falls short..

Overall I’m very happy with the results. I continue to tinker with the engine in hopes I can get the highway mileage up.

At some point in the near future I plan to transplant the drivetrain into a cleaner Miata.

If you want to know more about the swap and see Jim's many clever solutions to the various problems he encountered, see the build thread on Miataforum. Jim's now turned his attention to the Miata engine's little brother, the 1.3 SOHC found in the Festiva.

Previous Miata of the Month Winners

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