Friday, March 30, 2012

LeMons Good/Bad Idea of the Week: Two-Stroke Miata!


Dropping a Chrysler slant-six engine into an E30 BMW 3-series
is a very bad idea, and yet perfect for the 24 Hours of LeMons. We thought it would be hard to top that ill-advised engine swap, but a gang of wild-eyed California fabricators cooked up something even better (that is, even worse) for last weekend's Sears Pointless race at Infineon Raceway: a Mazda Miata with Polaris snowmobile power. Three cylinders, two strokes—and a weight savings of nearly 800 pounds compared to the Mazda drivetrain.

When they aren't helping us with LeMons tech inspections or building cages for LeMons cars, the folks at West Sacramento's Evil Genius Racing work on their bread-and-butter business: building and repairing cars for the Spec Miata world. Miatas are right there with E30 BMWs and Acura Integras on the "Cars We Aren't Very Happy To See In LeMons Races" list—unless they've been hacked up with ridiculous modifications. An Evil Genius customer stacked this particular car on the track, it ended up sitting around the shop for a while, and then the mental gears started turning. In the words of EGR chief John Pagel:

It was a very nice 1991 Special Edition BRG Miata. I looked after it for a customer, it got wrecked; right front frame rail bent way in and down, left front bent out. Bought it for $450 from the customer, proceeded to sell off $2500 worth of parts: engine, trans, left door and fender, interior, seats, dash, etc. It is a legit $0 car. We straightened it between two Ford Super Duties. Scott DeWinter had a Polaris motor and the build commenced.

For the full story of how this car's build process went, with technical details, check out this thread on the 24 Hours of LeMons forums.


So, a 92-hp Polaris 600 three-cylinder went into the Miata. There is no transmission; the Polaris variable-speed belt-drive unit with centrifugal clutch was used. The entire engine and clutch assembly weighed about 85 pounds. No engine hoist necessary!


All the power is transmitted through this belt. The team brought several spares.


Two gauges, two pedals.


There's no electric starter in this setup. Instead, we saw the first-ever pull-start LeMons racer. Watch this clip to see how the starting process goes:




In honor of its snowmobile ancestry, the car was named after the famous Alaskan sled dog. The team's name: Idiotarod Racing.


The end result was a Miata that weighs something like 1300 pounds. The Polaris engine makes about 20 fewer horses than the '91 Miata's factory engine, but the tremendous weight savings compensates for the power loss.


What's it like on the track? Fairly quick and shockingly reliable. We expected this SnoMoMiata to start spitting out drive belts in the first hour of the race, but that never happened. In fact, the team replaced the belt halfway through the weekend, but only as a preventive measure. Team Idiotarod's best lap was a 2:11, about eight seconds slower than the very quickest cars but fast enough to hold its own against the hordes of E30s and Porsche 944s.


We can't help but think that an MG Midget or first-gen Honda Civic would benefit even more from a Polaris engine swap. For now, Team Idiotarod's Balto is the only snowmobile-powered car in LeMons racing.



from Car and Driver Blog http://blog.caranddriver.com




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