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Project MR2: Part 1

A Daily Driver Go-Kart

Dave Coleman
Jul 15, 2002 SHARE
0203_01zoom+toyota_mr2_convertible+right Photo 1/13   |   Project MR2: Part 1

Axis Sport Tuning's tuned MR2 Spyder set three new records in our testing last June, but we're convinced we can do even better. Like most projects, we plan to show you each step of this MR2 Spyder's progression from mild to wild. Along the way, we're going to try more realistic and attainable combinations to find out what works at each level.

Project MR2 Spyder is a prototype that was used as an engineering mule, so there were some differences we immediately noticed between it and production cars. Parts of the dash and door panel plastics wear a different finish from production, the red fabric door panel inserts were painted black and the seats, instead of exterior-matching red and black upholstery, are the more understated gray and black. The antenna is also spiral-wrapped to eliminate wind whistle, something we miss on the production car. Apart from these things, our MR2 is exactly what could be expected when purchasing any used car.


New Battery
Because the car sat for months at Toyota's headquarters, we began the project by replacing the battery. Rather than buying a stock replacement, we called the folks at ThermoDynamic Inc., who sent an AP-1236 Reactor Power Cell battery. Using technology similar to an Optima battery, but in flat plates rather than coils, this compact, deep-cycle battery is sealed and weighs only 20 lbs., a savings of nearly 8 lbs. from that of the stock battery.

The day the Reactor showed up, Dave Coleman needed a smaller battery to clear the new engine in his rally beater. He swiped it and tested its deep-cycle capability by running it dead twice and pounding it through the Rim of the World Rally. The battery seems none the worse for wear.

Suspension
Although a great-handling car, a stock MR2 Spyder is hard on tires because it's softly sprung and has a lot of body roll--not a good thing with MacPherson struts. To simultaneously improve handling and make the car easier on tires, we would lower it, reduce body roll, add some negative camber and stiffen its chassis. Naturally, we would also add wider, stickier rubber.

Several other project cars have begun with expensive, custom suspension set-ups, because they were all we could get for brand-new cars. Coil-overs are available for the MR2 Spyder from A'pexi and Cusco. Truechoice offers custom Konis, albeit at a "custom" price. These have already won a national autocross championship, however.

Koni now says it should have off-the-shelf dampers in the United States by the time you read this, but had nothing six months ago when we were asking. We were unwilling to install sport springs with the stock dampers, because that combination always results in a horrible driving experience. With its engine in back, we weren't about to do anything questionable to the Toyota's underpinnings.

The only conventional spring/damper combination we could find was Toyota Racing Development's Sportivo set, which also includes anti-roll bars and the option of upper and lower chassis reinforcements. One-stop shopping and no dealer warranty issues made it an attractive first step.

To complement the chassis upgrades, we bolted on bigger, stickier rubber from The Tire Rack. Yokohama's A032R worked well on the Axis MR2, so we opted for the Yokes in the same 205/50R-15 size used on that car.

After considering 20 other wheels, we settled on the Kosei K1 Racing cast aluminum wheel, which is both lightweight and affordable. Although stock offset is 45mm front and rear, The Tire Rack told us the 15 x 7-in. Kosei K1 racing wheels require 38 mm offset to clear the front brake caliper brackets. Because the wheel is 1 inch wider than a stock front wheel, the outer edge of the tire can kiss the inner fender when going over bumps with the wheel turned but only very slightly. The Axis MR2 Spyder used narrower 15 x 6.5-in. Axis VPD wheels and gained a quarter inch of clearance.

Details of the installations, which went very smoothly, can be found with the photos. The additions added 17 lbs to the car, but it still weighs only 2,250 lbs. We aligned the car to the following specifications.

Camber: As much negative as possible.
Caster: 3.0 degrees
Front Toe-in: 0 inch
Rear Toe-in: 0.10 inch

Unlike previous MR2s, there's no provision for camber adjustment, so the Spyder's camber is adjustable only with the slop in the lower strut mounting holes. Crash bolts, smaller diameter strut-mounting bolts which increase the free play and the resulting range of adjustment, are available for the MR2 Spyder, but in our experience, this type of adjuster almost always slips when used with competition rubber.

The small caster angle and zero toe provide excellent turn-in without excessively wearing the inside edge of the tires while on the street. Steering effort is very low, especially with the power assist, but feel is good and there's little sense of on-center twitchiness or wandering. Slight toe-in at the rear helps keep the tail under control. Turn-in and tire wear could be improved with more negative camber, especially in front, but that will require the addition of camber plates.

As expected, the stiffer springs transmitted more force to the chassis, causing it to shake more than a stock car does. The TRD chassis braces, even with the new stiffer suspension, made a noticeable difference in ride quality, transient responses and the car's overall solidity, but because it's a convertible, there remains room for improvement. We'll address this after we improve other parts of the car.

Testing
We've hardly done anything and this car already kicks ass. Our basic, entry-level suspension choice was good enough to pull 1.03g on the skidpad at The Streets of Willow Springs. Exceeding 1.0g was our goal for this part of the build-up, so we're stoked.

Dave Coleman reports the most amazing thing wasn't the number, but the way the Sportivo suspension handled the rough, dirty, bumpy pavement of the Streets' skidpad. It was totally planted, easy to balance with the throttle, with no skipping, jumping sideways, or tail-out shenanigans.

Furthermore, Project MR2 Spyder went through our 600-ft. slalom at 72.8 mph. The Axis MR2 Spyder was only 1 mph faster in the slalom with more than twice the power and adjustable coil-overs.

On the street, this car feels as fast as it is. Everyone who has driven it is impressed with its grip. It's possible to spin the inside rear tire just slightly when exiting a slow corner in a low gear, but not to the point of oversteer. Though a traction-aiding differential would eliminate that, we don't plan to install one until we've seen big horsepower increases.

A roll bar, however, is a necessity. We called Autopower the day after we put the car together and a roll bar arrived two days later. We haven't had a chance to install it yet, but you can bet it'll be on the car in the next project installment.

Project MR2 Spyder is a joy to drive. The steering is quick and the car changes direction effortlessly. The next step is to see how much power can be gained with intake and exhaust modifications. Stay tuned.

WEIGHT BALANCE
Weight is so critical to the MR2's performance that we're keeping a strict inventory of every pound added or removed.
Here's what we've added so far.
NEW STOCK
Front anti-roll bar : 9.25 lbs Front anti-roll bar : 7.75 lbs
Rear anti-roll bar : 7 lbs Rear anti-roll bar : 4.75 lbs
Wheel and tire, front : 34.25 lbs Wheel and tire, front : 30.5 lbs
Wheel and tire, front : 34.25 lbs Wheel and tire, rear : 35 lbs
Springs : 15.25 lbs Springs : 13 lbs
Member braces, all : 10 lbs Member braces, front : 3 lbs
Front strut tower brace : 6.25 lbs Front strut tower brace : 6 lbs
Rear strut tower brace : 7 lbs Rear strut tower brace : 1.5 lbs
Battery : 20 lbs Battery : 27.75 lbs
Total : 211.75 lbs Total : 194.75 lbs
Net Gain : 17 lbs  
Vehicle Weight : 2250 lbs, +/-10  
(Precision +/- 1/4 lb)  

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By Dave Coleman
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