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Project MR2: Part 2

Exhaust System Testing

Dan Barnes
Jul 24, 2002

After the success of part one of Project MR2 Spyder, we got cocky. The first stage we did--suspension, wheels and tires--worked better than we ever expected, transforming a really good car into one of the best cars we've driven. But it needed more power, especially at 4,000 feet on Mt. Akina. Floored in second gear, we had plenty of time before the next turn to think, "this has got to change."

As most enthusiasts do, we tried the exhaust first. We bolted on several systems, put them on the dyno and drove with each for several weeks.

Here's what we found.

Team Moon
Mazcare, a Mazda specialist repair shop in Marietta, Ga., makes the Team Moon exhaust. The exhaust is built around a Magnaflow absorption muffler. The original model has a single, polished stainless-steel tip, cut at an angle. We like that it closely resembles the stock tip, only it's on the other side of the car, which requires you to cut a hole in the MR2's plastic rear undertray. Not knowing which exhaust we'd keep on the car, we just left the tray off for our test.

Team Moon also has a dual-tip exhaust that provides the same performance, but is about 5 lbs heavier. Both versions are available in stainless steel. We tried the aluminized, single-tip model. It weighs 17.25 lbs, 9.75 lbs less than stock.

Removing the stock exhaust was the most difficult part of the installation, but Team Moon's seven-page, black-and-white photocopied instructions made the job a lot easier.

Start by removing the downpipe/catalytic converter unit. Rather than remove the oxygen sensor, we hung that end of the cat from the body with some wire, ensuring there was slack on the sensor lead. Removing the stock muffler, we found WD-40 to be helpful for sliding the exhaust hangers out of the rubber mounts. I imagined a tool, and later found it in the Snap-On catalog (YA3202, exhaust hanger removal pliers), but there might not be space to use it in the MR2's cramped hindquarters.

The Team Moon exhaust pops in place comparatively easily, especially as the hangers are smaller diameter than stock and push through the rubber mounts easily. Reinstall the downpipe/cat assembly. At first, the Team Moon's tip contacted the rear fascia, but its placement can be adjusted by loosening the bolts connecting it to the catalytic converter. We were able to tilt the exhaust and achieve the perfect location, but after a few weeks, one of the upper hangers was pulling through its rubber mount. The easy solution is to get the fitment dialed in perfectly during installation by bending the hanger.

Stock, our MR2 Spyder made 125 hp at 6400 rpm and 113 lb-ft at 4300 rpm. With the Team Moon exhaust, it made 128 hp and 114 lb-ft at the same engine speeds.

The Magnaflow silencer's muffling ability correlates inversely with temperature. On cold start, you can barely hear the engine. Driving around town, it attracts little attention, and on the highway it's hardly noticeable over the tire, wind and engine noise. But attack a mountain road, and the little Taz within woke up. The muffler's raspy, urgent tone was exactly right, and just the right volume. We found ourselves frequently bumping the rev limiter just to listen to the sound. We were so happy with this exhaust, if the others hadn't been waiting to be tested, we would've left it on the car.

5Zigen
The 5Zigen Border Fireball exhaust is distributed by Bozz Performance and comes packaged with what appear to be complete instructions and documentation in Japanese. 5Zigen is a Japanese Automotive Sports Muffler Association (JASMA) member, which means its systems are legal in Japan, but means diddly in a U.S. court. The exhaust comes with a black coating. Fit and finish range from gorgeous laser-welded seams on the outside of the exit can to "serviceable" MIG welds on the coated areas. The 5Zigen system is 4 lbs heavier than stock.

When installing this exhaust, the order in which you tighten the flanges is important. Get everything connected and in place, then start at the downpipe and work your way back. Unlike the Team Moon unit, both Japanese exhausts use the stock, spring-loaded bolts at the connection to the catalytic converter. At the split between the main silencer and the end pipe, tightening the bolts was required to pull both sides of the flanges together. The tip ended up at the right height, but its hanger was even with the pin on the body so the rubber mount was horizontal and carried no load. Because of how the end pipe dips down, it would have been impossible to reinstall the rear undertray, even with extensive trimming.

The 5Zigen exhaust made 127 hp at 6300 rpm and 113 lb-ft at 4300 rpm and it had more initial smoke than any other did. After a few freeway miles, it looked like the car was on fire, and we smelled smoke for several days. Apparently the 5Zigen mandrel bending machine is very well lubricated. Other than the environmental impact, this smoke is harmless. The exhaust may be slightly louder than stock, but not enough that anybody would notice.

When removing the 5Zigen exhaust, patches of the black coating had already flaked off the muffler and piping. All the hangers had stayed in position, though, and the gasket at the split had maintained its seal between the flanges.

Tanabe Racing Medalion
The Tanabe Racing Medalion exhaust is very similar to the 5Zigen in appearance, except it's silver. It's easier to install than the 5Zigen, and it fit perfectly. Included documentation was contradictory regarding legality of the system, so we called Mackin Industries, the importer. We were told no CARB executive order is required because the exhaust is not within the loop of the emissions control system. Every Tanabe exhaust is tested to pass California's 95 decibel sound test with the included "exit plug" installed, but like every shiny exhaust, you can tell it to the judge.

No installation instructions were included, but it was the third exhaust, so we had the drill down. The Tanabe weighed 33.25 lbs without the "exit plug," 6.25 lbs heavier than stock. The plug turned out to be completely unnecessary. Without it, the Tanabe exhaust sounds just like stock. It also made stock power: 125 hp at 6300 rpm and 113 lb-ft at 4300 rpm, and after a week of driving, the powdercoating was flaking off the main silencer and piping.

In the end, we prefered both the sound and light weight of the Team Moon exhaust, so you can expect to see it on the car in the future.

Autopower Roll Bar
In our eyes, the MR2 Spyder looks better with the top up because the proportions are even. The Autopower roll bar balances them, making the car look just right. With the top down, the MR2's aura has changed from cruiser to serious sports car. The same feeling is conveyed to the driver.

Installing the bar required two full evenings. It bolts to the posts at the rear of the doors and to the cross member behind the seat using factory fastener locations. No holes are drilled in metal parts of the car. When an extra or longer fastener was called for, it was supplied.

Getting to the areas in question requires disassembling and removing most of the trim in the rear of the passenger compartment. The factory MR2 Spyder repair manual was a big help here, as it indicates the locations and types of fasteners involved, telling us whether we needed to look for another clip to remove or just pull harder.

Once the trim was removed and the bar was set in place, the holes in the bar didn't all line up with the holes in the car. A long process of fit, mark, file and fit again ensued. The "feet" of the bar where they bolted to the B-posts were also slightly narrower than the mounting surfaces in the car, requiring the bolts to squeeze the sides of the car together. With installation complete, the doors still shut perfectly and we can't tell the difference.

The plastic trim on the rear passenger compartment crossmember must be trimmed to clear the bar, which is another time-consuming process of carefully marking, cutting, fitting and repeating. We tried a hot knife, but the plastic just got gooey. The most effective means was some side nippers to hack off chunks of plastic, combined with a knife and file to do the finer trimming.

Never have a roll bar or cage in your car without padding. Even a show bar that isn't meant to protect in a crash is stronger than your head. We bought roll-bar padding at an off-road shop, trimmed it and zip-tied it to the bar.

Even with the padding, the Autopower roll bar doesn't interfere with the operation of the top. Though installation was time consuming, it's a part we'd recommend to anyone.

KumoSport Directshift Conversion Kit
The stock MR2 Spyder shifter is one of the best around. Nobody had complained about it being sloppy, or having long throws. Still, there's just a little bit of compliance in it. To fix this, KumoSport Racing Development sent us a set of its Directshift shifter mount bushings.

The Directshift conversion replaces the rubber shifter mounting bushings with anodized aluminum pucks, eliminating that source of compliance from the shift linkage. It's not a short-shift kit, as the lever and all motion ratios are unchanged. KumoSport includes excellent instructions printed with color photographs, making installation a breeze. Just a few simple hand tools and half an hour are required.

Whether the KumoSport Directshift conversion is better than stock is a matter of personal preference. It gives the shifter rifle-bolt precision and immediacy at moderate speeds around town. When shifting drag race quick, however, the increase in peak forces involved is noticeable. Since this load is being applied to the synchros, it's not difficult to imagine their life being shortened. We haven't had the MR2 in front of a radar gun since installing the Directshift conversion, so we can't be certain whether shifts are faster or slower than stock. We expect the difference would be minimal and we've observed no increase nor decrease in the tendency to miss a shift.

Updates
In part one, we sang the virtues and vaunted the praises of the Yokohama A032R tires we had chosen for this car. However, some very hard driving has heat-cycled the Yokes repeatedly, and what little tread there was, is now mostly ground off. The suspension is using them well, however, as they've worn evenly across the tread. Old-tire syndrome sucks, so we'll be trying out some new, fresh and sticky tires very soon.

When we first installed the TRD Sportivo suspension and Kosei K1 Racing wheels, some drivers complained the alignment specs we chose were too aggressive, making turn-in almost too sudden and giving the car a tendency to wander and follow ridges on the freeway. Changing back and forth between the Koseis and the stock wheels and tires has shown the problem is with the offset of the wheels, not our zero-toe alignment. As discussed, the Koseis would not clear the MR2 Spyder's brake caliper brackets at the correct 45mm offset, so we got them with 38mm. We can live with it, but if you haven't bought wheels yet, make sure yours are as close to 45mm offset as possible.

Looking Ahead
We've also been testing an intake, but aren't satisfied with the results as of the deadline for this story. We'll tell you everything next time. Once that's sorted out, the agenda includes brake and lighting upgrades and some better quality speakers. The original project plan calls for figuring out the engine management next, so we'll be working on that and maybe doing a few other things to prepare for what will be possible once it's dialed in.

MR2 Spyder part weights
All numbers in lb. precision +/- 1/4 lb.
Previous net gain: +17
StockNew
Exhaust27Team Moon Exhaust17.25
Rear undertray1.255Zigen Exhaust31
Autopower Roll Bar and padding15
Total:28.25Total*:32.25
Net Gain:+4
*using Team Moon ExhaustVehicle Weight:2250, +/-10
Sources
Bozz Performance
(510) 657-4393
www.bozzperformance.com
5Zigen exhaust

Mackin Industries
(562) 946-6820
www.mackinindustries.com
Tanabe Racing Medalion exhaust

Mazcare
(770) 859-9643
www.mazcare.com
Team Moon exhaust

Autopower Industries Inc.
(619) 297-3300
Rollbar

KumoSport Racing Development
(219) 403-5099
www.kumosport.com
Shifter Bushings

{{{Toyota}}} Racing Development
(800) 688-5913
www.trdusa.com
TRD Sportivo

Tire Rack
(888) 541-1777
www.tirerack.com
205/50-15 Yokohama AO32R 15x7-inch, 38mm offset Kosei Racing K1
By Dan Barnes
78 Articles

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