Driving Sports

We recently "unearthed" some of the original features that appeared in the January 2004 issue of Driving Sports Magazine. The Miata in this feature is the exact same car that now appears in our Build Battle series, and is an ongoing project for Forever MX-5 Magazine. For historical background; this car was sold several months after the feature appeared, only to return to the Driving Sports Garage four years later. The subsequent owner abandoned the poor little Miata, it was picked up by the police and returned to its prior home.

For over ten years Mazda’s little Miata has been one of the best values available in a modern sports car. And with over 200,000 cars rolling off the sales lot every year since 1989, it’s developed a bustling used market. Pick up any newspaper’s automotive classifieds and you’ll undoubtedly find a number of used models to pick from, at prices starting out at $1,000 for a rough-running first-generation (referred to as “NA”) model, to over $15,000 for a pristine second-generation (known as “NB”) limited edition.

When we decided to put together a Miata trackday project, our only consideration was for a first generation for two reasons. First, the early models are getting really, really cheap to acquire. Second, if we ever get the itch to do a full-on race buildup and compete in the SCCA Spec Miata series, we’d need a first generation model anyhow.

Available with either a 1.6-liter engine (1989-1993) or with the slightly larger 1.8-liter (1994-1997), there are otherwise very few differences between the NA model years. The newer of the two bears the burden of added weight (100 extra pounds of structure bracing and interior refinements), a lower redline (down 500 to 6500 rpm) and a 4.1:1 rear differential instead of a 4.3:1, all in exchange for the extra couple ponies the 12 percent increase in displacement grants. On the road, differences are mostly subjective.  Don’t assume you would personally prefer one over another without first taking both models for a drive around the block.

When shopping for this project, we drove several NA and NB models in various states of fitness and function. Our ultimate decision was based on which engine “felt” the strongest and had the most basic accommodations. As it was, we ended up with a 1989 NA, production number 9,313. It came with air conditioning as the only factory-installed option—it even lacked power steering. The only option we would have liked to have been included was an optional viscous LSD unit. Not a big deal, we would be swapping it out with a better torsen or clutched aftermarket LSD later in this series anyhow.

Safety First!
Given my recent history of rolling cars while on journalistic endeavors (Publisher Column, Driving Sports Magazine, Issue #1), it was decided by both my staff and my family that if I was ever going to personally drive the Miata project it would need an industrial-strength roll bar. For that “honor” we turned to Race Tech Fabrication in Portland, Oregon. Every year Race Tech churns out a multitude of cages for the local Spec Miata, and road racing scene. Made of 1.5-in diameter, 0.095-inch DOM steel tubing, the main hoop was designed around Spec Miata requirements—should we ever decide to “upgrade” to a full cage later. It’s welded to the body with additional reinforcement plates to avoid “punch through” if it catches air before slamming down top-side. Back bars are angled to allow the factory ragtop to function normally.

We hope we’ll never have to test this particular bar in the real world. For now, it looks quite solid; we’ll have to remain assured by that. If the roll bar ever gets a thorough testing, we’ll try to bring you the full “test results”.

Ground-up improvements
The entire staff here at Driving Sports is male. That said, the bright white Enki Aero wheels we inherited from the previous owner did more to reinforce the Miata’s “chick car” image more than it deserved. I like to think I’m comfortable enough with my sexuality to put up with a lot of foo-foo accoutrements, but those wheels had to go. In the place of the Enkis, we bolted on much more serious-looking 15” ROTA Circuit-10s. The ROTAs came in gunmetal black and each weighed only 12 pounds, which made for both a fashionable and functional upgrade.

All four corners were then wrapped in Hankook Ventus HRII H405 all-season performance radials. The H405s are primarily designed for wet weather—appropriate since we’re in Seattle—and general touring. On the other hand, in dry weather the long-life treadwear equates to a lot of slipping and sliding around a cone course when pushed to the limit. If you’re looking for a good long-lasting sport radial, the Ventus H405 is a good fit. Just don’t go looking to ace the competition in Street Tire class at your local autocross; get something stickier for that kind of abuse.

Begin with the bolt-ons!
Now that our little Miata is beginning to look the part of weekend racer, it’s time to start bumping up the power to match. As the exhaust it came with was still original and had a tendency to rattle while accelerating, adding a cat-back system was the first logical step.

Thanks to years of seeing racing legend Mario Andretti promote the Magnaflow exhaust systems in print ads and at shows, we felt that it would have to be our first choice. Really, would Mario promote a lesser product? The fact that Magnaflow’s systems are built from TIG-welded stainless steel, feature a free-flowing cat-back design with minimal bends, and sport a “mirror” polished finish was secondary in this process. It was more the Mario-factor.

But before we made any changes to our stock setup, we needed to get a baseline power test to make sure our Miata’s output was consistent with similar models and to give us a grounding point to gauge the effectiveness of future engine mods. For that, we hit up our neighbors, RPM/CarbConn, in Kirkland, Wash. After measuring the output from four “pulls,” John Racz, the master behind the controls, was satisfied.  “It looks like every other Miata baseline we’ve run on that model,” he said.

When it came to installation of the cat-back system, it was a breeze: we simply had someone else do it. Turning to the guys at STAGE Performance, they set to work as Driving Sports’ staffers downed triple mochas at a nearby Starbucks. The only problem they encountered wasn’t even related to the new system; it was getting the old stock exhaust system’s rusted bolts removed in the first place. One of the lugs on the catalytic converter even had to be replaced; it was so weather-worn it sheared with the nut. No doubt, crack mechanics we are, we would have just used duct tape and called it a day. But Tuan, the head wrench at STAGE, insisted on having it replaced and re-threaded. That’s why we’re writers and not mechanics, I guess.

Magnaflow included everything necessary for do-it-yourself installation: the exhaust system (shipped in two parts), straightforward instructions, bolts for the hangers, even a sticker for those inclined to apply them. When we finally had the old exhaust on the floor, and the new one sitting next to it in the shop, the Magnaflow unit stood out like a debutante at a tractor pull. The polished faces were indeed a “mirror finish” as advertised, all the seams were smartly welded, and every bracket and lip was made of solid materials and was without blemish. It’s a shame that within minutes it was going on the underside of the car and not a more visible location.

After the complete system was bolted into place and the Miata was back on terra firma, I turned the engine over. The mid-pitched roadster sound of the stock exhaust was replaced with a much more serious rumble. Though it was still within the original character, and only slightly louder than stock, the new deeper tone had everyone in the shop nodding with approval. The tip of the exhaust, it should be noted, is larger than “normal,” but not obnoxiously so.

Now the real question: how does it perform?
For that, we buzzed back to RPM/CarbConn to make use of its chassis dyno once again. Results were very positive; at 6,500 rpm we gained 2.5 extra horses (up to 102.4 hp, measured at the wheels) and an additional 2 ft/pounds of torque (up to 91.2 ft/pounds). Not bad for such a small displacement engine with just an exhaust upgrade. Results throughout the revs were fairly consistent, adding anywhere from 1 to 2.5 percent across the board. Better still, the new 2.25” tubing used on the Magnaflow exhaust will allow future intake, headers—or even forced induction—upgrades to work without restriction.

Mr. Andretti, it seems, chose a good product to connect himself with.

What’s next?
Now that we have the initial phase of modification complete, we can either move on to suspension (shocks, springs and alignment) or maybe dabble with some more engine bolt-ons (intake, header, etc.). If you have suggestions for which way you’d like to see our Miata trackday project develop, send us an e-mail. Otherwise, we’ll just continue to make it up as we go along. At this point there are enough “tired” components needing to be refreshed; we can be at this all through the summer before we start getting into advanced tuning. You can also keep tabs on this, plus all our other projects, at drivingsports.com.