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Project Miata Gen 2: Part 1

Introduction, intake and header

Shiv S. Pathak
Jul 16, 2002

What on Earth would possess someone to drive a Miata on a warm summer's day? Any dermatologist worth their salt will tell you to avoid direct and prolonged exposure to sunlight for fear of developing one of a nasty variety of epidermal assaulting diseases. Not to mention the windburn--and don't forget to kiss good-bye to the once-marvelously moussed coif. That leads us to an oft-posed question: "Why the hell are Miatas so enjoyable to drive, despite the inevitable tumbleweed hair, roasted derma, squinty eyes and chapped lips?"

After nearly a year of flogging our unadulterated long-term 2000-year Miata around the streets, byways and highways of Southern California, we have come to a series of conclusions: First, a perfectly balanced chassis is such a rare commodity that compromises in crashworthiness and power output are acceptable. Second, there is no tangible correlation between physical discomfort and driving pleasure. A baseball hat, sunglasses and lip balm should be considered required operating equipment when driving a Miata.

All of which bring us to yet another grand conclusion: In an effort to unravel the mystery behind the Miata's indelible charm, we need to make it the subject of another project series. And since Mazda North America won't let us put a wrench to our (OK, its) long termer, we need to get our own to play with.

Getting the Right Miata
If there has ever been a sports car that is dependable as the morning sunrise, it's the Miata. However, its innate reliability doesn't necessary mean its track record is completely unblemished. As with most top-to-bottom redesigns, the second-generation Miata, which debuted in 1998 as a 1999 model, did experience a few early teething pains. Minor cosmetic issues included mismatching trim pieces, a poorly stitched soft-top boot cover, and jaundice-prone wheel center caps. Among the mechanical problems associated with the new Miata was, according to Mazda, an "improperly machined number four main bearing...which may result in premature wear of the thrust bearing."

In other words, in engines equipped with this feature, the crankshaft will eventually be capable of excessive fore-and-aft movement. The solution? A new short block. Fortunately, this potential mechanical problem has been found only to have affected a relatively small number of Miatas, all of which had VIN numbers between X0100001 to X0126468. To determine if a particular car had this problem, Mazda had issued a service bulletin outlining an official testing procedure that measured crankshaft end play with a dial indicator. If end play is greater than 0.3 mm, the engine was to be replaced. If end play was less than 0.3 mm, the engine was free from defect.

After only a few hours of looking through the used car lots, we discovered a clean, 1999 emerald green Miata with the base option package for $17,800. With just 0.06 mm of crankshaft end play, no interior fit-and-finish glitches and an attractively low price tag, we are pleased to announce that we found our latest project car.

Baseline Evaluation
With base suspension, generic dealership tires and open rear differential, Project Miata can't hold a candle to its fully juiced Sport Package brethren, which is one of the most exquisitely balanced and best handling cars we have ever driven. In fact, the only characteristics these two Miatas share are their exhaust notes and alfresco touring capabilities. Whereas the finely honed Sport Packaged Miata responds immediately to even the most subtle of driver inputs, our project car tends to lag behind, requiring a bit more time to do its thing.

And when it finally manages to do its thing, its thing isn't as cool as it is in the Sport Package. Its suspension, for example, is obviously underdamped to suit the needs of the hairdresser segment. The open rear differential is yet another example of shameless compromise and cost cutting. Compared with the Torsen-equipped Sport Package, Project Miata haplessly spins its inside tire while exiting a turn. Not only does this disgusting trait reduce exit speeds, it also interferes with the ability to tighten a cornering line by using the throttle which, it turns out, makes an otherwise tossable Miata feel far less predictable.

But all is not bad about our new project car; its engine is a jewel. In fact, our 49-state Miata feels noticeably stronger than our California emissions-equipped long termer. To test our seat-of-the pants impression, we visited our Dynojet testing facility to whip out a baseline run. The results? 117 peak wheel horsepower with 112 lbs-ft of torque! While the results are hardly earth shattering, it's clear our project car commands a significant 5 hp and 6 lb-ft advantage over our Sport Package Miata. We suspect that most, if not all, of this advantage is a direct result of not trying to push exhaust gases through a close-coupled, California-mandated catalytic converter. We're not complaining.

Quantifying the Goods
In order to determine our plan of action in upgrading Project Miata, we really need to become more familiar with the changes Mazda made between the first- and second-generation cars. Only then can we feel moderately comfortable in taking additional steps in what we believe to be the right direction. After all, Mazda has never been known to drop the ball when it comes to engineering performance into its sport cars.

Let's start with the engine. Comparing dyno results of several first-generation Miatas, it is clear the newer car makes anywhere from 8 to 15 more horsepower at the wheels. This supports Mazda's claims of 140 vs. 128 to 133 crank hp. According to the information we were able to uncover from some friendly Mazda engineers, this power bump is brought to you by a new head design (with a straighter intake valve angle), a moderate increase in compression ratio (from 9.0 to 9.5:1), a new cam profile and something known as a Variable Intake Control System, or "VICS."

This new intake system uses a pneumatically actuated butterfly valve to effectively increase or decrease the length of the intake runners. The shorter the runners, the better the volumetric efficiency at higher engine speeds. The longer they are, the better volumetric efficiency at lower and middle engine speeds. This relationship has a lot to do with the speed and timing at which the column of air rushes through the intake runner and fills the cylinder. To test the effectiveness of the VICS system, we yanked off its vacuum control line. This, in essence, set the effective running length into "short mode." On the dyno, we discovered a very evident 5 to 7 lb-ft reduction in mid-range torque. On the road, partial throttle response also deteriorated. Needless to say (but we'll say it anyway), VICS works very well.

The chassis and suspension also received their fair share of structural updates and improvements. Among these were stiffer side sills, reinforced front pillars and a strengthened transmission tunnel. Front and rear crossmember rigidity also improved through the use of new materials--all of which go a long way to provide for a chassis that is noticeably less flexible than that of the earlier iterations of the Miata.

The ingenious engineers at Mazda also took the time and effort to extensively rework the suspension layout. In addition to increasing front and rear tracks by 10 and 20mm, respectively, they also increased rear suspension travel from 53 to 65mm--a whopping (and much needed) 18-percent improvement! Additionally, new mounting points for the lower control arms lowered the roll center, while new steering knuckles were implemented to reduce bump steer. To further improve steering response, front caster was increased from 5 to 6.5 degrees. It should also be noted the new soft top manages to be nearly 2.2 lbs lighter than the old top, despite upgrading the window material from plastic to glass! Additional weight was also saved in the even-lighter aluminum hood and exposed (as opposed to pop-up) headlight assembly. In other words, Mazda wasn't joking around when they said that the second generation Miata is, in every way, better than its predecessor. Likewise, we're not joking when we say we're going to try our hardest to not mess it up.

Where Do We Start?

Things that Roll
As with most of our project cars, the Miata came to us with stock 14-inch alloy wheels and no-name 185/65-14 tires that couldn't even spell "performance," let alone offer any. Perhaps the only thing going for the current wheel/tire combination is a total unsprung weight of just 27 lbs--less than many wheels by themselves! Knowing how critical unsprung (and rotational) weight is, especially in a lightweight and relatively low-powered car, we needed to take proper action. After a quick call to Discount Tire Direct, we decided to go with a set of lightweight (just 15 lbs!) 16x7-inch Enkei RPO-1 wheels and 205/45ZR-16 Nitto NT-555 high-performance tires. Much to our pleasant surprise, the wheel/tire combo arrived at our doorstep the next day, already mounted and fully balanced, ready for use! Outstanding.

On the road, the increased grip provided by the tires encouraged an ungainly amount of body roll and chassis flailing. Much of which is completely absent in the also sticky-tired Sport Package. This leads us to believe that we desperately need to do something about the 30,000-miles-old stock suspension before we get too far ahead of ourselves. But in terms of looks alone, the new wheel and tire package is phenomenal. The RPO-1's classic, five-spoke design, coupled with the seductive body lines of the Miata, brings back visions of Mazda's gloriously, stunning third-generation RX-7. There is no denying the family resemblance. And while our 205-mm wide tires won't make a Dodge Viper run for cover, they do fill out the Miatas wheel wells quite nicely.

Things that Roar
Following the a-little-more-horsepower-never-hurt-anyone philosophy, we immediately focused our attention to the area under the hood. Looking at the stock intake plumbing, which looked surprisingly non-restrictive, we suspected there wasn't much to be gained by an aftermarket intake. To test our theory, we contacted RSpeed of Marietta, Ga. The heart of the RSpeed intake is the patented Monster Flow air filter. Unlike most foam air filters, the Monster Flow filter is constructed around a rigid skeleton designed to reduce air turbulence. The rest of the system comprises an attractive plastic cross tube, silicon connectors and all necessary hardware. As with most aftermarket intakes, installation is a 5- to 10-minute job, depending on how long it takes for you to find your perpetually misplaced 12-mm socket.

So how does it work? Quite well. When wound out to the upper reaches of the tachometer, the intake adds a good deal of acoustic soul to an otherwise grouchy-sounding powerplant. If you think of a trombone belting away in a sea of mechanical white noise, you wouldn't be too far off. Throttle response seems to improve as well--no doubt a result of the less restrictive air filter element and shortened intake piping. As for power output? Well, from seat-of-the-pants driving, we would swear up and down that it added countless wheel ponies. But according to our trusty Dynojet, the intake added just 2 wheel hp and 1 lb-ft of torque, with almost all of the gains occurring above 4700 rpm. Still, the combination of improved throttle response, slightly sweeter top end, and a seductive intake wail makes the RSpeed intake a blue ribbon winner in our book.

With just 119 wheel hp under our belt, our hunger for more potency remains unquenched. But seeing as we have already addressed the intake side of the equation, it's only natural that we now focus on the exhaust system, the first component being the header assembly. Made of cast iron and weighing in at a portly 28 lbs, the stock header is comprised of two pieces, the header and the down-pipe which leads to the stock catalyst. From what we can tell by peering into the contraption, the runners are configured in a 4-2-1 design. Looking into the outlet orifice of the header section, we can see a divided housing, keeping exhaust gases from cylinders 1 and 4 separate from that of cylinders 3 and 2. This type of header configuration tends to offer a nice, broad torque curve at the expense of peak output.

Naturally, out it goes, in favor of a maximum power, equal length, 4-into-1 design from Brainstorm Products. Mandrel bent, ceramic-coated and tipping the scales at under 15 lbs, the Brainstorm header is a work of art. While not as simple to install as the RSpeed intake (duh!), the whole process was relatively pain-free once we realized we had to unbolt the stock header assembly into two pieces for it to clear the steering column as we pulled it out of the engine bay. Once removed, the Brainstorm header slid right in with nary a glitch. Once torqued down, we fired up the engine and were greeted by a pleasantly mellow exhaust burble.

Flogging down our usual testing strip, we immediately noticed significant mid-range torque gains. Apparently, our Dynojet concurred with our assessment and quantified a healthy 11 wheel hp and 9 lb-ft gain--very impressive. Much to our surprise, the headers improved torque throughout the entire rev range, proving to be yet another viceless upgrade to our Project Miata.

What's Next?
With a respectable 127 wheel hp at 6700 rpm, our Project Miata was off to a ripping start. And we have not even begun to fight! In the next installment of Project Miata, we'll attack the rest of the exhaust system in an effort to eek out every last bit of simple bolt-on power. But what good is power without traction? We've been asking ourselves that very same question every time we hear our inside rear wheel spinning madly while powering out of our favorite tight corners. In the next installment, we'll finally do something about that offensive open differential. All that, and a lot more, awaits. Stay tuned.

Sources
Brainstorm Products
2608 S. La Cienega Boulevard
Los Angeles, CA 90034
(310) 815-9825
Fax: (310) 815-9854
www.miata.org/cgi-bin/bsp_home.pl

Discount Tire Direct
(800) 589-6789
Fax: (480) 483-9230
www.tires.com

RSpeed
1011 South Marietta Parkway Suite 4
Marietta, GA 30060-2822
(888) 551-0025
(678) 290-7504
Fax: (678) 290-7535
www.rspeed.net
By Shiv S. Pathak
17 Articles

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