America's tuners take aim at the Viper and ZR-1, with go-fast packages for the Camaro Z28, Mustang, RX-7, 300ZX, Supra, and Miata.

by C. Van Tune

Look out. It's not safe on the streets. Not even for the big-guns of the boulevard. You may think you're invincible in that new Dodge Viper or Corvette ZR-1, but that's only an illusion. A temporary sense of security about to be blasted into oblivion by an undercover assailant. Better take a closer look at the orange-striped Camaro in the next lane, and give a listen to that yellow Miata with the rumbling exhaust. These aren't ordinary production cars. Not by a long shot. Their purpose: Wreak havoc on the performance-car establishment. In the old days, they'd be dubbed "sleepers" by the street-race crowd; cars that hide tire-smoking performance under unassuming sheetmetal. But that's not an accurate term today. Each of our highly specialized test vehicles has been maximized in performance, handling, braking, and appearance. So, there's little chance they'll be mistaken for base-model offerings. What we have here can be described more aptly as a cadre of highly trained assassins, with big-league firepower and orders to thrill.

Our objective was to test a sampling of the best "tuner cars" from the automotive aftermarket. Vehicles that could meet or beat Viper and ZR-1 performance, but do so at a lower price. We expected to find three or four that met the tough criteria; we ultimately steeled on seven that provide a tantalizing cross section of what's available on the tuner-car market.

The players range from the merely evil (a 375-horsepower Camaro Z28 from Morrison Motorsports) to the fully outrageous (a 400-horsepower supercharged V-8 Mega Monster Miata.) In between reside the talents of a 360-horsepower twin-turbo Mazda RX-7, 465-horsepower super-boosted Nissan 300ZX, mild and wild supercharged Mustangs, and the first massaging of a '94 Toyota Supra Turbo. Zero-to-60-mph times in the 4s and at least 0.92 g of cornering grip would be required to enter this prestigious contingent. And, just to be absolutely sure everyone met the bogey, we brought along a Viper and ZR-1. As the benchmark American performance machines, these 400-plus-horsepower cars are the ones to gun for.

Our test regimen for this burning rubber battlefield included the usual Motor Trend battery of acceleration, braking, and handling tortures, plus timed laps of the Streets of Willow Springs 1.3-mile road course. Constraints included the use of DOT-approved rubber, EPA-approved (or pending approval) parts, and an as-tested price cap of $50,000 to qualify as "cheaper than a Viper."

To help bring big-gulp performance to even more frugal budgets, each of these firms offers individual components so you can improve your car in stages. A few sell fully complete turn-key vehicles. You need only decide how fast you want to go, dial the requisite phone number and hang on for the ride.

Racing Sports Akimoto Toyota Supra

The first modified '94 Supra Turbo worthy of magazine coverage is the product of an aggressive young California company: Racing Sports Akimoto. Never heard of it? That's because just six months ago RSA's owner, Tad Akimoto, was merely a voracious consumer of performance parts. Today, he's not only designing and manufacturing (in America) performance equipment for Supras, RX-7s, and other Japanese sports cars, he's also working to import the stunning all-wheel-drive Nissan Skyline GT-R for sale in the States. If enthusiasm were a commodity, this man would rule Wall Street.

The most obvious external modification is the set of Chevion Racing 18-inch wheels. Measuring 8.5-inches wide up front and 9.5-inches at the rear, these lightweight rims utilize a center-lock hub, so you can play indy Car pit-crew chief in the privacy of your own garage.

Aside from adding a set of higher-rate Eibach springs and the hefty footprint of 235/40ZR18 front and 265/35ZR18 rear Dunlop rubber, the suspension components of this machine are s-t-o-c-k. So, suitably stunned were we when it bested a factory Supra's slalom speed by nearly 2 mph, then went on to annihilate the competition by posting Streets of Willow lap times nearly 0.8-second faster then the second-place car--this, with an automatic transmission. Only the Dodge Viper, with a lap time of 1:02.05, bests the RSA Supra (by 0.4-second).

Though hampered on the dragstrip by its numb four-speed automatic, the lightly modified (revised "SES" twin-turbo setup for more boost lower in the rpm range) Supra still managed to match its stock six-speed counterpart in 0-60 mph times. Attesting to the newfound high-speed performance, however, is the RSA car's quarter-mile run of 13.1 seconds/113.1 mph (a 0.4-second/6.4-mph gain.) We'd bet our next week's paycheck that this parts combo in a six-speed manual Supra Turbo would knock a half-second off those times. Internally, the car's engine remains stock, benefitting on the topside by Extrude-Hone flow work inside the intake manifold. Drive it sanely, and it's still every bit the luxo/sports car you bought it to be.

Vortech Supercharged Mustang

For today's computer-controlled, electronically fuel-injected V-8s, there's hardly a more cost-effective big-power producer than a supercharger Sure, you can blast the motor with a hefty shot of nitrous-oxide and achieve the same (or greater) power levels as those with a blower, but when the nitrous bottle's empty, your fun's over.

Vortech Engineering's project Mustang is a lot les flashy--and a load less pricey--than the rompin' Dominator IV shown on the next page, but under their hoods both cars use 5.0-liter V-8s topped by a Vortech Gearcharger. Compact in design and easy to install, the Vortech unit is a centrifugal (not a Roots vane-type) supercharger that delivers up to 8 psi of boost, but without the "lag" of conventional turbo system. Installed on a basically stock V-8 (JBA headers and a Flowmaster cat-back exhaust system are the only mods) the supercharger increases output from 205 to 318 horsepower. On the track, that's good for about a 1.5-second improvement in 0-60-mph and quarter-mile clockings. Giving you ZR-1 performance from a 50-state emissions-legal system that (without the exhaust mods) lists at $3375.

Big infusions of power should be followed by equally fortified braking and suspension systems. It's too late to remedy this when you find yourself slamming face-first into the puckerbushes at the first decreasing radius turn. With 13.5/12.0-inch front/rear cross-drilled disc rotors, frame ties, and a rear coil-over shock conversion from Baer Racing, plus meaty 17-inch Goodyear ZR shoes, this simple Mustang tied for second-fastest time through our slalom and pulled an unbelievable 1.01 g on the skidpad. All for a total price (new car included) of under $30,000.

Despite all its muscle, the Mustang can be driven in as plebian a manner as local law enforcement presence insists. The exhaust tone is decidedly more aggressive than stock, but only a bit of blower whine warns that anything menacing lurks underhood. Vortech's message: Speak softly and carry a big, supercharged stick.

J. Bittle Dominator Supercharged Mustang

If you're the type who's repulsed by subtlety, prepare to meet wretched excess. From it bulging fender flares and roof-high rear spoiler to its huge tires and fire-belching supercharged V-8, the nasty, noisy, non-politically correct Dominator GTB IV is the most intense street Mustang we've ever encountered.

Only a deranged racer would consider using this car as an urban commuter, but J. Bittle Performance swears that there are enough power-mad individuals in America to justify this machine's development.

Though individual components are available, the GTB IV is also sold as a--brace yourself--$29,500 package. That's on top of the price of the car itself, which just barely puts in under our $50,000 ceiling. A bargain? Not to those who judge a car by its nameplate. In terms of what's important to hard-core drivers, though, it's a sheer tire-blazing terror that'll make even a new Dodge Viper run and hide.

Bittle offers lower-drama variations of the Dominator theme, for humans with less red mist in their psyche, at an entry package price of $10,000. For race-only use, there are parts to fortify a Mustang with even larger displacement, or twin-turbo power.

The Dominator IV delivers a Ford SVO high-strength 5.0-liter block, Ross pistons, TFS heads, a Crane cam, and a Vortech supercharger pumping 10 psi of boost. Output is close to 450 horsepower. A Doug Nash five-speed and Gear Vendors overdrive unit provide driveline strength and highway cruising efficiency, though don't look for this combination to be a Tercel-beater at the gas pumps.

At the dragstrip, the Dominator proved true to its name with a 12.2-second/118.3-mph quarter-mile best that smoked the nearest challenger by several car lengths. Practice your power-shifts on the high-effort gearbox, then don the Kevlar-palm driving gloves you'll need to handle this brute. J. Bittle actually drives this car in his daily commute, but we'd have to recommend it only as a weekend warrior.

On the skidpad, the car's gargantuan 315/35ZR17 Goodyears and 17x11.0-inch Monocoque wheels paid off with a brain-draining 1.09g orbit. That's not only the top performance in this test, but a new Motor Trend record.

Morrison Motorsports Camaro Z28

Proving that endurance racing improves the bloodline of street cars, IMSA and SCCA multi-champion and FIA World Record holder, Morrison Motorsports, used its considerable on-track expertise to craft a package of high-performance equipment for the '93-'94 LT1-powered Camaro Z28.

It's tough to keep a secret this good to one's self, so when team owner Tommy Morrison and project manager Reese Cox called to hear our thoughts about their latest R&D vehicle, we twisted their arms to let us test it. The car shown here isn't in a production-ready state, but is fairly representative of the performance you can expect. Prepared with the focus of an optimized "show-room stock" or autocross race machine, the Morrison Camaro embodies a balance of power, handling, and braking befitting a champion.

The upgrades will be offered in two package "stages." Stage I ($4650) delivers a modified intake manifold with larger throttle body and cold air ducting, a recalibrated computer, headers and dual-cat exhaust, a battery relocation kit, carbon-metallic brake pads, and a 3.73:1 ratio ring-and-pinion. Engine output rises from 275 to 300 horsepower. Quarter-mile times drop by 0.5 seconds.

Stage II ($7500) add cylinder heads, a camshaft, Bilstein shocks with front coil-over spring conversion, higher-rate rear springs, revised suspension bushings, a larger front anti-roll bar, and custom-offset Ronal 17-inch wheels shod with big Goodyear GS-CS rubber. Dyno numbers have yet to be generated, but Morrison estimates 375 horsepower in this configuration. That's a 100-horsepower gain over stock and enough urge to move the F-body through the quarter mile in 13.0 seconds at 109.3 mph.

With this early development car already delivering 0.99 g of lateral grip, the best 60-0 mph braking in the test (105 feet), and phenomenal balancem it's clear Morrison's team has done its job well. But even more performance awaits: a 400-plus horsepower 383-cubic-inch LT1 engine should debut soon.

Monster Motorsports Supercharged Miata V-8

We can already hear wine glasses toppling at the local chapter of the "Jaunty Old Coot Sports Car Club." Just one mention of an automotive atrocity like a--Gasp!--V-8 Miata sends shockwaves of horror through the establishment. So, all it'll take is one good rap of the throttle on this 400-horsepower supercharged derivative, and half the population of Morgan and MG lovers should instantly succumb to violent heart explosions.

Face it, gents, times have changed. The basic Miata is a fine little runabout, but it's no Corvette-chaser. What it really needs is about 300 more horsepower, a set of mambo-gorilla brakes, and a blatant body pumping for image's sake. Sound more like a Cobra than a Mazda? That's what Dave Hopps and David Robinson of Monster Motorsports hope you'll think. We tend to agree, having been suitably wowed by their normally aspirated Mustang 5.0-liter V-8-powered concoction (June '93). But now, here's their next wild lunge toward the lunatic fringe: a bulging, burbling, bloodbath named Mega-Monster Miata.

It's not a Cobra, but it's about as close as you'll get in this homogenized era called the '90s. Though Lord Shelby probably bristles at the mention of such comparisions, there's no denying this is quite obviously an imported roadster stuffed with a modified Ford V-8. However, the mega-monster is bereft (so far) of anything approaching the Cobra's fabulous racing legacy.

Though more devolpment work is needed before the full potential of this car can be realized (specifically, in high-rpm engine breathing and suspension tuning), it's plenty obvious this is a machine for those who value brute force over finesse and live for the smell of burning rubber. Backing up the Bell/Whipple pressurized V-8 is a Ford five-speed gearbox and Thunderbird limited-slip differential, plus Mazda RX-7 R1 hubs, brakes, and spindles. Monster Pro-Lite aluminum wheels are wrapped with Dunlop SP Sport 8000 radials, sized 225/45ZR16 front, 245/45ZR16 rear. Plan on replacing the rears frequently.

At $45,000 for the complete car, this ferocious hybrid proves a viable Viper (or kit Cobra) alternative. What your insurance company doesn't know...

Stillen GTZ Nissan 300ZX

Okay, so it's too easy to get your left shoe wedged under the drilled-aluminum dead-pedal cover when holding down the clutch pedal. The rest of this blinding-yellow adrenaline pump is so well sorted out that only small nits are left to pick.

Credit veteran racer Steve Millen with the technique necessary to muscle-build a garden-variety Nissan 300ZX twin-turbo into a blood-thirsty beast, yet have it remain docile enough to survive urban gridlock. His company, Stillen, offers this big-winged GTZ model for monied enthusiasts who don't want to travel unnoticed.

Though this car had suffered through over 15,000 brutal journalist miles and was beginning to show signs of fatigue, there's no faulting Stillen's formula of manner of application. Its recipe calls for lots of boost, giant tires, race car brakes, and suspension finessing par excellence. But be prepared: The price tag is closer to Neiman-Marcus than Wal-Mart and actually exceeds our $50,000 limit if you include the bodywork. Because the car is available without the extra appendages, however, it was allowed to play in this test.

The raspy exhaust note signals that there's more than just 300 horsepower under this hood. Though we doubt that this particular motor is still producing a full 465 ponies (judging by the acceleration times and knowing its history of hard track usage), the larger Garrett turbos, intercoolers, high-flow injectors and low-restriction exhaust system certainly provide a rush--especially above 5000 rpm. Zero-to-60 mph takes just 4.7 seconds, and the quarter mile blurs by in 13.1 seconds at a trap speed of 111.9 mph. That'll put you fender-to-fender with any given Viper or ZR-1 on any given day, but be aware the fighter-jet bodywork and bee-yellow paint will probably give away your game.

The chassis benefits from Stillen's perfectly chosen stock of springs, shocks and anti-roll bars, plus a quartet of Yokohama A-008R SII 275/40ZR17s. The handling can only be described as impeccable, posting the fastest slalom speed of this test and 1.00 g of grip. The highway ride is a notch stiffer than stock, but is far from unpleasant.

Peter Farrell Motorsports Mazda RX-7

New Zealand's road racing and rally driver, Peter Farrell, is another motorsports figure to turn his attentions to the street. Specifically, modifying a Mazda RX-7 for increased performance, handling, and, glory be, ride comfort. Farrell's experience in preparing RX-7s for competition in the IMSA Supercar and SCCA World Challenge series has paid off well in this street version he modestly calls the "Peter Farrell Supercar."

Based on the tautly suspended R1 model, this lowered, fat-tire brute should now ride like the shocks had been replaced by bags of moon rocks from the Apollo 11 expedition and come equipped with a "chiropractor wanted" license plate frame. Guess again. Even as outfitted with eight-way adjustable GAB shocks and 60-percent-stiffer-than-stock anti-roll bars, this concoction proved more compliant over virtually every kind of road surface than not only a stock R1, but even the base RX-7. The secret appears to be Farrell's own "Comfort-sport" progressive-rate springs; ride comfort is nice on all but the choppiest of concrete highways, body roll is virtually nil, and lateral grip is a brawny 0.98 g.

Be advised, however, the car does suffer from low-speed understeer. A problem aggravated by use of smallish 235/45ZR17 front tires and mega-tread 275/40ZR17 rears. To a skilled driver, this is of little concern: A bit of clutch modulation and a hefty wallop of boost should clear it up. At higher speeds, the car feels far better, becoming very easy to point-and-squirt through tasty corners. Its curb weight (2780 pounds) remains the RX-7's best attribute.

We doubt anyone will gripe about this rotary rocket's acceleration. Fitted with a PFS intercooler that's twice the size of the stock unit (and can reduce charge temperatures by 100 degrees more than the factory piece), plus a recalibrated computer and 3-inch diameter exhaust, the boost limit is raised to 14 psi, delivering an estimated 360 horsepower. Combine that with a lower-ratio (4.30:1) rear axle, point it down a vacant stretch pf pavement, and you're to 60 mph in a scorching 4.4 seconds and past the quarter mile in 12.9 seconds/111 mph. Shazam!

ACCELERATION, 0-60 mph (sec) Bittle Mustang: 4.2 Monster Miata: 4.2 Farrell RX-7: 4.4 Dodge Viper: 4.5 Vortech Mustang: 4.6 Stillen 300ZX: 4.7 Morrison Camaro: 4.8 RSA Supra: 4.9 Corvette ZR-1: 5.2	SLALOM (mph) Stillen 300ZX: 72.9 Morrison Camaro: 70.4 Vortech Mustang: 70.4 RSA Supra: 70.3 Bittle Mustang: 70.3 Farrell RX-7: 68.9 Monster Miata: 67.3 Corvette ZR-1: 67.2 Dodge Viper: 66.8
ACCELERATION, Quarter Mile (sec/mph) Bittle Mustang: 12.2/118.3 Monster Miata: 12.6/111.6 Farrell RX-7: 12.9/111.2 Vortech Mustang: 13.0/109.7 Morrison Camaro: 13.0/109.3 RSA Supra: 13.1/113.1 Stillen 300ZX: 13.1/111.9 Dodge Viper: 13.2/112.1 Corvette ZR-1: 13.6/106.0	SKIDPAD (lateral g) Bittle Mustang: 1.09 Vortech Mustang: 1.01 Stillen 300ZX: 1.00 Morrison Camaro: 0.99 Farrell RX-7: 0.98 RSA Supra: 0.98 Dodge Viper: 0.97 Monster Miata: 0.92 Corvette ZR-1: 0.92
STOPPING DISTANCE, 60-0 mph (ft) Morrison Camaro: 105 Farrell Rx-7: 106 Bittle Mustang: 107 Stillen 300ZX: 108 RSA Supra: 109 Vortech Mustang: 116 Corvette ZR-1: 117 Monster Miata: 120 Dodge Viper: 129	ROAD COURSE LAP TIMES (min:sec) Dodge Viper: 1:02.05 RSA Supra: 1:02.46 Stillen 300ZX: 1:03.23 Farrell RX-7: 1:03.31 Vortech Mustang: 1:03.44 Morrison Camaro: 1:03.58 Corvette ZR-1: 1:03.76 Bittle Mustang: 1:03.81 Monster Miata: 1:05.75

CONCLUSION

It's a rare day when we test nine cars and all but one qualify for membership in the 4-second club for 0-60-mph scat (only the ZR-1 was left alone in the fives). The quarter-mile proved equally as impressive, with three cars cracking the tough 12-second barrier. We all know the horsepower should be equaled by braking power, and five of our fearsome tuner cars stopped from 60 mpg in less than 110 feet. On the skidpad, we hung on with every appendage available to control the lateral pull of race-car-like grip--three cars broke that one-g bogey. Our vision still hasn't returned to normal.

Though there's no denying that the Viper and ZR-1 are phenomenal machines, their production-formatted compromises (and high pricetags) may not appeal to your need for something extra. We hope this collection of tire-burning tuner cars provides you with some intriguing alternatives. Below you'll find our final picks and pans.

Bittle Mustang: Recaros and harnesses are required with this level of handling; with more runs at the slalom (a flat tire prevented them), we surely would've improved the number. Fastest quarter mile, tied for quickest 0-60-mph time, best on the skidpad by far. Overall, a fun-to-ride machine that's more Brahma bull than pony-car.

Farrell RX-7: Excellent track car. It growls, spits flame from the exhaust, and has enough brake reserve to stop the 5:30 Super Chief. Third quickest from 0-60 mph, second shortest in braking. The verdict: A lightning-quick car that rides better than you'll believe.

Mega-Monster Miata: Too much oversteer to be used efficiently, but you'll look like Joe Hero at every corner. Requires more suspension sorting before this can be a track champ. Tied for quickest 0-60-mph time, second fastest in quarter mile, tied for last on the skidpad and fully last place on the road course. It's definitely reminiscent of a 289 Cobra.

Morrison Camaro Z28: Smart, cost-effective improvements on a low-priced supercar. The only normally aspirated engine in the mix, it sounds like a '60s muscle machine and pulls like a big-block...even as tested with the stock computer chip. Handling is race-car precise, and the brakes are the hands-down champs of this group.

RSA Supra: Who would've thought a mildly modified Supra would kick everyone's tail on the road course? Not us, not by a long shot. Great balance is its secret, but the 18-inch tires didn't hurt, either. Its lackadaisical automatic transmission slowed acceleration times, but just opt for a six-speed manual, and that's magically cured.

Stillen 300ZX: The most expensive tuner car here pays back heaping helpings of beat-a-V-8 fun. Excellent suspension balance and a strong high-rpm charge let you leave behind a swath of broken egos. We'd opt to leave the exhibitionist bodywork behind and save a few thousand to help pay for bail.

Vortech Mustang: Tied with the Morrison Camaro for best value here, this unassuming hatchback delivers big-time performance at less than the prices of a stock 300ZX, RX-7, et al. Plus, it's got a real-human-sized back seat (strap Junior in tight for those 1.0g turns).