1986 Chevrolet Corvette Convertible
From the February 1986 Issue of Car and DriverTESTED
The editorial “we” has shuttled between enchantment and annoyance so many times on the Corvette since its 1984 redesign that our tests read like soap-opera scripts. Is this the most advanced production car on the planet, as we once asserted, or an aluminum-and-fiberglass reincarnation of Judas Iscariot, as we later intimated? Stay tuned for the next thrilling episode as “we” neatly dodge the issue by saying, “Boy, it’s sure a lot better than it was last year.”
There should be no arguing over this latest assessment, for two reasons. For 1986, after a ten-year absence, a convertible version will once again be available. If you like convertibles, hallelujah! If you don’t, the coupe continues as before.
The second reason to rejoice is the Bosch-derived anti-lock brake system, which is now standard on both body styles. The stopping distance from 70 mph is only 164 feet, the second shortest we’ve ever measured for a production car.
We’ll come back to this headline stuff after a rundown of the news. Starting in February or March, both the convertible and the coupe will have aluminum cylinder heads as standard equipment. Although this change was originally intended for the start of the 1986 model run, a few design details had to be revised at the last moment, resulting in a delay. The heads do more than just save 40 pounds per car, though this is no small thing in itself. They also contribute to engine efficiency, thanks to the spark plugs’ being more centrally located in the combustion chambers and to larger intake ports. And the compression ratio has been raised half a point, to 9.5:1—a typical change in the transition from iron to aluminum heads because of the faster heat transfer of aluminum.
Professional car thieves should have special interest in VATS, the new Vehicle Anti-Theft System, which is also standard equipment. Everyone will notice that the new ignition key has a black pellet inserted in the top of the blade just after the grooves and notches fade out. Anyone who tries to start a new Corvette without the right pellet in his key will notice a lot of cranking but not much starting. This pellet is the resistance module—Chevrolet has fifteen to choose from—and the ignition switch reads it along with the normal grooves and notches. If the key reader doesn’t like the proffered pellet, it tells the electronic control module to deactivate certain parts of the fuel system (thieves read this magazine too, so the less said about which parts, the better) for about two minutes. Therefore, a thief determined to use a key instead of a tow truck might have to shuffle little black pellets for as much as a half-hour before finding the right one. And the ordinary thief, Chevrolet says, thinks anything longer than ten minutes is working overtime. So there’s a reasonable chance he’ll ignore your Corvette, go on down the street, and pick out a nice Porsche instead.
Said thief will be missing out on a few other 1986-model changes. An upshift idiot light sits in the upper left corner of the tachometer. The whole instrument cluster has been slightly reangled to reduce glare. And a center-mounted brake light has been incorporated—at the top of the rear window on the coupe, at the top of the taillight panel on the convertible.
So much for details. Now back to the headlines. The convertible, clearly a nice piece of work, is a joint venture between Chevrolet and ASC, and it entailed far more than just peeling the top off of the coupe. The car’s frame is considerably revised, in part by adding stiffness (including an X-brace under the cockpit floor), in part by reengineering sections of the original structure. The result is a convertible uncommonly free of creeks and groans, particularly when you consider its stiff suspension. The few aftershocks you feel in the structure when you’ve passed over a bump are of high frequency–by itself, a good indication of stiffness–and they damp out quickly. Certain trim pieces quiver and rustle for a longer time, but they do that in the coupe, too.
Our subjective conclusions about chassis stiffness are confirmed by Corvette engineers, who say that the convertible is not as rigid as the coupe when the latter’s roof panel is in place, but it’s better than the coupe with the panel removed. (This conclusion may soon have to be revised, though, because the engineers are considering adding the convertible’s reinforcement package to the coupe.)
The convertible’s roof, and its system of stowing, continue very much in the Corvette tradition. Two toggles release the folding top from the windshield header. Unlatching two tapered pins below the rear window releases the rear attachment. Then you lift the rear of the roof to allow the rear-hinged deck panel to swing open. In effect, the trunk then swallows the top, leaving no trace of it once the deck panel is returned to its place and latched. (There is still room in the trunk for a good-sized suitcase under the folded top.)
Except for four electric latches at the rear (two to release the top and two to allow the deck panel to open), all of the folding and swinging are accomplished manually, but the efforts are hardly worth mentioning. Getting out of the cockpit is the hardest part.
Back on the road, you’ll find a top-down Corvette to be a mighty hospitable carriage. When there’s no crosswind, air flows smoothly around the occupants’ heads, with no buffeting of their ears and with only modest tousling of their coiffures. New for 1986, on both the convertible and the coupe, are plastic fairings between the windshield pillars and the side mirrors; they do much to smooth out the airflow across the window openings. They are hardly things of beauty when viewed from the cockpit—you see inside them, which is rather like looking under a fender—but at least they are functionally elegant.
The swept-back form of the windshield provides a pocket of still air just behind the glass, but the gradient of air speed rises quickly as you measure back from the visors. By the time you reach the headrests there is a stiff breeze, but the flow is smooth rather than turbulent and therefore is not unpleasant.
The convertible’s only serious annoyance exists only when the top is up: the rear quarters are so wide that they block the view to the corners. Visibility is so bad that you have to approach crossroads perpendicularly, no matter what angle the intersection, just so you can get a decent view of oncoming traffic.
Corvette engineers say there is no weight difference between the coupe and the convertible. Maybe that shouldn’t be a surprise, because the huge glass terrarium on the back of the coupe could have been traded for a lot of steel reinforcements. It could also have been traded for a small glass window in the back of the convertible top, but Chevrolet took the easy way out by using plastic film—the kind that gets foggy in a few years. Our test car weighed 3266 pounds, within a few pounds of previous coupes with similar options. In any case, we see no reason to disagree with the engineers: with all the additions and deletions taken together, the ’86 model, coupe or convertible, weighs virtually the same as the ’85.
Radical surgery of the type that produces a convertible usually has a negative effect on ride quality. The engineers went to work to avoid any such deterioration, and the result is that the convertible has its own package of springs, bars, and shocks. The convertible’s front spring rate is 310 pounds per inch, compared with 295 for the coupe. Both have 228-pound-per-inch springs in back and 26mm tubular front anti-roll bars. The convertible’s 19mm rear bar, however, is smaller than the coupe’s, which is 20mm. (In comparison, the coupe’s Z51 handling option has 380-pound-per-inch springs in front, 330 in back, a 30mm solid front anti-roll bar and a 22mm solid rear bar.) Shock-absorber calibration is different for each model.
The convertible also departs from GM’s usual 35-psi recommendation for tire pressure: its placard calls for 30 psi. This is purely a ride consideration. Corvette engineers admit that nothing bad will happen to the coupe owner with ride complaints if he deflates accordingly, though they can’t officially advise around the official recommendation, if you follow the logic here.
Interestingly enough, the convertible has the wide, 9.5-inch wheels of the Z51 as standard equipment, which suggests that they have a beneficial effect on ride. Obviously, they don’t hurt skidpad adhesion: at 0.85 g, this car’s performance is not significantly different from past Corvettes’.
In fact, except for the folding roof, this new Corvette continues much as before. Acceleration is about the same; top speed is down a few mph, to 144, probably because of greater aerodynamic drag over the convertible top. Braking is noticeably better for one or two moderate-speed stops now that the anti-lock system is in place, but the Corvette still shows some fading tendency when the brakes are used aggressively at high speeds. We don’t think this will be particularly noticeable in typical American driving—most buyers will probably instead be enthralled by the new anti-lock system—but Chevrolet has some work to do if it expects to match the best brakes available from Porsche and other European makers.
Keen observers will notice that a new logic is operating the manual transmission’s electric overdrive. Previously, one flick of the switch would lock out the overdrive forever. Now, if the engine has been off for more than ten seconds or so, the overdrive will automatically be engaged when the engine is started again. If the driver wants it out, he has to lock it out each time he starts the engine. Corvette engineers were afraid the old system would be considered a “defeat device” by the EPA; with overdrive engaged, fuel economy is improved by 2.5 mpg in the combined test, enough to escape the gas-guzzler tax.
Escaping the tax takes on new importance with the convertible. Its price has not been announced at press time, but Chevrolet spokesmen estimate a $4000-to-$5000 increment over the coupe’s price, which means a window sticker solidly in the $30,000 range when the usual options are figured in. That’s serious bucks.
And it brings up a serious question. Could a couple of drifters with no visible means of support afford to cruise Route 66 in a Corvette convertible today, the way they did on TV two dozen years ago? Maybe the question is moot, because Route 66 doesn’t exist anymore. The federal government, figuring that Interstates handle the traffic now—and, who knows, maybe figuring there would never be another convertible Corvette—decommissioned that famous old highway a few months back, replacing the “66″ signs with local route numbers.
So the Corvette convertible is returning to a changed world. The TV networks wouldn’t go with Tod and Buz anymore, either. Today’s adventurers would be Chip and Buffy, and they’d probably drive an automatic.
Corvette chief engineer Dave McLellan and his dedicated team are determined that the fast-paced development their car has enjoyed in its first three years will continue into the foreseeable future. Several clues to the Corvette’s continuing evolution are revealed in a bevy of experimental cars that we sampled during a recent visit to GM’s proving grounds in Milford, Michigan.
The first experimental Corvette we drove was named Bigfoot in honor of its wide racing tires, which are mounted on three-piece alloy wheels and covered with fender flares. To push its considerable traction to the limit, Bigfoot also has 400 hp under its hood. Bigfoot’s role is to provide experience with suspension calibrations suitable for wider, stickier tires than Corvettes have today—perhaps 275/40R-17s. A brief drive demonstrated Bigfoot’s excellent steering response and, surprisingly pleasant ride.
Another experimental Corvette, called Thumper, has a Ryan Falconer—built, NASCAR-spec V-8 that produces about 600 hp. Its tremendous speed potential will be used to test the braking power and fade resistance of the thirteen-inch-diameter brake rotors and the two-piston calipers that are scheduled for 1988.
These brakes are also being evaluated on some of the fourteen Puff the Magic Dragon prototypes. These Corvettes are fitted with twin-turbocharged and inter-cooled versions of the standard small-block V-8, yielding from 350 to 600 hp. McLellan and crew are using the Puff cars to explore turbocharging as a route to future power increases; in 400-hp form, the engine can push the Corvette to 180 mph, yet it is extremely tractable. Unfortunately, Chevrolet management has concluded that turbocharging the pushrod V-8 would have little technical or marketing appeal, so this approach will not see production. Chevy is, however, collaborating with Callaway Turbosystems, an aftermarket tuning outfit that plans to offer an emissions-legal twin-turbo package for those who don’t want to wait for the final solution.
Increased power is clearly in the cards, and the Corvette engineers are working on a traction-control system to help put it to the pavement. Their system works in conjunction with the sensors and the computer of the anti-lock braking system to detect and limit wheelspin by selectively applying the rear brakes and reducing the engine’s output. A brief drive in one of the traction-control cars showed impressive stability during full-throttle maneuvers on slick pavement. Different control calibrations to suit a wide range of traction conditions are currently under development for a possible 1989 introduction.
Active suspension is also in the works. A concept car with such a system will be unveiled at the upcoming Chicago Auto Show, but it’s only a teaser. A more serious effort is currently under way within the Chevrolet-Pontiac-Canada chassis-design group; it involves participation by Lotus in England, at least two Corvettes, and several other GM models. Active suspension is not yet scheduled for production, but the Corvette’s reputation for technical leadership and its high price make it a logical candidate for the new system when it is ready.
All of these developments suggest that there is a super Corvette on the way. Although the twin-turbo engine has been rejected, massive power increases have not. It appears that Chevrolet will join forces with Lotus to produce a version of the V-8 that was unveiled in the 1984 Etna show car. With four cams, 32 valves, and five to six liters of displacement, this engine could easily produce 400 hp. To harness this power and still produce acceptable fuel economy, the Lotus-Chevrolet engine would be coupled to a proposed six-speed manual gearbox governed by a computer-regulated shift pattern. All in all, the combination of a 32-valve engine, an improved manual transmission, seventeen-inch tires, big brakes, and traction control makes perfect sense to us.
The Corvette of Chevy’s dreams would not replace the current base model but might instead be offered as a king-of-the-hill version, with distinctive bodywork and a premium price tag. Although it might account for only a small fraction of total sales, such a car would indisputably establish the Corvette as the world’s fastest sports car–and that would please Chevrolet management very much.
Gradually, these various technological upgrades would spread through the rest of the line, along with further weight reductions, increased chassis stiffness, and a redesigned electronic instrument cluster. Such improvements should hold the Corvette in good stead until it’s replaced by an all-new design in the early 1990s.
New concepts are now under consideration for the next-generation model; in fact, preliminary drafting is already under way at Hawtal Whiting Design and Engineering in England. A full report on those plans will follow as soon as our moles hit pay dirt. –Csaba Csere
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