Road Tested
clunker, whatever-forget them. The new 5th-generation Corvette is here, bristling with fascinating technicalities and deserving a dedicated portion of any enthusiast's memory bank. Is it now the best exotic car in the world? The best exotic car value? Or merely an updated clunker?
To give us our first in-depth experience with the car, Chevrolet orchestrated a sequence of events that necessarily fell short of our usual road test procedure, yet was one helluva lot more informative than a few trips around GM Proving Ground's Black Lake. Reason for this was clear: the availability of only six Corvettes for a rather larger group of the world's automotive journalists. In fact, the six were in pilot car configuration; that is, cars built on the Bowling Green, Kentucky assembly line for evaluating components and procedures before actual production begins. Over a 2-week period, several staff members sampled the cars at various locations. These included a gale-swept Riverside International Raceway ("Forget the driving, folks, and adjourn to the tent. Forget the tent, folks."), the same raceway on a decidedly better day, Orange County International
Raceway for our instrumented testing and Orange County Fair
grounds for our skid-pad work. Also, our Engineering Editor
took a 300-mile high-speed loop through the flatland and mountains inland from Santa Barbara, a pleasant trip that gave the new Corvette the kind of workout it loves best. What we didn't get to do for this report was ordinary day-to-day driving; some of those aspects are covered in the accompanying report on the 4+ 3 manual-transmission version, which was not introduced until several months into the new car's production life.
The new Corvette was our first 1984 test car, and it was barely~1983 when all this happened. That's because Chevrolet decided to leapfrog the 1983 model year and call the new car a 1984 Corvette.
Yes, a 1984, from spring 1983 on-what is happening to the sacred autumn season for new models here in America? Chevrolet isn't the only maker to do this either; the BMW 318i comes to mind as another example. In any case, for reasons lurking in EPA definitions of model year, corporate scheduling of startup and shift-over dates and, we suspect, some good old fashioned hype, there were no 1983 Corvettes as such. Production began on January 3, 1983 and all Corvettes built between then and late summer 1984 will have vehicle identification numbers specifying 1984 as the model year.
This meant that the 1983 run of Corvettes had to meet 1984 emission standards, which are stricter in the sense that all the pollutant limits had to be met at all altitudes; previously, cars sold at high altitudes were tested differently.
This 1984-model business affects Corporate Average Fuel Economy and the Corvette's gas-guzzler tax status too. All Corvettes built between startup and the 1985 model year count toward the 1984 CAFE, up from 1983's 26.0 to 27.0 mpg in 1984. And for 1984 models the guzzler tax is triggered at 19.5 mpg, versus 19.0 in 1983. So the Chevrolet folk set themselves a harder task in these respects too when they decided to call. their new car a 1984.
So much for regulations and strange model years. What of the car itself? Let's examine this new Corvette by starting at the road and working our way up, pausing along the way to share our road test results.
We focused on that Corvette with the enthusiast's suspension, the Z51 package. Its contact with the road comes with four Goodyear Eagle VR50s, P255/50VR-16s, mounted on mirror matched finned alloy wheels, 16 x 8Y2 fronts and 16 x 9\12 rears,
As reported earlier these Goodyears were developed especially for and in parallel with the new Corvette. If you're an enthusiast, your intellect is excited by their unidirectional tread pattern derived from Formula 1 rain rubber and
your soul is enriched by their V rating (good for sustained running above 130 mph). But if you're a Corvette engineer, their section width on the 9\12 rear wheels also complicates your life. Seems that the rears stick out 4 mm beyond European regulations, so the export Corvette has to be fitted with 8 Y2 wheels at the rear as well. Our non-ZSl' (the base version, if you will) gets Goodyear Eagle GTs, P21S/65R-lSs, mounted on IS x 7 and IS x 7Y2 wheels, front and rear, respectively.
Whatever wheels, they mount to forged aluminum knuckles, front and rear. And these aren't the only nonferrous materials in the suspension. At the front, unequal-length A-arms are also elegant aluminum forgings. And gone are the previous coil springs, replaced by a transverse single-leaf spring of E-glass (the tough guy of the fiberglass clan) and epoxy. Though not in interchangeable, it's akin to the FRP rear leaf introduced on the
1982 Corvette and carried over on this one. Among advantages of the front FRP leaf are 50 percent less weight, better packaging than coils and higher fatigue strength (a typical steel spring gets tired after 7S,000 full compressions; one of FRP lasts beyond S million!). Tube shocks and an anti-roll bar complete the front suspension, along with rack-and-pinion steering that's new. What's more, - this steering has a leading-arm layout with the rack ahead of the wheel centerline, contributing some compliance understeer rather than a
trailing arm's tendency of invoking oversteer under heavy lateral load. The Z5 I steering has a quick 13.0: I ratio and 2.0 turns lock-to-lock; the base steering is 15. S: 1 and requires 2.4 turns of the wheel. Also, though the export Corvette comes with ZS I. it gets the slower steering as part of the handling setup with those identical width wheels front and rear.
The rear suspension has its share of beautifully forged alloy as well. It's a S-link design, counting two trailing links, a lower lateral link, another behind it for toe adjustment and the halfshaft itself. The transverse FRP leaf spring. tube shocks and another anti-roll bar complete things back here.
The shocks, though, deserve special mention because they were in a process of change during our testing. For the first few months of actual production. the ZSI suspension came with conventional shocks. valved more ~ car (or saving you if a curve tightened up unexpectedly). Nor was this new Corvette especially embarrassed by deteriorated road surfaces. The tires' communication level increased, all the better to tell you something had changed down there. And there was no mistaking the occasional feeling of fiberglass over steel (no, this 'new Corvette, though considerably better than the previous version, isn't carved from a solid block of anything). But much to its benefit, our Z51 displayed none of the chiropractic chagrin of the older Corvette's slalom suspension, even when the roads got particularly pock-marked.
And if speed needs to be dissipated in a hurry (i.e., your detector goes oft), there's no problem because the Corvette's vented discs front and rear are every bit as impressive as its handling. New aluminum caliper assemblies from Girlock (a joint effort of Girling and Lockheed in Australia) feature a separation of clamping force altered torque reaction, brought off via finite element analysis of caliper deformation under load. Semi-metallic brake pads sourced in Japan are also Corvette unique.
And all of this new hardware performs, with panic stops from 60 mph in an amazingly short 133 ft, 80-0 in 250 ft, and so little fade in six 0.5g stops from 60 that we report it as "nil." The Corvette's brakes displayed only two shortcomings to our eyes (our right foot, actually): At only 16 Ib for a 0.5g stop (a deceleration rate roughly midway between a gentle braking and
an all-out panic), their pedal pressure was lighter than we prefer. Also, though fore/aft balance was very good, the brake pedal proved relatively insensitive to modification as one or another tire probed lockup.
We've stopped and cornered this new Corvette. Now let's examine what makes it go. Move inboard from the rear suspension, if you will, and you'll see another elegantly shaped piece of aluminum on which rides the differential (of limited-slip variety 'with the Z51 option). Within are gears giving 'a 3.31: 1 ratio for said Z51, other final drives giving 3.07: 1 and a CAFE-motivated 2.73: 1. Move forward and you'll find an aluminum apoy propshaft that resides in yet another piece of aluminum, a C-channel connecting the differential to the rear of the gearbox. The point of this backbone drivetrain is at least twofold: elimination of two crossmembers (allowing a lower seating package) and spreading the torque reaction .over a greater length (permitting somewhat softer mounts for better drivetrain isolation).
The frame of the new Corvette is a spot-welded skeletal structure, as opposed to the previous arc-welded ladder frame. -Attachment of the fiberglass body is via bonding or bolting; the backbone drivetrain is mounted from below.
This brings us to the gearbox in a roundabout way; and even here the new Corvette has something innovative to offer: a 4speed + 3 aD. You reaq that correctly: four forward speeds p~us three more in overdrive. The basic gearbox design was known as a Borg-Warner T -10, though its rights and tooling are now owned by Doug Nash (of Nash 5-speed fame). At the' rear of the conventional' 4-speed is a Nash-designed, planetary gear set that reduces the direct drive ratios by 0.67. Now a little exercise with your handy calculator will confirm the adjacent figures anq a trifle redundancy in the resulting concoction.
Gear Ratio Overdrive
1st 2.88:1 1.93:1
2nd 1.91:1 1.28:1
3rd : 1.33: 1 0.89: 1
4th LOO: 1 .'. 0.67: 1
Not true, though, because it's all under the control of a computer sensing engine speed, road speed, shift lever position and throttle angle. Also, the computer is smart enough to know 1st OD is almost spot-on with 2nd direct, so it dispenses with 1st entirely. As for the rest, think of having a conventional 4-speed under the control of your right hand, with each overdrive ratio having an automatic kickdown under the control of your right foot. And, because you're an enthusiast, you'd like absolute predictability when you're really into it, right? So once 2nd direct or 3rd direct is invoked by a playful right foot, the computer sorts out your driving.
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Author: ArchitectPage
PRICE .
List price $23,360
Price as tested $24,705
Price as tested includes std equip (air cond, elect. window lifts, elect. adj mirrors, anti-theft), AM/FM stereo/ cassette ($895), elect. adj driver's seat ($210), Bil. stein shock absorbers ($189), Z51 susp pkg ($51)
MANUFACTURER Chevrolet Motor Div, General Motors CQrp,
30007 Van Dyke Ave, Warren, Mich. 48090
GENERAL
Curb weight, Ib/kg 3200 1455
Test weight 3450 1568
Weight dist (with driver), fIr, % . ... ... 51/49
Wheelbase, in.imm 96.2 2444
Track, front/rear 59.6/60.4 1513/1534
Length 176.5 4483
Width ..71.0 1804
Height. ~. .. ... .. . .. ... . . .. .. . . . .. ... .. .. . .46.7 . ... .., 1186
Ground clearance 5.0.. ..127
Overhang, f/r 40.5/39.8 1030/1009
Trunk space, cu ft/liters .11.6 328
Fuel capacity, U.S. gal./liters .20.0. .76
ACCOMMODATION
Seating capacity, persons : 2
Head room, in./mm .35.5. .., .., 902
Seat width.. 2 x 20.0 ... ... ..2 x 508
Seat back adjustment, deg .. . . . .. .. .. .. . . . .. .... . . 12
ENGINE
Type : ..ohv V-8
Bore x stroke, in./mm ' 4.00 x 3.48.. 101.6 x 88.4
Displacement, cu in./cc 350 5733
Compression ratio .9.0: 1
Bhp @ rpm, SAE net/kW 205/153 @ 4300
Equivalent mph / km/h 140/225
Torque @ rpm, Ib-ft/Nm 290/393 @ 2800
Equivalent mph / km/h . .. . . . .. . . . .. . . . .. . . . ., ... .. 92/148
Fuel injection GM Throttle Body
Fuel requirement ..unleaded, 91-oct
Exhaust-emission control equipment: 3-way catalytic
converter with oxygen sensor, exhaust-gas recirculation, air injection
DRIVETRAIN
Transmission .automatic; lockup torque
converter with 4-sp planetary gearbox
Gear ratios: 4th (0.70) 2.32:1
3rd (1.00) 3.31:1
2nd (1.63) 5.40:1
1 st (3.06) 10.13: 1
1st (3.06 x 1.85) , 18.74:1
Final drive ratio 3.31: 1
INSTRUMENTATION _'
Instruments: 85-mph speedo (with digital display), 6000rpm tach (with digital display)! 99,999.9 odo, oil press./temp, coolant temp/voltmeter, fuel level, mpg, trip odo/range, clock
Warning lights: oil press., oil temp, coolant temp, alternator, brake sys, choke, security, check engine, low fuel, hatch ajar, door ajar, seatbelts, hazard, high beam, directionals
ROAD TEST RESULTS'
ACCELERATION
Time to distance, sec:
0-100 ft .' 3.1
0-500 ft 8.3
0-1320 ft (Y4 mi) .15.5
Speed at end of Y4 mi, mph ..88.0
Time to speed, sec: .
0-30 mph 2.4
0-60 mph .. .. 7.1 .
0-80 mph ..12.6
0-100 mph 22.3
SPEEDS IN GEARS
4th (4200 rprp) 137
3rd (5200).. .. .. 110
2nd (5200), 72
1 st (4650) 34
FUEL ECONOMY
Normal driving, mpg est 18.0
HANDLING
Lateral accel, 100-ft radius, g 0.896
Speed thru 700-ft slalom, mph 63.8
BRAKES
Minimum stopping distances, ft:
From 60 mph 133
From 80 mph 250
Control in panic stop... .. . . . .. .. excellent
Pedal effort for 0.5g stop, Ib 16
Fade: percent increase in pedal effort to
maintain 0.5g deceleration in 6 stops
from 60 mph .. .. .. ... nil
Parking: hold 30% grade? na
Overall brake rating.. .. . .. .. ... . excellent
INTERIOR NOISE
Idle in neutral, dBA 60
Maximum, 1 st gear 80
Constant 30 mph 70
50 mph 74
70 mph 76
90 mph 80 '
SPEEDOMETER ERROR
.30 mph indicated is actually .30.0
60 mph ...60.0
80 mph ...80.0
CHASSIS & BODY
Layout front engine/rear drive
Body /frame fiberglass body on skeletal steel chassis
Brake system... .11.5-in. (292-mm) vented discs front &
rear; vacuum assisted
Swept area, sq in./sq cm 330 2128
Wheels cast alloy, 16 x 8Yz front, 16 x 9Yz rear
Tires .Goodyear Eagle VR50, P255/50VR-16
Steering type rack & pinion, power assisted
Overall ratio 13.0:1
Turns,lock-to-lock 2.0
Turning circle, ft/m .40.1 12.2
Front suspension: unequal-length A-arms, transverse fi
berglass leaf spring, tube shocks, anti-roll bar
Rear suspension: upper & lower trailing arms, lateral
arms, tie rods, halfshafts, transverse fiberglass leaf
spring, tube shocks, anti-roll bar
MAINTENANCE
Service intervals, mi:
, Oil/filter change 7500/15,000
Chassis lube. .. .. .. . .. .. .., .. .. . .. .. . .. .. . .. .. . .. . .. . .7500
Tuneup 30,000
Warranty, mo/mi . .. .. .. .. . .. .. . .. .. . .. ... .. . .. .. .. 12/12,000
CALCULATED DATA
Lb/bhp (test weight) .' .16.8
Mph/1 000 rpm (4th gear) .32.4
Engine revs/mi (60 mph) .1850
Piston travel, ft/mi 1075
R& T steering index .0.80
Brake swept area, sq in./ton 191
