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ZR1 Bremsen
#1
Beim Recherchieren nach diesem und jenem ist mir eine interessante Seite untergekommen. Da sie nur noch im Google Cache existiert setze ich einfach mal den Gesamttext hier rein.

Die interessante Passage zum Thema Bremsen ist folgende:

"The test criteria at Chevrolet for this system was 20 stops, at two-mile intervals, from 150 mph at 0.62g deceleration."


*****************SCHNIPP*****************

1989 Chevrolet Corvette ZR1

No Doubt, It's King of the Hill

A preintroduction update on what will be the fastest Corvette ever.



©1988, 1999 by Hib Halverson

Introduction by the ZR-1 Net Webmasters



This article was written in the fall of 1988, right after Chevrolet fessed up and publically admited the ZR-1 would not go on sale for ’89. Halverson’s story alludes to rumors of developmental problems with the engine. Those problems were some of the reasons Chevrolet changed the sales debut to 1990. This story was accompanyed by a highly-detailed piece on the technical specifics of the LT5 engine.

While freelance writer and ZR-1 Net member, Hib Halverson, has mostly been associated with Vette Magazine, he has worked for others and did two "tours" with Corvette Fever, the first in 1987-89 and a second in 1996-97.

Both these articles appeared in an early1989 issue of CF.The first of these is unique for Halverson’s narritive of his first ZR-1 "sighting" which appearently took place on a deserted section of Interstate-10 west of Phoenix, Arizona early on a Sunday morning in the fall of 1988.



The first time I got passed by a ZR1 was like being buzzed by a low-level stealth bomber. It blasted right on by almost before I realized what it was.

Late last spring, I was L.A. bound on I-10, about 30 miles west of Phoenix. It was early Sunday. Cool desert morning. Mo traffic. My ESCORT on. The speedometer hovering comfortably at 75. Then I saw the distant black spot in my mirrors.

In seemingly no time, the spot became a Corvette. I looked back at the speedo and wondered "Did the engine quit?"

It was a fast moving black Coupe, ("Captain! Klingons approaching at Warp Nine, sir!") closing on me with at least a fifty mile an hour surplus. From the front, it looked just like any other ‘88 Corvette.

It went by, ballistic in the fast lane. I got a fleeting look at the back of it, I saw the driver wave NASCAR style. Then, I got the joke.

This was the King of the Hill. I'd seen spy shots and here it was-fat rear tires, squared off back, different tail lights, a little emblem I couldn't quite read-out for a morning jaunt. I got my boot into my 365 horse 454. Not a chance! By the time I hit 130 or so, my '71 was redlined in fourth and out of gearing.

The King rapidly receded in the distance. Such is being stealth bombed.

It was evidence that best car on the planet was soon to get better.



Concept History

Two years ago in a now defunct magazine, CORVETTE Illustrated, I wrote predictions of a new Corvette with the provoking nickname "King of the Hill." I’m sure some thought my writing of a CAFE- and smog-legal, all-aluminum, 400 horse, 5.7 liter, dual-overhead camshaft engine; a six-speed gearbox; 3.54 axle ratio; huge brakes and 315/35ZR17 rear tires was so much dreaming. It was no delusion. The evidence just passed me.

The story of the Corvette ZR1 goes back to a program that got underway in late-1982. With engineering work on the soon-to-be-introduced '84 'Vette complete, Chevrolet's Corvette Development Group had begun work on a high performance derivative known internally as "The 400 horsepower Corvette". The first attempt at this was a twin-turbocharged 4.3-liter 90° V6 powered unit of which as many as 20 prototype "mules" may have been built. However, the Corvette Group found this approach totally unacceptable due to the V6-90's inherent nasty vibration problems and underhood packaging. One engineer told us that the induction system length from the turbocharger compressor exit, through the charge air cooler to the engine was seven feet and "-although the cars had lots of power, turbo lag was so bad, you could time it with a Big Ben alarm clock." A car such as that must have been dreadful to drive. With all these negatives, the turbo V6-90 idea was discarded.

From early-'84 to until mid-'85 the 400 horse Corvette program developed around an in-house, 5.7L, twin-turbocharged V8. The program matured to the point where 14 preproduction prototypes were built. After extensive testing and despite strong support for the concept, the twin-turbo V8 program was also killed, this time because of fuel economy and emissions problems. Additionally, the Chevrolet marketing department, although supportive of the 400 horse concept, felt that by the car's projected introduction date; turbocharging would not be the leading-edge technology characteristic of the Corvette and, thus, be a sales liability.

After the death of the in-house turbo V8 program, some of the 14 prototypes were dismantled. Chevrolet continued to use the few examples left intact for other testing programs: verification of 400 horse Corvette powertrain, brake and suspension pieces for three. Additionally, the remaining Chevrolet turbos were the media darlings of the '85-'86 period as subjects of feature articles in Car and Driver, Motor Trend, Road&Track and a test I wrote for CORVETTE Illustrated which is archived elsewhere on this web site.

Even though the turbo project was a Chevrolet stillborn, the Corvette Group felt it a crime to just discard the technology they spent several years perfecting. Along came Reeves Callaway with an idea and a technology transfer deal was cut. The fruits of that are the Callaway Twin-Turbo Corvette which we've road tested elsewhere in the magazine.



Viola! The ZR1

The final attempt at the 400 horsepower car got underway in spring, 1985. By then the program was known in-house as "The King of the Hill" Corvette, obvious reference to Chevrolet's want of a sporting automobile capable of exceeding the performance of the Ferrari Testarossa, Porsche 928S4 and 930 along with others in that market. The heart of this car was to be a new, aluminum DOHC V8 tagged "LT5." On paper, ZR1's new engine is a revolutionary milestone in American automobile history. In practice? Well-I guess we'll find out in a four months or so when we road test a production King. In the meantime, a technical rundown on this new powerplant is provided elsewhere, also.

The second jewel in the King's crown will be the new six-speed, ML9, manual transmission. It is a joint design from CPC's Manual Transmission Group and the famous West German transmission firm, ZF who also manufactures it exclusively for Chevrolet. The ZF S6-40, affectionately known as the "Zed-F", has ratios of 2.68, 1.80, 1.31, 1.00, 0.75 and 0.49. It's a constant mesh, all synchronized design incorporating a smooth-acting, rail-shift mechanism and the latest in design and manufacturing technology. The case is all aluminum and the ML9 is designed to handle 425 lbs/ft. of torque.

Without Zed-F, the King would not meet Federal Corporate Average Fuel Economy (CAFE) standards. Two of ML9's design features are aimed at CAFE. The first is the super-tall sixth gear. On the calculator, speed at peak horsepower in sixth would be about 280 mph. Even the King lacks the 1600 horses or so necessary to sustain that velocity. The ZR1's projected top speed is 180 mph and is reached in fifth gear leaving sixth as a gas miserly cruising gear.

Also to meet CAFE, the ML9, like the Nash 4+3 before it, is partially controlled by the car's ECM. If the car is in first gear with all of the following conditions present: Coolant temperature above 120°F, speed between 12-19 mph and 0-35% throttle opening; then the gearbox goes into its Computer-aided Gear Selection (CAGS) mode, locking out Zed-F's second and third gears. By forcing the one-to-four "skip-shift" action, CAGS helps ZR1 get the fuel mileage average it needs to get under CAFE and not be liable for the gas guzzler tax. At press time, projected EPA mileage ratings are a respectable 15 city and 22 highway.

At the Chevrolet long-lead press preview at the late, great Riverside International Raceway last June we had a chance to drive the Zed-F in a non-ZR1, 1989 prototype. It had a smooth, precise race car feel to it. In spite of the CAGS feature being a little hard to get used to, this new transmission is a sheer delight after four years of notchy Nashes.

Working in conjunction with the new gearbox will be a fresh flywheel/clutch assembly that incorporates a "dual-mass" vibration damping flywheel for reduced driveline shock and noise and an 11-inch, diaphragm pressure plate. A hydraulic, pull-type linkage, requiring less effort, actuates the clutch. The ZR1 also gets a heavier-duty, 3.54, limited-slip differential assembly.

Imagine this: the King, as it will be introduced will do the quarter in the thirteen-flat area at 105. What if you changed the car's axle ratio such that 180 came in sixth. The car would be even quicker through the gears and might get into the low 12s at 115 on street tires. Awesome stuff, eh? Anybody for a set of 3.7s or 4.11s?



Chassis to Match

At present, one and possibly two suspension packages will be offered with the King. The decision is strictly a cost and marketing question and is unresolved at our deadline.

If Chevrolet goes the two-tiered route, the base offering will be the tried and trued, Z51 Performance Suspension offered since 1985. The best setup, and what will either be standard or perhaps an up-level option, is the new, FX3 Selective Ride Control package. Another result of the collaboration between Delco and Bilstein, it consists of last year's Z52 suspension but with a set of "ride-adaptive" shock absorbers similar, but more sophisticated in design, to what other manufacturers have had for a couple of years. A rotary switch on the center console, sets one of three shock valving modes: Touring, Sport or Competition. Ride quality in the Touring mode is described as soft—probably softer than was '88's base Corvette. Sport is about equivalent to '89 base or '86-'88 Z52 level. Competition, serious stuff you see, is quoted as being "-Z51 and then some!"

An electric actuator, located at the top of each FX3 Delco-Bilstein, works a valve inside the shock through the piston rod. Varying the valve setting changes the shock's dampening characteristics. Besides being three-way, user-adjustable, the system is linked to a computerized control module (soon, the ashtray door in a Corvette will also be-computer controlled). This mini-ECM fine tunes shock action, within the parameters of the mode selected, according to the speed of the car. Chevrolet tells us, in the event of "-possible malfunction, all valves are rotated to a position that ensures safe vehicle behavior under all driving conditions."

When I was a little "squid", going to road races back in the sixties, I remember a racer I knew (he ran Corvettes incidentally) always saying, "You gotta have stop to match the go." Don't worry, the King stops! Last year, Chevrolet introduced an optional, heavy-duty braking system and it will be standard on ZR1. It had been developed through a year of testing on one of the original in-house V8 turbos and backed up with a season of showroom stock racing in the ESCORT series' old SS class during 1987. The system consists of larger, two-piston front brake calipers and 330mm front brake rotors. The rear got new single-piston calipers and slightly larger rotors. The test criteria at Chevrolet for this system was 20 stops, at two-mile intervals, from 150 mph at 0.62g deceleration. Now that, my friends, is a set of brakes! Of course, we can't forget that these excellent binders come with the Corvette antilock braking system (ABS) that's been standard since '86.

Any chassis development engineer will tell you that half of today's performance cars' good handling comes from tires. Because of the King's massive, tire-firing torque, the ZR1 carries monstrous 315/35ZR17 Goodyears on 11-inch alloy wheels at the rear. Much rumored 8-12 months ago was some form of electronic traction control. The Corvette Group ended up taking a more traditional approach with the new, foot-wide Gatorbacks. Perhaps things like true active suspension and traction control have turned out to be more complicated and expensive then their early supporters had figured. Up front, ZR1 carries 275/40ZR17s on 9.5 in. aluminum wheels.

Now don't think for a minute that the King's hard-core performance appeal is going to compromise the creature comforts. Most of the traditional Corvette appointments: the Delco-Bose stereo, the six-way articulated sport seats with leather upholstery, electrically heated mirrors and rear window defogger, transparent lift-off roof panel and automatic climate control will be available on the ZR1. About the only two ways you can't have Kings, are 1) as a Roadster, because that body style is not well suited structurally to the ZR1 package's performance potential and 2) with an automatic transmission, because the current Turbo Hydra-matic 700R4 just isn't strong enough to handle the torque of LT5.

Lastly, there's one interesting new convenience feature that will be optional and that's the UJ6 Low Tire Pressure Warning system. Tiny pressure transducer/radio transmitters are clamped to the wheel inside each tire. When tire pressure is low, they send a signal turning on a dashboard warning light. A humorous but rare occurrence could come, because all transmitters share the same frequency, when one passes another '89 Corvette equipped with this system. If the other car's transmitters are signaling low pressure; the light on your dash will come on. Imagine what happens at the Corvette plant when a car rolls off the line with low tires? Thousands of tire warning lights are on and-how do they guess which car? Roger Smith and Bob Burger will probably form a special committee.



The Look and Feel of ZR1

The people who style the Corvette must have taken a lot of evil delight in doing The King of the Hill. From the front (witness my Arizona stealth bombing) and the sides, the car is any garden-variety Corvette. However, once it's passed you (at a high rate of speed no doubt) you see the distinctive royal profile. The changes are quite subtile starting at the doors where the car begins to get slightly wider. This continues along the rear fenders and ends at a wider rear end. The extra girth comes from the need to house the larger 315/35 Gatorbacks in the back fender wells. The new rear treatment includes a noticeable duck-tail deck spoiler without which, when hustling at 180 mph, the King would get a bit loose. New square taillights and square exhaust outlets come with the facelift. Finishing off the restyle is a nameplate under the right side taillight unit. Prototypes have all worn "LT5" badges there but, due to GM's policy prohibiting divisions from displaying engine designations (which came out of the GM engine controversy of a few years back), production Kings will have "ZR1" badging. Expectedly, the few scores of LT5 nameplates struck have become the most sought-after, in-house souvenirs at Chevrolet.

So-the "King" (definitely a legend before its own time) is coming. "Mine eyes have seen the glory-" but I can't tell you anything about how the car feels. How this revolutionary new Corvette performs is for the most part a mystery. Although several ZR1 prototypes were on display at Chevrolet's June long lead and Corvette Fever had a chance to privately photograph a proto-King in July; both times we were denied a drive or even a ride. All that was allowed was my sitting in one (the seats feel the same, okay). The truth is, Chevrolet is experiencing difficulties with the ZR1's development, particularly with the LT5 engine. However the problems are those any completely new engine program should have. Chevrolet wants these problems eliminated before they start handing out Kings to the press for road tests next spring. Only the most senior editors at a couple of the largest automotive magazines have been offered drives in the ZR1 and these have been under controlled conditions at GM's two proving grounds. Hey, just keep supporting us! When our circulation gets to 300,000 we'll have that stuff first, too!

At the Riverside long-lead, the only time a ZR1 wheel turned was ex-showroom stock driver, Kim Baker's solo, three-lap demonstration. That didn't do a hell of a lot for my anticipation pains but, what the hell, the car sure sounded bitchin' as Baker hit 6700 in third blowing by the start/finish line. I can hardly wait to drive it.

So, as far as what the King's real personality is; stay tuned. We'll be be back in about four months or so with that story.
Gruß aus Aachen,

Ruben
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