page_title: Chevrolet Corvette (C4)
section_title: ZR-1 (1990–1995)
hierarchical_section_title: Chevrolet Corvette (C4) / ZR-1 (1990–1995)
caption_attribution_description: Deutsch: Chevrolet Corvette ZR1 1991 5.7L 6 Gang Schalter 400 PS in Reinach Aargau CH
context_page_description: The Chevrolet Corvette (C4) is a sports car produced by American automobile manufacturer Chevrolet from 1983 to 1996. The convertible returned, as did higher performance engines, exemplified by the 375 hp LT5 found in the ZR-1. In early March 1990, the ZR-1 would set a new record for the highest 24 hour-5,000 mile land-speed by going over a speed of 175 mph. Prices rose and sales declined, in spite of a completely new chassis, modern sleeker styling, and other improvements to the model. The last C4 was produced on June 20, 1996.
context_section_description: General Motors acquired Group Lotus, a UK based engineering consultant and performance car manufacturing firm, during 1986. The Corvette division approached Lotus with the idea of developing the world's fastest production car, to be based on the C4 generation of the Corvette. With input from GM, Lotus designed a new engine to fit in place of the L98 V8 that was powering the standard C4. The result was what GM dubbed the LT5, an aluminum-block V8 with the same bore centers as the L98, but with four overhead camshafts and 32 valves. Lotus also designed a unique air management system for the engine to provide a wider power band by shutting off 8 of the 16 intake runners and fuel injectors when the engine was at part-throttle, while still giving the ZR-1 a power output of 375 hp (280 kW) when at wide open throttle.
  In addition to the engine, Lotus helped GM design the ZR-1's (which in prototype version was called "King of the Hill") upgraded braking and steering systems. The ZR-1 is fitted with Goodyear Eagle Gatorback tires having size of P315/ 35ZR-17 specially made for the car along with bigger ventilated disc brakes. Due to the heavier engine and body work along with wide tires, the ZR-1 is 200 lb (91 kg) heavier than the standard C4 Corvette. The ZR-1 came standard with the UJ6 Low-Tire-Pressure Warning System along with an ABS system manufactured by Bosch. The FX3 suspension system was engineered by Bilstein and was similar to the system used in the Porsche 959 albeit with modifications from the Lotus Formula 1 division. The system used a gas-over-oil shock absorber whose hollow center shaft came fitted with an adjustable orifice which controls the flow of oil in the shock absorber. The system allowed for six damping settings in each of the three driving modes namely Touring, Sport, and Performance and had 14 total steps. Servomotors coupled with a microprocessor governed the vehicle's speed and adjusted the suspension system accordingly.
  The 5.7-litre 32-valve LT5 engine unique to the car had a central bore spacing of 4.40 inches. The distance was maintained by reducing the bore from 4.00 to 3.90 inches while the stroke was increased from 3.48 to 3.66 inches. The aluminum cylinder liners were Nikasil-coated and the engine block has a cast-aluminum oil sump. The crankcase has integral four- and six-bolt cast-iron main
  bearing caps which secure the forged steel crankshaft into place. The four camshafts of the engine are driven by a roller chain and actuate hydraulic lifters that eliminate valve lash adjustment. The four-valve combustion chambers feature centrally-located spark plugs which act in combination with dished aluminum pistons enabling for a compression ratio of 11.0:1. The engine held 12 quarts of oil, 7 more than the L98 engine. The LT5 also came with a unique two valve induction system along with 16 tuned-length intake runners and a specially designed intake manifold using three throttle bodies. The small primary throttle body was for responsive low speed operation while the two large secondary throttle bodies enabled for full-power usage. The engine used direct-fire ignition: Four coils ignite two spark plugs simultaneously, upon receiving their cue from a crankshaft sensor acting in combination with the ECM. Spark advance and
  retardation are electronically controlled by the ECM, which gets an additional information from a knock sensor. A distinctive cooling system incorporating a 15% larger radiator ensured that the operating temperature of the engine remained the same as the L98 despite the differences in construction and operation.
  In order to transfer power efficiently to the rear wheels, a unique 6-speed manual transmission manufactured by ZF was installed with a code name of ML9. The transmission used Computer Aided Gear Selection (CAGS) which forced the driver to shift from first to fourth under low power urban driving conditions. The transmission has a tweaked ring and pinion ratio of 3.54:1 and a lower final drive ratio of 3.33:1.
  Other exterior modifications include a hard coated acrylic roof pane
caption: Corvette ZR-1
exif: {}