1993 Acura Vigor- Powertrain

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OVERVIEW

The engine of the Vigor is a compact, all-aluminum inline 5-cylinder equipped with a single overhead camshaft, four valves per cylinder, Programmed Fuel Injection and a dual-stage intake manifold. It produces 176 hp at 6300 rpm and 170 lbs.-ft. of torque at a very low 3900 rpm. The standard transmission is a 5-speed manual with a rod-activated shifter mechanism. An electronically controlled 4-speed automatic is optional. The longitudinal arrangement of the powertrain achieves a number of desired goals. It creates an ideal 60/40 weight distribution for excellent handling and turn-in response. Also, it allows the use of softer engine mounts which reduce the level of noise and vibration reaching the cabin. By tilting the engine 35, the engineers were also able to achieve a low hoodline for maximum visibility and a reduction of frontal area to reduce aerodynamic drag.

BENEFITS OF AN INLINE 5

Initial experiments with an inline 5 engine indicated tremendous potential. Since it is only slightly longer than an inline 4, it could easily be packaged in a longitudinal location and leave adequate space for a properly designed double-wishbone suspension. It provided ample low-end torque and direct, linear response at all levels of the power band. It is also lighter than an inline 6 or V-6and in some cases more powerful.

VALVETRAIN

The Vigor engine features four valves per cylinder to optimize performance and improve breathing at all points in the power band. In order to achieve packaging efficiency and reduce weight, the valvetrain uses a single overhead camshaft design.

STAINLESS STEEL EXHAUST SYSTEM

To reduce weight and to improve durability the exhaust system is constructed of seamless stainless steel.

DUAL-STAGE INTAKE MANIFOLD

The Vigor inline 5 engine is tilted to the right, 35o from vertical. This has allowed the engineers to design a manifold with long, tuned intake runners to optimize engine breathing. Based on technology developed for the NSX and the 1991 Legend, the intake manifold is a dual-stage design to increase both low-end torque and high-end horsepower. Below 5000 rpm, the cylinder is fed by the primary runner. Above 5000 rpm, however, the engine vacuum opens a butterfly valve, allowing the passage of air through a secondary runner. This increases the volume of air entering the combustion chamber and also produces an inertia ram-tuning effect for more complete cylinder filling, increasing both horsepower and torque.

PROGRAMMED FUEL INJECTION (PGM-FI)

The new Vigor engine is fueled by the Honda R&D-engineered PGM-FI sequential port fuel-injection system. The system, which is controlled by a microprocessor, meters fuel on the basis of continuous information gathered by the array of engine sensors. By making thousands of calculations per second the system constantly adjusts the air/fuel ratio to maintain it at the peak of driveability, power, fuel economy and within acceptable exhaust emissions.

KNOCK SENSORS

The Vigor engine is equipped with two knock sensors, located on the engine block below the intake manifold. If a sensor detects engine knocking, it sends a signal to the microprocessor which in turn adjusts the engine timing. This system allows the engine to operate safely with low octane fuel, but with a reduction in power. Premium unleaded fuel is recommended.

HYDRAULIC ENGINE MOUNTS

A total of six mounts support the powertrain: two at the forward edge of the engine, two on the forward edge of the transmission and two more located in the middle of the transmission. Of these six, the two on the engine are of a new hydraulic design.

The hydraulic mounts damp out engine vibration by transferring fluid through a restricted orifice in response to engine movement, much like a shock absorber. The fluid inside the chamber has been tested in extreme conditions and won't freeze in cold weather or deteriorate in a hot environment.

TRANSMISSIONS

The standard Vigor transmission is a rod-actuated, 5-speed manual fitted with a pulltype, hydraulic-operated clutch. To enhance reliability and durability, internal oiling of the manual transmission is provided by a built-in, forced lubrication oil pump.

An electronically controlled 4-speed automatic transmission is optional. To achieve the desired smoothness, all shift and torque converter lockup functions are electronically controlled by means of the transmission's 32K microprocessor. This computer is linked to the 48K engine-control computer. On the basis of various operating conditions such as throttle angle, coolant temperature, vehicle speed and engine speed, the microprocessor controls shift speed and torque converter lockup.

To help achieve smooth shifting, the ignition is programmed to retard momentarily during upshifts and downshifts in order to reduce engine torque on the transmission's shifting elements. By now retarding ignition timing on upshifts in addition to downshifts, shift smoothness is further improved. The transmission also features a low-hold clutch. This system will hold the transmission in first gear, something drivers will find useful for trailer towing and for steep uphill or downhill driving.

The housings of the manual transmission, the optional automatic transmission and the differential are all cast in aluminum, to help keep the weight of the powertrain to a minimum.

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