Engine Systems General Information The engine plays a vital role in customer perception of the overall vehicle. Vehicle responsiveness, driveability and fuel economy are the basic ingredients that the engine brings to the vehicle. For a minivan, these ingredients come from a broad torque curve, rather from high peaks of torque and power. Quality and reliability are a primary ingredient that keeps customers as repeat buyers. 1996 minivan engines are expected to provide best-in-class quality, reliability and refinement. For the engine, that means both long lasting and utterly reliable - an engine that will never stop running or fail to start. It also means quietness and freedom from leaks. Refinement is reflected in, among other things, a smooth idle and pleasant, unobtrusive sound quality under all operating conditions. 3.3 and 3.8-Liter OHV SMPI V-6 Engines General Information Basic quietness, reliability and durability were ample in previous years; thus they only required minor refinement to meet 1996 requirements. See also 3.3 & 3.8-Liter V-6 engines under Powertrain Noise Reduction in the Quietness section. Changes required to adapt the engine to the new minivan engine compartment include a revised throttle body location, a new right (rearward in the vehicle) exhaust manifold to provide a common outlet location with other new minivan engines and a new cross-over pipe. Performance and Fuel Economy For improved performance of the 3.3 and 3.8-Liter OHV SMPI V-6 engines, a significantly broader torque curve is accompanied by a higher torque peak. Torque is increased substantially over 1995 levels between 2400 and 4800 rpm on both engines. The broad torque curves provide maximum customer perception of performance and also contribute to good fuel economy. Changes for better torque and fuel economy include the following items: -- Re-tuned intake manifold with longer - 16-inch (406 mm) - primary runners to increase torque -- Tuned, low-restriction induction system -- Reduced exhaust system back pressure -- Coated pistons to reduce friction (late availability) -- Calibration of the ignition and fuel injection systems for mid-range torque and fuel economy -- Addition of a knock sensor to the ignition system, allowing maximum spark advance under all conditions for high fuel economy, brisk response and high power while protecting against engine damaging knock -- Reduced idle speed for greater fuel economy See also Air Induction System Tuning and Idle Speed Control below. Ratings of these engines are as follows: Engine Rating Factor Rating 3.3 L Power 158 bhp (118 kW) @ 4850 rpm Torque 203 lb-ft (278 narrow) @ 3250 rpm 3.8 L Power 166 bhp (124 kW) @ 4300 rpm Torque 227 lb-ft (308 N*m) @ 3100 rpm Quality and Reliability Components and sub-systems throughout the engine have been upgraded to assure operation for 10 years or 100,000 miles (160,000 km) without major service. Specifically, valves, piston rings and bearings are made from premium materials. Platinum-tipped spark plugs are standard on 3.3 and 3.8-liter engines. They last 100,000 miles (160,000 km) under normal driving conditions. 3.0-Liter SOHC SMPI V-6 Engine Power and torque of the 3.0-liter engine benefit from the tuned, low restriction air induction system and reduced back pressure common to all 1996 minivan engines. Peak power is increased 8 horsepower (6 kW) and torque is up 3 lb-ft (4 N-m). Ratings of the engine are as follows: Power Torque 150 bhp (112 kW) @ 5200 rpm 176 lb-ft (239 N-m) @4000 rpm There are no internal changes to the engine from 1995. Externally, the right (rearward in the vehicle) exhaust manifold is redesigned to provide a common outlet location with other 1996 minivan engines. See also Air Induction System Tuning below. 2.4-Liter DOHC SMPI I-4 Engine General Information A 2.4-liter DOHC SMPI I-4 engine is new to Chrysler minivans but very similar to the 2.4-liter engine first introduced in the Dodge Stratus. Changes from Stratus are primarily associated with fitting the engine into to the minivan engine compartment. Compared to the 2.5- liter four-cylinder engine used previously, the new engine has far more power and torque - approaching the levels of the 3.0-liter V-6. While substantially increasing acceleration capability, the 2.4-liter engine maintains the fuel economy of its predecessor. Because of increased performance without loss of fuel economy, the 2.4-liter engine is expected to find greater market acceptance than its predecessor. Performance features include a 16-valve double overhead camshaft cylinder head, a tuned aluminum intake manifold and a tuned, low restriction air induction system. A high compression ratio, (9.4:1), also contributes to the outstanding power output. The 2.4-liter engine is also substantially quieter than its predecessor. See 2.4-Liter I-4 Engine under Powertrain Noise Reduction in the Quietness section. The 2.4-liter engine is available with either three-speed or electronically controlled four-speed overdrive automatic transaxles. Performance and Fuel Economy The 2.4-liter engine has a broad, flat torque curve with 90% of peak torque available between 2000 and 5000 rpm. The engine reaches peak power at a relatively low speed for a DOHC engine of 4000 rpm. The large "breathing" capacity of the DOHC head has been directed toward achieving high torque and fuel economy through camshaft design and intake manifold tuning. High torque for hauling heavy loads and good fuel economy, rather than peak performance, are the engine attributes that minivan buyers seek. Preliminary ratings are as follows: Power Torque 150 bhp (112 kW) @ 4800 rpm 167 lb-ft (226 N*m) @ 4000 rpm Relative performance of the 2.4-liter engine and its predecessor are as follows: Performance 2.4 L 3-speed vs. 2.4 L 4-speed vs. Parameter* 2.5 L 3-speed 2.5 L 3-speed Through Gears 5 second distance +5.0% +9.5% 0 - 60 mph +22.0% +19.3% In Gear 40 - 60 mph +22.0% + 25.8% 3rd gear grade % @ 55 mph +12.0% +50% EPA Fuel Economy (est.) City -1 mpg same Highway same same * + = improvement, - = degradation Basic Dimensions* Displacement 148.2 cu in (2429 cc) Bore 3.44 (87.5) Stroke 3.98 (101) Bore-to-stroke ratio 0.87 Bore spacing 3.78 (96) Block length 16.43 (417.3) Block height 9.36 (237.8) Rod length 5.94 (151) Piston height 1.43 (36.3) Connecting rod L/R 2.99 Compression ratio 9.4:1 * All dimensions are in inches (millimeters) unless otherwise noted. Cylinder Head The cylinder head is a low profile aluminum casting with pent-roof combustion chambers that house four valves per cylinder. The valve included angle is 48 degrees, allowing large valves. Dual camshafts run in six bearings that are machined in the head base material and have removable caps. Powdered metal valve seat inserts and valve guides are pressed into the head. Spark plugs thread into the center of the combustion chamber through wells cast into the head. Ports from each valve merge in the head, leading to a single branch (runner) in their respective manifolds. To provide turbulence in the cylinders that contributes to the rapid combustion necessary for low emissions and efficient operation on regular-grade gasoline, the ports cause incoming air to "tumble" from top to bottom of the cylinders. The degree of tumbling action was balanced against the conflicting need for high air flow to obtain high power output. Cylinder Head Cover Made of die cast aluminum, the cylinder head cover features an isolated mounting which uses O-ring type, silicone perimeter gasket. The DIS coil-mount is built into the cover. The PCV system is also integral with the cylinder head cover. Cylinder Block The block is cast iron with a cast iron ladder-type bedplate. It is 9.36 inches (237.8 mm) high. Bore spacing of 3.78 inches (96 mm) allows coolant to flow around all cylinders to assure long head-gasket life. To reduce radiated noise, the block and bedplate have no flat or single-curvature outer surfaces. Lower surfaces provide a constant clearance to moving parts and upper surfaces conform the water jacket contours. The bedplate is made up of a perimeter wall and transverse webs that support the crankshaft, giving structural rigidity for durability at high rpm's and for quiet operation. The bedplate also provides a flat sealing surface for the oil pan. The oil gallery is located on the right side of the block with dual feeds to each main bearing. The water pump housing and rear crankshaft seal housing are cast integral with the block. Intake Manifold The two-piece, cast aluminum manifold has a runner length of 17.7 inches (450 mm). The intake manifold combines tuned individual runners for each cylinder extending from an integral plenum chamber. The runners curve backward above the cylinder head cover to clear the hood. The manifold is cast in two pieces, separated in the middle of the runner curvature, for ease of manufacture. The throttle body mounting flange is at nearly the same location as the V-6 engines to simplify linkage installation and intake duct routing. The upper half of the manifold includes a raised-letter logo - "2.4 L DOHC" - cast into the top surface. Exhaust Manifold Made of cast nodular iron, the exhaust manifold has a 0.14 inch (3.5 mm) wall thickness with four-into-one runner design. It provides a common outlet flange location with the V-6 engines to simplify the exhaust system. Valve Train Dual overhead camshafts actuate four valves per cylinder. Valve diameters are 1.37 inch (34.8 mm) intake and 1.20 inch (30.5 mm) exhaust. All valves have 0.25 inch (6 mm) chrome plated stems. Valves have a 48-degree included angle. The exhaust valves are on the right (rearward) side of the head. Each valve is operated by an end-pivot rocker arm that has a 0.67 inch (17 mm) roller cam follower to reduce low speed friction and cam wear. Rockers pivot on inboard-mounted, fixed hydraulic lash adjusters. Single valve springs provide control of valve actuation to 6200 rpm. Camshafts of post-hardened nodular cast iron provide a 236 degree intake duration and a 240 degree exhaust duration. The intake cam centerline is 113 degrees ATDC, the exhaust is 110 degrees BTDC, with 15 degrees of overlap. Intake valve lift is 0.33 inches (8.25 mm) and exhaust valve lift is 0.26 inches (6.5 mm). A state-of-the art cog belt drives the camshafts. The belt system is designed to last the life of the vehicle without adjustment or replacement. High belt loads usually associated with operating were minimized by a systems design approach. A hydraulic automatic tensioner forces an idler pulley against the back of the belt, maintaining proper tension for the life of the vehicle. A three-piece molded plastic cover, completely encloses the belt to minimize belt noise and protect the belt from damage by foreign matter. Pistons Cast aluminum, single-size pistons weigh 11.7 ounces (332 grams) each. The pop-up top with valve cut outs allows broken-belt clearance. Piston pin diameter is 0.87 inches (22 mm); weight is 4.16 ounces (118 grams). Piston pins are held in place by press fit to the connecting rods. Connecting Rods The rods and caps are initially formed as one-piece powdered-metal precision forgings. Powdered-metal rods and caps are lighter than conventional steel forgings. The reduced weight results from good dimensional control that is inherent in the process and from elimination of the small-end balance pad. Lighter rods benefit the vehicle by providing smooth operation at high rpm. The cap is separated from the rod in a unique cracking process. Uneven mating surfaces which result give good rod-to-cap alignment during assembly. To make assembly easy and to reduce weight, the 9 mm cap mounting bolts thread directly into the rod, instead of into separate nuts. Crankshaft Cast of nodular iron, the lightweight crankshaft has eight counterweights. Counterweights straddle each crank pin to balance the bearing loads within each bay for smooth, quiet operation. Main bearing diameter is 2.36 inches (60 mm), rod bearing diameter is 1.97 inches (50 mm). The crankshaft main bearing journals are 1.0 inch (25.5 mm) wide for low friction. A torsional vibration damper is used. The damper has two poly-V pulleys that drive accessories. Balance Shafts The 2.4-liter engine operates very smoothly because a system of counter-rotating balance shafts counteracts second-order unbalance, the predominant cause of four-cylinder engine vibration. The two counter-rotating, eccentric balance shafts, interconnected by gears, are driven by a short chain from the crankshaft. They turn at two times engine speed to offset the reciprocating mass of the pistons and connecting rods and to achieve the desired balancing effect. The balance shafts are enclosed in an aluminum housing mounted beneath the crankshaft in the oil pan. The housing is bolted to the bottom of the main bearing webs of the bedplate and rests in the oil supply. When the engine is running, the balance shafts pump oil out of the housing to minimize parasitic drag which could occur if the shafts spun in the oil. Bearings The camshafts need no bearing inserts. They operate directly in the cylinder head. Main and rod bearings have bi-metal inserts. Lubrication System The powdered metal gerotor oil pump mounts in the front of the block and is driven by the crankshaft to reduce noise and complexity. The system that returns oil from the head is designed to prevent aeration during high-rpm running. The block is inclined to the right (rearward in the car) to allow the oil to drain from the head along the right face of the block. The crankcase is ventilated through an opening on the left side of the head. Oil capacity is 4 quarts (3.8 L) plus filter. SAE 5W-30 oil, grade SG/SH is recommended. A half-quart oil filter mounts horizontally to an extension of the oil pump body. The oil pan is stamped from sound-damping metal-plastic-metal laminate. Fuel Injection System Returnless, sequential multi-port injection (SMPI) uses four dual- spray injectors to provide balanced fuel delivery to all cylinders. Injectors direct separate sprays to the intake valves. A small slot in the top of each intake port allows proper location of the injector spray. Sequential injection improves throttle response and overall driveability compared to single-point injection. The injection system is returnless to reduce complexity compared to customary systems. This very important emission-control innovation also drastically limits the creation of fuel vapors which must be captured by the evaporative emission-control system. The fuel return line is eliminated and the electronic control has been refined to compensate for variations in injection pressure that result. Only the fuel to be used is delivered to the engine. There's none left over that needs to be returned to the fuel tank. Variable injection timing is used to provide good idle quality without compromising performance and fuel economy. The fuel injection system uses the same sensors as the ignition system to provide speed, timing and cylinder-selection data. These direct acting sensors provide more accurate response than a conventional distributor. In addition, intake charge temperature and coolant temperature are used to fine tune injection rate for economy and performance. The throttle body has a 2.05-inch (52 mm) bore to minimize restriction at high rpm. Ignition System The 2.4-liter engine features a direct ignition system (DIS), which offers several key advantages over distributor systems: -- Reduced engine length (no distributor drive) -- Reduced engine complexity (no distributor or related parts) -- Direct information to control the fuel injection system -- Quick starts because camshaft and crankshaft sensors give early notice of which cylinder is ready for injection and ignition -- Accurate firing because ignition and fuel injection timing signals come directly from the crankshaft and camshaft -- Smooth idle because timing variation is reduced -- Quick throttle response -- Low maintenance -- High reliability because of proven sensors Two sensors (one for crankshaft timing, the other for camshaft reference) provide the data to operate the ignition system. The crankshaft sensor, inserted through the side of the block, senses two patterns of four slots each in the number 2 counterweight, 180 degrees apart. The slots feed data for engine speed and timing calculations. Their positions on the crankshaft establish engine basic timing. The fact that they sense directly from the crankshaft means more accuracy than conventional systems. Individual slots are spaced 20 degrees apart. Spark advance and injection timing are computed from these points. One slot, called the "signature" slot, is 60 degrees wide; the others are approximately 5 degrees wide. The sensor output that comes from the "signature" slot combines with the signal from the camshaft sensor to determine the cylinder ready for fuel and ignition. The camshaft sensor is mounted on the outside rear of the cylinder head. It is triggered by a ring magnet in the end of the camshaft. The magnet's four poles are arranged at 150-degree and 210-degree intervals. Their relationship to the signature slot is established in less than one turn of the crankshaft, allowing injection and ignition to begin. A Chrysler-patented two-wire knock sensor is more costly than a conventional single wire sensor, but its signal is clearer. In addition, it is more sensitive, allowing maximum spark advance under all conditions for high fuel economy, brisk response and high power without producing engine-damaging knock. The four-lead direct-ignition coil is mounted on the cylinder head cover. As a result, secondary-wire leads are short. Cooling System and Water Pump To reduce complexity, the base of the water pump housing is part of the block. The body of the pump is die cast aluminum, bolted to the front of the block. The pump is driven by the timing belt. Crankcase Ventilation System To minimize oil pullover at high rpm, the crankcase ventilation system includes an oil separator in the cylinder head cover. The separator has baffles that inhibit the flow of oil to the intake manifold. Oil drains out of the baffling on a long, narrow plate pinned to the inside of the cover. Accessory Drive The alternator and air conditioner compressor are driven by a "poly V" belt from the crankshaft damper. Belt tension is adjusted with a pivoting alternator bracket that has a jack screw for easy adjustment. The power steering pump is driven by a separate poly-V belt that is adjusted by pivoting the pump mounting bracket. The belts are protected from road splash and debris by a large molded plastic shield. Quality and Reliability The 2.4-liter engine is designed to run for 100,000 miles (160,000 km) without major service. This has required use of top-quality valve, piston ring and bearing materials. It also required that the camshaft drive belt be upgraded over that used on the 2.5-liter engine in 1995. Air Induction System A tuned air induction system for increased mid-range power and torque on all 1996 minivan engines. The volume and length of the inlet duct between throttle body and air cleaner - called a "zip" tube - are tuned to increase mid-range torque. This has the effect of removing a dip in the torque curve that is associated with tuning of the intake manifold runners. The zip tube is tuned in conjunction with the air induction resonator. The air induction system is larger than that on prior models, reducing inlet air flow restriction by over 20% for increased power and torque. The air cleaner is part of the air induction system and is common to all engines. It includes a low-restriction panel-type filter element. For increased performance in hot weather, ambient air is ducted to the air cleaner. The duct passes through the left headlight mounting panel and draws air from behind the light assembly. Because a large air cleaner is used to minimize air flow restriction, the filter element replacement interval exceeds 30,000 miles (48,000 km). See also, Air Induction Resonators under Powertrain Noise Reduction in the Quietness section. Transaxles 41TE Electronically Controlled Four-Speed Overdrive Transaxle The 41TE transaxle available on 1996 minivans is a refinement of the 1995 minivan transaxle. It is the only automatic transaxle with adaptive controls that use real-time feed-back for all shifts available in a minivan. During a shift, the transaxle can modulate hydraulic pressure 143 times per second - 14 adjustments in the time it takes to blink (approximately 0.1 second) - to assure smooth operation. The 41TE transaxle is simpler, lighter and more compact than competitive transaxles of similar capacity. Basic features are unchanged from 1995. Customer requirements regarding the transaxle revolve primarily around proper function. A number of internal mechanical refinements increase the durability of the transaxle in response to greater customer expectations. Transaxle operation can also have a significant effect on quietness and driving experience that provides a sense of confidence. Additional refinements are directed toward meeting these requirements. See also Transaxle Control Module under Electrical and Electronic Systems below. 31TH Three-Speed Automatic Transaxle General Information Several internal changes increase durability of the 31TH transaxle to the corporate 100,000 mile (160,000 km) standard. Torque Converters Torque Converter For 2.4-Liter Engine The torque characteristics of the 2.4-liter engine require a new torque converter that is tailored to the engine. The converter uses a revised impeller blade shape to reduce converter slippage for improved fuel economy during city driving. It also includes a converter clutch to eliminate slippage during highway driving. Torque Converter Refinements Torque converters have been refined to increase durability and driveability. The following changes have been made: -- All converters use bonded friction disc in the converter clutch. This construction is more durable than the previous construction and provides smoother engagement for better driveability. -- A more durable thrust washer is used between stator and turbine on all converters. -- With 2.4 and 3.0-liter engines, a needle roller bearing handles thrust loads between the impeller and stator. -- With 3.3 and 3.8-liter engines, more durable converter clutch damper springs are used. Torque Converter Drive Plates Drive Plate With 2.4-Liter Engine - A state-of-the-art one-piece torque converter drive plate minimizes starter engagement noise through improved concentricity and more accurate teeth than previous drive plates. New technology, being used for the first time by Chrysler to manufacture drive plates, forms the ring gear teeth into the flanged outer diameter of the drive plate stamping. This manufacturing process also reduces weight and cost compared to the previous welded and broached ring gear which was welded to a stamped plate. Drive Plate With V-6 Engines - All V-6 engines use a lightweight drive plate with lightening holes and a thinner starter ring gear. All-Wheel Drive System The all-wheel drive system, which is functionally unchanged, will not be available at introduction. A new viscous coupling and an aluminum torque tube reduce system weight by 9.2 pounds (4.2 kg). As in previous years, it is available only on long wheelbase models. Powertrain Electrical And Electronic Systems Transaxle Control Module General Information The third generation TCM (Transmission Control Module), EATX III, used with the 41TE transaxle includes these new features: -- Full implementation of OBD II (On-Board Diagnostics, second phase) -- Increased computing speed and power that allows faster program execution by using a 16-bit rather than 8-bit data bus -- Double the electronically-programmed memory capacity - to 64k x 16 bytes from 64k x bytes These added capabilities provide better shift quality by altering shift characteristics based on engine and transmission temperature. This affects shifting during warm up and when engine and/or transmission are overheated. In conjunction with a new data link to the PCM, it also allows engine torque management. See also Engine Torque Management under Powertrain Control Module below. EATX III also provides a vehicle-speed signal for use by the PCM as did EATX II. The PCM in turn forwards the information to the instrument cluster for operation of the speedometer and odometer. Electronic Display Logic With the 41TE automatic transaxle, the transaxle gear indicator ("PRNDL") on the instrument panel is an electronic display that receives its signal from the TCM. Because the signal is verified by the TCM, no indicator adjustment is required and the possibility of a vague or erroneous reading is virtually eliminated. See also Computer Systems Network under Electrical and Electronic Systems in the Body section. and Instrument Cluster and Information Center under Instrument Panel and Instrument Cluster in the Body Interior section. Interactive Automatic Speed Control For increased driver confidence and comfort, interactive automatic speed control provides improved operation in circumstances where the system could not control speed or customers were uneasy about using speed control. Interactive automatic speed control also avoids unnecessary shifting for smoother, quieter operation and, when downshifts are required, makes the shifts smoother than competitive systems. Interactive automatic speed control is available only with 41TE automatic transaxle. "Interactive" means that the feature is accomplished through communication between the PCM (Powertrain Control Module) and TCM. It is included in the control software and consists of the following functions:Overspeed Reduction - Overspeed reduction helps maintain vehicle speed at the selected set point when descending a grade. The TCM first senses that the speed control is set. If the set speed is exceeded by more than 3 mph (5 km/hr) and the throttle is closed, the TCM causes the transaxle to down shift to Third gear. After the downshift, the automatic speed control continues its normal operation. Conditions leading to a return to overdrive after the descent is complete are monitored to assure that transaxle cycling will not occur. Downshift Delay - To reduce the number and frequency of downshifts when operating in hilly country and to reduce engine "flare" noise when a downshift is necessary, downshift delay logic has been added. A downshift is delayed or avoided by allowing the automatic speed control unit to provide much larger throttle openings than in the past. Only if vehicle speed drops more than 2-3 mph below the set speed and continues to fall does a downshift occur. When the steepness of the grade demands a downshift, engine flare is eliminated by reducing the throttle opening as the shift is made. Automatic speed control quickly resumes throttle control to maintain speed. The amount of throttle opening reduction is calibrated to provide approximately the same transmission output torque after the downshift as before it. Grade "Hunting" Prevention Refinement Grade "hunting" prevention - the ability of the transmission logic to delay an upshift on a grade if the engine does not have sufficient power to maintain speed in the higher gear - has been expanded to include 2-3 shifts as well as 3-4 shifts. The 3-2 downshift and the potential for hunting between gears occurs with a heavily loaded vehicle or on steep grades. When hunting occurs, it is very objectionable because shifts are frequent and accompanied by large changes in noise and acceleration. The system also compensates for the loss of engine output that occurs at high altitude through communication with the PCM. Grade hunting prevention works with automatic speed control as well as normal driver control. Powertrain Control Module General Information New minivans use SBEC III (single board engine controller, version 3), the newest version of the corporate PCM (Powertrain Control Module). It offers the following new features: -- Digital Control For Engine Cooling Fans - The control software monitors coolant temperature and air conditioning system head pressure to determine fan speed. For both parameters it adds the difference and the rate of change between target and actual values of these parameters to determine the speed at which the fans should operate. If the coolant temperature and/or air conditioning system head pressure is below target but the rate of change indicates that it will soon exceed the target, the fans are started or speed is increased. With this control strategy, it is possible to operate the air conditioning system with the fans off - a condition not previously available on any Chrysler vehicle. Power is supplied in pulses that vary from 30 to 100% of continuous operation - 30% "on" time produces a speed about half the maximum speed. Power is delivered to the fans through new electronic relays that are capable of cycling continuously where conventional mechanical relays are not. To assure ample life, they are attached directly to underhood sheet metal which helps to dissipate the heat created by the high switching rate. These electronic relays also eliminate the sometimes-audible click associated with conventional relay control. See also Cooling System in the Chassis section. -- Full implementation of OBD II -- Increased computing speed and power that allows faster program execution -- Quadruple the electronically-programmed memory capacity � to 64k x 16 bytes from 32k x 8 bytes See also On-Board Diagnostics under Vehicle Environmental Features in the Environmental Protection section. Engine Torque Management Engine torque management is used with 2.4, 3.3 and 3.8-liter engines equipped with the 41TE transaxle to give quicker, smoother shifts than would be possible without this feature. Torque management affects two separate operating conditions: shift torque and stall torque. Sophisticated shift torque management replaces the rudimentary spark advance-based system that was introduced on minivans in 1994. It improves shift quality and enhances transaxle durability. The new system uses a selective fuel shut off to achieve a 50% reduction in engine output torque and a 30% reduction in energy dissipation during shifts. It requires precise interactive communication between the PCM and TCM for successful completion. Stall torque management, which was also introduced on 1991 minivans, protects the transaxle against excessive torque during standing start acceleration with a heavy load, while climbing a grade or when brake- torquing - depressing the brake and holding the throttle open. The PCM controls the engine rpm-to-vehicle speed relationship below 7-8 mph to prevent excessive torque output by retarding the ignition timing. This has virtually no effect on acceleration and does not occur under most driving conditions. Starter Override In light of quieter engines and a quieter interior, the PCM provides a starter override feature that prevents the starter from operating if the engine is already running. This avoids embarrassment caused by the grinding noise and the potential for damage to starter and ring gear. Starter override is standard with all models and all engines. This unique feature, for which a patent is sought by Chrysler, is accomplished through computer logic alone - no hardware is added. Idle-Speed Control The PCM (Powertrain Control Module) determines idle speed on all engines. It actuates a stepper motor and valve in the throttle body to change idle air flow. This valve is also used to fine-tune air flow to avoid engine surge when the air conditioning system compressor cycles on and off. On V-6 engines, a Dual Idle Speed system minimizes idle fuel consumption. These engines idle at 625 rpm in Drive when lightly loaded, that is when the air conditioner or electric rear window defroster are off. This reduces idle fuel consumption by 10%, increasing (Environmental Protection Agency) combined city and highway driving economy by about 2%. Dual Idle Speed software in the PCM monitors engine operation and increases idle speed automatically to 680 rpm if necessary to provide sufficient power to meet air conditioning and electrical system needs. The electrical load compensation feature assures that all electrical requirements are met without draining the battery or resorting to a more powerful, heavier alternator. The idle speed is increased to 680 rpm if air conditioning is on (compressor button pressed) or if electrical system voltage falls below 13 volts. It returns idle speed to the lower value when battery voltage returns to normal. Air Conditioning Compressor Control To enhance vehicle performance when the air conditioning is on, the PCM stops the compressor during wide-open throttle acceleration commencing below a vehicle speed of 20 mph (32 km/hr). Charging and Cranking Systems To provide long battery life, starting capability at -20*F (-30*C), and protection against excessive discharge during storage, the standard battery with all V-6 engines is rated at 500 CCA (cold cranking amps). With the 2.4-liter 4-cylinder engine, a 600 CCA battery is required. Both are maintenance free and protected from life-shortening engine- compartment heat by a molded plastic Thermoguard. With the optional heavy-duty trailer towing package, which places added demands on the electrical system, the battery is rated at 685 CCA. The battery tray is made of strong, corrosion-resistant structural composite material. A 1.6 hp (1.2 kW) reduction-gear starter is used with all engines. A lightweight, compact 90 ampere generator is standard with all engines. It is driven at 2.9 times engine speed to minimize weight while producing the required output. A 120 ampere generator is included with optional heavy-duty trailer towing package, rear air conditioning or fog lights. Chassis Suspension General Information Based on customer inputs, the suspension system features a good ride with low harshness and noise. It also provides outstanding stability on two-lane highways. Ride and handling qualities begin with a rigid body structure which allows the suspension to work without being affected by body deflections. Ride and handling are refined to complement the characteristics of the structure through attention to detail in the calibration of suspension, steering and tires. See also Body Structure in the Body Exterior section. Standard Front-Wheel Drive Suspension The standard suspension is designed to provide ride and handling characteristics suitable for all load and driving conditions. Front suspension is by rubber-isolated MacPherson struts. It is similar in concept to that on previous models with added features to improve isolation and revised geometry. The upper strut mount is larger to provide increased vertical travel and increased fore-and-aft compliance to reduce harshness. A patent was granted for the increased vertical travel feature of the strut mount. The standard 1 inch (25 mm) stabilizer bar is connected to the struts through spherical-jointed links that minimize friction and harshness. Toe and camber specifications were fine tuned during development to provide excellent directional stability over bumps. Ductile nodular cast iron lower control arms have in line rubber isolation bushings to minimize friction. Arm design is asymmetrical, having one bushing opposite the lower ball joint to resist lateral load and the other rearward to cushion impact bumps. Urethane jounce bumpers enhance ride when fully loaded or when negotiating bumps that require full suspension travel. A rubber-isolated cast-aluminum front suspension cross member is the largest major structural member of cast aluminum in a US production vehicle. It weighs about 20 pounds (9 kg) less than a similar design in steel. The isolators are tuned in three axes to control vibration and damp out harshness and noise before it reaches the passenger compartment. The casting has a hat-shaped cross section to which a steel base plate is bolted. The cross member has the natural corrosion protection of aluminum. The base plate is isolated from the aluminum and protected against corrosion by galvanizing and a thick layer of electro-coat paint. Corrosion-resistant fasteners attach the base plate to the casting. On front-wheel drive models, the rear suspension has high strength- to-weight tapered, single leaf springs and a tubular beam axle with track bar. Rubber biscuits isolate the springs from the axle. The track bar increases lateral stiffness to provide a steady ride in the rear seating positions. The short - 27.5 inch (700 mm) - track bar supplements the lateral stiffness of the rubber-isolated leaf springs. Front and rear track are both wider than on prior models, contributing to handling stability. Front track is 63 inches (1600 mm) - 3 inches (78 mm) wider; rear track is 64 inches (1626 mm) - 2 inches (50 mm) wider. Heavy Load/Firm Ride Suspension A Heavy Load/Firm Ride Suspension is available for front-wheel drive customers who consistently carry heavy loads and/or those who desire a firmer ride than the standard suspension. This suspension has 15% higher front spring rates and 18% higher rear spring rates than the standard suspension. Front strut damping on long wheelbase models and rear shock absorber damping on both wheelbases is also increased for ride control. The rear suspension also includes urethane jounce bumpers to enhance ride quality when fully loaded or when encountering bumps that require full travel to absorb. Sport Handling Package A Sport Handling Package is available on front wheel drive models. It includes the same springs, struts and jounce bumpers as the Heavy Load/Firm Ride Suspension. The rear suspension also includes a 0.75 inch (19 mm) link-type stabilizer bar to improve handling. 215/65R16 Michelin MX4 "touring" tires and cast aluminum wheels are also included. See also Tires and Wheels elsewhere in this section. Load-Leveling Suspension Load-Leveling Suspension - self-leveling rear suspension shock absorbers - is standard on all-wheel drive models and optional on front- wheel drive models in premium or luxury equipment levels. Load-Leveling Suspension is available with or without Heavy Load/Firm Ride Suspension. Lower rate springs work with the self leveling shock absorbers to provide the same rate as vehicles without this feature to assure a smooth fully-loaded ride and a "normal" attitude. Vehicle appearance is also enhanced when fully loaded. The new minivans are the first US- built vehicles to use this system. When passengers or cargo are added, these units use normal ride motions that occur during driving, even on very smooth roads, to raise the rear of the vehicle within 0.8-1.0 inch (20-25 mm) of curb height. When the load is removed, the vehicle returns immediately to its unloaded height. Operation of the system is noiseless, simple, highly reliable and requires no driver attention. The Load Leveling Suspension units are self-contained. There are no external sensors, plumbing or wiring. Load Leveling Suspension will be introduced as a running change. All-Wheel Drive SuspensionAll-Wheel Drive front suspension is the same as the Heavy Load/Firm Ride front suspension. Design features affected by this commonization include the tall front cross member that provides for a high-mounted steering rack to clear the rear drive shaft and raised steering arm location on the steering knuckle. The steering rack and steering arms are 2 inches (50 mm) higher than on the previous front-wheel drive minivan. A unique combination of rear suspension components are used with all-wheel drive, including non-isolated multi- leaf rear springs, a unique shock absorber calibration and Load-Leveling Suspension. Increased lateral stiffness of the multi-leaf springs makes a track bar unnecessary. There are no suspension options with all-wheel drive. All-Wheel Drive will be introduced as a running change. Steering A precision, ground-edge valve is used in the rack and pinion steering gear to minimize steering valve hydraulic noise during parking and low-speed maneuvering. The valve also helps give the steering a crisp on-center feel. Steering effort is fine-tuned to balance steering characteristics with vehicle response characteristics. Wider front track allows a sharper turning angle resulting in a 3.4 foot (1.04 m) reduction in long-wheelbase turning circle and 3.0 ft. (0.92 m) in short- wheelbase turning circle compared to 1995 models. Long-wheelbase models now turn in less space than previous short-wheelbase models and new short-wheelbase models are even more maneuverable. Tires and Wheels Tires are larger and wheels are wider than those on 1995 minivans at all equipment levels to improve appearance and handling. The larger tires are consistent with market demand and contribute to car-like appearance. Standard tires with base equipment level are size P205/75R14 mounted on 6.0-inch rims. Most other models ride on newly available P215/65R15 tires with 6.5-inch rims. New 215/65R16 touring tires on 6.5-inch rims are available exclusively on Chrysler vehicles in the minivan market. They are standard on Chrysler Town & Country with LX and LXi equipment levels and are included in the Sport Handling Package. Touring tires have construction, tread design and rubber compounding features that favor handling over ride. Tire construction and tread pattern detail refinements for all tires reduce road noise in keeping with customer requirements. Spare Tire and Jack A full-size spare tire is standard on Town & Country LXi and optional on all other models, which have a compact spare tire as standard equipment. The spare tire is stowed under the cargo floor in both front-wheel drive and all-wheel drive configurations. Under-floor tire stowage is new for all-wheel drive models. A winch operated by the tire lug wrench raises and lowers the tire. The compact scissors-type jack and tire changing tools are stowed in a compartment in the left rear corner of the vehicle for easy access. Brackets to hold the jack are welded to the body structure. The compartment has a latching cover identified by a printed jack symbol. A jacking instruction label is on the back of the cover. Brakes Four-Wheel Anti-Lock Brakes Four-wheel anti-lock brakes (ABS) are standard on all models and equipment levels. The hydraulic unit is further simplified from previous units but provides the same performance and pedal feedback characteristics. Wheel sensors are the same and electronic controls are similar to those used in 1995. To reduce ABS operating noise transmission to the passenger compartment and thereby provide a perception of smoother operation, the hydraulic unit with its motor, pump, solenoids and valves is rubber-isolated from its lightweight cast magnesium bracket which in turn is attached to the rubber-isolated front suspension cross member. The magnesium bracket has a corrosion resistant coating for long life in the hostile underhood environment. Front Brakes Disc brakes with sliding, single piston calipers are standard on all models. Models with 15 or 16-inch wheels have 11.1 x 0.95-inch (281 x 24-mm) rotors; models with 14-inch wheels have 10.2 x 0.95-inch (258 x 24-mm) rotor. All rotors are made from damped cast iron for quiet operation and vented for heat dissipation. Caliper size is common to both applications, only the mounting location changes. Calipers slide on machined guides that are integral with the steering knuckles for light weight. Rear Brakes Rear drum brakes have dual-mode actuation that provides both smooth, consistent dynamic operation and a parking brake with powerful static holding ability. Under dynamic conditions, leading and trailing shoe actuation provides smooth consistent operation. The patented parking brake linkage provides added engagement action similar to that of a duo- servo brake to hold the vehicle on a grade with very low pedal travel and low effort. The cast iron drums are larger � 9.8 x 2.17-inches (250 x 55-mm) � than on prior models with transverse fins and flared inboard flanges to increase their heat capacity. The mechanisms are self adjusting. See also Parking Brake, below. Brake System Actuation A "zero lost travel" power brake booster increases customer confidence in the brake system by minimizing the amount of pedal travel required to achieve brake actuation. This feature had its first Chrysler use in the Dodge Viper sports car. The brake pedal height relative to the accelerator pedal - 2.3 inches (58 mm) - is ergonomically correct for easy transition without allowing the accelerator to be pressed during braking. The pedal pivots on a lightweight magnesium bracket. A conventional tandem master cylinder is recessed in the face of the booster to reduce its underhood space requirement. The master cylinder has one fluid reservoir for both front and rear brakes. A neck on the reservoir makes the yellow filler cap readily accessible. The reservoir includes a sensor that warns the driver if fluid level is low by means of a light in the instrument panel information center. The hydraulic system is split diagonally to provide stopping ability in the unlikely event that one of the two hydraulic systems loses pressure. Parking Brake The parking brake is pedal actuated as in the past, but the pedal is repositioned outboard and forward of the location on prior models to provide more driver foot space for ingress/egress and more room for the driver's left foot when driving. Forward mounting of the pedal is made possible by new parking brake linkage in the rear brakes, and by design of the pedal linkage which reduces pedal travel by 50% yet requires less effort than the 1995 system. A ratchet and pawl mechanism keeps the brake on; a pull handle on the instrument panel releases the brake. Contributing to low pedal travel and pedal height, is a separate ratchet and pawl operated by a torsion spring that automatically adjusts the cable by removing slack each time the brake is released. The new parking brake linkage also allows the use of lighter, less costly cables. Fuel Supply The fuel supply system uses the same 20 gallon (76 L) molded plastic tank for both FWD and AWD applications - an increase of 2 gallons (7.5 L) for the AWD model. The tank is mounted in essentially the same location as on the previous AWD model - under the cargo floor toward the left side of the vehicle. The filler cap is located forward of the left rear wheel A one-piece molded plastic door with integral hinge covers the tethered filler cap. The hinge has a detent to hold the door open while refueling. A fueling interlock is included with the optional second sliding door. It prevents the sliding door from opening when the fuel door is open. Fuel is delivered from the filler neck to the tank through a hose that is clamped to connecting nipples at each end. See also Sliding Doors under Door Systems in the Body Systems section. In keeping with current corporate practice, the fuel supply system is returnless, reducing the amount of fuel vapor that the evaporative emission control system is required to handle. A five-function fuel pump module is installed in the tank. This module includes the electric pump, fuel pressure regulator, fuel reservoir, fuel level sensor for the fuel gauge and a filter "sock". A large capacity main fuel filter is mounted forward of the tank has a conductive plastic housing for long life. It is designed to last the life of the vehicle. Cooling System General Information The standard cross-flow radiator core has a mechanically assembled tube and fin aluminum core with mechanically attached plastic end tanks. This results in a very lightweight cooling module that is resistant to corrosion. A transmission oil cooler is mounted in the left end tank. With heavy-duty trailer towing package, the radiator has brass tubes and copper fins for added cooling capacity. This radiator also includes a higher-capacity in-tank transmission oil cooler. Two fans are used to provide full coverage of the low, wide radiator and air conditioning condenser. The motors are lighter and less costly than previous two-speed units which required additional wiring to provide the second speed. Motor speed is controlled by the PCM (Powertrain Control Module). A molded plastic fan shroud guides incoming air through the full face of the radiator. All system variations includes a conventional remote-mounted recovery bottle. An air dam below the front fascia helps direct cooling air into the radiator. The coolant pressure cap is located on the radiator. The thermostat is vented so that trapped air can escape when the engine is not running. This makes refilling easier than with an unvented thermostat. All coolant hoses are peroxide-cured for longer life. Variable Speed Fans Cooling system fan speed is continuously variable so that fan speed is no higher than required to maintain proper cooling, minimizing fan noise. The lowest operating speed is lower than that provided by previous two-speed fan systems. To vary the speed, electrical power is supplied in pulses of varying width which is modulated by the PCM. In addition, fan speed at startup is increased gradually for a more esthetically pleasing sound. See also General Information under Powertrain Control Module in the Powertrain Electrical and Electronic Systems section Exhaust System With all engines, the exhaust pipe and manifold are flanged and sealed with a gasket for quieter operation than the spherical "doughnut" used on previous models. A bellows-type flexible coupling in the exhaust pipe allows relative motion between the engine and the pipe. This connecting system provides life-of-the-vehicle durability. The exhaust system uses stainless steel for all pipes, the catalytic converter housing, muffler and resonator in common with other corporate vehicles. Extensive development and tuning of the systems along with tighter control of production tolerances has produced quieter, more pleasant sounds with approximately 15% less back pressure than prior systems. Exhaust system mounting follows the concept used on prior models.