The 2.7, 3.2, and 3.5 liter V6 Engines (1998-2009)
The new, all-aluminum, 2.7-liter, dual overhead cam V-6 produces more horsepower-per-liter than any V-6 in its class today. It will appear first as the standard engine in the 1998 Intrepid and Concorde.
The new, all-aluminum, 3.2-liter V-6 produces more horsepower than the current cast iron, 3.5-liter engine. It will power the Intrepid ES and Concorde LXi. A new, all-aluminum, high output 3.5-liter V-6 will produce the most horsepower of any naturally aspirated V-6 on the market today (1998).
Chrysler spent more than $600 million to design this family of engines and will begin production in Kenosha, Wis. and Trenton, Mich. in August 1997.
The new high output 3.5-liter engine is the best performing V-6 available today in terms of total horsepower and torque - more than the BMW M3, Ford Taurus SHO, Lexus GS300, or Mercedes E320. with 250 horsepower at 6600 rpm, 250 pound-feet of torque and a compression ratio of 10.1:1 The high output 3.5-liter also is among the leaders in specific torque and the only one to optimally run using mid-grade fuel.
The 3.2-liter engine produces 220 horsepower at 6600 rpm, 222 pound-feet of torque at 4000 rpm, has a compression ratio of 9.5:1, and uses regular fuel. It is lighter and more efficient than the current 3.5-liter it replaces.
Engineers optimized a combination of components from air intake to tailpipe exhaust to maximize air-flow. All three engines were designed with low induction restriction, a larger throttle body, large intake valves and a large throat area to support the high flow intake port and chamber allowing more air to enter the system. Smooth intake manifold runner surfaces — made possible by using a composite material — eliminate air friction and allow more air to flow through the system.
The size of the exhaust valves and the shape of the exhaust ports, manifold and catalytic converter entrance were optimized for maximum flow exiting the engine. The diameter of the exhaust system pipe was increased to decrease backpressure, allowing more outward flow.
This, along with simultaneous engineering of the intake and exhaust systems, allows for a 20 percent increase in specific output for the 2.7-liter engine. Overall output increased 25 percent over the 3.3-liter engine it replaces.
The single overhead cam 3.2-liter and high output 3.5-liter engines have a three plenum intake manifold design with short runner valves and a manifold tuning valve to regulate the air-flow needed, and a higher lift camshaft for increased air flow. The 3.2-liter produces 220 horsepower and 222 pound-feet of torque using regular fuel.
Economy and Emissions
Fuel economy will improve as much as 10 percent on our new sedans using the new engines, due partly to the use of aluminum and computer simulations to optimize air flow. These engines have the potential to reduce hydrocarbon emissions by 30 percent. They will meet Tier 2 federal emission standards and California's Transitional Low Emission Vehicle (TLEV) standards in 1998. They also will meet California's stringent Low Emission Vehicle (LEV) standards by the year 2000.
The new family of engines was developed faster than any engines in the history of the industry. Development time was cut by 26 weeks by creating the industry's first "paperless" engine, using CATIA-based computer software for predictive modeling and a rapid prototyping process.
Service and reliability
One goal of this engine program was to make them completely "dry," — no oil leaks or even stains on the engine block.
The cylinders are lined with cast iron, with an industry-first process that permanently holds the liner in place and assures proper cooling of the cylinder walls.
The aluminum engine blocks are heat treated to make them stronger than engine blocks made of cast iron. To make the engines last even longer, the crankshafts were made of forged steel rather than nodular iron.
Oil drain passages are cast right into the block to improve lubrication by getting the oil back to the oil pan quickly, even under severe high-speed conditions.
Long and fragile secondary cables, traditionally the weak link in an ignition system, have been eliminated. Instead, individual coils are placed directly above each spark plug. This "coil-on-plug" ignition system, along with spark plugs with platinum tips, provide a maintenance-free ignition system for 100,000 miles.
Traditionally, the weak point in a powertrain is the joint between the engine and the transmission. The tendency is for the engine and transmission to bend in every direction and create unwanted noise, according to Keith Wright, Large Car Manager — Engine Engineering.
"Whenever you design a new engine, you start with the crankshaft, which transfers power from the combustion chamber, where power is created, through the transmission and ultimately to the wheels," Wright said. "Power train stiffness and engine block strength were critical issues early in the program."
In the 2.7-liter engine, for example, Chrysler engineers chose to make the crankshaft of forged steel, rather than cast nodular iron, making it 26 percent stiffer than the current 3.3-liter engine.
Other modifications that contributed stiffness include:
- using six bolts rather than two to secure the main bearing caps to the engine block, including four vertical bolts and two horizontal bolts, to keep the cap from bending and vibrating;
- connecting those main bearing caps together with a structural beam made of die-cast aluminum. The beam doubles as a windage tray, which separates the crankshaft from the oil pan and prevents the crankshaft from whipping the oil like an egg-beater. The whipping process would mix the oil with air and reduce performance. Windage trays are commonly used in racing. The current 3.5-liter engine has a steel windage tray but not a structural beam. The structural beam, windage tray and 6-bolt main bearing caps increase stiffness in the 2.7-liter by 28 percent;
- adding brackets to accessory drives such as the air conditioning compressor, the alternator and power steering to decrease vibration;
- adding reinforcement "ribs" to the transmission case;
- making the oil pan part of the powertrain structure; and
- using a die-cast aluminum transmission collar to bolt the transmission to the oil pan.
Given all the moving parts, engines have a tendency to rotate in a circular motion, what engineers call a coupling effect. That movement was minimized by 27 percent in the 2.7-liter engine, 13 percent in the 3.2-liter engine and 10 percent in the high output 3.5-liter engine. Key enablers include reducing the mass of the pistons by as much as 15 percent and reducing the tolerances (variation) of all rotating components.
Fuel economy: specifics
The 2.7-liter engine has a compression ratio of 9.7:1 (compared to 8.9:1 in the current 3.3-liter engine it will replace); the new 3.2-liter engine has a compression ratio of 9.5:1 (compared to 9.4:1 in the 3.5-liter engine it will replace) and the high output 3.5-liter engine has a compression ratio of 10.1:1. All these engines use knock sensors to assure optimum performance, regardless of the fuel used.
The new intake port improves the control of fuel and optimizes air flow into the combustion chamber, which ultimately means less fuel is wasted.
The speed at which the engine idles was reduced, improving the fuel consumption when the car is stopped at a light or in heavy traffic.
Two durability improvements also improve efficiency. Platinum-tip spark plugs don't erode like conventional plugs and high-voltage secondary coils are connected directly to the spark plugs, eliminating secondary wires that can deteriorate over time. Both steps assure the ignition system fires properly every time for a minimum of 100,000 miles without maintenance.
Electronic exhaust gas recirculation (EEGR) has been incorporated to improve combustion rates, therefore improving fuel economy and reducing hydrocarbon and nitrogen oxides emissions.
Hydrocarbon emissions have been reduced 30%. They will be certified at Transitional Low Emission Vehicle (TLEV) levels — cutting hydrocarbons in half at .125 grams per mile. The standards for carbon monoxide and nitrogen oxides stay the same. The following features contributed to lower emissions:
- Fuel injectors located in the cylinder head to better target how the fuel is sprayed into the intake port;
- The length of the water jacket used to cool the cylinder block was reduced, requiring less coolant to be warmed up when the engine starts and maintaining a higher, more uniform temperature in the combustion chamber as the piston travels down;
- Placing the thermostat on the inlet side to the engine rather than the outlet side to create a more even temperature of coolant during cold starts. Thermostats located on the outlet side tended to release bursts of cool water, momentarily chilling the cylinders and increasing emissions;
- Anodized piston heads (three millimeters thick) lessen the mass of hydrocarbons "trapped" in the crevices in the cylinder, assuring full burning;
- Warming up catalysts faster than before by reducing the mass of the exhaust manifold and placing the main catalysts much closer to the engine;
- Better placement of oxygen sensors to monitor fuel more precisely;
- Using platinum-tip spark plugs that are less likely to have eroding gaps than conventional ones and will last a minimum of 100,000 miles;
- Ignition coils are connected directly to the spark plugs, eliminating secondary ignition wires. This provides robust, maintenance-free, ignition for 10 years and 100,000 miles; and
- Electronic exhaust gas recirculation (EEGR) has been incorporated to improve combustion rates, therefore improving fuel economy and reducing hydrocarbon and nitrogen oxides emissions.