The 2.4 Liter PowerTech Four-Cylinder Engine
This page assembled from Chrysler press materials; minor modifications have been made to the 2.4 for use in different vehicles. If you would like information on boosting its performance, visit PTCruizer's performance section.
The 2.4 entered production in December 1994 for minivans and cloud cars with the four speed automatic transmission. In 2002, it was titled "PowerTech" in the Jeep Cherokee. It was slowly replaced by the 2.4 liter World Engine, from 2008 to 2010 being used solely in the PT Cruiser; the engine is projected to stop with the PT. The turbocharged version was dropped completely at the end of the 2009 model year.
The 2.4 liter turbo engine
A turbocharged version of the 2.4 liter engine was already used in Mexico at the time the PT Cruiser GT started development; but the Mexican and American turbo-fours were apparently developed independently (thanks, Paul Holmgren).
While the turbo-four engine was used in the Neon SRT4, Chrysler engineer Garry W. McKissick said it was created for the PT Cruiser GT. They were at first going to do a supercharged engine, but in the end used a turbocharger with a charge air cooler (usually referred to, loosely, as an intercooler). The main difference between GT and SRT versions was the intake manifold, engineered in both cases to fit within the underhood area’s tight constraints; the SRT group created their own intake. The development of the engine is detailed in this SAE paper.
The 2.4 turbo in the Neon SRT-4 (0-60 in 6 seconds, stock!) produced 215-235 horsepower and 245 lb-ft of torque. The same engine is used in the PT Cruiser GT (215 hp 2003-2005; 230 hp and 245 lb.-ft. from 2006 onwards), where 0-60 times came in the low-to-mid 7s, because the greater weight of the PT. It had forged C70-steel connecting rods supplied by Mahle.
The 2.4 turbo was superceded by a 2.4-turbo World Engine with 300 hp.
Hector J. Vega wrote:
This is a summary of the reports published by Automovil, Motor y Volante, and El Norte in Mexico. The test was performed at 2,220 meters (over 6,000 feet) above sea level. Far better performance is expected at lower altitudes.
Power: 215HP @ 5600 (later went up to 235 hp)
Torque: 224lb/ft @ 3200
Transmission: 4 spd automatic (in the SRT-4 and PT -GT, five-speed stick)
Gear Ratios: 2.84/1.57/1.00/0.69
Final drive ratio: 3.91:1
Max. Speed: 217 km/h (135mph) electronically limited
0 - 100 Km/h (0 - 62mph) : 8.13 sec. (average from the 3 tests)
1/4 Mile: 15.89
Comments include: "Turbo lag is present in the low RPM range" (Automovil). "Engine's response is explosive once the turbo spools up to the point that traction control is almost needed" (El Norte)
Common 2.4 liter engine repairs
TWX wrote that in his 1997 Dodge Stratus, his oil light would come on and he'd get a single drip of oil when he parked. He concluded his oil pressure sending unit was bad and dripping out the bottom; the part was only $10, but the location wasn't listed in the manual. It was on the back side of the engine, high up, above the CV shaft. It was difficult to reach. “I found it difficult getting a tool on to the device once I had the electrical harness off, and ultimately I ended up having to use the socket (1 1/6" deep, six point if I remember correctly), a swivel head adapter, a two inch extension, and a 1/2" drive ratchet. There wasn't a lot of room to work, and the wiring harness blocks viewing the connector fairly well; a flashlight is a must for this job. ... The oil pressure sending unit sits high enough that oil doesn't need to be drained to do this.”
“piece-it pete” sent Chrysler rep Steven’s note: “The 2.4 Liter (148 cu. in.) in-line four cylinder engine [has] hydraulic lash adjusters. The engine is free-wheeling; meaning it has provisions for piston-to-valve clearance. However valve-to-valve interference can occur, if camshafts are rotated independently.”
The 2.4 in general
The 2.4 liter Mopar engine is similar to the 2.0-liter Neon engine in design and construction, but has a longer stroke, a taller block, a dual overhead camshaft cylinder head and dual counter-rotating balance shafts that reduce engine vibration. The 2.4 has a high compression ratio, (9.4:1) and knock sensor. Along with the 2.0 liter engine, it has a partially open deck, bedplate, powdered metal connecting rods, crankshaft design, sealing features, fuel injection system and direct ignition system.
The 2.4 far surpasses the previous Chrysler 2.5-liter SOHC engine in power and torque. Ratings for first-generation Cirrus/Stratus/Breeze versions of this engine are (using regular gas):
Power @ rpm -- 140* bhp (104 kW) @ 5200
Torque @ rpm -- 160 lb-ft (217 kW) @ 4000
Dimensions in inches (millimeters)
Displacement --148.2 cubic inches / 2429 cc
Bore x stroke: 3.44 (87.5) x 3.98 (101) (.87 ratio)
Block length x height -- 16.43 (417.3) x 9.36 (237.8)
Rod length -- 5.94 (151)
Connecting rod L/R -- 2.99
Compression ratio -- 9.4:1
2.4 liter engine: Heads
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 with removable caps that are machines in the head base material. 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 balance against the conflicting need for high air flow to obtain high power output.
Made of die cast aluminum, the cylinder head cover features an isolated mounting with an 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.
The one-piece, cast aluminum intake manifold used on first-generation cloud cars has a runner length of 15.7 inches (400 mm). The intake manifold combines tuned individual runners for each cylinder with an integral plenum chamber. Made of thin-wall cast nodular iron, the exhaust manifold has a four- into-one runner design. The four-bolt outlet flange mates with a sealed flex coupling flange on the exhaust pipe.
Later vehicles used a plastic intake manifold. The PT Cruiser has a unique intake designed to fit within the confines of its teeny engine compartment.
Valves (standard, non-turbocharged, early-introduction version; turbo engines are different)
Dual overhead camshafts actuate four valves per cylinder. Valve diameters are 1.40 inch (35.5 mm) intake and 1.20 inch (30.5 mm) exhaust. All valves have 0.24 in. (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 20 mm roller cam follower to reduce low speed friction and cam wear. Rockers pivot on inboard-mounted, fixed hydraulic lash adjusters. Barrel-shaped single valve springs provide control of valve actuation to 7200 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).
Camshaft drive is similar to the 2.0-liter SOHC engine but the intake and exhaust cams have separate drive sprockets. A three-piece molded plastic cover, with inspection plate, completely encloses the belt to prevent damage from foreign matter.
Pistons and rods
Cast aluminum, single-size pistons have pop-up tops with valve cut outs allows broken-belt valve clearance. Piston pins are held in place by press fit to the connecting rods, which differ from those in the 2.0 liter engine only in length.
Cast of nodular iron, the lightweight crankshaft has eight counterweights and a 75 percent balance ratio. Counterweights straddle each crank pin to balance the bearing loads for smooth, quiet operation. Counterweights straddling each crank pin also allow smaller, narrower bearings. Smaller diameters reduce friction and, therefore, increase fuel economy and power. 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.
The 2.4-liter engine operates very smoothly because of a system of counter-rotating balance shafts which counteract second-order unbalance, the predominant reason for 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 rest 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.
The camshafts need no bearing inserts. They operate directly in the cylinder head. Main and rod bearings have bi-metal inserts.
The powdered metal gerotor oil pump mounts in the front of the block and is driven by the crankshaft.
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 clock. The crankcase is ventilated through and opening on the left side of the head. Oil capacity is 4.5 quarts plus filer. SAE 5W-30 oil, grade SG/SH is recommended. A half-quart oil filter mounts horizontally to an extension of the oil pump body providing easy access for service.
The oil pan is stamped of a sound-deadening metal-plastic-metal laminate material to minimize transmission of noise. A windage tray, integral with the oil-pan gasket, minimizes aeration of the oil.
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. The thermostat, radiator nipple, cooling system filler neck and overflow nipple are combined in a single unit.
The returnless, sequential multi-port injection (SMPI) uses four dual-spray injectors to provide balanced fuel delivery to all cylinders. Sequential injection improves throttle response and overall driveability compared to single-point injection. The returnless fuel injection system, which is similar to that on the 2.0-liter engine, is less complex than customary systems.
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.
The 2.4-liter engine features a direct ignition system (DIS), without a distributor.
The PCM determines idle speed. It actuates a stepper motor and valve in the throttle body to change idle air flow. An idle speed control sensor has been added to signal loads from the power-steering system. A switch on the power steering high pressure hose detects an increase in hydraulic pressure from steering action and increases idle speed when the steering wheel is turned.