The Mopar 2.2 and 2.5 Liter Engine - Carb and TBI
The 2.2 is one of the most reliable four-cylinder engines ever made, and in all its forms, from under 84 hp to 224 hp, was a long-lasting sturdy piece of equipment (though some years and models required an occasional head gasket). [2.2 liter engine specifications]
The 2.2/2.5 liter engines were originated by engineering genius Willem L. Weertman. He was Managing Engineer of engine design from 1955-62, Assistant Chief Engineer of Engine Design and Development from 1962-76, and Chief Engineer of Engine Engineering from 1976-87. He had a large role in just about everything from the small-block V8s to the 426 Hemi, including the slant six. Another major influence on the design was engineer Pete Hagenbuch, who headed Chrysler's engine performance group and, later, its emissions group. Marc Rozman was involved in tuning and testing; he wrote,
The 2.2L, code named E86, went into sales production in the fall of 1980 for the 1981 model year. We always do a fair amount of testing, especially final calibration checks and durability, before production launch. I was not involved in the early 2.2L performance testing, but we were given this engine to set up [new test cells] since it was one of the new engines and a lot was riding on it being good. Many of the auto reviews done in the fall of 1980 were positive, always a good thing.
The 2.2 was fitted with a carburetor in its earlier years; that gave way to turbochargers with multiple-port fuel injection, or a single throttle-body injector. The most common was the single throttle-body injector, or TBI. The reason both for keeping carburetors as long as they did (and for keeping them on the Omni and Horizon for longer than on other models) and for using single-point injectors was cost; carburetors reportedly cost half as much as the single injectors, and of course four injectors cost far more than one. The downside was lower gas mileage, lower power, and a less competitive vehicle.
The multiple-port fuel injection engines (using four separate injectors rather than just one, firing into the intake ports rather than the throttle body so fuel would stay atomized and time delays would be minimized) did not spray fuel into all cylinders at once, but alternated the injectors to avoid wasting fuel. This allowed the turbocars to avoid the aspirator or air pump.
Pete Hagenbuch wrote:
The throttle-body (TBI) EFI was certainly not anywhere close to port injection, but it gave a better control of the air-fuel ratio than did the trusty old carburetor. In fact, the principal reason we all wanted to get rid of TBI was the number of calibrations which would not have been needed with MP [multiple port] EFI. It was always a cost vs. quality argument and I imagine the decision was made at a much higher level.
If there had been an airflow meter available then, which gave accurate and repeatable measurements we might have been able to sell it to management. With TBI, fuel-air distribution was essentially the same as a carburetor, and a new calibration was needed for every engine-car combination.
Some 2.2 engines were made in China for the local market. In 1987, according to The Truth About Cars, Chinese automaker First Auto Works (FAW) built some Dodge 600 prototypes using imported 600s; they changed the grill, front lights, and hood ornament, and called it the Hongqi CA750F and CA760. Although the article reported that FAW wanted to buy the Dodge 600 line and make them in China, Volkswagen-Audi Group (VAG) offered to provide the Audi 100 design, along with investment capital. FAW did have tooling and rights for the 2.2 liter engine (which was still being made in North America as well), and used it to power their own cars, based on the Audi 100. This 2.2-powered line included a four-door pickup truck, station wagon, standard sedan, and limousine sedan. The 2.2 replaced a weaker Audi engine. (Thanks, George.)
The 2.2 was introduced in 1981 as an all-new design, the first metric Chrysler engine. It was originally built at the Trenton Engine plant, which made the slant six and 440 RB. Though the two have some basic similarities, Pete Hagenbuch, who worked on both engines, wrote that "As far as I know there was absolutely no commonality between the 170/225 engines and the 2.2/2.5." The design philosophy may have held commonality, but not the actual design. See our interview with engine designer Pete Hagenbuch , which covers the 2.2 and other topic, and our interview with Marc Rozman, who covers early 2.2 issues and testing.
There are several different 2.2 blocks. They feature siamesed cylinder bores (no cooling in between), a short crankcase skirt, and partial open deck; it was designed to be machined by milling to achieve lighter weight, but uses a cast iron (rather than aluminum) block because aluminum technology at the time was not what it is now. The oil pump is mounted internally. High performance versions, such as the Shelby engines, have modifications such as .8 mm milled off the top of the deck surface. Even on the 225 horsepower 2.2 Turbo III version, the engines had a timing belt. One of the engineers explained: "I always hated belts, but the weight penalty for chains was as big a factor as cost." Oil sealing was also a factor. 2.2 liter engines are all noninterference designs, so they generally are not damaged when the timing belt breaks.
The early 1981-83 blocks weigh about 87 lb; the turbo block weighs about 90 lb. A special racing block (96 lb) was designed for IMSA racing, before the turbo block was available and before a Champion RS series rule change made the 2.2 noncompetitive.
Pistons are aluminum with steel struts, and rings are iron. Different years and engines (e.g. turbo I, turbo II) used different pistons. Mopar Performance sold a heavy duty oil pump for most of the 2.2's life, which can be handy in high performance situations.
The 2.2 liter engine was originally to be 2.0 liters, but the K-cars needed extra power, so the engine was enlarged during the development. Priority was given to moving exhaust heat to the floor of the intake manifold, underneath the carburetor, to warm it up more quickly and get better cold responsiveness; the carburetor was moved as far back as possible to make it safer during a front-end impact, and also to make assembly similar to the 1.7 liter Volkswagen engines already used in the Omni and Horizon. This move made the spark plugs and oil filter easier to change. The distributor, belt adjustment, and power steering pump were also easy to access (reference for this paragraph: Chrysler Engines, 1922-1998.)
Carbureted models used a staged two-barrel carburetor, a Holley Weber design. Feedback units were used on domestic (American) cars, usually a model 6520 carb. Some Canadian and Mexican cars used a Holley Model 5220, staged nonfeedback dual venturi carburetor.
The 2.2 engine was brought out in 1981, and used an electronic feedback carburetor (except on turbocharged models); Chrysler phased in single-point, throttle-body fuel injection starting in 1985 (Laser, Lancer, LeBaron and LeBaron GTS, and Caravelle), with every car except Omni/Horizon and Turismo/Charger using fuel injection in 1986, and the final conversion, of the L bodies, in 1988. The electronic fuel control system on carbureted engines measured engine speed and load, starting condition, coolant temperature, throttle (open or closed), ambient air temperature, and output from the oxygen sensor to control ignition timing and adjust the air-fuel mixture at the carburetor. Engines with the 2.2 cut fuel during deceleration for better gas mileage, using a solenoid-controlled valve that opened during deceleration to allow more air into the idle system; it was also used to prevent “dieseling.”
Carburetors had one major advantage over fuel injectors: they cost far less, despite their growing complexity. They could not provide the emissions control of fuel injectors, though — even when just one fuel injector was used. Unfortunately, Chrysler was spending as little as it could on emissions controls; had the company used multiple point fuel injection from the start, its powerplants would have had more power, better gas mileage, lower emissions, and better responsiveness and idle quality, attracting more praise and more buyers. As it was, later TBI models were frequently dismissed by auto journalists as relics, despite their attractive pricing and, often, their advantages over Japanese and other domestic models.
The fuel injection systems were controlled by a pair of computers, the Logic Module and Power Module (these would eventually be combined); the logic module controlled ignition timing, the air/fuel ratio, emissions control devices, and idle speed, while the power module translated the logic module's demands for air/fuel ratios and timing into signals sent to the fuel injector (altering the length of its pulse) and the distributor. Input from the knock sensor allowed the computers to retard timing as needed to avoid damage to the engine with (for example) low-octane fuel (on turbocharged engines, engine knocking was dealt with both by reducing boost and by retarding timing for the knocking cylinder — and only that cylinder). The logic module was adaptive — it could compensate for changes in operating conditions, including altitude changes (this had been introduced in 1982).
The system could tolerate up to 10% ethanol. In 1984 it used fuel at 36 psi, passing through a small screen, with a pressure regulator mounted to the throttle body, downstream of the injector; the regulator used a spring-loaded diaphragm to uncover the fuel return port, returning excess fuel to the tank. Multiple-point injection systems used 55 psi in 1984, with injectors pulsed in pairs. The multiple point system included a fuel cutoff when the engine hit 6,650 rpm, which would return fuel at 6,100 rpm. It had a limp mode that limited the engine to 2,000 rpm when the MAP sensor failed completely or the wastegate failed to limit boost.
The system included an air conditioner cutout, so that under heavy acceleration, the air conditioning compressor would be shut off, providing more power for acceleration.
1986 saw a new “fast-burn” cylinder head that helped the air/fuel mixture to swirl from the ports (as illustrated below) for better combustion.
Dyno tester Ed Poplawski wrote, “I worked on this a little bit. We ran Fast Burn heads on the 2.5L and the big advantage that I remember was that with the Fast Burn head, wide open throttle spark timing was lower than with the standard head, so you didn’t have to worry about spark knock too much and you didn’t need premium fuel. That made a big difference for the turbocharged engine.”
The 2.2 ranged in power over its life. In 1985, the carbureted version was rated at 96 hp (but only 119 lb-ft of torque). The fuel injected version started out at 99 hp / 121 lb-ft, with a high output version (for the 2.2 Charger, etc) at 110 hp and 129 lb-ft of torque. The 2.6 had more torque but comparable horsepower. The 2.5 started out at 100 hp and 136 lb-ft of torque, comparable to the 2.6, and would stay at roughly that power output through its life (except with a turbocharger fitted).
|1982 2.2||1985 2.2||1986 2.2||1986 2.2 Turbo I|
|Displacement||2213 cc||2213 cc/135 CID||2213 cc||2213 cc|
|Compression ratio||8.5:1||9.0: 1||9.5:1||8.1: 1|
|Horsepower||84 hp @4800||99 @ 5600||97@5200||146 @ 5200|
|Torque (ft/lb)||111 lb-ft @2,400||121 @ 3200||122@3200||170 @ 3600|
|Bore/Stroke||3.44" x 3.62"|
|Coolant Capacity||8.5L (9.0 qts.)|
|Fuel Recommended||Regular||Regular||Regular||Premium (91 octane)|
|Mileage (Aries stick)||29/41||25/35|
More details on the 2.2 and 2.5 blocks
James Corrigan wrote: The 2.5 has a deeper stroke than the 2.2, the 2.5 has a bigger crankshaft with a bigger throw. Basically this means if regular length 2.2 pistons were used with 2.5 crank, the pistons would pop out the top of the regular 2.2 block. So what Ma Mopar did in '86-88 was to build the tall block, basically a 2.2 block but with a higher deck so the pistons won't pop out the top. The 1989 and newer common block is the most durable, but at naturally aspirated (nonturbo) power levels it won't make much difference.
Chrysler common block
Starting in 1989, all 2.2 and 2.5 liter engines, including the Maserati-built 2.2 used in the Chrysler TC by Maserati and the longitudinal engine in the Dakota, used the same engine block. This saved money and gave base engines a stronger block; so starting in 1989 the engines had stronger main bearing supports and caps, thick cylinder walls, balance shafts (on the 2.5 and late turbo 2.2), and cross drilling between the cylinders. Without a lengthened deck, the 2.5 liter engine maintained its displacement with a shortened piston.
The new block was not as high as the 2.5. Casting details were added to increase rigidity and integrity. An acoustical oil pan was added on all passenger car versions of the 2.2 engine, cutting noise; the 2.2 pan had a deep sump for uninterrupted supplies of oil during rapid cornering, braking, and acceleration (this was originally to be used only on turbo models). Crankshafts for all four cylinder engines were designed to use the old 2.5 engine's front seal and retainer; crankshafts were still cast, except on the forged Turbo II (and, later, Turbo III and IV). All engines also now used the old 2.5's camshaft and accessory shaft drive belt and sprocket system, with rounded teeth; a new water pump was driven from the back of the alternator Poly-V belt, increasing traction.
Along with the common block, the 2.5 liter throttle-body engine gained new, lightweight strutless aluminum pistons in 1989; these allowed for a much lighter counterweight.
An acoustic cylinder head was set up as a running change on throttle body models; turbocharged engines already used an aluminum cylinder head cover with better acoustic quality.
Performance and repairs
Mopar Performance used to list a supercharger for the carbureted 2.2 engine (P4349478). Development work was done at the Caroll Shelby Performance center, and it was manufactured by B&M (whose part number was 90601). Dealer cost on this in 1987 was $1400! It made 130hp@5200 rpm with the stock carburetor; with the Weber (PN P4349300) it jumped to 155@5200 RPM; by comparison the standard Turbo II package reached 174 hp, though presumably the supercharger built up power earlier and more gradually. (Thanks, Marc Medina!)
Chronology (courtesy of Aaron Karpinski, some additions by the Webmaster)
We’ve moved out most of the turbo information to our 2.2 / 2.5 turbo engine page.
1987 Slider Cam specs (courtesy Ed Treijs)
|2.2 Standard||2.2 Turbo||2.5 TBI|
|Intake opens (BTDC)||16||10||12|
|Intake closes (ABDC)||48||50||52|
|Exhaust opens (BTDC)||52||50||48|
|Exhaust closes (ABDC)||12||10||16|
* This might be a typo in the official guide; it might be 244.
2.2 - 2.5 engine pages