The Chrysler-Plymouth-Dodge 2.5 liter Trans Four engine
The 2.5 liter engine was the last gasp of the slant six era of engine design. With its long stroke, single fuel injector, and low performance - high durability design, the 2.5 provided better low end power and more torque than most competitive engines. It was also larger than most engines with similar power outputs.
A 2.2 liter engine with a longer stroke and balance shafts, the 2.5 was only available with fuel injection. It was smoother and quieter than the 2.2, and had more power at the bottom end. However, with its long stroke and balance shafts, it was not well suited to high performance applications. The 2.5 turbo engine was not supported for long.
The design of the 2.5 may have been influenced by the Mitsubishi 2.6, which also used balance shafts.
Dan Stern reported that the Slant Six and 2.2/2.5 liter engines were both products of the engineering genius of (amongst other people) Willem L. Weertman. He was Managing Engineer--engine design from 1955-62, Assistant Chief Engineer--Engine Design and Development from 1962-76, and Chief Engineer--Engine Engineering from 1976-87. This means he also had a large role in just about everything we love, from the Slant 6 through the LA engines on up through the Hemi. They pulled him out of retirement for the V-10 projects.
The following information (after repairs) is from the 2.5 as it stood in the 1995 Dodge Spirit. It was similar through its life, with some notable changes to help sealing and emissions. The 2.5, its fuel system, and its intake/exhaust system were close to identical in every vehicle it was in: the Shadow/Sundance, Daytona, Dakota, Caravan/Voyager, Spirit/Acclaim, etc.
(The 2.5 liter Chrysler engine is easily confused with the 2.5 liter AMC engine used in Dodge trucks through the 1990s; the latter can be easily differentiated in most years by its sequential-point fuel injection and greater power. The AMC engine was not turbocharged.)
Most repairs are covered on our central repairs and troubleshooting page. However, we do have a collection of odds and ends on our 2.2/2.5 liter repairs page. Also, one reader noted that the timing belts differ between the 2.2 and 2.5, and byyear, with the earlier engines having a square-notched timing belt.
2.5 Liter Engine Specifications
|Displacement||153 in3 (2500 cm3)|
|Bore x Stroke||3.44 x 4.09 (87.5 x 104)|
|Valve System||SOHC, 8 valves, roller followers, hydraulic lifters|
|Fuel injection||Throttle body, electronic|
|Construction||Cast iron block, aluminum alloy heads,
counter- rotating balance shafts
|Power (SAE net)||100 bhp @ 4800 rpm|
|Torque (SAE net)||135 lb-ft @ 2800 rpm|
|Max. Engine Speed||5950 rpm|
|Fuel Requirement||Unleaded regular, 87 octane|
|Oil Capacity||4 qt. (3.8L)|
|Coolant Capacity||9.0 qt. (8.5L)|
|Emission Controls||3-way catalyst, heated O2 sensor,
engine modifications, EGR
|EPA Fuel Economy (mpg city/hwy)||27/33 (In a 1993 Sundance 5-speed)|