1998 Dodge, Chrysler, Plymouth, and Jeep Changes

Engines

3.8 V-6

The 3.8 V-6, long-neglected and used only in top-of-the-line minivans, faced challenges from stronger GM and Ford engines. It now provides another 14 hp and 13 lb-ft of torque, and has lower emissions and better gas mileage. The boost came from better airflow, including ducting, a revised intake manifold, and a 24% larger throttle bore. (Airflow was generally poor among Iaccoca-era powerplants). The heads and combustion chambers were redesigned to raise the compression ratio from 8.9 to 9.6:1.

2.4 Four

A smoother cylinder bore finish and new piston design allowed quicker engine break-in.

V-10 (Viper)

Tubular stainless steel exhaust manifolds replaced cast iron components, saving 24 lbs. A new reduced overlap camshaft resulted in a smoother engine idle and allowed an increased spark advance at idle without compromising emissions.

V-10 (Ram)

Calibration revisions, including outside temperature data input, increased power from 295 bhp to 300 bhp and torque from 425 lb-ft to 440 lb-ft.

5.9 V-8 (360)

A new camshaft added up to 15 bhp and the torque curve was widened to provide more responsive performance in the normal driving range.

5.2 V-8 (318)

In the Grand Cherokee, 15 degrees more spark advance (which requires premium fuel) and a 25 percent reduction in backpressure added 25 bhp over the current 5.2L engine. The cooling fan motor was now electric, eliminating a power drain of up to 20 bhp.

Less pollution across the board

They used to say that reducing pollution meant cutting power. Not true, as shown:

The Viper had new, lighter exhaust manifolds that heated up faster, allowing for quicker light-off of the catalyst. This allowed the engine to burn cleaner earlier in the cycle.
New combustion chambers, smoother cylinder bores, and new piston designs cut emissions by 17% in the 3.8 and by 33% in the 3.3 V-6. (The engines are closely related).
The 2.4 engine's hydrocarbon emissions were reduced by 20% by a new cylinder head gasket and smoother cylinder bore finish.

Car and truck changes

Most car and truck changes for 1998 were designed to reduce noise, vibration, and harshness:

The passenger compartment in the Dodge Ram pickup was quieter due to a completely new interior package that absorbs more sound. Better chassis tuning resulted in reduced body vibration.
A new anti-lock braking system allowed smoother and quieter operation for Chrysler Cirrus and Sebring Convertible, Plymouth Breeze and Neon and Dodge Stratus and Neon.
Improved aerodynamics on sunroof option for Cirrus, Breeze and Stratus reduced wind noise.
A structural transmission collar made of lightweight aluminum was new for all vehicles with 2.0L and 2.4L engines, to reduce noise and vibration at high engine speeds.
A new intake manifold for the 2.4L engine on Plymouth Voyager and Dodge Caravan minimized "rumble," improving the sound quality of the engine.
Added foam in the dashboard, dampers that reduced steering wheel vibration at idle and a refined cowl screen between the hood and windshield reduced wind and road noise in the Stratus and Breeze.
Softer rubber on the exhaust hangers for Neon transmitted less exhaust noise and reduced vibration.