The Eclipse 420A engine (also known as the Chrysler 2.0L DOHC engine) was commonly found in the Mitsubishi Eclipse, as well as the Dodge Neon and Dodge Avenger vehicles. It is a non-turbocharged 4-cylinder engine. While the 420A is a capable engine, it's important to consider both its strengths and limitations when deciding whether it's worth building for power.
Strengths of the 420A Engine:
Relatively Robust Bottom End: The 420A has a decent bottom end that can handle moderate power increases, especially when properly tuned and supported with quality parts.
Availability of Aftermarket Parts:
There is a significant aftermarket for the 420A engine, with CI Motorsports being the leader in this platform, with performance parts like pistons, cams, valves, and turbo kits.
Cost-Effective Build:
Compared to more expensive engines like the 4G63 (Eclipse GS-Turbo engine), building the 420A can be a more budget-friendly option, especially if you're doing the work yourself.
Potential for Turbo Conversion:
The 420A engine can be turbocharged with the right supporting mods, and many enthusiasts have successfully built turbo setups, achieving reasonable power gains.
Weaknesses/Limitations of the 420A:
Lower Performance Potential: The 420A is not inherently designed for high horsepower. It lacks the strength and capability of turbocharged engines like the 4G63 or modern turbo 4-cylinders. As a naturally aspirated engine, it can only be built up to a certain power level before reliability becomes an issue.
Weak Cylinder Head:
While the bottom end is relatively strong, the cylinder head can be a limiting factor. It doesn't flow as well as other performance-oriented engines like the 4G63, which limits its power potential. Aftermarket heads or porting can help, but it's still a weaker aspect compared to some other engines in the same class. This is were we come in. CI Motorsports can make most of the power gains with cylinder head porting and using oversized valves. Add on a custom bored CI Motorsports 55mm throttle body and your picking up an easy hp gains.
Crankshaft and Piston Limitations:
The 420A's internals, particularly the pistons and crankshaft, are not built to handle extreme boost or nitrous. Stock pistons can handle a max of 7psi, with some cases 10psi but the engines wont last long. Aftermarket Wiseco forged pistons and Eagle forged rods are the solution to this problem. The only limiting factor at this point becomes the factory crankshaft which Chrysler has stated can hold 500hp out of the box. We have several customers pushing upwards of 600hp on stock cranks without issue on their daily drivers.
Limited Turbo Potential:
While turbocharging the 420A is possible, it will require careful attention to tuning and supporting mods, such as a stronger fuel system, better cooling, and stronger internals. Unlike a turbocharged engine designed for high power (like the 4G63T), the 420A has a limited margin for error when pushing high boost levels. It is crucial to find a good tuner who can work with the 420a platform and preferably a Megasquirt ecu.
Reputation and Community:
The 420A doesn't have the same extensive aftermarket support or tuning community as engines like the 4G63 or newer turbocharged engines, which might make it harder to get the best performance from the engine.
Conclusion:
The Eclipse 420A engine can be worth building for power if you're looking for a budget-friendly, moderate-performance build. With proper turbocharging and supporting mods, you can make anywhere between 250-400 hp reliably, but beyond that you will need extensive tuning and fuel modifications to support the power levels. Reliability declines after 500hp in our opinion with this platform. It is best suited for a build with a goal of moderate performance rather than extreme power levels.
If your goal is to push for high horsepower (400+ hp), then other engines with a higher base performance, like the 4G63T (from the turbocharged Eclipse GS-T), might be a better option. However, if you're prepared to spend on performance upgrades and are realistic about the engine's limitations, the 420A can still provide a fun and engaging power build.
Don't forget, we are the 420a engine experts so if you have any questions feel free to reach out to us!