The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support RTM Racing
Please Support Rix Racing

420A 420a easy power?

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Aside from nitrous use, I wouldn't use "easy" and "power" in the same sentence about a 420A. The easy spectrum would include typical bolt ons such as:
- Cookie cutter exhaust headers
- "cold" air intakes
- Ignition coils/cables
- and crankshaft pulleys.
None of which make a huge difference alone, and even the conjoinment of them wouldn't add much power. Aside from the cylinder head being a restrictive factor, the stock ecu is unable to advance ignition timing above a certain value- which happens to be quite low at only 6 degrees of timing. It is also unable to recognize increased airflow at the MAF to add fuel accordingly. If I were to build another 420A, MegaSquirt would be my very first upgrade (aside from any overdue maintenance). Though this isn't necessarily easy or cheap, it will be the single best upgrade on your journey. And a great opportunity to learn a new skill.

MegaSquirt aside, here's my recommendations. Don't waste your money or time on cookie cutter bolt ons, not yet. Start with getting a 60mm throttle body. I actually have an extra that needs to be modified. Message me if interested in that, but you'll also need to bore the plenum opening to approximately 58-59mm. Doing this will remove some of the 420A's airflow restriction. I still had the stock computer installed when I performed this modification for the first time. This will greatly increase throttle response. I'm sure no one has researched this modification on a dyno or a flow bench, but the result speaks for itself. This isn't hard to do, but will take time and patience. A proper plenum porting could take a few hours.

The next most effective modification I found was raising compression ratio. But we're talking about a full engine rebuild here. Either with forged pistons, shaved cylinder head, semiflat valves or all of the above. This improves horsepower at every rpm. I would only consider this "easy" if you're experienced with building engines, though the 420A is not very complicated.

This is not to say that the basic bolt ons are useless or unnecessary. Each one shines in a specific scenario. For example: the exhaust header. Bolted up to a stock engine, it won't do much in terms of power gains. It is shiny though. Now: bolted up to an engine with oversized valves, high lift camshafts, and efficient intake: it's the very modification you need to ensure that the exhaust is not a restriction! Remember, the engine basically  is an airpump. The ability to evacuate more air is helpful if the intake has also been increased. Otherwise you risk slowing air velocity, which is counteracting.
 
I'll never be the person to advise selling it and getting a turbo model. But I will say that an equal investment in a 4g63T engine build will indefinitely produce better results. In fact I greatly enjoying tinkering with 420A's, and researching ways to improve their performance. But we're yet to see a 420A equipped Red Demon
after all :beatentodeath:
 
Well porting definitely isn't out of the question, I've got plenty of experience rebuilding it wouldn't be hard just time time consuming. And easy is a general term just modifications with proven results.

I've considered just buying a tsi or gst/x but everything is clapped out and expensive so not even worth it

Start with getting a 60mm throttle body. I actually have an extra that needs to be modified. Message me if interested in that, but you'll also need to bore the plenum opening to approximately 58-59mm. Doing this will remove some of the 420A's airflow restriction. I still had the stock computer installed when I performed this modification for the first time. This will greatly increase throttle response.
What throttle body are you using? 60mm off of what?
 
Last edited by a moderator:
What throttle body are you using? 60mm off of what?
It's from a 4.0L Mopar Jeep engine. We use this because it shares the same IAC and TPS as the 420A. I have an extra in good condition, it just needs the throttle shaft swapped over and bolt holes expanded.
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top