Originally Posted by
Loren
Man, there are so many different ways to approach something like this. A lot of it has to do with what your actual goals are.
Is it a street car? A dyno queen? A show car? Will you actually RACE it? If so, what kind of racing? Drag racing? (yawn) Circle track? Road course? Autocross? Hill climb? Rally?
IMPORTANT: If you're going racing, stop right now! Decide what kind of racing you're doing and start looking at the rule book. Decide what class you want to race in, and what kind of modifications are permitted within that class. It's very easy to modify yourself right out of the class that you could potentially be competitive in and into one that would require a LOT more money and effort.
If I were doing it, it would be just for a fun street car, and I'd want it to mostly be a sleeper. It doesn't need to be crazy fast, just not "slow". HP is just a number on a dyno. Give me torque, responsiveness and drivability. Being a Mirage, some mild fender flares would almost be a requirement, but otherwise... stealth mode.
I also want simplicity and reliability, so... unlike most people, I wouldn't go for a turbo swap. Just some reliable NA power.
Modern engines do amazing things with small displacement, so I wouldn't be looking at anything older than about 2010 for a donor. Part of me would want to stay Mitsubishi, but, really... it's a custom project and there may not be all that much benefit in worrying about it.
I did give this some minor thought when I bought the car. I think I'm mostly over it now since I've decided the platform isn't great for the kind of racing I like to do. (tall, narrow, top-heavy, tippy... and I'm not willing to completely re-engineer the car more than I already attempted to do) The Mirage engine is pretty well-designed, for what it is. It will give you 75-80 hp all day long without complaint and do it efficiently. It is of the 3A9 engine family, which was designed by Mercedes engineers. Cool. There is a related 4A9 engine family. You guessed it, same basic engine, but with 4 cylinders.
So, there's a 4A92 engine that's 1.6 liters, with all the same VVT and other features of the Mirage engine. Of course, I don't think it was ever used in the US market. But, that was one of the first things that came to my mind. It's "only" 115 hp, but I think it would be fun in a Mirage. Super reliable, and still economical.
But, really, what I would want is something that, just like the Mirage engine, is new tech, reliable, economical, lightweight, and is CHEAP and PLENTIFUL on the salvage market.
So, what are there a million of around here that meets all the criteria?
And then... your goals might be different. If you're constantly chasing HP numbers on the dyno, you'll want something with good aftermarket support that responds well to common bolt-ons... and you don't want to have to DESIGN all those bolt-ons from scratch.
It really all depends on what you want to do.
But, back to my dream... I kind of like modern Mitsubishi. I think they've come a long way with design and reliability. But, they're not the most PLENTIFUL in the US. If I'm stuffing an oddball engine into my car, I want it to be something that's literally EVERYWHERE. My first thought there is Hyundai/Kia. They use the same engines in pretty much all of their cars.
Oh, and I want an engine that comes in a car with a proper manual transmission so that I can lift the entire drivetrain (including axles, hubs and brakes) from the same donor car. Bonus points if the hubs are 4x100 to match the Mirage... and all the spare Miata wheels that I have in the garage.
So, FWD Hyundai/Kia, plentiful and cheap. The Hyundai Accent and Kia Rio from 2017+ have the 1.6 liter Gamma engine. VVT, direct injection, all aluminum, etc. And it won awards when it came out in 2012. 138 hp, 123 ft/lbs. 6 speed manual trans. You can find the same engine in the Elantra, Veloster, Sportage, etc. It's an "everywhere" engine.
I think that would be a tidy little "simple" swap into the Mirage. No added complexity of a turbo. Just a simple, reliable, lightweight 4-cylinder that would pretty much double the power and torque of the 1.2 liter Mirage engine.
A Kia Rio weighs around 2700 pounds. So, it would be like putting a Rio on a 700 pound diet... but, you'd still get to keep full interior and air conditioning.
Or, you can go nuts with a much larger engine, turbo, whatever. Just remember, adding more displacement and turbocharging and all that will inevitably add more HEAT in the tiny Mirage engine bay in addition to just trying to "package" it in that small engine bay. Somewhere in there... there's the proper balance of power for the Mirage that won't be a constant pain in the ass.
But, for a "get your feet wet" kind of project... you don't need "all of it". Just "enough of it". You could easily get 100-120 hp from adding boost to the 1.2... and maybe it wouldn't blow up if you tuned it just right. But, dropping in a 1.6 would give you the same power with stock reliability, which would be awesome!
And if you choose the right 1.6... maybe you have the option of swapping to a factory turbo version of the same engine in the future?