If you're tired of that massive hunk of lead taking up all the room in your engine bay, an evo 8 battery relocation is probably the next big project on your list. Let's be real, the stock battery in the Lancer Evolution VIII is huge, heavy, and sits in one of the most inconvenient spots possible. If you've ever tried to work on your intake or install short-route intercooler piping, you know exactly what I'm talking about. It feels like Mitsubishi designed the car and then realized at the last second they forgot the battery, so they just shoved it right in the way of everything useful.
Moving that battery isn't just about making things look pretty, although a shaved and tucked engine bay is definitely a vibe. It's mostly about functionality. Once you get that heavy plastic tray and the group-size battery out of there, you suddenly have all this real estate for things that actually make the car faster.
Why everyone ends up doing this
The most common reason I see people tackling an evo 8 battery relocation is to make room for a short-route intercooler pipe. The factory intercooler piping on an Evo 8 is well, it's a bit of a maze. It snakes all over the place, which creates more volume for the turbo to fill up before you actually feel the boost. By relocating the battery, you can run a pipe directly from the intercooler up to the throttle body in a much straighter line. This sharpens up throttle response and makes the whole setup way more efficient.
Beyond the piping, there's the weight distribution factor. The Evo is already a bit nose-heavy, as most all-wheel-drive turbo cars are. By taking 35 or 40 pounds off the front left corner and moving it to the trunk—specifically over the rear wheels—you're helping the car's balance. It might not turn you into a pro time-attack driver overnight, but every little bit of weight transfer helps when you're carving through corners. Plus, it just makes the engine bay look ten times more professional.
Choosing your new battery location
Most people decide to put the battery in the trunk, usually on the passenger side. This is the classic "diagonal" weight distribution trick. If the driver is sitting on the front left (in US models), putting the battery in the rear right helps even things out.
Some guys try to get fancy and put it under the car or in a custom bin, but for an Evo 8, the trunk is the path of least resistance. You've got plenty of room back there, even with a trunk bar or a small sub, and it keeps the battery away from the heat of the 4G63. Heat is a battery killer, so getting it out of that scorching engine bay can actually help your battery last a lot longer.
What you're going to need for the job
You can buy a pre-made kit for an evo 8 battery relocation, or you can piece it together yourself if you're a bit of a DIY nerd. If you go the DIY route, don't cheap out on the wires. You're going to need a thick gauge power cable—usually 0 or 2 gauge—to run from the trunk all the way back to the starter and fuse box. Because the cable is so long, you lose a bit of voltage along the way, so using thin wire is a recipe for a car that won't start on a cold morning.
You'll also need: * A sturdy battery box or a tie-down bracket. * A high-quality circuit breaker or a massive inline fuse (near the battery). * New terminals and lug connectors. * A distribution block for the engine bay. * Grommets for where the wire passes through the firewall.
Safety is huge here. You're essentially running a "hot" wire through the entire cabin of your car. If that wire rubs against a sharp metal edge on the firewall and shorts out, you're going to have a very bad, very fiery day. Always use a fuse or breaker right at the battery source and make sure you use plenty of loom and grommets.
The installation process and the "fun" parts
Actually doing the evo 8 battery relocation isn't incredibly difficult, but it is time-consuming. You'll be ripping out the back seat, pulling up the carpet, and trying to find the cleanest path to snake that thick power wire through. Most people run it along the door sills on the passenger side. It stays tucked away and protected there.
The trickiest part is usually the firewall. You have to find a spot to drill or an existing grommet to push through. Once you're in the engine bay, you'll need to mount a distribution block where the old battery used to be. This is where you connect the new power wire to the car's existing electrical system.
Grounding is another thing that people mess up. Don't just run a tiny ground wire to a random bolt in the trunk. Scrape the paint off to bare metal and use a solid chassis ground. If your ground is weak, your car will struggle to crank, and you'll be scratching your head wondering if your alternator is dying when it's really just a bad connection.
Dealing with battery fumes
If you're using a standard lead-acid battery, it's going to "off-gas" hydrogen. In an open engine bay, that's fine. In a sealed trunk? Not so much. That's how things explode. If you're sticking with a standard battery, you must use a vented battery box that has a tube leading outside the car.
Better yet, just upgrade to an AGM (Absorbed Glass Mat) battery or a dry cell like an Optima or an Odyssey. These don't off-gas in the same way and are much safer for interior mounting. They're also usually smaller and can handle the vibrations of a modified Evo much better than a cheap parts-store special.
Maintenance and long-term thoughts
After you finish your evo 8 battery relocation, you might notice the car cranks just a tiny bit slower than it used to. That's the "voltage drop" I mentioned earlier. As long as you used thick enough wire and have solid grounds, it shouldn't be an issue. But it's something to keep an eye on.
One thing I love about having the battery in the back is how much easier it is to jump-start the car—or jump-start someone else. You don't have to nose your car in and worry about your front bumper getting scratched; you just pop the trunk.
Also, once that battery is gone, you'll realize how much dirt and grime was hiding under the factory tray. It's a great time to grab some degreaser and a wire brush to clean up that corner of the engine bay. Maybe even throw some touch-up paint on there if the old battery acid has started to eat away at the finish.
Is it worth the hassle?
Honestly, yeah. An evo 8 battery relocation is one of those "rite of passage" mods for Evo owners. It opens up the engine bay, improves the look of the car, and allows for better performance parts. It's a bit of a project that takes a full Saturday to do right, but the first time you look into that cleaned-up engine bay and see your intercooler pipe sitting pretty where a giant battery used to be, you'll know you made the right call.
Just take your time with the wiring, double-check your fuses, and make sure that battery is bolted down tight. The last thing you want is a 40-pound weight flying around your trunk when you're hitting the local track or a backroad. Once it's done, you'll wonder why you didn't do it years ago.