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Vancouver, WA


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2007-2013 Mazdaspeed 3 51r Battery Box

Price: $199.99
Price in points: What are Points?200 points
Mazdaspeed 3 51r Battery Box. Easy to use design allows the front and top to open to gain access to the battery and ECU
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CorkSport is proud to offer the first complete solution for your (up to) 4” intake, 51R battery, and ECU all in one clean enclosed package. Don’t settle for an engine bay full of loose wires, unprotected battery terminals, and an increased chance for corrosion. The CorkSport 51R ECU Relocation Box provides a clean setup relocating your ECU inside the box while providing ample clearance for your 51R battery and (up to) 4” intake. Manufactured from ABS plastic for an OEM fit, finish, and durability. #ZoomZoom!

Read The Blog4 inch Intake and a Clean Engine Bay? The CorkSport 51R Battery Box & ECU Relocation is NO Compromise

Check out the installation instructions below. Share your performance review with the CorkSport community once installed!

2007-2013 Mazdaspeed 3 51r Battery Box Video

The CorkSport Advantage


Performance Advantage

Designed to work with up to 4" intake systems, the 51r ECU Relocation Box provides approximately an extra 0.75" of clearance (compared to the full-size CorkSport Battery box) without sacrificing fit and finish.

The ECU is relocated to the driver's side of the battery box with the wiring harness routed inside the box for a clean and purposeful look. The single lid design provides easy and ample access to the battery and ECU.

Mazdaspeed 3 51r battery kit

Fit & Finish

The 51r ECU Relocation Box is designed to use the OE mounting points for an easy installation with very little modification required to the wiring harness. The internal dimensions are designed around the industry standard 51r battery to fit all brands.

Mazdapeed3 upgraded battery box for 3 inch intakes

Materials & Manufacturing

CAD designed and manufactured from durable ABS plastic, the CorkSport 51r ECU Relocation box fits great and will stand up to the test of time. Battery restraint is completed with M6 studs and a 0.120" thick anodized aluminum plate.

Additional Features

  • Compatible with:2007-2013 Mazdaspeed 3
  • Designed in America: Designed in Vancouver, Washington, in the Pacific Northwest.
  • CorkSport Service & Support: 2-year limited warranty, full-color installation instructions, all necessary components, and knowledgeable telephone support at (360) 260-2675.

How To Install Your CorkSport 51r Battery Box

It will take you two hours to install the CorkSport 51r Battery Box with our easy-to-use instructions.

1 hour Install Time

1 hour Install Time

Difficulty: 2/5

2/5 Difficulty

2-Year Warranty

2-Year Warranty



installation instructions image

This box is super easy to install. I can have it in and out with little effort by only removing the filter on my 4” Corksport intake. Using factory hardware for mounting is a nice touch! Makes the install that much simpler. I have multiple other wires ran to my battery for various other mods. They all run through the various provided ports on the box so I didn’t have to drill any new holes for them which is a huge bonus for me!

I love the cleaner look of my engine bay with this battery box! I prefer this look a lot more than my old 51R tray setup. It keeps the rats nest of wires and thick wire harness loom hidden and tucked away. Knowing my ECU wiring and battery are being protected from engine bay conditions is a good reassurance too. Having hood vents makes this a must buy for me.
As far as the engine bay goes on my 2010 speed3 goes, few mods have been as easy to install as this battery box. It took no more than a half hour to install but it has drastically improved the aesthetics by helping me hide a few wires and fits my optima 51r yellow top perfectly. I love the satin black look, and the fact that it also fits the ECU so you can run a bigger air intake!

Also should add that this box has plenty of room to accommodate wiring for aftermarket upgrades. I have both air suspension and a mild sound system and all my wiring still fits, though it is admittedly a bit tight.
Had to do minor trimming to fit the 3.5" JBR intake, but it is a lot better fitment than what I had to do with the original box. Lasted well, too.
Helped create plenty of room and cleaned up the look of the engine bay a little, works well with my CS intake.
Huge fitment issues with JBR 3.5 Aluminum WP Intake.

If you want use of the lid you're going to have to twist the intake down towards the ground which makes it all sit awkward. You have to slightly force the ECU cables inside and the lid to squeeze in between the intake and even then you can only use one screw to secure the lid because the other side wont line up properly.

If you don't care about the lid closing then you can keep the intake as it should be, however, the CS battery box will be touching and probably rubbing against the coupler that connects the MAF to the intake. You can probably figure out away to close the lid but I said screw it.

Wish more testing went into this. But I plan on getting an HTP later on so I'm keeping it.
Using this with a 4 inch HTP intake. Plenty of space and it cleaned up my engine bay.
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Will any 51r battery work? Or what specifications do I need?

Asked by Will Miles | 10/09/2022, 01:10 PM | 1 answer(s)

Would this fit a 2006 Mazda 3S Sedan? Looks like they have the same stock battery setup....

Asked by Jay Adams | 05/08/2021, 07:20 PM | 1 answer(s)

Will this fit with the Cobb intake and filter box? for the 2013

Asked by Jon Gatewood | 03/01/2021, 10:02 AM | 1 answer(s)

Will a Optima D35r fit?, thanks.

Asked by Lou | 08/29/2020, 02:03 PM | 1 answer(s)

Will this fit a 2008 Mazda3 sedan?

Asked by Wyatt Jeffery | 01/27/2020, 10:53 PM | 1 answer(s)

Will this fit properly with a Bosch Platinum Series AGM Battery Group, Size 35 and a front Tanabe strut tower bar?

Asked by Silas Galdamez | 01/14/2020, 07:22 PM | 1 answer(s)

Ok, well I wouldnt mind looking into it as maybe trying to mock one up to fit, I dont want just the plain old 51r tray. If I can get some that fits the 51r and has some aesthetically pleasing looks to it...Umm, like a Corksport Logo, Id much rather have that. Why do the Speed 3 owners get all this stuff anyways but the sixes get pushed the Speed 3 lower front lip, the battery box, the steering guys should make a carbon fiber trunk lip for the speed 6 similar to like an M1 I think. If i could get some pictures of the Speed 3 battery box from all sides, the bottom and inside and dimensions, so I can check to see if its even worth trying. THanks

Asked by Tim | 10/24/2017, 07:50 AM | 1 answer(s)

I understand its not listed for a speed6...but what exactly is so different in the battery/ecu area that this couldnt fit, it looks like a beautiful product. I am looking to put in your guys 3 inch intake to add to my already CS turbo and pump internals n map sensor n EBCS, but I'm reading alot of people say you need an ecu relocation or a 51r battery to make anything fit as big as the 3inchers or larger. I've also read people fit them with no problem so I dont know. I know this seems like an intake question, but I was really wondering if this would fit in my speed not an r tard, I realize you don't list as fitting that...would it take extensive work TOO fit?

Asked by Tim | 09/26/2017, 10:32 AM | 1 answer(s)

Is the factory Panasonic battery in the 2013 ms3 considered a 51r?

Asked by Kirk | 09/12/2017, 01:23 PM | 1 answer(s)
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Will not work with BNR S4 V2 due to shift in a larger compressor outlet