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Battery Relocation NC Chassis


What’s there to it??

Interested in relocating your NC’s battery into your boot? I’m going to make this guide extremely simple yet give you everything to do a proper job. Now relocating your battery as an overall idea sounds incredibly simple right? What’s there to mess up? There’s quite a few things you’ll need to do and take into account when relocating your battery from the engine-bay to the rear of your vehicle. Before we start, I’d like to mention there is only one downside when doing this. That’s, your chosen battery will now be taking up space in your boot. If you’re happy that you can live with that, then let’s get started.

Choosing your battery and mounting hardware

Let’s start at the heart of your car’s electrical system, the battery. Whenever mounting a battery outside the engine compartment, it should always be a sealed AGM type battery. Period. Why’s this incredibly important? Two reasons, first let’s say the worst thing happens… Your in a wreck, the vehicle’s upside down. If you were to re-use the original battery you’ll find mounted under the bonnet, you’re quite likely to have hydrochloric acid leaking out everywhere. Terrible situation. The second reason is an AGM dry-cell battery does not need any venting. A regular car battery will have a tube that is used to vent away hydrogen gas as your battery charges. So to avoid both of them issues we use a dry-cell sealed AGM type battery that can be mounted in the passenger compartment and can also be mounted any orientation, no problem.

What options are on the market then for this? There are many options, entirely dependent on what you want and how you intend to use the car. Names that are popular are Oddessy, Dead-weight batteries, Optima, Yausa. In this part, I thoroughly encourage you to do your research and see what will suit your requirements as a battery. Now, once you’ve decided on a battery, you’ll need to find the appropriate hardware to mount it securely in the boot of your vehicle. You will find enclosures like mine, which is a Motamec standard size battery cage. However, if you intend to use the Oddessy style, say PC680 they and many other companies sell an enclosure suited to that batteries dimensions. Again, this is something for you to decide. But what is not up to you is you need to use M8 grade 8.8 steel bolts at a minimum, in my case I used four M8 bolts to secure it to the boot floor. Now in the event of hard driving or an accident the battery is thoroughly secured and not going to become loose and become a flying projectile.

Components and diagrams.

All I’m about to mention is suited for the NC chassis. So what cable will you need? What you’ll want is 40mm2 oxygen free copper (or ofc) welding cable. I purchased 5 metres that would allow enough length either end. In addition extra length to make a short little ground-cable from the battery to a suitable chassis-ground. There are many ways to wire a racecar. But this is the simplest way to do so on this platform.

To simplify this article even further, I have created a diagram below that explains the setup in my personal car. So let’s start from left to right. The first location is the boot. In the boot we have the main vehicle battery that has one short ground-cable from the negative battery terminal to a suitable chassis ground. On the NC that location is one of the bolts near the fuel filler protective metal cover. A small portion of paint is removed. Just enough to still be covered by the crimp-lug. But this will allow a much better ground path and not rely solely on the zinc-plated bolt. By providing an increased surface area.

Working away from the positive battery terminal, we make the first stop at the power-distribution box. This neat little box is configured in the image attached below. As the positive path enters the power-distribution box it splits. One path runs through a 200amp Megafuse and the other is used for future circuits that are NOT related to this battery relocation. As we carry on we leave the power-distribution box and head onwards to the front of the car. Routed past the rear shock tower and along the passenger side and sill oem wiring. We then leave the passenger compartment and penetrate through the firewall into the engine bay.

Once we get through the firewall and under the bonnet via a small hole in the bottom section of the oem firewall grommet we connect to a 3way power-distribution joint box. The starter motor/alternator leg which is a 25mm2 cable has a crimp lug attached and connected to the joint box. The last leg is a new leg. This leg replaces the fusebox main supply. This new leg is a 16mm2 supply. I actually ended up up-rating this leg as I couldn’t determine it’s original size. From the joint box we have a 16mm2 crimp-lug that goes direct to an inline Midifuse (with a 125amp Midifuse) (please see pictures to best understand). Then from there alongside the oem wiring loom under the bonnet. Then turns off near the main fusebox and goes to a 90 degree 16-6 crimp lug. Then attaches to the oem connection point.

Complete list of parts and associated links

Listed below are the parts you’ll need to complete the job and replicate exactly how I’ve done this on my personal vehicle.

  • A suitable AGM battery.
  • A suitable battery enclosure.
  • 5 Metres of red 40mm2 ofc welding cable.
  • 1 Metre of black 40mm2 ofc welding cable.
  • 5 Metres of plastic conduit non-split (16.9mm I.D.). [To protect main battery cable through vehicle].
  • x Metres of plastic conduit non-split (x I.D.)
  • MTA power-distribution box.
  • 200amp Megafuse.
  • Suitable crimper that has 50mm2 crimp dies.
  • 6x 50-8 crimp-lugs.
  • 1x 25mm through-crimp. [For starter motor cable join with more 25mm2 battery cable to reach joint box location].
  • 1x 25-8 crimp-lug.
  • 1x 16-8 crimp-lug.
  • 1x 16-8 90 degree crimp-lug [For connection to oem connection post inside main fusebox under bonnet].
  • Midi inline fuse holder.
  • 2x 16-6 crimp-lugs. [To splice in inline-fuse between joint box leg and main fusebox connection, situated straight after joint box. Please see article photos above for visual reference].

Links to the parts I used below.

Battery –
Battery enclosure –
Cable –
Plastic conduit –
Heatshrink –
200Amp Megafuse –
Cable Crimper –
Through-crimp –
Crimp lugs –
HPDE sheet –

DIY Rear heatshield replacement

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The straight-forward aftermarket steering-wheel install in NC/MK3 Mazda MX-5/Roadster/Miata

Confused.. Overwhelmed.?

Interested in installing a aftermarket steering-wheel into your car? But not sure what’s involved and what you’ll need? Hopefully this guide should clear that up for NC/MK3 owners.

What you’ll need?

Let’s keep this article real nice and simple and straight to the point. I will now cover all of the parts you’ll need in a logical order and explain them.

Boss Kit

Essentially all vehicles will have a unique spline on the steering shaft. A boss’s job is to translate that spline to a universal and standard PCD (bolt pattern) for installation of aftermarket steering-wheel.

Boss’s also come in different lengths, the most common is the short (55mm) style boss. However they do sell longer boss’s that will essentially place the wheel closer to your body. If your looking into a snap-off quick-release such as a NRG or WorksBell unit then I strongly suggest you choose the short (55mm) boss so you don’t end up with the steering-wheel too close to you.

SRS Resistors

To counteract the fact your airbag is now out of the vehicle, we will now use resistors and an inline-fuse-holder assembly to fool the SRS-Module (Airbag system) to believe the airbag is still in its original location and if the vehicle is in an impact the inline fuse (2amp fuse) will blow and create an open-circuit. Acting as a airbag would, this is the best way to replicate the factory airbag. The SRS-Module will be non-wiser.

The NC1/MK3.0 chassis will require just one of these SRS-Resistor-assemblies. The NC2/MK3.5 and later NC3/MK3.75 will require two of these assemblies. Most high-quality boss manufactures like WorksBell will supply these assemblies in their kit and will work with any year vehicle.

Your boss-kit will explain how to install these resistor-assemblies.


Everyone knows what a steering-wheel is, so let’s skip the explanation and jump head first into the different types, styles and sizes of steering wheels you need to know about before spending your hard-earned money.

The most common size of steering-wheel is a 350mm wheel. This size is most likely very close to your stock steering-wheel from the factory. It is quite a good size and will enable you to still read your gauge-cluster with no obstruction. You can however go to a smaller size steering-wheel, a few people do this in really small cars where interior space is limited and the benefit is a little more leg-room. However speaking of the NC/MK3 chassis I personally would recommend you stick to a 350mm wheel.

That’s great now I know the size, what else is their? Well secondly you’ll need to choose the style of steering-wheel you’ll want to use. Aftermarket steering-wheels come in mainly two different categories. That is “deep dish” (like the name suggests the wheel has depth and will ultimately sit closer to your body) and the second is “flat” this is also straight-forward to understand.

The third thing is the material you’ll want. Speaking from experience leather steering-wheels are the most durable and can be driven daily with no need for any gloves. They are also nice if you don’t wish to wear gloves at the track-day. Personal experience right? The other main option is suede. Now suede steering-wheels may look awesome to some, they have a massive drawback for driver’s who wish to keep their car for some time.. That is without wearing driving-gloves the oils in your skin will deteriorate the suede material and can change the feel. Not good. However if you are going to be mainly driving your car predominately around the track then a suede steering-wheel with proper gloves will be a good choice! In fact some claim that suede wheels will have a slightly better grip with gloves, perfect for a true racecar. Now if your like my friend Olly you may also like to have a wooden steering-wheel. A massive throwback to classic cars, a wooden steering wheel will look great in a vintage style car. To get the best feel of a wooden-steering wheel it is recommend to use a pair of leather driving-gloves. This is also where the term “glovebox originates from”. The last real material you’ll see is neoprene. This material will feel similar to your stock-wheel and is cheaper to produce than a leather wheel but is not as durable as a leather-wheel.

I’d just like to add that you should check what style PCD (bolt pattern) the steering-wheel you like has. As their are two types of PCD for a steering-wheel. The “Sparco” style, with the single countersunk-screw being at the top of the wheel. The second is the “Nardi” style, which has the two countersunk-screws at the top of the wheel. I have attached a photo above, the first is the “Sparco” PCD and the second is the “Nardi” style for clarity. This is important as if you do not run a quick-release and just the boss you may need a adapter to change the PCD of the wheel.

Optional – Quick-release

You’ve probably seen these used in many racecars. There’s a good reason for that. With a full bucket-seat and 6-point harness setup it may be difficult to get in and out of the vehicle with the wheel in the way. This way the steering-wheel can be detached and re-attached once the driver is in. This is not essential however if you intend to fit aftermarket bucket-seat’s this could be worth it.

The ULTIMATE guide to installing bucket seats into a NC/MK3 Mazda MX-5/Roadster/Miata

What? How? Will it fit?

Having trouble or just straight-up confused about fitting aftermarket bucket seats into your NC/MK3? Stress no more. This post should hopefully clear-up most of and hopefully all of your concerns and questions!

Finding the perfect seat for you!

The first part your going to have to consider is what seat you wish to fit. Now of course not just any seat will fit the profile of the NC/MK3. So I have compiled a few links below to articles and forum posts that show what seats WILL fit in your car. But first just naming a few popular seats off the bat for the NC/MK3, Sparco Evo QRT, Cobra Monaco Pro, Sabelt GT-090 Racer Duo, Sparco Sprint.

Now what’s more important than the seat fitting in your car is it fitting you! Yes, bucket-seats won’t fit everyone. A properly chosen seat should fit you snug but not too tight that your uncomfortable. That last part is very important. The second most important thing for anyone wanting to take their car to the track is the upper two harness pass-through holes are at the appropriate level in relation to your shoulders. Too high and when the harness is tightened up it could potentially crush your spinal-cord and that is not something to joke about.

Sounds a little intimdating for a newbie buying their first bucket seats right? Well maybe a little bit but if you have a supportive bucket-seat retailer nearby you should be able to find the seats that you have been told will fit your NC/MK3 and try them out both for your butt and also your car! That way you will know they will fit before you spend the cash.

However if for whatever reason you cannot test fit a seat because you have no local bucket-seat retailer then you can still make sure your seat fit’s by using a few simple measurements and questions back and forth with a reputable online-retailer. So what measurements do I need to take and how?? Let’s first start with your butt-to-shoulder measurement. To take this I recommend you sit on a flat floor with your back straight up square with another straight object such as a wardrobe, wall (if possible), basically any object taller than you and straight/square. This does help if you have another person double check your doing this correct but now you measure from the ground (bottom of your butt) to the highest point of your shoulders (this will be closer in near your neck). This will give you the measurement to confirm if your harness pass-through’s will be safe for harness use. The second measurement is your waist. Pretty straight forward right? Like buying a new pair of trackies lol. The third is the width of your shoulders. You do not want a seat where the upper side-supports are too small. For correct fitment your shoulders and body should sit back into them. Don’t be too worried if you think your shoulders are too wide for the seat you think will fit you. They will not wrap around your shoulders but simply you just sit back into them. (I am not referring to high-spec halo seats here but the classic bucket seat style). The main target here is to find a seat that is comfortable for you.

Mounting your new seat!

Once you’ve got the right seat that will both you and your car, you need to think about how you wish to mount your seat to your car’s floor. Now their are two options here. Sliders or a fixed position mount. Sliders are good for street use where a harness won’t be used. HOWEVER, if you want to run a six-point harness the lower two crotch belt’s will need to be fixed in a permanent position making the slider not an option. Most bucket-seat retailers and motorsport shops/websites that you are getting your seat from will also sell the mounting hardware. Speaking of before I forget to mention you will need four M8 bolts to fix the seat via the side-mounts. Some seats do have bottom mount mounts but MOST bucket-seats will only use side-mount’s which allow the seat to be lowered more than a bottom-mount.

Now you’ve made the decision on sliders or a fixed position, you will need to know what you actually need to do either option. Both setups will require the four M8 bolts to attach the seat to your mounting solution. Both setups will require what we call a “vehicle-specific base mount” as referred to as “VSBM” from this point on . This hence the name is unique to the floor of your vehicle in our case the NC/MK3. Now the difference between sliders and a fixed setup is here.  If you want sliders you will now of course need a pair of sliding-rails that will attach to your VSBM and then to the seat. So to run a sliding-seat setup you will need a VSBM, four M8 seat bolts and a sliding seat rail. If you wish to permanently fix the seat in one position you will need a VSBM, four M8 seat bolts, side mounts (that will go between the VSBM and the seat itself). When looking at purchasing a fixed setup you will find a few VSBM’s come as a kit with side mounts. These are usually just called bucket-seat mounts. Some even come with holes for the two lower crotch belts for a 6 point harness.

Electroni.. what..?

Here’s the tricky part coming up. Electronics! Hate them or love them they are tricky at times. With some help from awesome forum users I have supplied the info you will need to get your new bucket-seats in without any irritating SRS-Airbag and OEM seat-belt light flashing and beeping in your Mazda. Trust me that beeping would drive you insane in a matter of minutes lol.