Planning Guide

Note: this Planning Guide is specific to the K24A2 Miata swap! Planning guides for the K24Z3 swap and the K24 E30 swap will be released soon.

 In addition to this guide, you can also check out our full installation guide, updated August 2017. In addition, our BMW transmission upgrade guide can be found here (updated December 2018)

Engine Selection

For most swaps, we feel the best engine is a K24A2 from a 2004-2008 Acura TSX. However, the 2006-2008 engines are preferred as they are built with stronger internals, and feature larger valves and higher lift cams. Most other 2002-2008 K series engines can be used. Once the necessary Type S oil pump upgrade is done, these engines spin freely to 8000 rpm and are good for around 220whp and 180wtq in stock form with the right supporting bolt-ons and tune.


Transmission and Differential Selection

Any NA or NB Miata transmission and differential combo can be used. However, for track use, we recommend going with parts from 1.8L cars (1994-2005). The best combo we have found for road racing, assuming a redline of about 8000 rpm, is a 6 speed transmission with a 4.10 Torsen differential.


Basic Swap Components

Every build requires our K Series Conversion Kit. This includes:

  • Subframe
  • Engine mounts
  • Engine/trans adapter plate
  • Flywheel
  • Oil pan
  • Oil pump adapter and pickup
  • Wiring conversion harness

This is enough to get an engine bolted in your car and wired, but additional parts must be selected based on your build goals. (Note: be sure to check out our new Ultimate swap package that includes many of the accessories listed below. It makes your build even more straightforward and cost-effective.)


OEM Honda Parts Needed

The following list of OEM Honda parts are either required, or highly recommended:

  • Type S oil pump conversion - we sell it as a full package and include a pump that’s been machined to fit a K24A2 block. There is physically no way to fit any K24 into a Miata without upgrading to this pump. Our oil pump adapter is designed to bolt to this OEM pump.
  • Engine wiring harness and starter harness. Our conversion harness currently supports a 2002-2004 RSX Type S harness from a K20A2, or  2003-2006 Honda Element manual harness. The RSX harness should be used if you're using Hondata Kpro for engine management, and the Element harness should be used if you're using KTuner or the KMiata ECU reflash. Regardless of the harness used, there are several plastic covers that will need to be removed from the harness in order to clean it up and fit it in your RWD vehicle. The plugs for the K series transmission can be removed.
  • Starter - the easiest will be the starter that comes from the same vehicle as your engine harness, but any K series starter can be used. 
  • Alternator - you’ll want to use one specific to your engine (K20 or K24) as the mount is a bit different depending on engine.
  • Honda J35 flywheel bolts (K series bolts are too short for our flywheels)
  • If using a K24, a 50 degree VTC intake cam gear is highly recommended to replace the 25 degree gear. This increases mid-range power significantly, and is easy to install when you replace the oil pump.
  • Timing chain tensioner - we recommend replacing the tensioner when you have everything apart for some preventative maintenance
  • Flywheel dust cover - used to cover up the flywheel behind the oil pan that would be exposed to the elements otherwise.
  • If using an RSX engine harness, a K20A2 knock sensor and crank position sensor are both needed. Alternatively, the K24A2 harness connectors can be cut and spliced onto your K20A2 harness. With the Element harness, no sensor changes are needed.
  • Air/fuel sensor that matches the engine harness you're using. We like the Denso ones that can pick picked up on Amazon, since Denso is an OEM supplier.


Intake Setup Choices

Intake manifold:

As of September 2019, all Ultimate Swap Packages will include our new KMiata RWD intake manifold

This new part provides the best fit and finish, the best powerband, and the elimination of all adapters that were previously needed for Skunk2 manifolds. 

    Throttle body:

    We recommend a 74mm B series throttle body like the one we carry. Depending on the brand, extra water ports may need to be cut off the bottom. A B series TPS is required, and is a much more durable option than the K series sensors that constantly break.

    Intake piping:

    We recommend 3 inch intake piping. A hole needs to be drilled and a grommet added to fit the OEM intake air temperature sensor. The intake can be routed in a variety of ways, but we recommend getting the filter out of the engine bay if possible.


    We offer a K series to B series TPS jumper harness. This saves you from cutting up your wiring harness, and extends the length of these wires to the proper length.

    Header and Exhaust Choices

    We now exclusively offer our K24A2 race header for our swaps, and we now also have a bolt-in race exhaust system. The header also does include a V-band flange and clamp so you can make your own exhaust. 



    Any 1.8L Miata clutch can be used. After testing several units, we’re most pleased with the ACT HD Street clutch with organic disc, found in our online store. Others will work as well, but be sure they can hold at least 200wtq. The pilot bearing for your kit will be discarded, as your KMiata flywheel already has a specially-sized bearing installed.



    For either a K24A2 or K20A2 style head, some sort of modified coolant neck is needed. We offer a solution for each type of head. The K24 piece includes a provision for your OEM Miata coolant temperature sender as well.

    A K20A2 style head will require the Tractuff coolant neck, and some sort of heater hose reroute. We recommend plugging the OEM heater hose port with a K-Tuned plug, and adding a T fitting under your Tractuff piece to route a line into your heater core.

    Heater lines can be made with any ⅝” hose from your local parts store, and we now have a heater port adapter to make routing easy.

    Coolant hoses can be made in a variety of ways. While we eventually plan on releasing a full set of hoses, a quality cooling system can be put together with some 1.25” aluminum pipe and some universal silicone 1.25” hose bends. The factory Miata radiator (or similar upgraded unit) can be used. Finally, -16 AN hoses can be used. We supply our upper coolant necks with either a 1.25” or -16 fitting.

    Engine Management

    A modified ECU is required to run a K series engine in a Miata. A factory ECU cannot work, due to the factory immobilizer. 

    As of June 2020, we are exclusively supporting Hondata Kpro for our engine swaps, and will only carry Kpro spec conversion wiring harnesses. 

    Kpro must be installed in a 2002-2004 Acura RSX ECU, base or Type S, manual or automatic. Wiring harnesses from the same vehicles are the only harnesses that are compatible.


    Fuel System

    NA Miata (return system):

    • Upgraded fuel pump
    • External fuel pressure regulator
    • Fuel line from regulator to fuel rail
    • Return fuel line from regulator to connect to Miata return line
    • Injectors of your choice (K series 310cc injectors should be fine at 60 psi from the Miata regulator, RDX 410cc injectors can be used if more fuel is needed).

    NB Miata (returnless system):

    • Upgraded fuel pump
    • Fuel line from hard line to K series rail
    • Injectors of your choice (K series 310cc injectors should be fine at 60 psi from the Miata regulator, RDX 410cc injectors can be used if more fuel is needed).

    Basic rubber fuel injection hose can be used, but most customers prefer to build their setup with -6 AN hoses and an aftermarket fuel rail. We sell the Hybrid Racing rail, but there are many other options on the market.


    Additional Parts Needed

    You’ll need a pulley setup of some sort. We recommend the four pulley setup we sell. The Skunk2 manifold requires you to delete the OEM Honda tensioner, so our kit is a perfect solution. In our experience, the alternator relocator kits on the market will not clear your steering rack with this swap.


    Additional Parts Needed Specifically for an NA Miata Swap

    • NB steering rack and bottom section of steering column
    • Modified valve cover or a small cut in the hood
    • More advanced fuel setup, as noted above
    • NB throttle cable. an NA one can be used, but they are usually way too long and don’t work as well in our cable brackets.