Planning Guide


Updated October 2020 with general information for all of our K24 swap options. The most detailed information can always be found in our installation guides here.


Engine Selection

For most customers, a 2.4L Acura TSX engine is the ideal starting point for any of ours swaps. The K24A2 from the 2004-2008 TSX is the most potent K24 in stock form, and can also be built to make significantly more N/A power. The JDM K24A engines with an RBB head are nearly identical to the TSX engines and are also a great starting point.

For Miata customers specifically, the K24Z3 from the 2009-2014 TSX is also a fantastic choice. 

For a comparison of both Miata packages, see our blog post here. We currently only support the K24Z3 platform for the Miata chassis, and recommend a K24A2 for other cars. 

A stock K24A2 engine with a 50 degree VTC gear typically makes 220-230whp and 180+wtq with the supporting upgrades in our swap packages. We generally set the rev limiter to 8200 RPM for track use.

While other K series engines can be used for these swaps, they will all make less power than the engines we recommend. A K20 swap can be done with some minor adjustments to our K24A2 swap parts, but K20 engines are more expensive, harder to find, and don’t make as much power or torque. 


Transmission and Differential Selection

For Miata swaps, we recommend an NA or NB 5 or 6-speed transmission for naturally aspirated builds, and one of the BMW transmission options we support for turbo applications. 

A Miata 5-speed paired with a 4.30 Torsen differential is a common choice, as well as a 6-speed with a 3.90 or 4.10. Use our gear ratio calculator to determine the best ratios for your application.

E30 swaps generally do well with the stock transmission and rear end for street use, but a closer ratio setup is generally ideal for the track. Our favorite all-around combination is the ZF 5-speed paired with a 3.73 LSD differential.


Basic Swap Components

Every K24 swap will require the following components from KPower, regardless of application.

  • Engine mounts (and tubular subframe if applicable)
  • Engine/trans adapter plate
  • Flywheel
  • Oil pan
  • Oil pump adapter and pickup

This starting point will bolt a K24 engine into your chassis, and will be needed regardless of the direction of your build.


OEM Honda Parts Needed

The following list of OEM Honda parts are either required, or highly recommended, for every swap.

  • K20 oil pump conversion - we sell it as a full package and include a pump that’s been machined to fit a K24 block. There is physically no way to fit one of our oil pans on a K24 without this pump. Our oil pump adapter is designed to bolt to this OEM pump. K24Z3 users will need to order our K20 pump kit specifically for that application. 
  • Engine wiring harness and starter harness. Our conversion harnesses currently support a 2002-2004 Acura RSX wiring harness. This harness is required to run Hondata Kpro, and plugs directly into our conversion harnesses. Any plugs for the K series transmission can be removed. Alternatively, we do offer a custom aftermarket replacement for the OEM harness.
  • K series starter - A K20A2 starter is the cleanest if using an OEM RSX harness, but any K20 or K24 starter can be used
  • Alternator - you’ll want to use one specific to your engine, as K24A2, K24Z3, and K20 alternators are all different.
  • If using a JDM K24A engine, you will likely want to switch to a USDM K24 water pump housing and alternator. New JDM alternators aren’t available in the U.S., and the belt routing is easier with the USDM parts.
  • If using a K24, a 50 degree VTC intake cam gear is highly recommended to replace the 25 degree gear. This boost mid range power significantly, and is easy to install when you replace the oil pump. K24Z3 engines already come with a 50 degree gear.
  • Timing chain tensioner - we recommend replacing the tensioner when you have everything apart for some preventative maintenance.
  • A knock sensor and crank position sensor that matches your engine wiring harness. RSX harness users will want to use K20A2 sensors, or splice the K24 connectors to the RSX harness. Customers using our aftermarket harness can use the sensors that came on the K24 engine.
  • Wideband O2 sensor from 02-04 RSX-S, which plugs directly into our conversion harnesses. we like the Denso sensor, available everywhere. Part 234-9005

Intake Setup

All of our swap packages include our KPower Intake manifold.

This new part provides the best fit and finish, the best powerband, and the elimination of all adapters and tight packaging from the Skunk2 manifolds we previously used.

Our manifold accepts any K series fuel rail and OEM style K series injectors.

Throttle body:

We recommend a 74mm B series throttle body like the one we carry, with the appropriate diameter throttle cable pulley for your application. A B series TPS is used, or the Acuity K series TPS with the adapter we supply.

Intake piping:

We recommend 3" intake piping. A hole needs to be drilled and a grommet added to fit the K series 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 for cars used on track.


Header and Exhaust Choices

We offer a header or downpipe for all applications we support. For Miata swaps, we also offer a full 3” race exhaust system for both K24A2 and K24Z3 swaps for a complete bolt-in exhaust solution.

All of our headers end with a 3” outlet. So if our off-the-shelf exhaust isn’t used, we recommend going with any custom 3” exhaust.  


Clutch

The required clutch is listed on each product page. Selecting a clutch that can handle your torque output is critical. For Miata swap retaining the stock transmission, we recommend the ACT HD 1.8L Miata clutch that we carry. 

All BMW transmission setups require the larger E46 clutch with 240mm disc and pressure plate, such as the OEM LuK clutch or the ACT HD clutch for E46.


Cooling

For any K series engine, some sort of modified upper coolant neck is needed. We offer a solution for each type of head. All coolant necks include a provision for the OEM coolant temperature sensor for each application.

If deleting heat, use the Hybrid Racing heater delete plug to delete the hard black pipe in the thermostat housing. If retaining heat, use our Heater Port Adapter paired with ⅝” heater hoses. 

See the specific installation guide for your swap for more details on sourcing the best radiator hoses for your swap.

For heavy track use, we recommend an aftermarket aluminum radiator of your choice. Naturally aspirated K series engines generally don’t have issues with overheating.


Engine Management

Currently, Hondata Kpro is required for all KPower engine swaps that use our engine conversion harness. A factory ECU will not 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.

Any ECU that plugs in directly to an 02-04 RSX can theoretically also be used with our swap and conversion harness, but we do not offer product support for other ECUs at this time. 

If you are using a standalone engine management system, do not order our wiring conversion harness, as you will need to wire up the system yourself.

We recommend using the stock 2004 TSX basemap in Kpro to get your car started, and then having it dyno tuned immediately by a qualified tuner.


Fuel System

Detailed information on fuel systems can be found in the installation guides for each application. 

Return fuel systems, such as used on the NA Miata and E30, will require the following components. 

  • Upgraded fuel pump (recommended but not always required)
  • 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 

Returnless fuel systems, like on the NB Miata, need the following items:

  • Upgraded fuel pump (recommended but not always required)
  • Fuel line from hard line to K series rail
  • Injectors of your choice

For mild naturally aspirated builds, we recommend the stock 310cc injectors. We also typically use the stock fuel filter unless running e85. 

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 such as the Karcepts rail we carry.


Additional Parts Needed

You’ll need a belt and pulley setup of some sort. We offer options to both retain or delete the factory K series auto tensioner. Our 4 pulley setup can be used in any application to delete the tensioner. However, thanks to our new intake manifold, the popular EP3 idler pulley setup can be used so the factory belt routing and tensioner can be retained.


Additional Parts Needed Specifically for an NA K24 Miata Swap

  • NB steering rack and bottom section of steering column (K24A2 only, with tubular subframe)
  • Custom valve cover to provide more hood clearance
  • NB throttle cable. an NA one can be used, but they are too long and don’t work as well in our cable brackets.