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K24A2 vs. K24Z3: which swap is right for me?

David Calzada

K24A2 vs. K24Z3: Which Swap Is Right for Me?

Since the initial news of the K24Z3 swap coming to market this fall, we’ve received non-stop questions asking about the differences between the K24Z3 and our original K24A2 swap. 

Here’s a breakdown of the advantages and disadvantages of each option to help our customers choose the engine that suits their needs best.

 

Cost

A primary reason we developed the K24Z3 swap was to offer a more affordable K swap option. Thanks to the less expensive engine, simpler exhaust setup, and the ability to retain the stock subframe (more on that below), the K24Z3 swap can be done for about $2000 less than the K24A2 swap. Since the K24Z3 engine has it’s limitations, we do still feel there will always be a place for our original K24A2 swap, but the K24Z3 is a very attractive option for customers looking for a simple and reliable 200+whp.


Tubular Subframe vs. Stock Subframe

Our original K24A2 swap uses an aftermarket tubular subframe to provide adequate clearance for a true 4-2-1 style race header. Fitting proper length primary and secondary runners and merge collectors takes up space, and the tubular subframe gives us the space we need. Additionally, the tubular subframe allows for adequate space to route the header between the rear oil capacity and the adapter plate/flywheel. 

Since the K24Z3 exhaust setup consists of a single 3” downpipe, less exhaust clearance is needed. However, even with a single 3” pipe, there isn’t enough clearance with the factory Miata slave cylinder in place. Our hydraulic release bearing inside the bellhousing solves the issue. 

For turbo cars we recommend going with one of our BMW transmission options for the additional strength, and the BMW slave cylinders are also on the opposite side of the bellhousing which makes routing a 3” turbo downpipe easy with the stock subframe. 

Retaining the stock subframe can be considered an advantage to the K24Z3 swap thanks to the lower cost and reduced amount of installation time. However, the tubular subframe does give additional clearance and flexibility for any exhaust setup.

It’s worth noting that the oil pans and engine mounts are all interchangeable between the K24A and K24Z blocks despite the drastically different designs. However, the exhaust setups are not.


N/A Power Potential

The major advantage to our original K24A2 swap is the naturally aspirated power potential. A K24Z3 engine is a very solid option for 200-210whp, but in order to make much more power, a K20 head (or K24A2 head) needs to be swapped on, which comes with its own share of complications. The largest being the lack of header clearance with the stock Miata subframe. 

On the other hand, a K24A2 (or any K20A or K24A engine) can be built to push some impressive power figures. Even stock, most customers with a K24A2 will make 220+whp, and 300+whp N/A engine builds have been common for years. This is the primary reason why the K24A engines are still the first choice for Honda engine builders worldwide, and also why the K24A2 engines carry a premium over their newer counterparts. 

So if an easy 200+whp will suit your goals and you won’t be looking for more N/A power down the road, the K24Z3 swap is for you. However, if the option of additional power is appealing, it may be worth the extra investment in a K24A engine setup.


Turbo Power Potential

Any K series engine has a lot of power potential with forced induction. It’s common to make 450-600whp out of a stock K20A or K24A. A K24Z3 cylinder head doesn’t flow quite as well, but the single exit exhaust port makes adapting a turbocharger that much easier. Additionally, the K24Z3 rods are stronger than all older K24 rods. Combined with the low cost of the K24Z3, we suspect that they will be a great engine choice for a turbo setup, and we’ll be doing some turbo testing in the coming months. We’ve seen them easily make 500whp in Hondas before, but we’d like to play with one in the Miata chassis as well. 


Engine Management Options And Drive By Wire

We’ve designed our new K24Z3 to be compatible with all older K series electronics to keep things simple. Previously, K24A3 engines couldn’t be easily used for swaps thanks to the completely different wiring harness and ECU, a drive by wire throttle body, and the required flash based tuning. Our goal was to make the K24Z3 compatible with Kpro4 and KTuner, and to do this we had to design a custom timing chain cover that accepts the older style K series crank position sensor. 

We’ll be releasing detailed K24Z3 wiring instructions that will include details on exactly which older K24A sensors are needed, and which connectors can be swapped from a K24Z3 harness onto a Kpro4 or KTuner compatible harness. 

Additionally, we are looking to support at least one standalone engine management option soon, as well as a compatible drive by wire throttle body and pedal. This setup would be intended for race cars requiring multiple maps for easy detuning for power to weight ratio classing, as well as straightforward traction control integration.


Compatibility Between Components

Our two K swap kits share the following components:

  • Adapter plate
  • Flywheel and 1.8L Miata clutch kit
  • Oil pump adapter
  • Intake manifold
  • Throttle body
  • Wiring conversion harness

Additionally, our A/C kit can be configured to either engine, as well as our electric power steering kit.

Oil pans are interchangeable between the two engine blocks, as are engine mounts. However, engine mount placement is different for the K24Z3 mounts due to the stock subframe, and K24Z3 mounts are incompatible with our 4-2-1 race header. 

Because of this, it would be easy to drop a K24Z3 into a K24A2 swap kit, but not the other way around. So do your homework and decide the best swap for you and we’ll help you make it happen!