FAQ's: Swapping K20 K24 into 2000-2005 Toyota MR2 Spyder

Question: Which engine and transmission will work with this swap?

Answer:  You have many choices on which engine and transmission you can use with this swap.  The easiest, in terms of installation, is the K20A2 (Acura RSX Type-S) engine and transmission.  Other engines such as the K20Z3 (06+ Civic Si) can be used but be warned that you will need to purchase additional parts and swap various sensors out to make this work. A comprehensive guide to the engine codes and their compression and what model they come in can be found here. There are also options to switch the cylinder heads and bottom ends.  Commonly referred to as the "Frankenstein swap".  This will require more work and various cylinder heads/various bottom ends can be used based on your goals (Turbo vs NA). Additionally, you can utilize the K24 engine.  There are multiple variations, the most common include the K24a, K24a2, K24a4, and K24a1, the most common and easiest to swap for the K24 is a K24a2, we have used JDM engines available here. The K20a2 is more straightforward than any K24. We have a good write-up on performing this type of engine build can be seen here

Question: Can I use the stock ECU?

Answer:  No, you cannot use a stock Honda ECU.  Due to the Toyota system speaking one language and the Honda system speaking another language, the two cannot properly communicate.  You can wire in both a stock Toyota ECU and a stock Honda ECU to make it work.  But you will have to make your own wiring.  It is recommended that you use a Hondata ECU or another aftermarket computer, like Haltech, AEM, or now LinkECU.  The Hondata is a modified Honda OEM ECU that will give you the standalone tuning ability and allows you to turn functions of the ECU on/off like error codes which will help make the swap very easy. Best of all we are the sole producers of the only wire harness which makes everything plug-and-play.  

Question:  Will my car pass emissions?

Answer: Emission testing varies from state to state.  To date, Mitch's Auto Parts has not had an issue with any swap we installed passing emission with the use of our wire harness adapter and the PPE exhaust system.  Our wire harness adapter also has a function OBDii connection that works through the stock OBD reader. Therefore, you can still read diagnostic codes just like when you had the original 1zz engine in the car.

Question: Will the AC still work?

Answer: Yes, Mitch's Auto Parts has recently developed an AC mounting kit and an AC control module to use the stock Toyota compressor without extensive modification, some movement of the firewall may be needed as well have the removal of a very OEM brace that is not needed.  Simply install the module behind the speedometer with the provided instructions found here, use our wire adapter for AC and everything will function as it did with the 1zz in it and best of all we offer them as a package deal to help save you more money.  Our modules may be compatible with any other engine swap in case you decided to get crazy with the LS swap or a rotary. Limited support will be provided for any swap that is not K series related. 

Question: What functions will the car lose?

Answer: Due to the complexity of the Toyota multiplex system, the water temp gauge, oil pressure warning light, and the battery warning light previously would not function correctly.  Recently in partnership with MoltenCore Industries, we were able to develop the new MIM (MoltenCore Interface Module) which can translate the Toyota "language" to Honda "language" and vice Versa allowing FULL functionality of your OEM Toyota dash unit.  With this new module, no additional gauges or ECU are needed.

Question: Can I still do the swap if I have an SMT?

Answer: Yes, you can. Some additional wiring changes need to be made in order to make it work but we can help you with those changes and you will need to switch the car over to a manual. The use of the SMT transmission will not work.  The parts to make this switch are readily available.  You will also need to install the SMT-MT kit

Question: Do I have to cut the car to make this fit?

Answer: Absolutely not, this swap will fit in the car without any modification to the frame or chassis.  Certain intake manifolds may require you to "massage" the firewall but nearly all OEM intake manifolds will fit without issues. Simply email us to inquire if your intake manifold will have issues. 

Question: Which engine harness do I need?

Answer: The recommended harness should be the 02-04 Acura RSX Type-S engine and charge harness.  Using this will eliminate much of the wiring hassle that is seen with these swaps.  You can use other harness' but you may need to switch plugs and sensors based on which harness you choose.  Our wire adapter is designed to work perfectly with the above listed OEM harness. 

Question: Will the stock Honda/Toyota axles work?

Answer: No, Unfortunately, the splines on the ends of the two axles will not work. Luckily, we sell axles for this swap from multiple manufacturers with different horsepower ratings up to 1000 whp. 

Question: Which engine mounts do I use?

Answer: As of today, there are two manufacturers of off-the-shelf engine mounts for this swap, one is us, Mitch's Auto Parts (MAP) and the other is Innovative Mounts, which can be seen on our website. Due to early testing of the Innovative Mounts, the 60A durometer was discontinued after seeing multiple failures due to the increased torque and horsepower.  The minimum durameter available for these mounts is now 75A but is available up to 95A. But many users have found that because Innovative Mounts adapted RSX mounts to fit in an MR2 Spyder, this has caused the rear subframe to bend, hence why we have created our own mounts centered around the MR2 Spyder's OEM mounts.

Question: Do I have to buy new shift cables?

Answer: There are 2 options, you can retain the original MR2 Spyder shift cables and use the  Innovative Mounts or purchase the MAP Adapter which replaces the often damaged driver cable. The MAP version uses a custom made cable with 25% larger cables making them more robust and less likely to break like the OEM version.  This allows for a precise feel and great feel while shifting, unlike the Innovative version.  Lastly, the MAP version has an adaptation to work with the Acura RSX transmission (Base 5spd or Type S 6spd/DC5), 02-05 Honda Civic SI (Ep3), or the 06+ Honda Civic SI, whereas the Innovative will only work with the RSX and EP3 transmissions.  The install guide for the MAP adapter can be viewed here

Question: Do I need to buy new coolant hoses?

Answer:  With the K20A2, No.  The stock MR2 Spyder hoses will work perfectly with the K20, we do recommend the purchase of the swivel housing to make for greater ease of installation and coolant flow.  If you choose the K24 or the K20Z3 you may have to make some modifications to your current MR2 hoses, we recommend using a Dayco hose P/N 72166 Hose B for K24 swaps.   Email us for more details.

Question: Will there be any fuel system issues?

Answer: No, unless you are planning on turboing or modifying the engine internals the stock MR2 fuel system will adequately handle the needed supply of fuel.  We suggest using our custom fuel hose as it will connect the Honda fuel rail to the MR2 fuel system with no modification.  If you're looking to upgrade the fuel system we offer complete kits or the DIY option. 

Question: What about the exhaust system?

Answer: If you can weld you can certainly fabricate your own system.  If you do not have the ability to do this, PPE Engineering and Mitch's Auto Parts came together to create a full exhaust system that bolts on for the swap with no modification. We also collaborated with Toyonda to produce another similar exhaust system.   You can see this system in the exhaust section for K swap parts. It is available with and without a catalytic converter if you live in a region that requires emissions testing.

 For Additional information, you can view posted information on the development of the swap we helped to contribute to (Warning there is a lot here)