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1992 BB2 Prelude k24A3 Swap
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Discussion Starter · #1 · (Edited)
I wanted to create a guide for my swap to help outline for myself but others as well. I was following a thread on honda-tech but the poster stopped providing updates after he got the engine in the bay. From this point on I have been figuring it out on my own and it has not been easy. I know some of you may be interested in this as well. I will keep updating this as I go because I am not at completion yet. Though I am very close. This will be for everyone but the end result will be turbocharged. However, I have included the info if you want to go N/A.

I don't feel it necessary to rewrite every step so here is one of the many threads he posted:
k20/k24 swap 4th gen prelude. - Honda-Tech - Honda Forum Discussion

This should clear up everything to actually get the engine in the bay. I chose to do a cheap quick engine bay clean and paint just to make things look nicer since the lude I bought was very dirty.

So then everything comes out

Once out start prepping and painting

I chose to stay as OEM as possible so I used the stock fuel filter, kept the abs, the clutch master works just fine with the new slave and basically everything that isn't a sensor for the old power plant.

Now pop the engine in

Now lets talk about the traction bar a little. If you do not plan to use A/C then you will not need to replace the traction bar. You will need to remove the compressor and the mount for the compressor to clear the traction bar. If you are planning to have A/C you will need an aftermarket traction bar and custom A/C lines. This shouldn't be difficult for a shop to do. Just make sure you save your condenser setup and any lines/fittings so you can explain to them what needs to be done. Really though they should just be able to look at it and know.

Engine Mounts
There are two options. Innovative or Hasport. Hasport pioneered this swap so I chose them but either should be fine. Any kit will require you to cut off the stock passenger mount and weld on a new K mount.

There is a chart someone was keeping on a forum I cant recall but basically any K24 should fit with the Hasport mounts. As long as the block has the same mount points as the k24 it will fit. As for trans you must use a TSX or RSX case. I also don't know if this is 100% but from what I understand the civic trans is mounted differently. You can swap the gear sets but you must still use the TSX or RSX case. I went with the TSX six speed because I got the engine and trans together.

Engine Harness
This depends on what ecu you want to use. The easiest way is to use a PRB ecu if you want to retain lockout for a six speed. They are only a specific model though like PRB001-005 or something. Its listed on the Hondata site. In fact most of the info is so I will leave it at this:

Use a K20 harness from an 02-04 RSX and an 02-04 RSX ecu. My harness was marked as "Blemished" which just means it looked kind of ugly and some wires were maybe too long or something. It is a mil spec so I really didn't care as it will be tucked anyway. When you do this you will find some plugs don't match. You will need to wire on a K24 crank sensor plug and a knock sensor plug. At least I think its the crank sensor on the bottom of the block near the crank pulley.

ECU Harness
I decided to go with the Hybrid Racing universal K Swap Harness which is not cheap but surprisingly the most inexpensive route. I checked RyWire and after speaking with the person on the phone I was told to email them so I did. I never heard back from them and the cost was almost $200 more. Rant over lol. The universal harness is super easy to install. Just follow their directions. Although I have to admit, at first I was confused why I need 3 new relays that were wired in but eventually I figured it out. Everything will connect right at the prelude harness inside the car at the ecu. Here are the pinouts:

Prelude ECU Pinout
.:FFS TechNet : OBD1 ECU Pin out Schematics :.

Hybrid Racing

I found that wiring to the fuel pump did not work because the circuit was broken when you remove the ecu I guess. So you will need to run the fuel pump wire to the driver side fuse box area. The large yellow wire that feeds the relay will need to be spliced into on the back side. So the side that appears to be coming from the back of the car. I don't have a picture now but I will get one. You can verify the wire with a multimeter. it will send 12v to the pump when you turn the key to the first on position.

Fuel System
I used the kmod universal fuel rail kit but the FPR was very leaky. I contacted them and they sent a new unit but I instead when with the k-tuned FPR. So basically any k series fuel rail and FPR setup should work here. As you can see in the photo the line from the filter to the rail fits almost perfect. I initially mounted the FPR to the end of the fuel rail but I decided to mount it to the firewall to get more clearance for the throttle body area. If you are going to used forced induction this is a good time to replace your fuel pump. I will need to get a more recent picture to show the FPR setup.

The fuel rail is not optional. You must use a new fuel delivery system because, in this specific setup, it uses a dead head. Which means no return to your lude fuel tank. The prelude uses a FPR that's fixed to the end of the stock fuel rail where the RSX/TSX uses a FPR inside the fuel tank.

Throttle Body and Cable
The TSX is a drive by wire setup (DBW) and the prelude is a drive by cable setup (DBC) so this means you will need to do one of two options:
  1. Convert your pedal to a DBW and use an 06+ RSX/TSX ecu. TBH I don't even think this will work even if you use the 06+ ecu but I think its doable.
  2. Make a custom throttle cable from the prelude and a 05 accord with a k motor. You will basically snip of the end of the prelude cable and splice on the throttle side of the accord cable. You will also need a throttle body from the 05 accord or the one like hybrid racing sells. The 02-04 RSX ecu is DBC from the factory so this is the best option IMO. I still have not done this as I am still working out my coolant options but I am almost positive a bike shop could make this for you.

Coolant and Hoses
You have two options here as well:
  1. Use the stock radiator and make custom hoses. This will be tough because the top port will sit so close to the intake manifold. You will need a custom or aftermarket coolant overflow tank because the mount point for the stock on is on the battery tray which is no longer there because the fitment of the k motor.
  2. Use an EP3 radiator and the hoses for it as well. I have not yet test fitted the stock hoses but in theory they should fit since all these parts are form a k setup. I will update this if I find they don't work.
If you are using a turbo then you will most likely need a new upper coolant neck. This will allow more clearance for the heater hoses if using a sidewinder manifold. If not going with a turbo then I believe you don't need one of these.

Power Steering
It is possible to retain power steering without having to notch your hood and any wacky stuff. You have a couple options here with regard to the low pressure lines:
  1. Loop the line that use to run through the prelude trans and leave it in place on the subframe. This is by far the easiest method but may not have that clean look we tend to shoot for.
  2. Have a shop make you a small line you can bend and loop from one hole in the rack to the other and then you can remove the line mounted to the subframe. Picture coming soon.
I went with k tuned kit and it worked ok. The fitting will work fine but the line they give is too short for the prelude swap. You will need about 5-6 feet of PTFE line and a 90 degree PTFE fitting. You will make a new line just like the k tuned line only it will be longer and you will need the 90 fitting for the power steering rack. Be sure to mock it up first before you start cutting your new line. I reused the fittings that came with the kit and that should work but we will see. I have reused ferules before but not on something with 1000 psi so here's hoping lol.

The shifter will not bolt up to the stock holes so you will need to decide which method you want to do:
  1. Weld on a plate that is tapped for the correct size of the shifter pattern. I suck at welding so I did not do this.
  2. Mock up the shifter, mark it and drill holes. Insert rivet nuts for an M8 bolt.
I went with option 2 since it was cheap, quick and easy. The rear threads will need to be offset more toward each other than you think. The metal there is not flat and will cause the bolts to bind and jump a thread or strip the rivet out like I did mine. Luckily it was only one. You can see what I mean in the picture.


If you have any questions about the more detailed stuff like hose size, location of things and what not or you see something incorrect let me know. I will also be posting a spreadsheet of my parts and their costs.


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