I just finished swapping in a k20z3 engine and trans into my 2006 base RSX (5 mt) and I wanted to provide a write up based on my recent experience. This write up is for 05-06 base 5 speed rsx’s who want to swap on a k20z3 motor and trans.
I will caveat, it may be more cost effective to just buy a Type S, but here in Nashville it was hard to find one at a reasonable price and condition. I picked up my really clean 06 for $3000, with 230k miles. I paid $2600 for the z3 motor and trans with 160k miles.
I waited until my throw out bearing fried itself until I performed this swap. It’s a little challenging but totally doable.
Here are the steps I took / lessons learned:
parts needed before you start;
02-04 type S (or base) ECU with hondata
Throttle body adapter for RBC
New clutch kit
Maintenance items like timing chain etc at your option
-6 speed type s shifter (I opted for a hybrid racing shirt shifter)
1.)check compression of the motor you are buying if you can. I neglected this step, and I would have found my #4 cylinder was low, due to bad valve lash, possibly bad valve (not sure yet time will tell)
2.) put in a new clutch, much easier to do this now with your motor and trans sitting on a pallet/garage floor
once your trans is apart, spin the input shaft, make sure your bearings are still good. Mine sounded like sand paper, so I changed the input shaft bearing along With the countershaft bearing. This is not for the faint of heart, but it’s doable.
here’s a good write up for a 7th gen civic but it’s basically the same:
Transmission DIY - DIY: Input Shaft Bearing - This is an Input Shaft Bearing DIY for 7th Gen Civics with a manual transmission. It can also be used to replace the clutch. This guide involves removing the transmission from the top so that you don't have to disturb the sub-frame and get an...
3.) depending on the mileage and intended use consider changing the timing chain, oil chain, tensioner, idler tensioner, belt, water pump. Type s oil pump and pan, now would be the time. I opted to leave the z3 pump in place. I’m not sold that that it is that much better to switch it out. I am planning on time attack for my rsx and will report if I have oil starvation.
4.) take the z3 shift selector out, take the a3 shift selector out. Swap everything over from the z3 shifter onto the a3 Arm. Alternatively just buy and put in a type S shift selector. For reverse lock out I’ve read you can utilize the IMRC wires and repin the ECU. I haven’t done this yet and will update this once I do. Search forums.
-next put the Franken shift selector in the z3 trans and bolt in the two bolts that do fit. Punch the holes/drill a pilot hole. You need m6 1.0 tap. Tap the holes.
-Honda bond your selector in and case as well if you were brave enough to change out your bearings.
Here’s a link to a write up I followed: Write-Up: RSX-S Shift Selector installation into a...
5.) optional: take your valve cover off and perform valve lash adjustment. so much easier with it out of the car on an engine stand.
6.) swap out the following sensors:
-oil pressure sensor
all other sensors I found plugged into the base wire harness. Not getting any abnormal readings on my MAP or crank or TDC sensors, and VTC and VTEC all working normally. I will update if I find that I need to change any of the sensors out.
-I elected to use the MAP sensor that is on the RBC manifold, just pull the wire out of the harness a bit to make it reach.
7.) swap the A3 starter and AC compressor onto the z3. The wires will not plug in otherwise
8.) bolt in your power steering pump.
9.) install serpentine belt / valve cover.
10.) remate your engine and trans.
11.) take out your base axels, I just took out the two strut bolts instead of the lower ball joint.
12.) remove a3 engine and trans. If you care about the environment take your car to get its AC lines discharged. Otherwise vent that shi out I guess but really not hard to just do it the right way.
13.) I installed upgraded engine mounts, went with innovative 85a mounts. They are an absolute PITA to install though. I’d recommend using the factory driver side mount and passenger side mount, then change them one at a time once you have all four mounts in.
-reuse your RSX mount brackets, except the Passenger side bracket, that should remain the z3 bracket and it is much beefier. It will line right up with the factory mount.
14.) use the A3 shift cable brackets, the bolt into previously unused bolt holes. This is contrary to another post that said you can’t reuse your brackets, not true!
-drop in the z3 motor and trans. Be careful and make sure you have two points of attachment on both sides. I had the passenger side mount stud rip right out on me while lowering into place, took a chunk of thumb out and it was a mess. Bent my power steering pump in the process. I ended up using the two bracket bolts going through the timing cover.
15.) install RBC adapter. I used a cheap bull boost one, had To grind it to make sure it didn’t interfere with the throttle body. I installed the a3 TB, for now but do plan on upgrading to a 70MM one.
16.) you may need to grind a bit on your hood latch support to make your TB work. I had to remove the cover plate in the TB as well for additional clearance. The RBC manifold is way biggerz
17.) plug everything in, you will need to cut up your wire protectors/tape to make the factory a3 harness reach you coolant temp sensor, reverse sensor, map sensor.
The VSS is the same so no worries it will plug right in and work. This is for 05-06’s onky
18.) connect evap, IACV, pvc. Or do like me, cap all of it off.
19.) hook up intake, I didn’t bother with the stock air box, I suggest a CAI. I installed a $20 flex hose and a $45 k&n filter for now till my CAI gets here. The stock air box doesn’t look like it will fit, the manifold is in a way different location.
-use rsx exhaust manifold. Z3’s is a different angle the dangle.
20.) hook up coolant hoses. The upper radiator hose fit fine. The lower was a struggle, I ended up using a 24” 1 1/4” flex hose from advanced auto. It will fit but it’s not great. I will update if I find a better solution. Right now it’s pressing on my cooling fan hard but working. You’ll need longer heater hoses as well. I haven’t installed those yet and I will update with solution once those are uncapped. It was hard to find a good match at the part store, the coolant thermostat housing cock stick up like a teenagers stiffy, so the hose has to go up and down pretty severely.
21.) install your k-pro or tunable ECU. Don’t forget you need an 02-04 primary O2 sensor for the kpro ecu to work.
-note: I was able to drive it on the a3 ecu, but it’s giving a lean code 1157 along with all cylinders misfire codes. So in a pinch you use the a3 ecu but it’s not going to run right.
22.) use the Base Axels, they bolt right in.
23.) bleed power steering pump. Burp the coolant. Add 5w30. Add 1.6 quarts of tranny fluid.
24.) tune and enjoy your new swap.