The Notorious H23A to H22A Swap

[AcesHigh]

Okay, let's put this to rest. This is by far one of the most frequently asked questions in the 4th gen Prelude community. First off, this applies primarily to 92-96 Prelude Si owners. Prelude S owners will have a very similar swapping experience, except that their tranmission gearing is slightly shorter than the Si's.

The JDM H22A (No numbers... just h22a) is a desirable swap because it is relatively easy to do and more or less bolts right in. It has VTEC capabilities, a higher redline, slightly more torque, and in the end, a very nice 200hp the the flywheel. I have heard also that 4WS Si's can retain their four wheel steering and use the H22A.

The swap is very doable in your own garage. But what do you need for the swap? Well first, and very importantly if you don't have the mechnical knowledge for the swap, you will want a Helms manual for the Honda Prelude. You also need an engine lift, and the actual engine.

There are many places you can buy JDM engines. Here's a few:
http://www.hmotorsonline.com/
www.importautosalvage.com
http://www.totaljdm.com/
http://www.hondamotorsonline.com
http://www.ForceFedPerformance.com
http://www.japaneseusedengines.com
www.total-boost.com
www.jdmclub.com
http://passwordjdm.com/
http://www.modacar.com/
http://www.jbap.com/

I got my JDM h22a from http://www.jazzproparts.com/. Pick the perfect union of low mileage, condition, and price for you. Generally these places can't tell you the exact mileage on the motor (unless you buy a full front clip), only a range of numbers, so keep that in mind. While your engine is out, you should also look into replacing your clutch and flywheel. I am running a lightened ACT Prolite flywheel and am not experiencing any disadvantages to it. Just make sure it isn't lighter than about 8 lbs, or else it will be too flimsy. Take this chance also to change any belts that have been broken or worn, as well as water pumps and radiators as needed.

So then, you have the engine? You don't really need everything on there (although its safest to get a complete engine), so there are a few things you should know. The intake manifold for the h22a and h23a are identical. If the engine you are ordering doesn't have one, then don't sweat it. The exhaust manifold from the h23a will NOT work with the h22a; you need a new exhaust manifold as well as a downpipe. If your engine doesn't come with one, this is a chance to upgrade your exhaust manifold with a ceramic coated stainless steel header. Go with a cheap 4-2-1 header from ebay, and steer clear of regular stainless steel headers. You also have the option of going all out with this and purchasing the very desirable, and very expensive, Mugen 4-1 header. The 4-1 design sacrifices lower end torque for high end power. It is worth it.

You also need a new ECU. The p14 ECU from your Si will work, but the VTEC will not engage. It is okay to temporarily run the p14 ECU with the h22a block, although you may experience minimal amounts of knocking, resulting from improper compression. It won't kill your engine if you drive it softly. Anyways, you need a p13 ECU from a Prelude VTEC. If you are feeling that your wallet is a bit too thick lately, you can also choose to buy a p72 or p28 ecu from an Integra Type R and Civic, respectively. You do NOT want these ecu's for their stock properties, but rather you will want it because a neat little piggyback called Hondata (www.hondata) can be used with it. Hondata is important if you want to get the most out of your engine. The p13 will be your easiest thing here, and if you don't have alot of expertise in tuning, this will also be your safest bet.


The ECU is found under your passenger side dashboard. It is beneath your carpet and is protected by a metal shield. Take out all the screws, pull back the piece of rubber that conceals the ECU, and pull out that metal shield. Unscrew out the ECU.

The actual engine swap is pretty straightforward. The h22a block more or less drops right into your Si's engine bay. Mount everything up, put the header/downpipe on, and then you'll encounter your first problem. The fuel lines on the JDM h22a comes out on the wrong side! But fear not, there is a simple solution: You simply swap the fuel lines and rails from your old h23a block to the new h22a. It now works. You might also want to swap the emissions valve on your intake manifold.

Your old h23a tranny bolts right in. However, you have the very cool option of taking the JDM h22a transmission, complete with true limited slip differential (LSD). It will cost you more, but is entirely worth it (considering some people are buying LSD kits for other cars that are several grand).

You then run into the second problem, the ignition coil for the h22a is internal. To make it work, you must look again to the h23a. You have to use the h23a's external ignition coil. It plugs in, but you have to get a mounting bracket for it to hold it in place. I got mine from here (http://www.hondaautomotiveparts.com/...=IGNITION+COIL) for about twenty five bucks. You can also go to your dealer. It's #2 and #4 on that chart. If you don't have the bolts lying around, you might also want #6,#7 and #8.

Last, switch out the ECU. It should be a simple plug and play. The p14 ECU *will* start and run the car, but you will experience slight knocking resulting from improper compression. It's nothing to sweat about, you can still drive around. Swap over to the p13. You now need to run three wires. The first wire is a black wire on the pressure switch near the VTEC solenoid. You need to run this wire to the engine block as a ground wire. You now have two wires left. The green and yellow wire on the VTEC solenoid goes to A4 on your p13. The blue wire for the VTEC oil pressure sensor goes to D6. You will need the pin heads to plug these wires into your ECU, you can acquire these at your Honda dealer.


The arrow is pointed to the VTEC solenoid and those are the three wires you need to run to the ECU.

Here is a pinout of the p13 ECU:


The A, B, and D clusters are found as above. You can kind of see the VTEC solenoid wire in the picture above, it's the yellow and green wire in the 'A' pin cluster.

A1 brn Injector #1
A2 yel Injector #4
A3 red1 Injector #2
A4 grn/yel VTEC Solenoid Valve
A5 blu Injector #3
A6 or/wht HO2S heater coil
A7 grn/blk1 PGM-FI Main Relay coil
A8 grn/blk2 Shorted to A7
A9 blk/blu IAC Valve
A10 - -
A11 red2 EGR Control Solenoid
A12 blu/red Condenser Fan Relay
A13 blu/wht MIL
A14 - -
A15 red/blu A/C Clutch Relay
A16 wht/grn Alternator
A17 pink IAB Solenoid Valve
A18 - -
A19 wht Intake Control Solenoid Valve
A20 red/grn EVAP Purge Control Solenoid
A21 yel/grn1 ICM
A22 yel/grn2 Shorted to A21
A23 blk1 GND
A24 blk2 GND
A25 yel/blk PGM-FI Main Relay (power)
A26 blk/red VTEC Pressure Switch (GND)
B1 yel/blk PGM-FI Main Relay (power)
B2 brn/blk GND
B3 - -
B4 - -
B5 blu/blk To A/C Switch
B6 - -
B7 - -
B8 red/grn PSP Switch
B9 blu/red Starter Cut Relay
B10 orn2 VSS
B11 orn3 CYP
B12 wht CYP
B13 orn/blu TDC
B14 wht/blu TDC
B15 blu/grn CKP
B16 blu/yel CKP

D1 wht/yel Battery
D2 grn/wht1 Brake Switch
D3 red/blu KS
D4 brn/wht SCS
D5 - -
D6 lt blu or lt grn VTEC Pressure Switch
D7 lt grn/red Data Link Connector
D8 - -
D9 wht/red ALT
D10 grn/blk ELD
D11 red/blk TP Sensor
D12 wht/blk EGR Valve Lift Sensor
D13 yel/blu ECT Sensor
D14 wht HO2S Sense
D15 red/yel IAT Sensor
D16 - -
D17 wht/blu MAP Sensor
D18 - -
D19 red/wht EGR Valve Lift Sensor
D20 yel/wht TP Sensor
D21 blu/wht MAP Sensor
D22 grn/wht2 TP Sensor

There are no pin changes necessary, or any additional rewiring. After this you should have full VTEC capabilities. You'll hear a distinct sound when the VTEC comes on. One final note on the ECU, make sure the p13 you buy is for your respective tranny; the automatic ECU is not made for a manual transmission.

***
If you're lucky, many +93 USDM Prelude Si's come already wired for VTEC. You will notice that in the A4 and D6 slots there already exists a green and yellow, and a light blue wire. If this is the case, then it is easier for you. The end of the VTEC Solenoid (green and yellow) wire comes out at the passenger strut tower. It's near the area where your intake pipe crosses the battery and the strut tower. You will find a green and yellow wire that comes out of a bundle of wires.


The VTEC solenoid wire comes out and ends right at that connector. It doesn't connect to anything. You can either use that connector, or splice the wire.

The pressure switch (light blue) wire is near the fuse box. In that one of the two bundles of wires that comes out of the firewall, to the right of the fuse box, you will find a light blue wire. You'll know its the pressure switch wire because it connects into a terminal but doesn't come out of the other side.


Here, I outlined in light blue the pressure switch wire. You can use that connector or splice it. I spliced the wire, and temporarily taped it together using electrical tape. The purple wire is the new wire I connected the pressure switch wire to, it runs to the pressure switch.

***

Write down what your odometer says, and remember that number to keep track of your new engine's mileage. Drive safely. And remember that you should give the engine a "break in" period to get it to get used to the car. Some people say up to a thousand miles. Don't drive it hard. It's a good way to train yourself not to be a complete idiot and race at every single damn stoplight.

There you go. This is quite an easy swap and it's easy to see why many h23a owners opt to swap for their more powerful VTEC brother.

I hope this was easier with more pictures.

[integra111]

WOW, that helped alot. Im about to do the swap. How clean was the engine when you got it. Does it require any additional cleaning.

[AcesHigh]

My engine was more or less in excellent condition when I got it. It was supposed to be about 25k miles.

The chains that carried the engine to the shop and the ones I used to hoist the engine damaged the valve cover a bit, the paint was kind of chipping. Otherwise everything was in decent condition.

[510prelude]

how long did it take you?

[AcesHigh]

About two weeks. Most of it was from waiting for parts to arrive. If you brought it in for someone else to do the swap, they can probably get it back to you the next day. Provided you have all the parts ready and they don't have any other cars they need to work on.

[error54]

Excellent Post Aces. I was wondering what was the typical lifespan of a tranny? Is it better to get a new(used) one with an engine swap?

[510prelude]

dont most jdm motors come with a tranny already?

[ShoofIsLudin]

Aces your post was greatly helpful although i still have a problem with my non vtec h22a...I don't have all the vtec plugs. Is there a way to hook it up without getting the plugs...or is it a must for the plugs?

[error54]

Originally Posted by 510prelude

dont most jdm motors come with a tranny already?

I think it is an option from most online retailers. Its like 400-800 more expensive (depending on whether or not you want the lsd with the tranny). My question was asking if its worth it or not to get a new tranny with the new engine. I hear good things about the stock prelude tranny so it becomes a economic question whether or not to get a new one. I don't want to have put 5000 into my engine and have the tranny go.

[AcesHigh]

Yup, some offer it, some don't. I didn't buy a transmission knowing that Honda manual trannies are extremely durable, but... I do regret missing the chance to have LSD.

[crzyCollegeKid]

read this post out of sheer curiosity (5th gen owner) and now i'm curious. my car is jdm (not sure if all 5th gens were made over there), non-SH, would it normally come with an lsd?

[AcesHigh]

No, if I am not mistaken you have the USDM 200hp h22a4. All USDM models have a number after them. The 190hp motor from 4th gen and early 5th gen Preludes is the h22a1. There was no UDSM h22 that has LSD.

If you aren't sure if your block is JDM or not, you can check right here:

The engine code is printed right there, JDM ones do not have any numbers after "h22a".

[AcesHigh]

Originally Posted by ShoofIsLudin

Aces your post was greatly helpful although i still have a problem with my non vtec h22a...I don't have all the vtec plugs. Is there a way to hook it up without getting the plugs...or is it a must for the plugs?

Which plugs are you talking about? The pin heads needed to plug the wires into the ECU?

[ShoofIsLudin]

Originally Posted by AcesHigh

Which plugs are you talking about? The pin heads needed to plug the wires into the ECU?

I'm talking about the plugs of the vtec wires coming off the solenoid, and there's another green plug coming out of the block...sorry i don't know which ones they are. Coming out of my solenoid is 1 wire with a green plug at the end of it, and on the engine it self it looks like i should plug something in below the solenoid. I'm really sorry if this is confusing i wish i could post pics.

[AcesHigh]

Check the section in asterixes that I just added above. Do you mean those wires and plugs?