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H22A swap guide

Update! Distributor Wiring Now Included!

If you are in a giving mood  

Most people know about swapping B16's and B18's into civic's.  It's the most common swap that anyone can undertake.  Most people do not know of another easy, but not quite as common engine swap.  The H22A Prelude engine into an Accord.

Why is this an easy swap?  The fourth generation Prelude was well known for it's Si and VTEC trims (H23a and H22a respectively) but the less common S trim was available with an F22 accord engine.  If the accord engine fit in the prelude, then why not put a more desirable prelude engine into the accord?

Mechanically, it is a very easy swap.  There are details that need to be covered, and I'll just focus on them.  Writing a how-too is more than I was willing to undertake for this particular project.

Research

While researching the swap, I discovered that the '96, '97-'99 H22a engine wiring harness plugs are different than those found on '96 and up F22a plugs.  This leaves you with one option:  You must modify the accord harness to work with the new engine.  Please note that at this time, I have not investigated the plugs found on '95 or older F22a's.  They may be the same allowing you to use the H22a harness on a older accords.

Engine Harness

Since I was dropping a '93 H22a into a '96 Accord, I had to modify the accord harness.  The '96 accord used crank triggering that is located by the crank rather than the inside the distributor.  Careful cutting  and splicing is necessary to reroute the wires to the distributor.  The trigger is the same on the crank as it is on in the distributor allowing you to use any ECU.

The Dirty Work

The most difficult part of this project was the wiring change from an OBDII Accord to an OBDI H22a.  This chart will provide you with the info that you need to do a similar swap.  As you can see, there are great similarities between the OBDII Accord and OBDII H22a.  The only wires necessary for this swap would be the addition of a VTEC pressure switch wire, Knock sensor, and IAB solenoid.

Note:  The chart can be used to convert an OBDII Accord to an OBDII H22a

Below the chart is a picture of the wiring necessary for an OBDII to OBDI conversion. 

ECU PIN Prelude '97 Accord '96 93 Prelude
A1 INJ4 INJ4 a1
A2 INJ3 INJ3 a2
A3 INJ2 INJ2 a3
A4 INJ1 INJ1 a5
A5 SO2SHTC SO2SHTC x
A6 PO2SHTC PO2SHTC a6
A7 ESOL ESOL a11
A8 VTS VTS a4
A9 LG1 LG1 a26
A10 PG1 PG1 a23
A11 IGP1 IGP1 a25
A12 IACV  IACV a9
A15 PCS PCS a20
A16 FLR FLR a7 a8
A17 ACC ACC a15
A18 MIL MIL a13
A19 ALTC ALTC a16
A20 ICM ICM a21 a22
A22 LG2 LG2 b2
A23 PG2 PG2 a24
A24 IGP2 IGP2 b1
A25 ICSOL IARSOL a19
A26 IABSOL x a17
A27 FANC FANC a12
A28 2WBS 2WBS x
A29 VSV VSV x
       
C1 VREF    
C2 CKPP CKPP b15
C3 TDCP TDCP b13
C4 CYPP CYPP b11
C5 ACS ACS b5
C6 STS STS b9
C7 SCS SCS d4
C8 K-LINE K-LINE x
C10 VBU VBU d1
C12 CKPM CKPM b16
C13 TDCM TDCM b14
C14 CYPM CYPM b12
C15 VTM x d6
C16 PSPSW PSPSW b8
C17 ALTF ALTF d9
C18 VSS VSS b10
       
D1 TPS TPS d11
D2 ECT ECT d13
D3 MAP MAP d17
D4 VCC1 VCC1 d19
D5 BKSW BKSW d2
D6 KS x d3
D7 PHO2S PHO2S d14
D8 IAT IAT d15
D9 EGRL EGRL d12
D10 VCC2 VCC2 d20
D11 SG2 SG2 d22
D12 SG1 SG1 d21
D13 x SHO2SG x
D14 SHO2S SHO2S x
D15 PTANK PTANK x
D16 EL EL d10

Distributor Wiring

I've had quite a few requests for distributor wiring so I've taken the time to add this update.  The only wiring I have is for the H22a equipped with an internal ignition coil.

Sensor OBDI wiring (prelude dist) OBDII wiring (accord dist)
TDC Orange/Blue Green
White/Blue Red
CKP Blue/Green Blue
Blue/Yellow White
CYP Orange Yellow
White Black

This is exactly how I wired the distributor and it worked flawlessly.  You may want to twist the wires and wrap them in tin foil to reproduce the shielded wiring that makes up the wires to the distributor.

The '96 Prelude

This was the only 4th generation prelude that had an OBDII engine computer.  This makes the '96 ECU a very desirable ECU for H22a swaps into OBDII accords.  In '97, Honda incorporated a theft deterrent immobilizer system that makes using '97-'99 ECU's much more difficult. 

Motor mounts

In order to drop the H22a in without any hassles, it will be necessary to use the rear, passenger side and front accord engine mounts.  The prelude mounts will NOT work.  Also, you will need to grind down the driver's side prelude mount to make it fit properly.

Air-conditioning

A little experimenting always goes a long way.  You can retain your stock AC system as long as you use the accord AC bracket and compressor.  The prelude AC mount will work if you want to try and use a prelude AC compressor.  However, if you have a working system in your accord, there is no need to replace the components.

Main Crank Pulley

If you use the Accord AC compressor, you will definitely need to use the accord crank pulley.  This makes it easier to buy belts.

Axles

You can use either prelude or accord axels and intermediate shaft.  They are essentially the same.  On the intermediate shaft side, you cannot mix accord and prelude parts.  The connection is different between the two

Cruise control

On the '96 accord that I worked with, the cruise control used a second cable that attached to the throttle body.  Most Hondas run the second cable into the cabin where it attaches to the gas pedal.  A set of prelude pedals should take care of this problem.  The other solution would be to use the accord throttle body.  This will give you a smaller throttle body so an aftermarket accord throttle body may be the answer.

Power Steering

The only success that we had with the power steering setup, was to splice the the accord line with the prelude line.  You will need the original high pressure line from your car and most of the H22a line that came with the donor engine.  Take the lines to a reputable shop that does high pressure lines.  Use the complete line from the prelude along with the hard line from the accord (the hard line from the rack side).  This setup worked flawlessly.

Immobilizer

'97-'01 Prelude ECU's have the immobilizer function built-in and will either require you to rebuild the immobilizer function or have the computer modified.  Your best bet is to try and find a '96 prelude ECU or convert to OBDI in the case of '96 or newer Accords.