JDM vs. USDM H-series Ignition System

I received an email from a fella who dropped a JDM OBD1 H22 engine into his ’94 Prelude Si. He mentioned having engine performance issues whilst using a JDM OBD1 P13 ecu. Issues like, engine revs up slow – vehicle feels sluggish – and backfiring. He also mentioned that he retained his Si/H23 engine wire harness, ignition parts (distributor + external coil), and injectors. After pondering a bit, I vaguely remember H-series equipped JDM vehicles (Accord SiR family / Prelude) have a slightly different ignition system setup vs. their USDM counterpart (Prelude’s mainly) and that this may be the reason for his ignition issues – He’s using a JDM P13 ECU with a US an OBD1 Prelude ignition system.

H/F-series Internal/External Coil Hierarchies

• JDM 92-95 Prelude fam = internal coil ignition / distributor
• JDM 96-01 OBD2 Prelude family = internal coil ignition / distributor
• JDM 90-97 OBD1 + OBD2 Accord family = internal coil ignition / distributor
• US 92-95 OBD1 + 96-01 OBD2 Prelude family =  external coil ignition / distributor
• US 94-02 OBD1 + OBD2 Accord family = external coil ignition / distributor
• US 90-93 OBD1 Accord family = internal coil ignition / distributor (blacksheep!)

So, regardless of OBD type or SOHC/DOHC engine make, JDM 4-cyl Accords & Preludes all have an internal coil ignition systems while US 4-cyl Accords & Preludes all have external coil ignition systems (excluding 90-93 Accords lol). I’m just gonna say it, I hate how Honda complicated these vehicles compared to civics & integras.

Because this fella is using an internal coil dizzy on his US prelude (and luckily all parts being OBD1) he just needs to make light changes to his external coil wiring in order to comply with internal coil dizzy use.

The fix he needs is mentioned here: http://www.preludeonline.com/3015632-post5.html but since photobucket has gone full retard recently, the images are not showing up. So try this thread: http://www.cb7tuner.com/vbb/showthread.php?t=84028

The mentioned fix/life hack is to unplug the external coil connector – since it is not required with an internal coil dizzy – and to jump two of the female pins within that harness side connector with a 30amp blade fuse to bridge the connection (as shown). Alternatively, the two wires leading to the female pins can be cut and spliced or soldered together effectively eliminating the whole external coil plug, if you really wanna dick around with doing that (skip!). Personally, I wouldn’t cut the plug off as there may be an unforeseen time in the future when you may need to go back to an external coil setup….you never know.

There are several other ignition related scenarios I will post up at a later time. Scenarios mainly surrounding the mismatching of OBD1 & OBD2 distributors, ECU’s, and full on engine swaps:

• JDM OBD1 to US OBD1 prelude/accord & vice versa
  as mentioned above, this is simply an external to internal coil conversion job (i.e. fuse trick)
• JDM OBD1 to US OBD2 prelude/accord
  a common scenario when swapping a JDM OBD1 H22 into a 96-97 accord or 96-01 prelude, ecu being used plays a major role in this scenario. A detailed write on this type of swap can be found on my friend’s website HERE.
• JDM OBD2 to US OBD1 prelude/accord
  swapping a JDM OBD2 F/H engine into a 92-95 Accord or Prelude. There’s several points with this type of swap that need to be taken into account but the easiest route is reusing the existing OBD1 wire harness/ecu/and all ignition parts on the JDM OBD2 engine being swapped in. The problem that can occur is if the end-user wants to use the JDM OBD2 ecu that comes with the specific JDM OBD2 engine swap (i.e. JDM Accord Euro-R H22A / JDM Prelude H22A Type-S).
• JDM OBD2 to US OBD2 prelude/accord
  ex. JDM H22A Accord Euro-R / JDM H22A Prelude Type-S/S-Type / JDM H23A VTEC into a 96-97 Accord or 96-01 Prelude. While the ignition system is easy to deal with, the ECU + fuel injectors become a factor in this motor swap scenario specifically for the 96-97 Accord and 1996 prelude. 

The choice of ECU being used with the mentioned scenarios play a big role in what mods are required to stay clear of ignition problems. As you can see, the ignition topic segues into motor swap territory.