How to Use 450cc DSM Injectors on the 420a

A very cheap route to increase your fuel delivery capabilities are to combine
450cc injectors from a 4g63 motor with a hi-flow fuel pump.

450cc injectors can be bought used off eBay for (I've seen) as low as $25,
but typically they sell around $50 for a set (generally the ones not advertised
as working on Honda's sell for less). This should be a good search string
to paste into eBay, "(dsm,4g63) ((blue,black) top, 450*) injectors".

The required resistor pack needed to run the low impedance injectors can also
be found on eBay, and for about $8. You can use a resistor pack from a
4g63 or from a Honda. I'd try searching with this string "(dsm,honda,4g63)
resistor pack". I'd stay away from the home made packs because they lack
the heat sink shell, which could possibly prevent a fire, a lean (or rich)
condition, and definitely keeps the resistors alive longer.

If you don't want to pay to have them cleaned and balanced before installing
at least have a bottle of injector cleaner ready to use.

Buy some replacement injector o-rings for the 420a stock injectors. I went to the dealership and they sell them in pairs, and they
wanted $16 per PAIR (that's $64 for 8!). I kindly laughed, then went to
O'Reilly Autoparts and bought 4 pairs of 420a injector o-rings for about $5.

To install:

• Remove the injector harness and then the fuel rail from the car
• Make your new injector harness
  • Take off all the electrical tape and wire loom protecting the
    harness (you can leave a couple inches of electrical tape on the
    injector plugs)
  • Solder and heatshrink (<··· highly recommended) the connections as
    shown in this diagram,
    using 14-16 AWG wire, leaving around 18" or so, to locate the resistor
    pack on the firewall. (This is a slightly modified
    version of a diagram I had on my computer, I'm not sure who made it, but
    email the admin to claim credit.)
  • Cover in newly assembled harness in some protective wire loom.
    You can use an existing bolt to mount the pack.

• Next, you need to fit the 450 cc injectors into your fuel
  rail

  • Remove the stock injectors (pop the retainer clip off,
    then pull them out)

  • Remove the o-rings and rubber stoppers on the 450 cc
    injectors (may not have any one them)

  • Install your new 420a injector o-rings onto the 450 cc
    injectors

  • Lube the o-rings w/ engine oil, and carefully put a
    little around the inside wall of the fuel rail (where the injector's
    slide in). If your fingers are big you can carefully use a
    q-tip to lube up the inner walls (just don't get any stray fibers left
    in there).

  • Push the injectors into the rail.

    • It's very important the o-rings don't get pushed out
      of there groove when trying to get them started.

    • It's a tight fit, but I found that carefully using a blunt, flathead screwdriver you can push the little nub in
      that will try to resist when you have the majority of the o-ring
      pushed into the fully rail. It's critical you don't scratch
      the inner wall of the fuel rail when doing this, or damage the
      o-ring (although they are pretty tough actually).

  • Ignore the injector clips. The 235 cc injector
    retaining clips don't fit the 450 cc injectors, perhaps some clips for a
    4g63 would work, but I didn't have time to get some to try it.
    They aren't necessary.

• Now, with the lower o-rings lubed, carefully position the
  fuel rail into place.

• Tighten the two bolts alternating between the two every
  quarter to half turn (this is to keep the tight fitting o-rings going in
  straight

• Install the injector harness

Just as a side note, I keep my idle fuel pressure at 16 psi, and
static (0 psi intake manifold pressure) at 17-18 psi. I still have plenty
of head room on my fuel trims.

Enjoy!

This Mod was written and submitted by Joel Baldridge, aka WickedESi