We have been driving our Nissan 240SX on some Low Impedance Mitsubishi EVO 550cc injectors and running the car on low boost (wastegate spring pressure at 12psi) on a totally stock KA24E motor for some time now. Earlier this summer the KA24E was rebuilt with new pistons and headwork to see how much we could crank out of a motor long forgotten and overlooked.
We will be shooting for 18psi on pump gas and the OEM Mitsubishi injectors were maxed out, so it was time for an upgrade. We choose Injector Dynamics 1000cc High Impedance Top Feed Injectors for their excellent tunability. These are some of the best aftermarket injectors and are some of the most consistent and reliable injectors we have used to tune with. After making a call to our friends at Injector Dynamics we had a set of their injectors for the KA24.
This is basically what you get from Injector Dynamics, 4 injectors, harness clips, and the fuel rail adapters. There is also the option to get a pig tail harness so there is no need to rewire anything, it is a simple plug and play install. We will be going through a rewired install, still very simple and takes about 2-3 hours total.
1. First remove the fuel rail and old injectors. In our situation we had a resistor box to run the Low Impedance Mitsubishi injectors, so that was removed as well.
2. Once all of the old injectors are removed and the fuel rail is out, it is necessary to drill out the injector ports on the fuel rail to 11mm. Nissan is the only manufacturer that strayed out of the standard 11mm and 14mm injector ports and on some motors use a 10.5mm port. This is easily done with a trip to the local hardware store to get a 11mm or 7/16″ drill bit. Make sure the fuel rail is locked down solid. It is best to use a drill press to do this, but can be done with a hand drill if done very carefully.
3. Now we are ready to start wiring in the new injectors. Since the injectors work on a signal and aren’t polarity specific the wires can be installed either way. For cleanliness and possible troubleshooting if ever needed it is best to stay consistent. There is a constant 12v wire and a signal wire from the ECU that tells the injector to open. You can see we used a extra length of red wire for the 12v and a blue wire for the signal wire. Make sure to solder the connections!
4. After getting the extra length of wire in and soldered, get some tubing shrink wrap and slide it over and heat it up to shrink it down.
5. Slide the green waterproofing seal over the end of the wires. Now we can install the metal wire clips that hold the wires into the injector clips. Cut about a 1/2″ length of the end of every wire and slide into the wire clip. There are two metal crimps. One crimps down over the exposed wire, the other longer crimp clamps down on the wire still with the insulation in place.
6. Once all of metal clips are in place, grab the plastic injector clips and slide them on. You will hear a quiet click as the metal clip snaps into place inside the plastic injector clip. Push the green waterproof seal down into the injector clip.
7. We are now ready to put the fuel rail back in. First slide the injectors into the fuel rail. Put the fuel rail back in place and make sure that the O-rings that seal the injector into the manifold are in place and lined up. Bolt the fuel rail down.
8. Snap the injector clips into place on the injectors. 
9. It looks like it will run! There is one last thing that is critical after installing new injectors and that is a boost leak test. This will insure that the injectors O-rings are seated correctly and they won leak under boost.
10. Make the necessary changes to the EMS and the car should fire right up! After the car has started make sure to check for any fuel leaking at the rail.
11. Of course tuning is going to be necessary with the new injectors installed. But the changes are fairly simple and should be able to be applied over the entire fuel map.