For your money, I don't think there's a more cost effective injector upgrade available when you consider how little modification is required to make this work. Sure, you can get used S15 450cc injectors that require no modifications, but the yellow top Subaru injectors are more readily available and have a higher flow rate.
Any time you want to install used injectors, I'd highly recommend having them professionally cleaned. Lots of companies offer cleaning and flow testing services, but most want to charge extra for side-feed injectors for some reason. I've dealt with Witch Hunter Performance and would recommend them to others. For about $100 total, you can ship your injectors to them, get them tested, cleaned, retested, and shipped back to you with new seals and pintle caps. They're basically refurbished to like new condition. If you get a good deal on injectors, you could end up with a full set of like-new yellow-top injectors for less than the cost of one new Nismo or Tomei injector.
I did this upgrade on my S14 SR20DET, but it should apply across all Nissan engines that use side-feed injectors and want to use Subaru side-feed injectors. You wouldn't think there would be much difference since they're all made by JECS; but the connectors are different. From what I had gathered from the intrawebnets, there were two options: splice in the Subaru pig-tails, or simply re-pin the Subaru connectors onto the Nissan injector harness. I chose to change the connectors for three reasons: 1- When I bought the injectors, they only included the clips. 2- My initial inspection made it appear that the pins were identical, so re-pinning should've been a piece of cake. 3- Even if I had the pigtails, I didn't want to solder splices on fuel injector wires.
After I got into this, I cursed everyone who said to just re-pin the connectors. It turns out, they use different pins as well. The Nissan pins are square and won't fit into the Subaru pins which have a notch.
Nissan clip:
Subaru clip:
I back-lit the clips so you can see inside where the pins go. You can see that the way they attach to the injectors are completely different, but that's not really a big deal. In both pictures, the pin retainers are on the top. Notice that in the Subaru connector, there is a very slight notch. Why on earth they felt the need to notch the pin is beyond me, but that tiny little piece of plastic makes this swap 4-times more difficult than it should be. I would have preferred modifying the connectors, but I couldn't figure out any way to make that happen. Maybe an extremely fine point on a soldering iron could have melted them. Maybe a very tiny and very sharp chisel could have scraped them out. Maybe a very thin strip of sand paper could have ground them down. That all sounds like a lot of trouble. My best solution was to notch all of the pins to fit the connectors.
Let's start at the beginning now that we know what we're up against here. First, you'll need a set of picks. You can get them at Harbor Freight for free with a coupon sometimes; otherwise, they're a whopping $2. You could also spend big bucks on some fancy electrical pin tools, but I rewired my entire engine harness from ECU to engine with the HF set. Also, I'm going to assume you've all ready got your fuel injector sub-harness removed and that you've got your Subaru connectors. I'd suggest labeling the wires on your sub-harness just because it's best practice. If you're not removing the loom or doing extensive rewiring, it should be pretty easy to figure out that the wire lengths correlate to injector position. I don't know if the polarity is important on the injector, but I'd think it would function whether or not you get the wires crossed. I kept the pin orientation relative to the retainer and my car runs great.
The first few pictures don't have any wires because it was easier to photograph and illustrate the procedure this way. Most of this work requires two hands, so taking pictures and doing this simultaneously is impossible. You'll figure it out. Anyway, unpinning either clip is the same process. In fact, the orange retainer inside the clip is identical for both.
Lift/pry on the inside of the tab on the retainer.
You'll be able to see the little notches that secure the retainer, once those are clear, you can use a second pick to lift the retainer out of the connector.
Here's what it looks like now.
This part requires pretty serious dexterity or another set of hands. You need to lift/pry on the inside of the pin clip (just like we did for the tab on the orange retainer) and gently pull the wire from the back. If you do this correctly, it should slide out pretty easily. If it's not coming out easily, you're doing it wrong. Don't force it because you can easily pull the wires from the pin.
Once all of the connectors are unpinned, go ahead and start notching the pins. I used my Dremel with one of the small cuting discs.
Don't go crazy here. Keep the pin and the disc parallel and only remove as much material as needed to get the pin to fit securely. That will require a few test fits to figure out, but once you get the hang of it, it goes pretty smoothly. Be very careful though as you can easily wreck the pin, cut the wire, or cut your finger. All of which result in a bad day. I'd recommend holding the pin with small pliers to keep your digits out of the kill zone.
Here's a before and after shot.
Now just insert your modified pins into the Subaru connectors and you're all set. Reinstall your fuel injector sub-harness and continue with your fuel injector upgrade. Good luck!
