When we last left the RB25 S13, the injector duty cycles kept us from bumping up the boost and making some real power. The solution? some 760cc top feed Precision Injectors to help our S13 crack the 450whp mark.
Parts you will need for this conversion
First we begin by opening the fuel cap and disconnecting the fuel feed lines, engine harness and fuel filter setup.
Next unbolt the 3 12 mm bolts to the rail and lift the entire rail along with side feed injectors, take care when doing this because you don’t want to lose your fuel rail isolators ( the plastic pieces that space out your rail from your head.
Jesse was using a Z32 fuel filter, which we will be ditching for a Aeroquip -6 1000 micron inline filter.
Someone light a match and throw it at John! QUICK!
Next, install your injectors into your aftermarket rail, take care when pushing the injectors in so to not damage your o-rings. Without any damage to our o-rings, we test fit the aftermarket rail onto our RB25.
The particular rail setup we are using is the JGY unit, and although the fitment is rather questionable, the low cost of this piece makes it manageable.
Ahh... so much nicer
If you own a JGY rail, now is NOT the time to tighten it down to the head unless you feel like removing the rail to plug your injectors in.
After installing the injectors into your rail, install your liquid filled fuel pressure gauge into the 90 degree 1/8th inch NPT fitting, and then screw the entire assembly into the regulator. Depending on your setup, you may need to install the fitting before the gauge.
Next, take the rubber fuel lines off of the hard lines located on the passenger side of the vehicle.
Take a pipe cutter and pick a spot on the hardline that has a fair amount of straight section to it.
Make sure to use caution as to not kink or bend the hard lines, this setup is meant to terminate at the firewall, so if you intend on running full stainless line back to the tank you’ll need more than 4 feet of the hose.
Next take your -6 AN to hard line compression fittings and slip the cone end over the hardline you just cut.
The S13 uses 1/4inch size hardlines, make sure the brass fitting slides snugly over the line and compress the two ends together to create your seal.
After both compression fittings are installed, it’s time to move onward to the injector wiring.
Most companies sell their injector setups complete with pigtails to convert from the old clips to the new ones. If not MSD sells them seperately for around 2 dollars apiece at most retail stores or websites.
Wiring of these injectors is straightforward, make sure to have the injector clip orientation consistent for all six new clips.
Use your -6 male to 3/8th pipe fittings now on either end of your rail,depending on where or how you want to run the lines, the other 4 swivels will comprise the rest of the fuel setup.
Once all the lines and hardware is installed, then tighten the rail brackets onto your head.
We had to use 2 of the brackets as JGY did not properly machine their rail to take 3 mounting brackets. Further we had to use the factory isolators on the opposite side of the bolt to make things tight and secure.
Once bolted down, turn the key to the on position to pressurize the lines so that you can check for leaks. Once we found no leaks we started the car and adjusted the fuel pressure accordingly. Make sure to double check for leaks after the car is started, as pressure will be significantly higher than it was with the key at the “ON” position.
With no leaks and the fuel pressure adjusted, we are now ready to tune the car. With time running late, i use Jesse’s hand held Power FC Commander to make some small adjustments to the part throttle map and the cold start map along with the idle map.
The Power Commander is quite useful if you are in a bind, or need to clear up a rough spot in your tune.
But with a viewable map grid of 9×9 cells, it makes tuning a vehicle such as this rather cumbersome.
Come get some... RB25 Power
Next we will hit the dyno with a full laptop and FC Edit to squeeze as much power out of the S13 as possible.