GaryRudolph

The following briefly documents what I had to do to install larger (low impedance) injectors on my S2000 to run stock fuel pressure with my Vortech and AEM EMS. FYI, sorry about the blurry pictures. This camera doesn't have a lot of ways to focus at close range.

First, I opted to purchase the 685cc injectors from Ultimate Racing as they are slightly cheaper than RC Engineering. This sizing allows me to eventually run a 9 psi pulley on the Vortech. This should support up to 460 hp at the crank with stock fuel pressure, and should still allow a decent idle.

The first step I took was to remove the old injectors and get the fuel rail height figured out. As you'll notice in the next pictures the injectors are signficantly different.



Removing the old injectors is straight forward and follows the Helms manual. Basically, depressurize the fuel system, and start dissassembling. To calculate how much I would have to raise the fuel rail (as the URL injectors are taller) I put both sets of injectors into the fuel rail (with the rubber seat removed from the stock injector). Remember to add some oil to the o-ring before inserting into the fuel rail. I then measured the respective heights of the injectors using a caliper. The height difference is about 0.27 of an inch.



I then purchased an assortment of washers from the hardware store to raise the fuel rail by the size difference in the injectors. I had to place spacers on both the bottom and top of the fuel rail studs, and a longer bolt for the "arms". I had to make sure that there were still enough threads on the fuel rail studs so that it can still be torqued down without stripping. Because of sizing I had to mix some brass and steel washers. I really don't recommend the brass as they are easily compressed. I'll be talking to a machine shop about making steel spacers to the right height.

Here is the final raised fuel rail stud.



Here is the final fuel rail "arm". This utilized a longer bolt.



The next step was the wiring. These injectors are low impedance injectors and as a result require a resistor block. UR shipped the resistor block with the injectors.

I mounted the injector box near the master brake cylinder as such.



The OEM injector leads won't work with the UR injectors, and as result UR shipped injector leads with the injectors. Basically, what we did is cut the power leads (yellow/black) to the OEM injectors, and rewired through the resistor block. All the power to the injectors get tied together. Then they run out of the injector box back to the injectors. This adds additional resistance to the injectors. The ground lines are wired straight into the new connector.

The following is the cutting of a wire to tie all the power leads together to go the injector box.



The next piecture shows how the yellow/black wires were tied together into a single power wire to the resistor block. Then the resistor block is tied into the injectors with individual wiring. The ground lead is attached as is.

Here's a picture of the wiring before being wrapped in a loom.



Next, the wiring was all tidied up in a loom.




The AEM EMS fuel map was resized and car started. It should idle and tuning should commence as resizing the injectors is not as simple as rescaling the fuel map. The car behaves differently with a different size and type of injectors.

That's mostly it. I ended up throwing out my UR wiring diagram, but if I find one I'll post it.

honda9krpm

Gary, did you remove the vortech FMU and use the OEM fuel pressure regulator?
I've been told that it's best to use standard fuel pressure and bigger injectors than smaller injectors and increased fuel pressure. So with your bigger injectors, do you remove all the Vortech FMU and returns the fuel line as standard?

GaryRudolph

Yes, I forgot to mention that. The FMU from Vortech was removed. And the fuel line modifications that were made for the FMU were restored to stock configuration. So, everything regarding fuel except the injectors are stock under the hood, and should be stock fuel pressure.

But, I am still using the upgraded fuel pump from Vortech. As I not sure if the stock fuel pump can handle the flow.

dougiepants

Nice little write up