Biggest injectors on stock fuelrail
 

I'm getting ready to upgrade some of my fuel system parts and wanted to know if you could fit Nippondenso 850cc injectors on the stock fuel rail without modifying the rail? Can you fit bigger than that without modification?

Also what type of fuel pump would work the best for an FD with all bolt ons and stock twins, 15psi?

The FD has 850 cc/min injectors in the secondary rail from the factory. The primaries are 550 cc/min and are a little longer than the 850s. You can use extra o-rings on the 850s to fit them into the primary rail. Or cut about 1/8" off the top of the primary rail injector housings to run the 850s in there.

You can also get your 850 secondaries enlarged to 1200 or 1300 cc/min at places like RC Engineering.

Or get a new rail to use 160 lbs/hr (~=1680 cc/min) top-feed injectors in place of the secondary rail. But you have to remove the ACV and get a block-off plate for that (which is no big deal, unless you need/want to keep the ACV for emissions testing and/or roadside "pop your hood" inspections by cops).

You need a stand-alone ECU (PowerFC, AEM, Haltech, others) to use larger injectors. Piggy-backs (PFS PMC, EFI PMS, A'PEXi S-AFC, etc.) and chip upgrades don't work very well with larger injectors.

-Max

A popular and good upgrade for a fuel pump is a Walbro 255lph pump. Look to pay about $75-$100 for one.

Hey max,
You say you can use the extra o-rings from the secondyary's to fit the 850's in the primary rail?
Will this cause a problem or I mean no fuel leaks or other problems

93 FD

I haven't tried it, but someone whose opinion I respect did it and it seemed to work out okay.

I'm putting 850s in my primary rail soon, and I plan to mill 1/8" off the top of the rail. I don't trust the extra o-rings, and I don't want to have leaks or have to go in there again to fix it if it doesn't work out for me. It sounds like an easy modification to the rail, and seems like it would both position the injector better and be more reliable.

-Max