well the O-Rings on my injectors are leaking and I was thinking I might as well replace the injectors.. If I am planning later on to upgrade to a single turbo set-up can I upgrade my stock injectors to 720cc primaries and 1220 secondaries without any fuel mods? Right now all my car has is an greddy ti exhaust and ARC box intake.

 

If you have a Aftermarket ECU you can run bigger injectors

What car is it FC/FD?

FCs you can use normal injectors
FDs use Side feed injectors so there is alot of moding to make new injectors work.

 

I have an fd? so I can just change and go with new injectors? I have to side feed? what about the stock ones I have now, they are leaking

 

you would need a new fuel rail due to the fact that MOST aftermarket high flow injectors are of the top feed variety. You will not be able to simply swap stock flow rate injectors for Higher flow rate injectors without software modification. Your stock computer will be holding the new injectors open for the same time as the stock injectors, but since they will be of of a higher flow rate they will be injecting a much higher volume of fuel causing your car to run waaaay too rich...for example. If you were to swap the injectors as you propose you will be running (720-550)/550 = 31% more fuel from your primaries and (1220-720)/720 = 70% more fuel from your secondaries, assuming the fuel pump can provide it, and the injector opening times remain the same. Therefore you can not simply swap injectors without modifying the computer to hold the injectors open for that percentage of time less then stock, assuming you want the same fuel supplied. NOTE* due to the higher inertia of the pintle valve in high flow rate injectors the actual fuel supplied will be somewhat less then the figures quoted if the pulse width is reduced by that percentage, but that is irrelevant to this case cause it will still be too significant a departure from stock to function without software modification...My suggestion is to simply replace the o-rings in the current injectors and call it a day