ok i got 1600 and 720 injectors, a walboro but how can i make my fpr work with the sotkc fuel system what do i got to do and how do i install it u knwo the stard stuff oh and what part would i need also

 

....... Let me see if I understand you.
you have a Walbro fuel pump and larger injectors.
you want to know how to make the fuel pressure regulator work on the stock fuel rails?
what regulator do you have? what ECU are you running? why are you against new fuel rails?
There is not enough info for us to help.

 

If you want them to work with stock rails, you have to make sure the injectors you get are Japanese/Denso style or they won't fit. the Greddy/Denso 720's are exactly like the stock injectors and fit in perfectly. I've been told they are in fact originally the stock injectors for 1st gen turbo 12A motors. For the 1680's I've been told that the ones at the very bottom of this list: http://www.injector.com/fuelinjector...5e7d18448669db

will drop in. Then you need to make sure you have the right connectors. They usually just use the older Bosch "EV1" style : http://www.rx7store.net/product_p/injector%20clips.htm . Then you will need to make sure your car has resistors for the injectors. With all of that you should be able to use the stock FPR. FD's run 850/1300 on stock FPR all the time. But it's going to take a good tune to keep it from running rich at idle.

 

are you runing a stand alone ECU?

with that big a difference in injector sizes, you should run a parallel system.

 

Wouldnt a piggy back like a safc2 work?

 

No.

I also suggest an aftermarket fuel pressure regulator. The Walbro outflows the stock regulator and will raise fuel pressure. Not a big deal with a standalone, but an aftermarket regulator will give you more control.

 

how come?

what problems are associated with running them in serial with a large range of injector sizes?

(just curious, because i'm running 550/1680 and I'm about to swap the 720s I have lying around into the primaries)