So I'm thinking about running picking up an Xcessive/GZ lower intake manifold with 4 injector ports and would like to run a 4-port FFE fuel rail with two ID2000 injectors in the outer ports for secondary injectors and two ID725 injectors in the inner ports as primary injectors. This would eliminate the need for the primary fuel rails. Has anyone ever done this?

If so how did you/they block off the primary injector ports on the center iron?

 

I have heard that running your primaries further away from the port can affect idle negatively.

 

Anyone got any first hand experience doing this? Interested as I'm planning to do the same, would make the top of the engine a lot tidier.

 

This is something that I was a bit worried about as well, but feel like that could be compensated for in tuning.

I'm sure someone has run this setup before, just haven't been able to find out who thus far.

 

I remember researching this back when I had my xs lim. You can run prim and sec in the same rail...just as you said tuning is the key here (injector phasing, staging, etc must be compensated for the longer distance from stock location. I know there is a guy on nopistons who ran 4 1000cc yaw injectors and reported it idled fine around 750-850 rpms using an AEM EMS. So its all in the tune. My concern would be trying it on a PFC, is there enough range in the tuning to compensate like the aem can?

 

I don't think PFC would have the range of tuning required to do this. I'm setting up a new Megasquirt MS3-Pro which will have plenty of adjustability to dial in the idle.

 

You will be fine. If you running a fuel management just add some more fuel to compensate for the distance / load. I'm running RC 1200 and I have no problems thus far.

Andre

 

Good to know Andre.

Any other opinions before I decide to try this my self?

 

I contacted FFE & Excessive. both advised me not to if I wanted a decent idle. I'll be running a primary rail based on those recommendations. For a track car, I'm told it would be fine.

 

Using what ecu?

 

That might be my car's setup: 4x ID1000's in the Xcessive LIM, the OEM primary injectors have been blocked off using a modified Racing Beat injector blockoff kit. It's been running nicely for a few years now. I posted some info in this thread here on rx7club:
https://www.rx7club.com/single-turbo...ve-lim-750406/

I posted some more info on another rotary forum, should be easy to find if you google '1994 RX-7 Xcessive LIM'


After comparing against a few other local (piston) cars with the AEM ECU's, my car's response if you smash the throttle at 1000-2000 RPM isn't as good as theirs... not sure if that's related to the the longer distance from the injectors to the intake port, decreased air velocity due to the larger primary runners in the XS LIM, the fact that I'm not the best tuner, or 'just a rotary thing' due to all the additional overlap a stock rotary engine has compared to most piston engines. Once the car is above 2000 RPM it behaves nicely.