Hello! I searched around for people with the same problem and found fuzzy answers. In have a pineapple racing lower intake manifold and an OEM LIM as well. The aftermarket one that I have installed now has space for 4 secondary injectors. I am aiming for 300-400 hp on a single turbo. Can I use 4 secondary injectors? If so what cc? How do I hook this up to the ECU and that, do I just have them run half the time I would with 2 secondaries? Thinking of running Link ECU. It’s an Efini FD rx7 from 1992, so some stuff on the UIM is already blocked off. Any help would be greatly appreciated. Thank you



Should I use this with 4 injections or the OEM LIM and block off vacuum and all that?

 

for 300hp the stock FD injectors are totally ok, 550x850, to do 400 you would need more like 4x1000. i don't think it makes any difference weather you run 4x1000 or 6x660 or 2x550 and 4x725's it all comes out about the same amount of fuel.
its more like which would be simpler and less expensive to do. since you give a range, you'd probably want to have enough fuel for the higher number.

 

Remember that the additional holes in that LIM are sending fuel to the primary intake runners, which already have injectors in the center iron. The primary intake ports are smaller than the secondaries on most engines, so it doesn't make sense to add a lot of fuel to the primary intake runners. The OEM injector flow rates are about 40% from the primaries and 60% from the secondaries. So if you do add extra fuel injectors, try to use the ECU's injector trims so you're not doing something silly like sending 70% of the total fuel through the small primary intake ports.

 

welcome to the board.

here's what i think. unless you got that manifold for free or you can sell it for what you paid, then you might as well use it. as noted above, it has provisions for 4 injectors. for the power you stated that you wanted, i think it is unnecessary to complicate your life by running 6 injectors, so block off the primary ones on the manifold and just use 4 in total capable of flowing the amount of fuel discussed two posts above.

that said, you're also going to be running a Link ECU, so it may not be too much more complicated. i don't know.

 

for your power goals just use the stock LIM. no need to think about anything or do anything extra. that LIM will sell quickly since everyone is wanting the xcessive but cant get one.

 

I recall that Andy from Adaptronic discovered on the dyno that biasing the Pri2 injector flow on the 2004-2008 Series 1 Renesis 6-port/injector engine over to the Sec injector instead improved power and transition compared to dumping the extra fuel into the smaller Pri runners/ports. Even Mazda switched it from 6 to a 4-injector manifold on the 2009+ Series 2 Renesis engine.

So as stated by others, sticking with 4 injectors and imo going with larger Sec injectors to bias additional fuel flow there for the larger port/flow area size will likely make the most sense.
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