Barwick

I searched and couldn't come up with much.

Where would I install additional injectors at on a 13bt? Say 2 1000cc or 1200cc (or heck even 1600cc) injectors. I've got 4 720cc's in it now, and want to have the additionals put in.

But where? Upper intake manifold? Lower intake manifold? Where would I put them?

Cosmo Donk

Any reason you don't just go with bigger secondaries? I have seen people place them in the UIM in the port runners. There is also a special spacer they sell in Japan that places them between the UIM and the LIM.

Barwick

cause I want to avoid having a stinkin' huge glob of fuel dump right into my intake every time the 1600's open up.

Project84

I've seen them in the elbow right before the throttle body.

1987RX7guy

iTrader: (3)

When they open up they do not go to 100% you know. They go to a certain percentage that is adequate to what the car needs. If they would just dump all the fuel in the car they would make your car run like crap. And why would you need 4x720+2x1000cc's that is a hell of a lot of fuel man. Even by what I had planned(previous thread I had wanted to drop in huge injectors in the TII). Using rx7.com's fuel calculator with all that fuel you would be at 700hp at 80% DC. O_o

Bebesito21

greddy makes an elbow that attachest to the throttle body and has ports for two injectors

Barwick

4 720's and 2 1000's is under 500.

And yes I know they don't open up 100% of the time, they only open for a little bit, but for that little bit they're dumpin' a TON of fuel, especially at the high power and low RPM I'm going to have to open them at with just 720's in the primaries.

Digi7ech

iTrader: (1)

Get a SAFC or EMS and you can tune the fuel in correctly.

fcfdfan

Get the "Mazda RX-7 Performance Handbook" by Mike Ancas because it covers that in good detail.

Robert at the Rotary Shack has experience with adding injectors in the UIM.

There is also my personal RX7 noob experience, which you will not want to repeat. Some years ago I was naive enough to let those arrogant, overpriced trolls at Tripoint add a 5th injector in a Greddy piece that sections into the intake between the intercooler and the TB. The injector was controlled by the Greddy Rebic IV injector controller. It was a complete disaster -- whadda pos! It never worked right and probably contributed to my engine detonating on Tripoint's dyno as they tried to prove to me that I would have "300 HP" in my 2G. I disconnected it years ago, can't recommend it, and don't know if the additional injector approach is one worth pursuing.

NZConvertible

Additional injectors were common when aftermarket programmable EMS's were too expensive for most. It's a crude method at best, because there's no control of the other injectors at the transition point. You get a big rich spot as they turn on, which is exactly what you said you don't want.

EFI manifolds don't like fuel in them either, they were designed to flow air only. You get fuel hitting the sides and condensing on the walls, upsetting mixtures.

Larger injectors controlled by a decent EMS is a much better idea. If you use mismatched injectors (i.e. larger secondaries) then the EMS can be tuned so that there's no change in AFR during the transition.