720cc Injectors
 

Will the 720cc injectors from www.rx7.com fit in the stock fuel rail or do I need to get a custome one made?

They will physically fit.

Hey!!! Your sig says that you already have 720's. You gonna put them in the primaries? If so, you'll need a remapped ECU or an aftermarket ECU.

No.. look at the Top "being Installed" :D

What do you mean Physically Fit? Like the orings will seal and the the feed will set securely, or is there more that has to be done, The SAFC will control them not the ECU...umm sorta ;)

They will physically fit. They aren't electrically compatible, you will need to wire resistors in-line with them, unless of course you have an early 1987 wiring harness in there that already has the resistors for the low-impedence injectors. RP (RX7.COM) has the resistors too, they can send you the proper ones. You probably want to start with your S-AFC tuned DOWN just a bit at WOT from 3800 RPM and up... it will be really rich with the bigger injectors if you don't.

I'm not quite as far along in my swap process as you... but I DO have the drivetrain part done... :)

Hey ragtop.

I can't seem to find the final word on this. I installed 720 secondaries in my '87 TII. Will they work with the stock ECU, or do I need a fuel management device. I have the intake off, should I leave 'em or put the stock injectors back on?

Thanx

Shamrock:

It sounds like he is saying that the 87 and early 88 ECUs use the proper impedance for the 720s, but the newer ECUs need resistors. The car will probably run rich when the secondaries are on unless you have your exhaust opened up such that you are running higher boost which I assume you probably are since you're putting in bigger secondaries in the first place.

Buddy:

I can't wait to get back to Chico, mostly to be with Meagen, but also to see your car with hopefully the new motor installed. It sounds like it's going to be pretty quick.

Meagen told me you were looking at her in awe when you found out she was driving my car while I'm gone. Hehe...she is a really good driver and I trust her with my car, like I said in this thread:

My girlfriend is an awesome driver.

She joined the forum. How fuckin' cool is that?

I don't know if the ECU can run anything over 680cc? Not too sure though...

The ECU doesn't recognize that injectors are bigger than stock, but as long as they fit the fuel rail and are the correct impedance, the ECU can control them. The result is that when the ECU thinks it's running the stock injectors at some percentage, it is really running the 680s or 720s or whatever at that percentage, therefore putting in a lot more fuel than it thinks. This is a good thing as long as you have something counteracting this richening effect such as more boost so that you get something at least close to or exactly stoichiometric, but with a SuperAFC, it should be possible to get it right on.

All this rich/lean talk reminds me....did you get an Air/Fuel or EGT gauge yet? Both would be best.

Thanx Nathan,

I have a RB turbo back exhaust, no cats. Upgraded turbo compressor, am doing the TB mod as we speak, Greddy boost control
So, 720 cc secondaries should be OK with stock ECU, right?

Gregg

I'm no expert, but from what I have read and heard, I would say yes as long as they are the correct impedance and they fit. I'm sure RETed would know for sure, if not a bundle of other people.

You might need a S-AFC to lean it out a little...