I'm running the stock 850cc injectors in the primary position and 1300cc secondaries. I also have stock twins running at 14psi and am pushing 320 to the wheels. My primary injector duty cycle is at ~64% using a PFC and a safe (high 11s AFR) tune. The low rpm response is great and i would say that 850s are fine for primaries, as long as you have them properly tuned. I really don't need the large secondaries, but wanted to keep my options open for going single sometime in the near future. The biggest you'll ever need with stock twins is 850x850, or even 550x1200 would work fine. The beauty of the PFC is that you can custom tune your injectors so that the secondaries will kick in earlier or harder and make up for a bit of lack on the primary side. You just tune it so the primaries run up to 80%, and then the secondaries provide any extra fuel that you need from there. Sounds like your guy knows what he's talking about. Whatever option you choose to go with, just make sure to get a proper dyno tune and that your tuner knows what he's doing. If he does, he should be able to make most any combination work well for you.

 

I tried a search and nothing is coming up.

 

Do yourself a favor.. and leave the primaries alone.
and Just go ahead and bite the bullet and get New 1600 secondary
injecters.

Because down the road, Your either gonna either go Single turbo, or start
pumping up the boost on your twin. Or what ever.
Never hurts to over kill on the fuel system, Now and for future mods.

BTW: 1300 secondaries are bored out 850secondaries and have a reputation
of sticking, and POPing Motors..

Do a search on injecters and make the right choice.

 

If they are high milage, then just get new ones. That way your safe.

 

i have 1680 secondaries and just got the rest of the kg kit with the primary 850's what is the procedure to setting up for the 850's in the pfc? ernie... kevin...?

 

Its been years since I had the Power Fc, but Im pretty sure you need the data logit to change your injector size, but I do know the pwr fc doesn't go up to 1680cc, but have your tuner do it for you so your safe anyhow.

 

...if you're planning on running 850cc primaries, consider milling an ~1/8 off the top of your primary rail to get the injecter lower into the rail and better prevent leaking past the o-ring. Some people just add a smaller o-ring behind the bottom o-ring to push it lower. This does not always work, especially if you fuel pressure exceeds 38psi. If you're running a 1:1 rising rate FPR they will most likely leak without this mod...in my experience. also if you decide to go with the smaller o-ring trick, use one that is not affected by petrol...

 

I have 850 primaries and the car runs fine, but it's pig rich at idle (10s), with or without the narrowband hooked up

I also tried letting the car idle for 10 minutes ("learn" function) and that didn't help, either

 

what is the best way to confirm leakage past the o-ring?

 

The best way to run 850 primaries is to get KG's primary fuel rail.

 

Ern, Keith's rails are for top feed injectors, which necessitate splicing resistors into the injector wiring because of their low impedance. You also have to modify the fuel diffusers, which I most definitely did not want to mess with. I've heard there are ways around both of these problems, but I prefer the simplest method using oem parts and mounting.

I didn't want to mess with that, so went the stock side-feed route: brand new 850cc injectors (stock secondaries) in a milled primary rail. Works perfectly without leaking etc.

Also, my AFRs at idle are in the mid to high 13s with these injectors, so it is possible to run proper AFRs at idle. Mark, sounds like you need some tuning.

 

Out of the car fuel leakage test...page F-107 in the service manual

...I used an extenal power source to simulate the rising rate voltage/amps to the fuel pump and tested to a maximum of 60PSI.

...in a stock set up "key on" max is 36-38PSI.

...I may be wrong, but assuming that the stock ECU controls voltage to the fuel pump for a 1:1 rising rate, then @10PSI boost that's 38-42PSI minimum that "I think" you should test at...if your fuel pump/regulator set up is stock.

if you ground f/p at the diagnosis connector, you can get 71-107PSI from the fuel pump.

 

car is tuned (and running great at about 11.2, 14 psi), but there is no adjustment for idle using the datalogit that I know of, it is reportedly set automatically by the PFC (unless I have the wrong information)

 

thanks led

 

rich id like to know how you achieved the "13s" afr at idle with 850 primaries. . . im tired of the 10.9-11.x afr on my car. . . care to explain?

 

i have the kg primary rail now... keith never said anything about splicing in resistors i dont have any resistors for the 1680's! i guess i'll have to go round two with mr. gibbons and ask him what the deal is with this setup. there is no specification to modify anything here its suppose to be pretty strait forward. thanks for the info guys as usual. and rich i'll be checking that shortblock for a price for you but how did you want to go about getting it? i would rather you come and pick it up so you can also check it out to make sure its to your liking. you can also see my new motor and all the work im doing in my shop

 

would you need to change primaries from 550 to 850 if you plan on runing the bnr stage 3 turbos sequentially? i wanna try and get around 350 rwhp, no more then 400. Can the 550 handle this with out to much load?

 

It's been discussed on the Datalogt yahoo group and in the PFC forum here but from what I recall, you play with the injector lag times. Some including Ralph from Excessive use a negative lag time (I believe -0.04) for 850 primaries. Be warned that once you change the lag time, the rest of your map will need retuning.

Jack

 

Bump for a good discussion of larger injectors.

I was planning on doing 850cc's x 4 and having things tuned with the Power FC.

So how many people have actually had leaks useing 850cc injectors as the primaries?

Thanks,
Justin Wade

 

After 1+ years, no leaks so far.

I had my primary rail milled down, so no issues with sealing, and PFC tune by Mr. Kan.

:-) neil

 

I heard there was actually a debate between damean the track car guy and someone else that the resistor way is the wrong way and he had specified some kind of little box that adjusted the impednce properly

 

The PFC maps run rpm on the x axis and vacuum/pressure on the y axis. Thus, you can tune for idle.

 

right there on the first page

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/fuel-system-upgrade-how-write-up-kgparts-kit-404091/

A driver for the injectors

 

checked for leaks today by pulling the stock primary rail out and running a jumper on the fuel pump...no leaks, so hopefully I'm good

the primary rail has not been milled

 

so why did you bring back an old thread if you have no problems?