rx7FDrider

iTrader: (16)

okay so i have been reading up on injectors the past few days and it seems like there isn't a clear answer to me as what's the best way to go about setting up my injectors....

i just ordered 2 used secondary injectors that i plan to make fit on my primary. so i plan to run 850 x4 setup. but i was talking to one of my buddy who had 3 fd and he said i should go 850 & 1300. but then i also read somewhere that if i get my 850 boarded to 1300... there is some reliability issues?

can anyone give me some insight as to what you would do?

i am trying to get to ~ 350 rwhp and here is my setup & plan:
- fmic
- intake
- h20 AI
- dp, mp, and rb dual tip
- simplified turbo system
- pfc
- port wastegate
- koyo rad
- fuel pump

Smokey The Talon

iTrader: (33)

coming from someone running a 850x4 setup....I'd go with stock primary injectors and larger secondaries.

While I don't have any drivability or running issues, you'll never be able to lean it out enough to not have a serious fuel smell at all times....my car stinks. I knew that going in but will still consider changing down the road.

rx7FDrider

iTrader: (16)

should i just go 850 1300 then? i mean i got a 2nd set of secondary injectors and i am gonna get them cleaned at RC eng anyway.

thewird

iTrader: (8)

No, run 550 in the primaries, 850's primaries are a pain in the ***. Go 550/1300 (if you want to stick with stock side-feed setup) or 550/1600cc (top-feed).

thewird

Smokey The Talon

iTrader: (33)

This

oo7arkman

iTrader: (2)

I agree with thewird also. You don't really have any reason to go any bigger than stock in the primary injector location. 850's in the primaries are a PITA.

IRPerformance

iTrader: (41)

I don't really like to change primaries. You never get a decent idle. For some people this is fine, but I have dealt with enough customers that desire a stock idling car. If anything put the 850s in the primary location. I just don't like running top feeds in the primary location with the power fc. With other ecus its not as bad.

fendamonky

iTrader: (6)

I'm currently running 4x850's with a Bosch 044 pump and an Aeromotive FPR set to 50psi (vice the stock 38-40) as the base pressure.


My car does NOT smell like fuel, I have not had any problems with a rough idle, and I'm only hitting 85% IDC at redline while pushing 18psi on BNRs with stock ports (roughly 400rwhp, depending on dyno used).


I don't presume to know more than anybody else when it comes to tuning and injectors, I just figured I'd share my experience.


If you're going to be putting used injectors in there I would definitely suggest having them professionally cleaned and flow tested prior to installation!!!

thewird

iTrader: (8)

Sounds about right for BNR's. I have never heard of fuel smell either. The problem with the 850 primaries is running rich at idle and peaky throttle (which you get used to). With proper tuning and a good ignition system you can make the idle not as rough, however you can't change the fact that it is running rich at idle (11's or worse). This is bad because your fouling your plugs and accelerating carbon buildup. If you compare the idle of an 850 primary and a 550 primary on the exact same motor (I DID), you'll see the 550 idles so much more smoother because you can lean it to 13 AFR where it should be. Even with negative lag on the 850's you can't lean it enough to have a smooth idle. And negative lag brings more tuning problems with throttle maps. Like Rotary Experiment Seven said its worse on the PFC.

thewird

FD3S2005

iTrader: (11)

aww, and i was going to go 850/1300 with my brn setup... got me thinking now tho. i will go 550 first and see what i get, if i need more ill throw the 850s in there

thewird

iTrader: (8)

550/1300cc is more then enough for BNR's. I took my BNR's to 18 PSi and was only around 85% duty on a street port.

thewird

FD3S2005

iTrader: (11)

seq or non seq

thewird

iTrader: (8)

Sequential but it doesn't make that much huge of a difference (10% at most). Besides you won't be running 18 PSi on pump so you have leeway anyway. As long as you have a good fuel pump, you'll be fine.

thewird

TwinCharged RX7

iTrader: (14)

I just upgraded to 1600cc's from my enlarged OEM 1300cc secondaries. They worked fine for me at 380whp and I never had any problems with reliability. From what I've read, if you want to go past 400 whp, you'd be pushing the cycle too much with them, but you are only looking for 350. pm me if you are interested in taking them off my hands.

Julian

iTrader: (14)

Anybody bother to enlarge the primaries say 10%-15% 600-625cc or so. I realize money spent for not much gain but I figure if you can get a little without screwing up the idle then so be it. Also I understand the 850's bored to 1200 are much more reliable than to 1300cc's

arghx

iTrader: (3)

why don't you just open the wallet get the1600 secondary's? You're going to want them anyways because some day you'll want to make more power and you'll need them. Everybody does. 550/1600 will be fine to 400rwhp, and you don't have the increased hassle of tuning larger primaries.

zack4173

iTrader: (3)

I dont have any personal knowledge on my car about this but through my years of readings on the forums running 850 primaries can cause more issues than they are worth. I am going for the 1600 secondaries.

gracer7-rx7

iTrader: (16)

Read this thread for GoodfellaFD3S while you are researching:
https://www.rx7club.com/3rd-gen-archives-73/some-fuel-system-ramblings-578521/

Aren't the Archives great

rx7FDrider

iTrader: (16)

well it sucks that i already got the 2nd set of 850s.. but whatever . thanks for the help everyone. i am gonna run 550/1300 for now then.

thanks for the thread gracer7

muibubbles

iTrader: (36)

really? i have the same injectors, fpr and supra fuel pump and im maxing my injectors out at 356whp @ 14psi....

are you running 550 or 850s for the primary?

mono4lamar

iTrader: (32)

Who's your tuner? When you say maxed out do you mean the 85% rule or the true 100%? At 100% with a "good" tuner you should be able to get really close to 400whp... Assuming 30% drivetrain loss that is.

Chadwick

iTrader: (12)

With 550/1300's using the stock FPR and a Supra or Nippon Denso fuel pump upgrade you will hit 100% injector duty cycle at around 16.5 psi with a good flowing street port.

I suggest you go with 550cc primary and 1600cc top feed injectors in the secondary and a FJO injector driver. This should give a little head room above what the BNR's can put out to be safe if your boost controller wigs out.

Dan

muibubbles

iTrader: (36)

dave at kdr.. i mean 100% injector duty... really 400whp with the stock seq???

i have an aeromotive FPR and i believe the supra fuel pump.. im at 14psi..

im actually debating with 550/1600 or 850 all around..

T2 Tsunami

iTrader: (3)

definitely stay with the stock primaries...otherwise you will never be able to idle at the correct RPM without running extremely rich. You'll be wasting gas all the time.

thewird

iTrader: (8)

+1, if you can find 650's, that would work too.

thewird