2RotorsNaDream

iTrader: (7)

OK guys, my car will finally be done tomorrow. I did the full non-sequential conversion along with some other goodies and got a question. With my mods will I need new injectors to run 14psi on stock twins professionally tuned on my Apexi PowerFC?
MODS:
3" downpipe, 3" gutted high flow cat, 3" catback exhaust, Apexi intakes, Greddy elbow, Greddy M-Spec FMIC, stock twins running fully non-sequential with ported wastegate, PowerFC.

As you can see from my list I have NO fuel mods done at all. I can have a Denso Supra TT fuel pump tomorrow if I need it but I'm wondering if I'd need at least larger secondaries to safely run this setup on 14psi. I've searched extensively and some threads argue that the stock fuel system will easily be able to handle it even with 100% duty cycle (wtf??), which just doesnt seem right. Others say at least 1300cc's in the secondary rail. Looking to get the car back up and running ASAP because it has a paint appointment so I'd like it if it can be done at least w/ the new pump.

Smitter

i ran a setup similar to yours previously, i had the fuel pump though. I saw 85-90% duty at 14lbs on the stock injectors.

Just get the fuel pump and u should be good

2RotorsNaDream

iTrader: (7)

Not bad, my duties weren't bad before running 12psi, stock intercooler, stock elbow, and stock cat either but I wasnt sure at 14psi how high they'd be.

mono4lamar

iTrader: (32)

You'll be fine with the supra pump. People are going to disagree though. I will somewhat agree with them too as it's not the "smartest" idea to max out your duty cycle. Adding 850's to your primary slot is simple as you use the factory lines and it will surely give you more than enough fuel. If you want a modified primary rail with fresh 850's installed I have them done and in stock. My units are acid dipped and brushed to a sparking shine. I could have you one by the weekend... PM me if you're interested.

2RotorsNaDream

iTrader: (7)

I agree, definitely not the smartest thing to do but 85% duty cycle is not horrible for the most part I guess for now. I'll probably go and get the fuel pump tomorrow then. Also, I've heard that tuning the 850s in the primary fuel rail is a PITA. How much of a concern would it be? Soon enough I'm going with a basic WI setup and larger injectors, so if I can run stock injectors in the meantime w/o the hassle of dealing with 4 850s I'd rather do that.

Turblown

iTrader: (12)

I have seen 100 percent duty cycle @ 13psi with a highflow cat even with a bigger fuel pump. Upgrade your injectors, just not worth it..

FDWarrior

iTrader: (6)

I used 4 secondary injectors with my stock twin set-up. I ran 14psi and had a custom built straight pipe exhaust(turbo back). I only saw 85% duty cycle. I also forgot to mention I only used a walboro 255 for a fuel pump, your supra tt pump should work perfectly.

FearNoPiston

iTrader: (17)

with my mods in my sig on stock primaries and 1300cc secondaries I am hitting 85% duty cycle.

moconnor

iTrader: (14)

I'm getting 90% duty at 14 psi with stock twins and the usual bolt-ons with the stock fuel sysem. AFRs are 11:1ish under boost. I'm about to upgrade the pump but have no plans to upgrade injectors until I swap out the stock turbos.

People have happily run 90% duties (and higher) for years on these cars. Running 100% is looking for trouble though.

FearNoPiston

iTrader: (17)

what I dont get is I used a fuel calc and it suggest I can get 478 flywheel horsepower @85% duty cycle but yet I have 317 rwhp and am hitting 85% and I am on 13psi.

WaachBack

iTrader: (21)

I blew my motor with the mods in my sig...just upgraded to 1200cc Secondaries.

moconnor

iTrader: (14)

You likely blew your motor because you ran lean - but that may have had nothing to do with injector duty.

WaachBack

iTrader: (21)

It was my injectors, I was running high 90's duty cycle and pushing the limit for a bit too long.

moconnor

iTrader: (14)

Ah - ok. High 90s would scare me.

liv4psi

iTrader: (9)

It's my personal opinion, but if you are wondering if you should, then almost always the answer is yes. Rebuilds aren't cheap, so why risk it. When it comes to building a car, patience truly is a virtue.

2RotorsNaDream

iTrader: (7)

OK I got the Supra pump today so I'll see what the duty cycles are looking like after it gets tuned, if theyre alittle too high I'll probably go with stock injectors and rail modded to 1300cc. I'll let everyone know next week or so what the cycles looked like after the tune. Thanks to everyone who answered in the thread, I appreciate the time you took to help me out.

arghx

iTrader: (3)

with 550/1300 and a Cosmo pump I have seen 80% injector duty cycle with a street port and ~14psi with all the supporting mods. that's after I tuned it to 11:1 AFR

hiboost

iTrader: (1)

Why just not get bigger injectors and done deal... You dont wanna runout of fuel... Your engine might cost you more then getting bigger injectors..

Aeka GSR

iTrader: (4)

side question, when should one upgrade to bigger than stock fuel lines that run from the tank to the injectors?

moconnor

iTrader: (14)

Only if you are planning on 500+ whp.

TwinCharged RX7

iTrader: (14)

i'll be removing my OEM enlarged 1300's this weekend, they still work but i'm going for 500hp so i need 1600's. If you are interested pm me, they will be going for sale shortly for $250 shipped, i will also offer to have them cleaned and flow-tested by KG but will raise the price $50 to do that.

mono4lamar

iTrader: (32)

That's a very good deal! You should have no problem finding someone to take those off your hands

Azcamel

iTrader: (1)

injectors are cheaper then a motor.. i dont like to see more then 85% duty, i had 1kcc primary and 16002ndary on mine just to be safe, but i was pushing 500+rwhp

Azcamel

iTrader: (1)

thats why you saw 80% duty, 11:1 is safe for a piston motor, but not for our motors, 10:1 - 10:4 is alot better and safer for a our motors

Azcamel

iTrader: (1)

because it uses generica AFR to calculate fuel and HP, our motors is safer in the low 10AFR, piston motors are in the 11's which explains the difference.