Do I need to upgrade fuel yet?
 

So I have a stock FD and Over winter I have picked up some new parts. Have a FMIC, power FC with controller, greddy pully kit (air pump deletion), full downpipe and midpipe, greddy profec 2. I have already replaced the stock pump with the supra tt. I am wondering how far I can go with the stock injectors? I did pick up some bosch 1680 secondaries with kg rail but everything I have read is there is lots of modding to get them in and I need the FJO Low impedance injector driver. I have no problem doing that if it is needed but If I am able to run fine for now I would rather just keep it the way it is. I am sticking with the stock twins for now. I do plan on getting the car tuned after all the mods I just wondering if I should put in the secondaries and just keep the primaries stock. Just curious as to what you guys think is needed with the mods Ill be putting on. thanks!

Tune conservatively, check current injector duty cycle and go from there pending your numbers. You should be fine for now...key is to tune conservatively until you know where your base is.

I think you could achieve 310-330whp with stock injectors and twins......I got 309whp with similar mods w/auto tranny.

k perfect. I just not in the mood to have even worse fuel economy yet lol

330whp is around 100% injector duty with stock injectors.

Get a wideband and don't go crazy with boost.

I plan on just running stock boost or maybe 12psi if anything. still got the stock twins so dont want to push them. I want to more so install the new injectors when I go single turbo

I have similar mods and at 14-15psi i was actually reaching the limit for the stock injectors; if you plan to got to a similar boost level then change them, if you plan to stay at 10-12 they can run fine

I have similar mods as well but with a street port and up to 14psi their good.

Similar mods (minus the midpipe) and 12psi and I was fine on the stock injectors. Really the keys you need to pay attention to are listed above. Get a GOOD wideband and reference that. You will need one anyway as you plan on going single turbo later.

One thing you also need to watch is boost creep. Surely you have read or heard about this on this site in your reading. It is NOT a spike and cannot be controlled with the boost controller. That will be what may endanger your engine if anything does with correct tuning for the appropriate boost level you wish to run.

I have read into it yes. I know the profec wont stop it. Someone was saying to just bore out the wastegate (factory) so that it can hold more. Never done this so not 100% how to go about that haha. Maybe my friend knows :)

here's how to properly answer the question:

the stock FD makes 255 flywheel hp.

that's approx 217 rear wheel hp.

the FD requires 1.92 CFM of air to make one rwhp.

so, stock, 217 X 1.92 =s 416 CFM

416 / 14.471 changes CFM into pounds per minute

416/ 14.471 =s 28.75 pounds of air per minute

now i am going to make an AFR assumption:

(feel free to factor in your own number)

i am going to assume an AFR of 11.3

so 28.75 pounds of air/ 11.3 gives us a need for

2.5449 pounds of gasoline per minute.

gas weighs 6.35 pounds per gallon

2.5449/ 6.35 =s .4007 gallons per minute or

1517 cc/min.

stock FD:

2 X 550 primaries
2 X 850 secondaries

2800 total at 100% duty cycle.

we want to run no more than 85% duty so

2800 X .85 =s 2380

2380/ 1517 =s 1.56

1.56 X 217 =s 340

340, given 11.3 AFR and 85% max duty at OE fuel pressure is max for the stock injectors.

whenever i design a fuel system i build it so i can run down to 10 AFR just for backup.

howard

Howard Coleman. You are the man. It's actually simple math, I just wouldn't know the conversions, weight of gasoline, etc...

^^ excellent... I just figured out I have a LOT of head room for my 550s and 1300s. Thanks Howard!