420A max boost with my setup

[daltah]

What would be the max boost I could run with my s16g, 440's and sfmu? My motor is fully built ect ect. Also what should my idle fuel pressure be at with the max boost?

 

[BigRand]

Well damn, you make that all complicated.

Max boost kind of depends on your idle fuel presssure and air fuel ratios, and other factors such as turbo effeciance and duty cycle of injectors etc etc.

Idle fuel pressure is up to you too. If your running 440cc injectors and leave the idle fuel pressure around stock (about 40lbs), then you'd be flowing about 440cc's.

Now if you were to run idle fuel pressure higher than stock, then the injectors would "act" like they'd flow more. Like 440cc with a fuel pressure of about 70psi might flow for like 600cc. (I don't have the formulas on hand, but this was just explained to me today while working on my car)

Either way, with 440cc injectors, SFMU, your good to go for a while, probably 20+, but that all depends on other factors as well. Running close to stock fuel pressure probably wouldn't be such a bad idea either.

 

[XMasta19]

I've heard of guys maxin out at 15ish pounds with 440's WTF


I'm gonna go with 550's just for shits and giggles

 

[BigRand]

I've heard of guys maxin out at 15ish pounds with 440's WTF


I'm gonna go with 550's just for shits and giggles

Same with me.

 

[clipsit]

You know yours truly has those 550's...

 

[baxsom]

Well damn, you make that all complicated.

Max boost kind of depends on your idle fuel presssure and air fuel ratios, and other factors such as turbo effeciance and duty cycle of injectors etc etc.

Idle fuel pressure is up to you too. If your running 440cc injectors and leave the idle fuel pressure around stock (about 40lbs), then you'd be flowing about 440cc's.

Now if you were to run idle fuel pressure higher than stock, then the injectors would "act" like they'd flow more. Like 440cc with a fuel pressure of about 70psi might flow for like 600cc. (I don't have the formulas on hand, but this was just explained to me today while working on my car)

Either way, with 440cc injectors, SFMU, your good to go for a while, probably 20+, but that all depends on other factors as well. Running close to stock fuel pressure probably wouldn't be such a bad idea either.

will the car even idle at stock pressure with 440s
i thought you would have to drop the idle pressure to like 20psi to get the car to even crank without flooding

 

[XMasta19]

the bigger the injectors, the lower the idle fp needs to be.

 

[daltah]

Yeah I heard with 440's you needed your fuel pressure to be around 18-12 at idle. If I get it to idle fine with the 440's cant I turn the boost up to 18psi and the sfmu will adjust itself since its a rising rate fmu? Or do you have to adjust it your self for ever psi you go up?

 

[baxsom]

it will adjust itself but it depends on what ratio you use as to how much

for example if it is a 12:1 you get 12psi fuel increase for every 1 psi boost increase

get the car idling and the air fuel at stoich (about 14.5 to 1 afr)
then do your run with a wideband hooked up
try to stay in the 11.5 to 12.5 range
(very broad but its a start you can tune with)
you can fine tune with a SAFC to take away fuel if necessary
i have seen on here a few times on which disc and ring to use for 440s but cant recall it off the top of my head as to what ratio to use

 

[GSGoinFast]

Running close to stock fuel pressure probably wouldn't be such a bad idea either.

Wouldnt that be more then double the fuel at idle then with the stock injectors?? You definitely want to go lower then stock.

 

[baxsom]

exactly
at stock idle fp of lets say 40 psi

with a 12:1 at 15 psi of boost

12*15+40=220 psi of fuel pressure

your injectors would be stuck open at that insanely high pressure

also it would be a good idea to get a pocketlogger
that will show short term fuel trim

keep turning down the idle fuel pressure until your STFT is as close to 0 as possible

at 40psi of idle with those injectors it would max out the trim in the negative direction
and then still need some more

 

[BigRand]

Sorrry guys, I don't want to confuse anyone, I'm running smaller injectors than 440cc's, plus all my calculations are done with a calculator and chalk board, and pocket logger, (none of which are near the computer) So I'll gladly retreat to my little hole and come back out when its safe to play (and when I have something to say that is useful, )

 

[daltah]

So if Im at 18psi on a s16g and 440's what should my idle fuel pressure be? I have a electric fuel pressure gauge and how do you tell what the static pressure is? I have a pocketlogger to and what should my short fuel trim look like? Sorry for all the questions.

 

[selmerguy]

I am going to try to clean this up a little bit. What turbo you run has nothing to do with idle fp.
The most psi I have heard of running with that turbo and 440's was 21 psi. This was suieclipse's setup before he went to the portfueler. He just dynoed at that psi and drove at 16 psi daily. He said his injectors were at 100% dc and is still ran alittle lean.

As far as your idle fp I think his and most others with the same size injectors is around 34 psi. Stock fp is 55 psi or so. For fuelinjection you will have a hard time finding an afpr that goes lower then 20 psi.

If I was you I would shoot for 15psi first and work from there. And get a wideband if you are going to push the boost up. Good luck