bigger injectors

[baxsom]

I want to install bigger injectors so I can raise my boost level
it has the stock injectors and rails installed and currently running at 10psi
i have a hahn stage 2 in with everything that came with it
the only thing i have done to the turbo system is install a greddy spec II controller
i keep reading about SAFC and SFMU changes before I can go to bigger injectors
i am reading that the afc changes air fuel and fmu changes fuel pressure
my gauge says that idle fuel pressure is 40psi and under boost it goes way up
i see posts for apexi, greddy emanage etc
please someone tell me what changes to the car I need to run bigger injectors
the norm on injector size and what brands should i look for

thanks

 

[talongod]

RC 550's
255 fuel pump
s-afc II
FPR
should be good for 18-20 psi on aftermarket turbo

 

[green95hrcgs]

I would get 440cc injectors and a Vortech SFMU to start with. I am not sure about the S-AFC2, but I know that if you adjust the mix too much with the S-AFC1 that you start to mess with the voltage that the MAP sensor see's and will cause it to advance timing to levels that may be harmful to the motor.

You can use a S-AFC on the N/T's, but only for VERY fine tuning after all other tuning instruments have been tweaked.

Also, I have heard that getting good idle characteristics on anything larger than 440cc injects is tough or impossible.

Anything further than that, and I would recommend getting the 8 injector setup or going to something more of a standalone.

 

[baxsom]

ok let me make sure i have it now
take out the hahn racecraft fpr (the big silver disk thing that the fuel line goes into)
replace it with a vortech sfmu
add injectors
perferably RC 440cc

no need to adjust ecu, air/fuel, or timing to to get this setup running
and i already have the waldpro 255l fuel pump


SAFC II later

 

[siueclipse]

I would get 440cc injectors and a Vortech SFMU to start with. I am not sure about the S-AFC2, but I know that if you adjust the mix too much with the S-AFC1 that you start to mess with the voltage that the MAP sensor see's and will cause it to advance timing to levels that may be harmful to the motor.

You can use a S-AFC on the N/T's, but only for VERY fine tuning after all other tuning instruments have been tweaked.

Also, I have heard that getting good idle characteristics on anything larger than 440cc injects is tough or impossible.

Anything further than that, and I would recommend getting the 8 injector setup or going to something more of a standalone.

what he said. however, i still dont run an afc

if you dont have a built motor.. don't go higher than 10psi.. even 10 is pushin it.

 

[green95hrcgs]

That seems to be a good starting point for most people. You do not need to do anything to the ECU.

All you need to do is set a good base idle fuel pressure according to what size injectors you buy. You find what ring, disk, and spring, in the SFMU gives you the best idle and fuel under boost conditions. You need a fuel pressure gauge to do help you set the idle pressure and see what kinda pressure you are getting under boost.

You will also want to take the bleed valve off of the HRC FPR and install that in the Vortech. That way if you are running too rich under boost, you can bleed off the excess pressure.

 

[baxsom]

i am pretty sure the motor can handle quite a bit
can someone look at my mod list and help me figure out an estimated boost limit once the new injectors are in place

i didnt build the car i bought it already built but supposedly according the mechanic the engine was built to handle a lot

 

[SnoopySLR]

ok, I'm confused about this. I thought our MAP sensor got funky when it see's boost. Thats why there is that Missing Link (which I'm still not to clear on what that is). If the Missing Link does something to the MAP sensor, how can a S-AFC work on it. All that thing does is trick the MAP sensor signal. I'm still a little fuzzy with making our fuel system work with high boost.

 

[green95hrcgs]

I am not really sure about the Missing Link. My car does not require it because I am a 95. I think that the cars with the "late" fuel system require them. Hopefully someone else can shed more light on that subject.

 

[baxsom]

just out of curiosity how big of injectors could i install without changing anything
i have read that on a NA GS you can install venom 210's without changing fuel pressure
regulator

and how much of an improvement would that show

 

[eclipseman99]

Sorry to hijack the thread but do you get a good idle with 440cc injectors? Would 400cc be fine to run 10psi - 15psi or would 440 be better?

 

[green95hrcgs]

I heard you can get good idle with 440's with some time tweaking. I would not get 415's, thats what I have and I cant boost more than 10-12 psi without running lean. If you want about 15psi, then I would get the 440's and tune accordingly.

As far as the Venom 215cc injectors, there is NO POINT in getting those. Stock injectors are 235cc. Dont waste your time and money.