i just thought about that, almost forgot about injectors.

Injector size all depends on how much boost you want to run. From there you can decide on injectors, however, you definitely should replace the injectors when you have the engine out of the car. It makes no sense to install a built block with stock injectors.

I just recently installed a rebuilt engine in my car and also put in 390cc/min injectors as I plan to run about 16 psi. I didn't want to go with the 440s as I wanted to control these injectors with just the SFMU. I am not sure if you can control the 440s with just the SFMU as you might have to lean them out with a SAFC at idle. I haven't begun to tune with my injectors yet as I am still in the break in process and working out the bugs in my built block. I would also assume that you would have to run some extremely low fuel pressure with the 440s - somewhere in the neighborhood of 12-14 psi to get them to idle correctly. I know with the 390s my idle fuel pressure is 17-18 psi with the Hard Spring and 2.62 disk.

Hopefully someone with 440s will post about their experience. The 390s are just another option you have if you don't want to go all the way up to the 440s.


--Kurt

440's work great. I use them and I can run 18 psi on them. Anything smaller isnt very good for high boost levels. I am using ford lightning injectors. They are black and bright green.

Not to steal this post, but can I run my stage 2 set-up w/ 30lbs and JUST a SFMU and not have start up and drivability probs on 8psi?

yes

yeh with just a SFMU but not a FMU hehe, I tried it and it idles too rich O_o

ok...this goes with the main post, but what is the maximum psi you can run with the 310's, 390's, 440's?

I haven't tuned my car yet with the 390cc injectors for boost yet as I haven't finished the break in period for the clutch and engine. I have tuned the 390cc injectors at idle.

Here is a breakdown of what I would think is possible with the following injector sizes. This list is based off of setups from fellow 2gnters.

310cc about 12-13 psi daily (XtremeRS)
390cc about 16 psi daily (Me)
440cc about 18-20 psi daily (Dave FL)

Like I have said, I haven't been able to boost my car yet so I am not exactly sure what I can do with the 390cc injectors. These numbers above are just approximations and should give you a general idea. No matter what injectors you choose, you will have to tune according to EGTs and o2 sensor readouts. For larger injectors, you will also have to make sure you STFT at idle are in the -5/+5 range (as close to zero as possible) to allow the ECU to make instant fuel corrections.

Hope this helps,
Kurt

so with 310's, you said someone's running 12-13 psi....can you boost it up higher if youre going to be racing?.... and with the 390's let me know what youre maximum boost is with those....what fuel pump are you running with those

Originally posted by lickscissors
so with 310's, you said someone's running 12-13 psi....can you boost it up higher if youre going to be racing

Matt (XtremeRS) will have to answer that question. I thought I read a post where he said 13 psi maxes out the 310cc injectors - meaning running a high/unsafe fuel pressure.


I am running two fuel pumps. The Accel Inline fuel pump that came with the HRC kit and the Walbro 255 HP intank fuel pump. I purchased the intank pump to quiet down the Inline fuel pump. It may be a while until I can tell you the max boost pressure with 390cc injectors I am working out some severe bugs with my VTEngines built block. Stay tuned as I plan to post an update to my built block leaking oil post. (I borrowed a digital camera from my friend and he needs to burn the pictures to a CD for me.) I think many of you will be very surprised/shocked.


Hope this helps,
Kurt

well right now i have just the warlbro 255....do you think that will surfice with 390's at max 18psi i would say?....
doug