nishfish871

iTrader: (5)

Would this cause any issues on the stock fuel pump or would I need to go with a walbro.

I'm looking to install Cobra fuel injectors to compensate for the larger MAF (3.5" soon to be 4") and keep my timing curve up.

I have a VAFC2 to trim if I run a little rich with the 3.5" MAF.

Kevlo911

iTrader: (36)

are you boosted?

if not, you likely wont need the fuel demand and thus wont ever max out the 470's and thus wont need a bigger fp

nishfish871

iTrader: (5)

Correct, but by increasing fuel on the VAFC2 you are effectively lowering your timing curve. By using larger injectors with a larger MAF and some math you can bring your timing curve back and by not having to add fuel. Its been proven on the altima forums with the 440s.

shrek

you have a 5ht gen or a 5.5?? i plan on doing the same (ford 40lbs inj,with a cobra or lighting 4" maf) on a 4th gen ECU,i dont think it matters what FP you use ,is the injectors the ones that flow more and the pump will only be keeping static pressure

nishfish871

iTrader: (5)

5.5g with every bolt on, I can tell when I add fuel my timing is being retarded, this is probably the hardware way of fixing it...I could go utec or vmanage.

shrek

im using the same style...using DE-K injectors at 60psi of fuel pressure and a Q45 maf,.... i have to take like 5% across the entire powerband

nishfish871

iTrader: (5)

I have to add quite a bit of fuel with vafc. Like high 20s at idle and it lowers as i go to redline.

NmexMAX

iTrader: (22)

My 440's with 3" MAF requires little to no fuel, in fact, it's about 12.5 @ WOT and normal everywhere else, so I remove a bit to get it to 13 or so @ WOT. Also, like Kev's stated, unless you're pushing upwards of 280+ dynojet FWHP, you'll be fine with the OEM FP.

nishfish871

iTrader: (5)

What I'm truly aiming for is to bring my timing curve back in with the larger injectors and removing some fuel from the vafc2. Should be a win based off of your timing graphs...unless I get carried away with 470s instead of 440s.

This is my maf (math) to bring it back to stock spec (which would be rich cause of headers):
315/2.75 = 114.5
470/4 = 117.5

NmexMAX

iTrader: (22)

Yup, but we then have the factor of the IN/OUT settings of the SAFCII vs the VAFC.

Like I said, I had to change my in/out to 1/1 because without that, the 440's I had to remove 27% or more just to be in the low to mid 12's @ WOT, don't even get me started on normal driving.

And yeah, you say my graphs from the 3" to 3.5", and 0 to -10-12% timing affect.

From what I've seen the IN/OUT does not affect the timing curve, only the actual +/- correction does.

So, in short, yeah that math looks valid, I have yet to install the 4" though.