What fuel pressure should I run my setup at to get the most fuel out of it? I dont want my pump to not be able to push the pressure but i want enough pressure to spray more fuel. any suggestions?

basic math says 720*4(injectors)*(unit conversion) = 172.8lph.

so the injectors are maxing out before the fuel pump, but what fuel pressure are the injectors rated at and what fuel pressures are the fuel pumps rated at?

Thanks.

I found this: (i have the HP)

from here: http://www.lightningmotorsport...h.htm
some descent info ^^

so i did some calcs on that pic, with the HP, i got the following numbers:
@40psi: (40*60) = 2400 "fuel units"
@50psi: 50 * 56 = 2800
@60: 60 * 51 = 3060
@70: 70 * 47 = 3290
@80: 80 * 43 = 3440
@90: 3420
@100: 3500
@110: 3190

So i guess bring your fuel pressure up to 100 if you have to (and your FPR will hold it), but at 110 it will fall. Looks like I answered my own question .




Modified by Cyphear at 3:06 PM 1/12/2005

 

injectors are rated at 3bar pressrue 43.5 psi approx. Most fuel pump are rated in GPH or LPH depending on which company and area you live in.


In your example you would want to set your base static pressrue around 35 on the FPR and boost with a 1:1 regulator you are can take it up lets say max of 30psi

that would make your new fuel pressure at full boost 65psi which is well within the ranges of the walbro 255lph

 

Thanks. So i think i'll try ~55psi base + 20psi of boost = 75psi total pressure. should be good.

PMed about a fan

 

you dont need that much base pressure on a 750cc injector i would go with a smaller base pressure and then run it that way your idel tuning will be alot easier

 

they are almost maxed out right now. looks like they will max out at around 22psi of boost @ at stock fuel pressure (45psi when i had a gauge on it).

 

if your injectors are maxing at 100% duty cylce at that low of boost on 780cc what power are you pushing down at 22psi

then the problem could be your injectors you have are nto flowing correctly

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18bturbo &raquo;</TD></TR><TR><TD CLASS="quote">if your injectors are maxing at 100% duty cylce at that low of boost on 780cc what power are you pushing down at 22psi

then the problem could be your injectors you have are nto flowing correctly </TD></TR></TABLE>

they are 720's. well, im getting near 100%, acording to uberdata, but i've also heard the uberdata duty cycle #'s are 10-20% off. anyway, its a 2.0L LS, making ~425whp (just a guess). they were balanced and tested by RC before i bought them.

 

fyi

i had dsm 450's with a adj. fpr, i set fuel pressure to a base 70psi, and i was able to run 17psi on my drag t3/t4b, duty cycle was almost 75%. i also had a 255 high pressure walbro intank pump. btw.....this is according to AEM EMS datalogs.

 

base pressure 70 good ******* god!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hella_JDM &raquo;</TD></TR><TR><TD CLASS="quote">base pressure 70 good ******* god!</TD></TR></TABLE>
damn right 70 psi is a little for a base.

 

yeah i agree with that my base pressure is at 70 also with a walbro 255 rc 400cc so it can take it the only thing is make sure to change to a stronger line on the fmu

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Cyphear &raquo;</TD></TR><TR><TD CLASS="quote">
they were balanced and tested by RC before i bought them.</TD></TR></TABLE>

is it a street car? running a huge base pressure could be an issue with the injector response.

 

yes, its a street car. whats injector response? thnx.

 

i'm no engineer, so double-check everything i post and everything else you read on the 'net.

basically, it's when the fuel pressure exceeds the opening pressure of the injector... the injector response could become non-linear at higher fuel pressures.

rc can tell you what the fuel pressure limits of your injectors are... fwiw, some people believe that base fuel pressures of 60psi are a realistic limit, depending on what the fuel pump can handle... make sure that you have full voltage and current capability present at the pump.

increasing fuel pressure isn't very efficient... in order to double the fuel flow, you have to quadruple the fuel pressure(?).

 

 

I know from the info Seimens gives to OEM's on their Deka injectors (ball-style, mostly low-z, high flow), they can take up to 105psi. I would imagine it will be similar for most of the higher flow ball and disc-type injectors.