This is what stock injectors look like on a 4.8 at 10 psi. I know your only running 6, but you've got to be over 100% duty cycle...

 

So what happened to your previous motor??? That is still high hp for stock injectors no matter how you look at it. Many of the site sponsors carry the 44lb injectors, mine are racetronix I believe, cant remember. Did they have a wideband hooked up durring the run?

 

Holy S..., 189% duty cycle.

 

i blew 2 already lean # 7 gave out on both so what would be the goal for a duty cycle under 100% ? yea the had a wide band they retarded the timing and added fuel they said and its shifting at about 5,000 rpm and i get no kr till about 3rd gear (90 mph) and its about 0.63. will i need a pump if i get the injectors?

 

You need the 44 lbs/hr injectors (see below for reasoning). You don't necessarily need a pump right now, but will when you turn up the boost (I ran my stocker up to 10psi -- where I was definitely out of pump).

duty cycle describes the amount of time the injector is commanded open. For illustration purposes, let's say your injectors can be open for a second at max. The injectors take time to both open and close, so you have: opening the injector .. inj open and dumping fuel .. closing the injector in each cycle. 100% IDC means that the inj open time would be the full second that you have for the injector to fire, leaving 0 time for opening and closing. Anything more than that means you are commanding the injector open for longer than the maximum amount of time for a single injector opening. For further illustration, let's assume it takes .1 of a second to open the injector and .1 of a second to close. The optimum cycle then becomes: opening injector (.1), injector open and fueling (.8), injector closing (.1).

A good IDC target is 80%. Based on your listed rwhp figures, I'm estimating 450 at the crank. So, using a BSFC of .65 (top of the turbo range), you need 40# injectors at your current power levels. It's probably fair to guess that your current injectors limited you on the dyno, so the 44s are perfect.

 

ok so #44 injectors it is. i will get the pump as well to but i will need to retune right? or what if i just change the injectors will i still need a retune?

 

The PCM will HAVE to be adjusted for the larger injector and a good general street tune is always a good thing

 

I have alot of broken pistons sitting around from people not wanting to do injectors. It would suck to have to do motor work just from running lean.

 

very true am going to let the truck sit or baby it for a while and get injectors pump fmic and some drivetrian then a retune does that sound good or am i missing somethin?????

 

thats a good thing to do till ya get fuel upgrades for sure....