fuel pressure issues - Boost Forum

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fuel pressure issues
Monday, May 23, 2011 1:51 PM
Ok, yes I know i have no pics of car yet or stats or any of that im getting their but anyways i have a 2000 z24 cavalier 5spd with a turbo runing 7psi and nos with a 50 wet shot. I have a regulator with a vortec fmu and a walbro 255. the walbro sounds like its dying with a loud whine and i have stock injectors that need to be much larger which I am working on. I am using hptunners and have the gm sc reflash but changed the constant on the injectors to stock constant. I know i have a bad lower o2 . the problem which is recent is at idle it misses like no other. when i lower the fuel pressure to near ten psi it idles fine but wont run worth @!#$ due to lack of fuel if i crank up pressure idles like @!#$ but runs like a champ reguardless of pressure it is running super rich all the time. i know i need to get better injecters with a newley flashed constant to match asap but im wonderinf if anyone has any thoughts on why lower fuel pressure like 15 psi would make it idle better is one of the injectors messed up from abuse and running them way more than meant to be or what . I tried new plugs no diff. also with walbro whine it never whined loud as it does now before is it dying? I know i also need to replace lower o2 could it being bad be messing with my afrs. my wideband reads lean at idle super rich when driving no matter the pressure always reads lean at idle tho . and does anyone have any plug n play ford greentops for cheap or any 42 lbers. I know im kinda a stray i need to update my profile im from altoona pa and like many of you love the jbody platform im a newb to tunning but not to other things. I will post pics sometime this week of my setup and routing of turbo piping as Ive seen many on here and Id have to say my routuing is very different and in my opinion looks better as far as placement of turbo and filter.

Re: fuel pressure issues
Tuesday, May 24, 2011 8:38 AM
use either the sc reflash or hptuners. use the recommended injector size for the sc reflash. i think its 42 # injectors. @!#$can the fmu as its not needed since you have a tune.
Re: fuel pressure issues
Tuesday, May 24, 2011 10:29 AM
pm me if u want sc injectors and there 30lbs like 310cc



MP-62 Intercooled 2.9" Pulley
Re: fuel pressure issues
Tuesday, May 24, 2011 1:22 PM
please name a shipped price for the 42lb injectors or the 30lb ones r cheaper I can make work. And as far as s*t canin the fmu would i still use it and just tune for it as i paid like 200 bucks for it and would suck to be not used?
Re: fuel pressure issues
Tuesday, May 24, 2011 1:50 PM
if you have an fmu then yes @!#$can it. if you have a 1:1 boost referenced fuel pressure regulator then keep it. an fmu is not need as you are tuning your ecm. fmu's were used back in the 90's before electronics came along. they raise your fuel pressure to dangerous levels and they exponentially dump fuel. fuel cannot be controlled with them so there useless. also the more fuel pressure your fuel pump produces the less flow it has.
Re: fuel pressure issues
Tuesday, May 24, 2011 5:44 PM
thanks, and yes i do have a 1.1 regualtor as well as the 8.1 fmu. i guess ill toss fmu on shelf. If i get 42lb injectors how would i calculate the injector constant to use with them in hp tuners. also a few questions bout hp tunners. My injector constant does not show up as well as any histograms or ve tables why might this be and does hp tunners have a dyno chard i havent found one but i heard it does. thanks
Re: fuel pressure issues
Tuesday, May 24, 2011 7:40 PM
i believe the sc reflash uses a 2.5 bar map sensor. i dont think ve tables are used in this case because the computer is actually reading boost not calculating ve. i never used hp tuners with a 2.5bar map sensor so im sure someone else on here would be able to give you a better answer as i am unsure. as far as the constant i dont see a reason why you wouldnt be able to see that. not many people have posted about using hp tuners on a gm reflash. maybe somehow it cant be changed with hptuners. where are all the tuners when u need them........
Re: fuel pressure issues
Tuesday, May 24, 2011 7:46 PM
I have a new set of said injectors pm if interested.... 100 shipped



Re: fuel pressure issues
Tuesday, May 24, 2011 7:51 PM
my bad meant injector duty doesnt show up and from what I read supercharger reflash uses a 2 bar map which i have and the reason i am on a supercharger reflash with hp tunners is it was in the repositiory and it was the easiest way to get the car to read boost. as far as the 100 shipped if its for the 42lb injectors how can i pay you . i would be able to pay this friday. do you have any pics. thanks
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