gts500

hay guys
I took my car today to the dyno to tune it i just had instal my lg g5x-3 on the motor

and i had these good darts 205 heads and all bolts on plus the NOS

my project is to hit 450hp and 550 with NOS but wht happen is

the car make 390 first run then...

after we tune the car it make 420hp and couldent reach more cuz we found that the injector had a duty cycle of 116% on high rpms?? and its going lean to 14.1 afr givin me no chance to hit the juice

ofcourse i couldent use the nos but the quistion now is...

wht is the problem ?? i already had high fuel pump (we checkd the fuel pressure and it was 40psi on high rpm)

and the tuner said its must be the injector problem so i need bigger injector.

is that right? and i have an 42lb injector ready to install but i think is too big should i go for it ????

please guys help need your advice.

ls1muscle

iTrader: (16)

Heads, Cam, 150 DRY n20.. Stock injectors will work just fine

No, they're not too big, they'll work great.

GTObsessor

iTrader: (2)

so why didn't you put in the 42's from the get-go again? ... wow....

P Mack

iTrader: (6)

40 psi at high rpm? Isn't fuel pressure supposed to be 58 psi or so?

383LQ4SS

iTrader: (33)

you need to adress your fuel pressure issue. You have tuned your injectors in an attempt to make up for a lack of fuel flow resulting in the high duty cycle. Youll probably need to pull the fuel pump and see whats up. or if its stock...get a new one..or a walbro.

DuronClocker

iTrader: (25)

And if by "high fuel pump" you mean it has a Walbro already, sounds like you either have a very clogged fuel filter or desperately need a hot-wire kit.

BOWTIE

That was my thoughts as well.

jub jub

Get your fuel pressure up to where it's suppose to be - 58 PSI, and put in the 42# injectors and rescale the IFR table (tuner needs to do that). That should be plenty.

gts500

yah it should be and it was 58psi from idle up to 4500 then start droping

Juiced

iTrader: (2)

With a 150 dry shot you are going to need the 42'lbs

fix the fuel pressure and get back on the dyno.....

gts500

wht is the proper way to fix the fuel pressure???

and i just want to know why is the fuel pressure is dropin???

Juiced

iTrader: (2)

Check the voltage at the pump.

Low voltage, a clogged fuel filter/pre-filter or improperly installed pump might be the problem.... sometimes walbro pumps just don't flow worth a crap out of the factory.

gts500

well thank u guys u help me alot am on it now will take the car today to check the voltage and replace the fuel filter and see how it performe

lovescamaros28

(lol)How do you get over a 100% duty cycle?The injectors are on constantly during 100%.I suppose 100 plus would be where the injector is open past 360 degrees of crankshaft rotation.

jub jub

It's theoretical. In other words, it's shy 16% of what is required to maitain proper fueling.

Irocss85

iTrader: (1)

wait, let me get this right. you already have a walbro and the fuel press. is dropping off above 4500rpm? somethings not right. my stock pump (dads car) is still around 50psi at over 6000rpms and his car put down 417 to the wheels on a mustang dyno. (also stock inj.s for 2002) do you know how the pump is installed? wonder if its just stuffed inside the factory fuel bucket and its sucking the bucket dry at higher rpms? there's many diff. ways to do it I guess, but I cut big holes in the bottom of the bucket to allow lots of fuel to easily enter the bucket and pump. trade off is no road racing on low fuel cause your losing the buckets purpose mostly.
let us know man.

gts500

verey good i dea cris ! yes the man who instald it he just do it like pump swap

just inside the factory buckets and my car star when the fuel reach last 1/4

start to hestaite specialy around corners sometime the fuel cut off for a sec and i still have 1/4 tank???

am going to kick that man ***

ok i will do this now and i will see the diffrence

1:open the fuel pump and see wht is going on and i will open holes on the bottom
2:replace the fuel filter
3:check the fuel pump voltage
4:i will let you guys know wht we found seeee yaaa gotta go now

Irocss85

iTrader: (1)

I'll post a couple pics for you later. the reason for cutting the hole's, is one the new fuel system and eng. will demand more fuel and volume then the stock setup. the stock pump has some sort of setup that pumps fuel into the bucket and keeps it full. once you put the walbro in, it doesnt have that extra setup that keeps the bucket full, so your relying on the very tiny opening at the bottom so even when the gas tank is mostly full, the bucket can go empty around corners or under WOT for setups like yours that will demand alot of fuel quickly. but you will still not be able to race with a low fuel tank because the fuel will still slosh to the back or sides of the tank and possibly uncover the bottom of the pump. just keep it at or over 1/4 and you'll be fine.