knappbunch

Hey guys what types of injectors and how many # on 402 through 408 with fast 92/92 and big cam 11.5.1 comp. tfs 235 cnc heads. my motor was on the dyno today and I was told that My injectors were at 107% duty cycle at 4000 rpms and 11 degrees of timing. I am new to lsx's but I thought the 42# i had would be fine.

kenp

iTrader: (9)

You need to read the posts about this. If you have a 42lb injector at 58 psi that could be a problem. If you have a 42lb injector rated at 43.5 psi, I think that should be good to about 610hp at 80% duty cycle. That would be a 48.4 lb injector @ 58psi. If you have a forced induction car, you would need more injector.

DrkPhx

iTrader: (15)

The 42-lb injector should be fine, but if you're at 107% duty cycle at WOT you definitely need bigger injectors. I run the Delphi 42-lb injector with the fuel pressure set to 61 psi at the rail and I see no higher than 77% duty cycle at WOT (it's usually about 73%).

405HP_Z06

iTrader: (11)

In theory, if the injectors are rated at 42 lbs/hr @ 3 bar, you SHOULD be fine. What kind of power were you making? An overly rich tune will also cause IDC's to be way out of wack.

FICINJECTORS

iTrader: (30)

I agree completely. If they are 42's properly rated at 3 bar then they should be fine for that kind of setup N/A.

I also agree, and am wondering what your A/F looked like.

knappbunch

not sure what the a/f were at. Or the tune for that matter will take a closer look at the injectors Monday and try and sort it out with builder/ tuner

knappbunch

the injectors are the bosch green top 42# are these capable of 640 at the crank or do i need bigger and if they are capable what do i need to do tune wise to get it there. i think they were running at 50 sumthing psi how do i get them to 60 psi and i do have the walbro 255 pump. this is a n/a set up trying to reach 540 at rear wheels.

FICINJECTORS

iTrader: (30)

Stock fuel pressure on an LSx is 58psi. If you are not reaching it, it could be the pump not keeping up with the demand, or there is something wrong with the injectors, causing them to go static, and the pump not keeping up. This could be mechanically with the injectors, or in the tune or ECM.

Have to remember, the injectors are rated @3 bar, the LSx uses a 4 bar pressure, meaning that 42lb injector flows 48.5

DrkPhx

iTrader: (15)

GM service manual calls for a steady 55-60 psi at the fuel rail, so if you're if that range you should be good. You need to install a mechanical gauge on the end of the fuel rail to test the pressure. I use an Aeromotive adjustable fuel pressure regulator on my car. Keep in mind any increase or decrease in fuel pressure will usually require the car to be retuned.