OK so I have been searching the site for a while but have not found a definite answer. Does anyone run the flex fuel pump with boost? If so, how much boost? I recently purchased a P1SC for my 08 5.3 flex fuel and am trying to gather all my fuel parts. The pulley I have is a 3.4" so i'm assuming around 9-10 psi? correct me if i'm wrong please. So will 44# injectors and the stock flex fuel pump hold up with that amount of boost? Help will be greatly appreciated!

 

I'm not sure on the pump, but you'll be close to the limit of those injectors.

 

I don't know much about flex fuel ,but in a stock 5.3 (IDK if yours is) , a P1 with a 3.4" pulley should give you 12# or more,I also think you should go with 60# injectors. My truck is not flex fuel and I'm still using the stock pump at 9-10# with a 3.6" pulley. I also have the cam in my Sig .

 

Yes it is a stock 5.3, so looks like i need to find me a larger pulley. Will my 44# injectors work fine with 8-9psi? Obviously the stock flex fuel pump will hold up if you are still running yours.

 

I got 52# injectors at 9-10# of boost ,I'm not sure if your 44s are enough ,I would say
A 3.7 or 3.8 pulley will get you 9-10#.

 

I'm at 8 psi with a flex fuel pump in my Tahoe.

 

Well I already have the injectors so looks like the cost effective way to go is to just get a bigger pulley. I'm sure i'll still see a pretty good power gain with 8 psi still.

 

I run 12 psi with 42 # objectors and haven't had any problems. I have ran up to 16 psi with an a/f ratio of about 10.9

 

I may just set it all up and see how it acts during tuning. If I lose fuel pressure or the injectors are running too high of a duty cycle then i'll grab a bigger pulley.

 

Trade for a 4" pulley?