Originally had the 706 heads and 8psi all stock 5.3 motor and tuned w/ sct tuner at Procharger. Tuned to 11.8 afr. Found the cracked 706's and went to the 243's. I know the bigger chambers would drop the base compression and lose n/a horsepower. Finally got it back on a dyno (local guy). Reading 12.4 afr. Maybe because they flow better? Anywho...needs some adjustments.

Question: Since the Procharger install i have had a fuel pressure gauge. It has always dropped from 60-53 under a full pull... is this normal? The new tuner (local guy) does not like this and wants me to upgrade fuel system. OR, he says i can slow the blower down to like 6-7psi.

I really don't want to pay to retune the truck at a lower boost level. He says that we could lessen the boost and adjust the timing (due to the larger chambers) and probably end up around the original horsepower numbers. And i really dont want to dump a bunch of money in redoing the fuel system.

Just looking for everyones thoughts on the situation as what you think the best route would be. Thanks

 

On a 04 yes that is normal, you have a returnless fuel system so its basically going to drop 1psi fuel pressure for every 1lb boost. What are you running for Injectors and fuel pump? Your 12.4afr is too lean......

 

As the other guy said, what do you have now?

 

Have stock pump with 44lb injectors. And yes, too lean.

 

What should the afr be? When tuning my motorcycle I aim for around 13:1. Never tuned a automobile though.

 

I am looking for prolly 11.8

 

A stock pump isnt going to hold up to that much power. You might be able to get away with sticking a walbro or bosche intank in there.

 

I would at a minimum go with a larger fuel pump, or even add a Kenne Bell Boost-a-pump. Also what is your duty cycle on those 44 lb injectors? With lower compression your should be able to run a little more boost.

 

You are going to need to upgrade your fuel pump, and at 8psi your injectors are going to be pretty much maxed out. What fuel pump setup you run depends on what your ultimate goals are. At 8psi I would target like 11.5-11.6afr on a procharger. 11.7-11.8afr is ideal but being that you are procharged you are running the stock truck intake correct? If so #7 cyl. typically runs .1-.2 lean from what I have found. This is why I say 11.5-11.6 ( little safety margin)

 

I did not data log the run it was just one hit on the Dyno to check afr. But I would think I have room on the injectors. I am picking up a little boost due to better flowing heads. So a new fuel pump and tune it? So is dropping in a bosch going to be ok with a returnless system? I haven't looked into the pumps yet...