Is it normal to have 4-5 psi fuel pressure drop on a returnless system
 

I am seeing 4-5psi drop at WOT in boost. I'm going from 64-60 psi with my MP112 on a 5.3 with returnless fuel system.

Perfectly normal

What is the maximum acceptable drop?

mine dropped from 68 psi to 64 psi under full boost. It is normal

Thanks for confirming that. It still bugs me though, and if I add more boost which I plan on pretty soon. Is there a way I can add or make the pressure more stable without switching to a return system? Or is this the main reason why people switch to a return system?

return FTW

im currently running a returnless with 255 intank and 72lb injectors and im running lean past 5k rpm with 10lbs of boost.

I should be converted over to return by the end of the month

I think you are concerned about an issue that does not exist. I have run up to 10 psi to 6600 RPM without any issues on a return less system....can it be better, sure.....

However I would not be too worried about it.

sure, but if you plan on upping the boost its only going to get worse.

how much boost do you plan to run up too?

well shit, for all i know im prolly still running the factory pump. i was TOLD there was a 255 intank when i purchased the truck.

10 psi.......I do have a pump in the tank, as I can only assume the OP does as well.

I plan on going up to 8 pds of boost maybe 10. But for sure 8, so from what BLownchevy is saying I should be ok. My other question is do I need bigger injectors like 60#. The one's I have are the one's that came with maggie mp112 kit.

I used to run a returnless system on my procharged truck with 60's and a single intank 255 for 2 years. Pressure would drop to around 40-45 psi at WOT and resulted in 120+ inj. duty cycles. Now, I'm by no means saying that this is ok or ideal, however if you can keep your afr in good shape it'll work. I ran like this for 2 years without breaking any parts. Never even burned a plug.

That being said and regardless if you stay returnless or go return, I would recommend a dual intank setup and 60's. Search lonnie's or nasty fuel systems as they make turn key dual intank setups for the returnless and return style trucks.

Happy Boosting.

just FYI, both of those dual set-ups require you to convert to return. You send in your sending unit and they rig it all up for a return ect... Hence the "returnless requires additional parts" on the website.

Anyone with a returnless try a single big Bosch? I figure that pump and some bigger rails/lines would be the max

I'll be converting to a return soon, all my parts should be here this week

Reason I went to return is for the added room in the bucket for the twins, and the problem with trying to tune bigger high impediance injectors at a constant 60# FP @ idle on the returnless.

I have a bosch 040 in tank, works perfect so far

My bad, I could have swore that I talked to them and they told me it could be done. It was a while ago, so I can't remember all the specifics. :bang:

Brian,
Is your fuel system similar to a dead head system?

affirmative.