Ksths2

iTrader: (1)

Ok guys need some help diagnosing my EFI fuel system issue

Got a new build (combo never ran other than on dyno trying get tuned) it’s a LS 408, Vortech YSI/+20psi, 1700cc injectors, E85, TBD but approx. 1100max rwhp -- (3) 450LPH Walbro in-tank pumps w/ sock pre-filters, Fuelab 10micron “after pumps” inline billet filter, -8an PTFE .7/16”ID supply, “Y” into back of rails, then directly into Magna fuel 9950-B boost ref regulator then a -6an PTFE .3/8”ID return back to tank. FYI according to many reputable people the -8 supply and -6 are plenty big for my requirements.

I’m having uses with the fuel pressure falling off at 70psi at WOT and it can’t keep up. With these big injectors and 3 pumps I’ve got more than enough supply but after talking with Magnafuel they say that they would go to a 25min micron filter rather than a 10micron.
Here’s how I have the pumps wired up, 1st pump runs all the time, 2nd is triggered by a hobbs at 8psi, 3rd pump is triggered by a 2nd hobbs at 15psi.

I tested all the pumps and they work, and tested both hobbs with air pressure and they work as well. I also unhooked supply line at the “Y” and hooked up 140psi to it to see if the pumps/lines/fittings were leaking internally but 0 air came from vent or no air noise at all.

My thoughts are the hobbs psi are set too high and not letting the pumps ramp up to full volume/pressure but according to my tuner that wasn’t the issue. Or the after filter might be too fine? What are you guys using for micron in your inline filters?

LilJayV10

iTrader: (39)

Have you verified you are getting enough voltage to the pumps under load buy doing a voltage drop or that the 2nd/3rd pumps are actually coming on under load?

Ksths2

iTrader: (1)

technically no I haven't but I'm confident they are good to go as I have my battery relocated to the back, 3 separate short wires to 3 40amp circuit breakers, then 3 separate wires going directly to LR wheel well for the 3 relays and common grounds etc. - Total length of wires is less than 5'

Lonnies Performance

iTrader: (16)

Lots of problems here....

First with your injectors you should be running a lower base pressure.
No need for anything over a 43psi base plus boost reference.
Personal I may consider 35psi base.
The pumps are not designed for extremely high pressure.

At your power level 2 450's will support all the power you are making.

Second if you have a 10micron Fuelab filter you have the wrong element for E85. You need the 6 micron fiberglass element. Either should flow enough for your power level, you just have one that is not compatible with E85

Ksths2

iTrader: (1)

The tuner originally had it at 43 base but I'm not sure why the tuner raised the base to 58
Fuel lab said the filter I have is a paper element and I need a 6 micron SS mesh for E85 but wouldn't the 6 micron cause even more of a restriction?

Lonnies Performance

iTrader: (16)

Restriction is not your problem, the element disintegrating & plugging your injectors is what you should be concerned with.

I've put over 1100rwhp through a 6 micron element.

Realcanuk

I would log the voltage at full throttle. If you are using a flip drive, it is not uncommon for the alt belt to slip and voltage can drop.
It may not be the case, but I would rule it out before digging too much further.