LS EFI fuel system help? - Pressure falling off
#1
TECH Regular
Thread Starter
iTrader: (1)
Join Date: May 2008
Location: Iowa
Posts: 475
Likes: 0
Received 0 Likes
on
0 Posts
LS EFI fuel system help? - Pressure falling off
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?
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?
#3
TECH Regular
Thread Starter
iTrader: (1)
Join Date: May 2008
Location: Iowa
Posts: 475
Likes: 0
Received 0 Likes
on
0 Posts
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'
#4
LS1TECH Sponsor
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
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
#5
TECH Regular
Thread Starter
iTrader: (1)
Join Date: May 2008
Location: Iowa
Posts: 475
Likes: 0
Received 0 Likes
on
0 Posts
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?
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?
#7
TECH Apprentice
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.
It may not be the case, but I would rule it out before digging too much further.