LS1 PWRD

I did a search but came up emptyhanded.

I have an external fuel pressure regulator and it has a vacuum port which lowers the fuel pressure at high vacuum (idle and light throttle). There is a return line on this regulator which returns by-passed fuel to the fuel tank.

I am wondering if I should infact remove the vacuum line. Would I not be increasing the workload of the PCM/ECM because it has to correct for the varying fuel pressures being delivered to the injectors? Let's say 1500RPM at 45PSI light throttle versus 1500RPM at 60PSI. The pulse width of the injectors would vary considerably, They would anyways because of throttle opening but I am hoping someone can understand what I am trying to explain.

The LS1 engine is designed to operate within a certain fuel pressure range (55-62) if I remember correctly. Am I creating a problem for myself by operating at a lower pressure?

Your comments are appreciated.

Thanks,

Neil

MIGHTYMOUSE

iTrader: (59)

what is your application? forced induction?

what regulator and how do you have it plumbed in?

what kind of fuel pump, what are your fuel demands, hp level?

is this on a f-body with an ls1??

do you have stock computer tuning?

why did you put it on in the first place?

if you have stock tuning and not many mods you really dont need the regulator

the regulator really only comes in handy when you are running boost. it adjusts the fuel pressure accurately for you instead of having to pump around the flowrate table in the computer.

LS1 PWRD

Thanks for the reply.

The engine is a normally aspirated 98 LS1 installed in a 94 Astro AWD. The 94 Astro has a high pressure fuel pump with return line (fuel reg at CPI unit) hence the need of a regulator. The regulator is an Edelbrock adjustable. I do not plan on racing this unit, just having fun which I do. I have done some tuning with LS1 Edit. The fuel pump is the stock Astro in-tank unit and has so far handled the fuel delivery with no problems. When the pump fails I will install a stock F-body pump in it's place.

Hope I have answered all your questions. By the sounds of your questions I have done a lot of "overkill" on this project :-)

Thanks again

rich

If you were to remove the vaccum from the reg. you will be creating a rich condition at idle the car is made to idle at 59 psi and at wot say 55 psi if you were to remove the vaccum it my go up even higher at idle because the engine isn't useing any of the fuel the duty cycle of the injectors is not up. If you want I have a walbro 340 pump for sale brand new. I have the same pump in my 2000 SS and I have 61 psi at idle and with a 2 stage wet kit, heads and cam at wot I see around 55 psi.the ls1 has a bypass by the tank a return so to speak. the les fuel being used the more that reurns to the tank befor it sees the regulator your set up has the fuel returning after the regulator.with thw vaccum dissconected I would adjust the fuel pressure to 59 psi and with a fuel pressure gauge and the vaccum line connectedI would make a wot pass and record the fuel pressure and if it stay around 55 psi and don't drop lower than 52 psi I would leave it alone. If you can't get the 59 psi at idle or it drops to low at wot I would upgrade the pump or you may get knock retard from the lean condition. Good luck with your project. Hope this helps a little. Rich

Speartech

iTrader: (14)

The fuel table in the PCM is set up to NOT be vacuum referenced. You should not hook up a vacuum line to your regulator.

The only fuel tables set up to be vacuum referenced are the 97-98 Corvette and the 4.8, 5.3, and 6.0 truck.

We use these EFI fuel pressure regulators on all of our LS1 conversions; we just leave the vacuum nipple open.

LS1 PWRD

Thank you, gentlemen

Vacuum line will be disconnected and fuel will be supplied at 59-50psig.

Neil

PS. Never had a problem with it's performance. It runs like a scalded cat. Well, I think it does. It weighs in at 4780 lbs and turns a flat 15.00 in the 1/4.

Thanks again.

MIGHTYMOUSE

iTrader: (59)

if you are using ls1 edit you can easily rescale the injector table to work with the regulator just fine.. but if your not forced induction then its no gain either way you go.