Just curious what people's thoughts are on the stock fuel rail setup with a single Walbor 255 pump. I have 83llb injectors, no FMU, 2 Bar stock PCM mod in there with no problems running a 4" blower pulley at about 8-9psi and around 570rwhp @ 6200rpm.

Yesterday I put the 3.4" blower pulley on and took it for a cruise, as expected I'm seeing much more boost, being afraid to run lean, I only revved to 4500rpm but I see about 9psi compared to 6200rpm with the smaller pulley.

With no changes to the PCM, Im seeing an even 12.3-5 AFR all the way to 4500rpm. My wideband is installed in the D-side collector which should be safest in regards to running lean since that side of the fuel rail is the last to get fuel, due to that it should show the leanest AFR in the event that I begin coming up short on fuel pressure. I also have the stock regulator so I'm likely not getting the 1psi fuel per psi of boost increase like many people recommend.

My question is am I ok running 83lb/hr injectors, stock rails/regulator/lines/single 255 pump or am I overdue for a rail modification and second pump? Has anyone maxed out the stock fuel rail or know where it becomes a restriction?

 

? The stock regulator is a 1:1 rising rate.

In see no reason the stock fuel rails wouldn't handle 1000hp with a big enough pump; thats around 105cc of fuel per second.

The Walbro GSS340 255lph pump is rated for about 530hp for forced induction. They're only $100, just hose clamp one on your sending unit and Y it into the supply line. Trigger it with a 3psi hobbs switch and relay.

 

I want to say a few guys around here have run the stock lines & regulator up to 700 hp before it started to become inadequate but I don't recall exactly. I've just about finished replacing every line & fitting on my 97; just waiting for a y block and another fuel pump.

 

We're about to see how far those can go. Soon as I get the FAST box back I'm going to be road tuning my setup and as soon as it's broken in and roadworthy to satisfaction it's hitting the rollers to see how limited the stock fuel lines/regulator/rails will be with nothing more than a double pumper and big injectors (85 lb low-z).

I've got rails and a planned out fuel system on standby, but if I gotta swap, that's going to take a whiel as money is a worry for me with my current situations.

 

You are getting close to the limitations of a single pump, but your rails/lines should be fine from what I have read. Have you increased the voltage on your pump at all?

 

I run stock fuel rails and 50Lb injectors on my 12 psi procharged set up no problems
also i use the ractronix hot wire set up (make a nice difference and no voltage drop to the pump)

 

Everything in the fuel system aside from the pump is stock including the power, maybe Ill add the second pump for safety. Thanks everybody.

I thought the stock regulator didnt notice boost? I dont actually know but assumed that.

 

It does, and it has to in order to maintain a constant fuel pressure with varying manifold pressure since LT1 tuning has an injector constant as opposed to a injector curve.

 

Well I upped the RPM a bit more tonight, it's hard to keep traction in second but I hit about 5800rpm and 11.3lbs of boost in 2nd at 75mph while tires were smoking and staring to grab, showing no knock, AFR flat at 12.0AFR; and flat injector pulse width from 5600-5800, so looks like it's at least good to 5800rpm. I normally ran to 6200rpm which should now be around 13psi I'm guessing.

Thing is I dyno'd 570rwhp at 7-8psi at 6200rpm which is ~630-640hp motor, well above the rating for that fuel pump.

 

Yeah, unless you hit the lottery or something it will take a while. I've been working on my fuel system for a few months now. I think my friend is naming his boat the "SS Fuel Pump" in my honor.

 

i run stock lines stock rails duel intank walbro 340 255's (ones on a hobbs switch) 80# high Z injectors@ 60 lbs of fuel pressure. still doing good...

 

I searched for adding a second fuel pump didnt find much... how does one run the wire to the second fuel pump, is there a through connector somewhere out there that has two wires and is sealed that you add by drilling a hole?

 

You can use a sealed bulkhead fitting if you feel like doing it that way. I used the remains of the charcoal canister tube with a grommet and epoxy to run my wires through. After that you run a relay with main power, ground and trigger wires.

There are quite a few posts on building the setup on LS1 Tech. Dual pumps are fairly easy to setup; it's the rest of the plumbing that kills the budget.

 

I'm running the 3.4" pulley on a 383 D1/ MM6. I had fuel starve @ around 6k rpm. Went to dual walbro pumps w/ stock lines. Still had the problem. Then, re-run all fuel lines w. (2) -6an to (1) -8an fuel feed line. Worked very good and that's where I am today. Of course I had to mod the fuel sending unit and bulkhead.
I still running the series stock fuel ail set-up, but, with a larger fuel reg off the rail. I think better fuel pressure distribution on cylinders 5 and 7. Also, very easy to adjust the reg bypass pressure which is a plus.

B.