Boost reference fuel pressure regulator

[08G8V8]

I have the Lonnies dual pump system installed and when I originally was talking to Lonnie about it, we discussed the system as constant pressure and the hobbs switch to kick the 2nd pump on. The system was shipped directly to my installer and it was installed and setup as a boost reference system. I talked with Lonnie, and discussed the current boost reference setup and he said that is fine, but to ensure only positive pressure is hooked to the FPR, otherwise when the regulator sees vacuum it will reduce the fuel pressure and the fuel transfer setup requires around a 53-55 minimum pressure to function properly. Otherwise, it could suck only from the pump side of the tank and run out of gas, even though the other side of the tank is not empty.

But there is no way to get positive only pressure to the regulator with the Maggie. The base fuel pressure was set at 60-61, so when at idle, pulling 7psi vacuum fuel pressure will drop to 53-54psi, and under cruise I have seen vacuum of up to 11psi, dropping fuel pressure down to 50.

So, I need to get back to my installer/tuner and either set this up for constant pressure or up the baseline pressure so to 65/66 so I don't fall too far down under high vacuum.

If I stick with the boost reference setup, at 6.5-7.0 psi of boost, and baseline fuel pressure of 66, do you see the 72+ rail fuel pressure being an issue with the Maggie fuel rails? I am going to try and contact someone from Magnason, but I can see them simply stating their rails are designed for GM spec fuel pressure of 58psi.

Or, should I go with a constant pressure setup? Either way will require a re-tune, so I just want to get some opinions before I take the car back.

Thanks for any input.

[STL_G8GT]

When I first installed the V pump, it would spike to low 70s on shutoff as the pumps inertia caused it to continue to spin after the car was shut off, if only for a second. I witnessed no issues with that... now steady pressure, that may be an issue.

I see what you're saying about the power and flow needed to ensure the system pulls from the other side.

I would imagine lonnie knows his system better than anyone else, and if he says he needs a minimum of 55, then that's that... that said, I haven't heard of anyone running a side dry, or an issue with that, and im sure plenty of tuners set the base fuel pressure at the 42psi mark on forced induction cars to get 50ish across the injectors at idle.

Maybe that means with your current setup you should set a constant pressure at 58 and tune to that, due to the limitations of lonnies system.

[08G8V8]

I was expecting the system to be constant pressure. I talked with my tuner yesterday, and he can do either way, but if I stick with boost reference, I was just curious to the limits of the rails.

The system is well above what I need for my power level, but plenty of room to grow. I would have liked to have gone with the ZL1 or CTS-V setup, but that didn't get ironed out until just a few months after I already purchased my kit from Lonnie.

[08G8V8]

I found this thread from Wreckwriter on LS1tech, where Lonnie states 58 minimum psi, but in talking with him on the phone, he told me 53. He said this is for other models with tank transfer systems, not just the G8.

http://ls1tech.com/forums/forced-ind...rocharger.html