Engine and Transmission Tech

Feeding (4), 160lb/hr injectors with E85. Idea is to use (2), in parallel, "Walbro" 255L/hr. pumps. Run on (1) untill boost comes in, and turn on # 2 with the boost ? Using a boost referenced regulator with fuel return. Suggestions ? Thanks, roverman.

Should work although you may want to install pressure check valves after the pumps, to prevent the fuel pressure from back-feeding to the in-active pump.

I simpler option might be to use one large pump with 1/2" feed and 3/8" return lines. With a 1/2" supply line and the right pump, it should easly be able to support up to 1000hp or more!

With 4 injectors I assume you will be using TBI's? If so, then they won't have boost pressure exposed to the injector tips. So you can get away with running lower fuel pressures as long as you have the volume.
Most boost sensing regulators are 1 to 1. When using a 1 to 1 regualtor with a port injection system, "technically" you do not gain any additional fuel flow as boost pressure increases. This is because for every pound that the rail pressure is increasing, manifold pressure exposed to injector spray tip is also increasing at the same rate, pushing backwards on the fuel flow. If that makes sense:-)

Fuel management units (FMU) work well with port injected systems and boost. Vortec makes units from 1 to 3 all the way up to 1 to12.
With a 1 to 3 unit you can dial down the main regulator to say 25 psi for good idle and low speed performance. Then as boost pressure builds to say 10 psi the fuel pressure will ramp up to approx 55psi for proper fuel flow at high loads. This help keeps injector pulse widths in a normal range.

Most GM TBI systems operated in the 10-13 psi range with some big block applications running around 27-29 psi. With a 1 to1 regulator on a TBI system (at 10 psi of boost) would be 20-23psi or 37-39 psi of "actual" calculated fuel flow.

Bill



Edited 3 time(s). Last edit at 03/31/2011 12:57AM by MG four six eight.

Hey Art,
Bill does have the better idea with one large pump.
Two pumps are going to be problematic and the control system will be cumbersome and unreliable.
You can over supply the system with one big pump and tame it down with a pump controller.
Put a fuel cooler in the system as the pump(s) will likely heat the fuel significantly
The controller slows down the pump when demand is low and steps it up when needed.
I use the Aeromotive ones as they are pulse modulated vs. voltage dropping. There are many other suppliers and even OEM units out there now.
Pressure sensing regulators on a tbi will just make tuning a hassle as you try to compensate for boost that the injectors never see.
If you blow through the throttle bodies the regulators will be exposed to boost pressure, wanted or not.
FMU's are usefull in low boost near stock situations but in your case I would rather see a proper program written into the ECU,
unless you use Alpha N. Then all the rules change and you might as well use a carb.

If complexity is your game why not take on the BMW idea and run each throttle body as a separate entity?
Along the v12 lines.
Two separate management systems per bank.
Make the throttle bodies progressive, running on separate ecus and pumps.
Thats crazy complex but really sexy at the same time.
It would give you bragging rights at the WTF cafe.

Cheers
Fred



Edited 2 time(s). Last edit at 03/31/2011 04:01AM by DiDueColpi.

Thanks for the skilled input guys. No WTF cafe needed. I'm blowing into (2) tbi's,(converted Thermoquads). How do the injectors "not" see boost ? Other than the "centrifugal", I'm goin for the retro look.Eddy, dual plane/quad manifold has fairly long runners, and the "quads" are a direct fit, other than 2 1/4" secondaries hitting. I was considering the dual pumps because reduced amp draw and fuel bypassing,(heat-up). I'm looking at 550hp, approx at 8psi, E85, 60% duty on these injectors? Megasquirt III for this set up, with cop. ? Cheers, roverman.

If you're doing a blow through system then the injectors will see boost pressure.
And so The ECU should be tuned accordingly.
With new engine management systems, manifold pressure referenced fuel pressure regulators are becoming redundant.
They just add a variable to the tuning that isn't required anymore.
I must be a bit behind.
I thought you were using a roots blower with wet rotors which would mean a draw through system.

Cheers
Fred

Fred and clan, other thread is "blown/inj hemi ".So with Aeromotive pump controller # 16306, doesn't require fuel return, is programable, why need a regulator ? Between this and Megasquirt III = enough controls ?Water/alchohol, pre-injection. I think I "want" wet runners, for intercooling(E85). I just bought "Performance Fuel Injection Systems",(HP Books), and yes this is my first time.Update, It appears the Accel,port injectors will nest nicely, in the former primary bores. I need an air horn/velocity stack that will fit the secondary opening, any ideas ? Onward, roverman.



Edited 2 time(s). Last edit at 04/01/2011 04:39PM by roverman.

Ah yes, blow through will have boost pressure exposed to the injector tips as Fred mentioned. I was thinking draw through and using a roots blower.
You may not need a regulator with fuel pump control module. Although it may not be a bad idea to have one to use as a max pressure limiter in case something goes wrong with the system electrically, such as a overcharge condition.

Fuel pump control modules are getting more common in newer vehicles. I know that new Tahoes/Suburbans have them and that they communicate with the ECM via a CAN line. The ideal system for using a fuel pump control module, would be to use a fuel pressure sensor that sends a signal to the module. Then the module would know what the fuel pressure is at all times and could adjust the pump speed through pulse width modulation. The ECM constantly sends a signal to the FPM telling it what it wants for fuel pressure based off of engine rpm, temp, load, etc. Then the FPM adjusts the pressure based off of a preprogramed table.

Bill

With 15.896 sq. inches of butterfy area, I'm thinkin I'll want a "slow" opening ratio.I'm attemting to blow "only" into the secondary areas, to reduce potential for boost leaks. Properly rated fuse on the pump to prevent overload pressure ? These port injectors will probably have a narrower cone pattern the oem tbi's. I suspect "staight shot", in the primary bores, should be acceptable. Megasquirt III, my best bang/buck option ? Thanks all, roverman.

Probably would be best to use a regulator for overload protection. It could be done with a fuse, however to make it work the fuse rating may be to close to normal working amperage of the pump, which may cause un-intended fuse failures.
For reference most GM fuel pumps draw in the following ranges depending on volume and pressure, 4-6 amps, 6-8 amps and 8-12 amps. The 4 to 6 amp pumps are usually found on cars, while the 8 to 12 amp pumps are most common on full size port injected pick-ups and SUVs. The running pressure difference between the two is not that great, maybe 10 to 15psi max.

Mega-squirt III should work well for your application, due to it's wide range of tuning abilities.

Bill