The Nov 2018 issue of Car Craft has a very interesting article called "LT Engine Swap Shop" (Pg 36 by Jefferson Bryant). No - I'm not changing brands ... but I have been very interested in PWM fuel pump controllers that sense pressure at the fuel rail and then drive the fuel pump just enough to maintain pressure and feed the engine (no return - no tank fuel heating).

On page 38, they discuss the LT fuel system and GM Fuel Pump Controller. I have an in-tank Aeromotive Eliminator Fuel Pump and the Aeromotive PWM Fuel Pump Controller. But this controller senses RPM and PWM's the pump based upon the tach signal. That's good but there still is a return line and fuel heating. RichN always recommends a return line system for EFI applications and he's never steered me wrong but I wonder what he has to say about these pressure sensing PWM fuel pump controllers? All the new factory cars/trucks seem to have gone to returnless systems. The article says that you need the GM ECM to talk to the GM Fuel Pump Controller and I'm using the XFI so a hack for that would have to be figured out. My EFI map was learned/tuned on the dyno at 50psi fuel pressure. The LT System looks like it is set at 60psi so that would have to be remapped or figure out how to fool the controller to think it is 60 psi when it really is 50 at the fuel rail. I think that a PWM Fuel Pump Controller that senses fuel pressure and modulates the pump to supply fuel without a return might be the way to go. That and very well insulated fuel lines and fuel rails to keep the heat out of the fuel as much as possible might make for an optimal EFI fuel system.

What do you guys think?

Setting a fixed rail pressure will cause a loss in dynamic fuel range. If the system is truly set up as a closed loop pressure sensing control, why not make it follow(or better yet expand) the pressure changes of a real regulator?
I see no benefit of keeping fuel in the engine compartment any longer than it needs to be there. Most generic fuel rails hold a large amount of fuel. If hot fuel is bad(is it???) then, would this style system not make the heat at the injector worse? who cares if the fuel tank gets warm really? Example... I wouldn't want to limit the water flow out of my engine to keep my radiator cool. The goal is to keep the engine cool. Targeting the radiator temp is not the goal. Seems to me that the same would apply to the fuel system.
Not sure about the XFI, but the Holley system can be configured directly to control a ssr to drive the fuel pump with pressure feedback/ map control if you wanted or needed to do that sort of system.

I am obviously against this setup, but it does offer some interesting abilities/tricks that may be beneficial in some applications.

My Megasquirt system has an option to PMW fuel pump based on pressure readings(2 sensors) but the learning curve looks much steeper than the benefit.

I have seen others have good results by isolating fuel system components from heat sources with fiber washers etc, they have had more of a benefit this way than by using a pump controller. Some claim the pump controller makes things worse?

Ford has used this for a long time on the Mustangs,it is the principle of having a fuel rail pressure sensor to detect pressure drop when the injector opens and tell the PCM how much(fuel pressure there is)which then tells the driver module how to adjust pulse width to maintain. add or remove. It can be done, I just don't know about the aftermarket controllers.

Anthony

Chrysler has been running return less for a while too

Holley recommended a returnless system for my Duster. I don't have it running yet so I can't say how it works but that was what Holley engineering recommended. It is just a pump with a regulator mounted in the fuel cell and then a single pressure line to the front. So it does have a return, but it is all done in back at the fuel cell rather than a return from the fuel rail.

Yeah Chrysler has run a returnless system for a
number of years(about 15).. I remember working
on them in the lab.. the regulator and pump were
all in one so the return just dumped in the tank
then they were talking the PWM about the time
I retired

Especially with E10 fuel, and also if you get unlucky and have winter blend in the tank on a hot day, you can still get boiling in the fuel rail at EFI pressures. The only solution is to increase pressure and/or keep the fuel cooler by trying to isolate the rail. The PWM controllers reduce pump output at idle when it isn't needed, which is fine for most situations except when you have high underhood heat. If you could measure fuel temp and increase pressure when the temp is warmer that would be the best of both worlds. Would be cool if the Megasquirt could do that.

I went with a non-PWM high pressure pump in a surge tank system with constant fuel circulation using a low pressure pusher pump mounted just outside the fuel tank.

As many know, that set-up circulates fuel at or near 0 psi from the tank to the front mounted surge tank and back to the tank at high flow rates. The fuel rails are fed by a EFI pump mounted in the surge tank and a regulator bypasses fuel from the fuel rails back into the surge tank.

The end result is cooler fuel in the fuel rails due to any fuel not shot out the injectors being constantly flushed back through the tank.

We are putting together a friends EFI system together using the recently released Pro-flo 4, a custom larger capacity Rick's stainless steel tank and an in-tank Aeromotive pump module.

His system has PWM capabilities, but we are using a bypass return regulator that is plumbed back to the tank.

It is unclear to me if using both the bypass regulator and the PWM pump control would result in unstable fuel pressure at the rails.

Interestingly to that end, I have a 2 speed Fuelabs low pressure pump on my carbureted motor controlled with a micro switch on my outboard mechanical sixpack carbs. It kicks up to high speed when the outboards are cracked.

The fuel pressure is dead stable at the bypass regulator whether on low speed or high speed. That surprised me due to the pressure and flow increase that occurs when the pump is on high speed flow. I suspect the same results with PWM and a bypass regulated set-up, but have not seen it for myself.

I remember when Chrysler went to returnless EFI systems as I was working at a Dodge dealer when they did. It was in the later 90's I believe when they changed over. They had to compensate in the inj pulse width since they did not have the vacuum to the press regulator. Ron

Do you guys remember if Chrysler was using a pulsation dampener with the efi systems?

Yes. The first externally returnless system Chrysler used was on the neon. In tank return with an accumulator/ damper.