Chevrolet Cruze ECO "returnless" variable pressure fuel pump
 

GM is promoting the crud out of the Cruze ECO these days, with gas prices being near record highs.

Just spotted this tidbit about the car's variable pressure fuel pump, which does away with the need for a fuel return, and reduces load on the engine (through reduced electrical demand):

source: GM - Canada - News & Information

Neato.

...they're also touting their Regulated Voltage Control (RVC) system that is effectively an "on-demand only" field regulator system that holds battery voltage at ~ 12.3VDC instead of 14.7VDC all the time.

...instead, it only pumps the voltage up to 14.7VDC right after a heavy load (starting) then backs off to ~12.3VDC while cruising; but, goes back UP in alternator output voltage (if needed) during decelerations and breakings.

...good news for lamps and light bulbs, but not so good on batterys themselves.

Look under the hood of any Ford Focus made in the last 5 or so years and you will see a return less system. Sensor at the front of the fuel rail, sends signal to ECU, which sends a signal to the fuel pump modulator, which controls voltage to the in tank pump.

Smart alternators will eventually go into full charge when engine is in DFCO and AC compressor is not cycling, then if that is not sufficient charging will max during higher vacuum parameters.

Stop start alternators will have much greater capacity to charge quickly and will really pump the juice in a larger capacity battery under forced deceleration.

I still think lower displacement with electric supercharging under high loads will be a factor, especially with start stop alternator-starter systems and higher capacity lightweight batteries.

regards
Mech

Good additional info, guys. Thanks.

...augmented by super-capacitors which are great for sudden dumps of current.

Most new cars have return less fuel system. I remember when GM was promoting the same thing on the LS1 back in the late 90s.

Interesting.

Is returnless automatically the same thing as having a variable output fuel pump? (I don't know.)

Probably not. I'm sure there's some difference, albeit a small one.

Yes for the most part all returnless systems have variable output fuel pump if not then at higher speeds and loads when demand for fuel is high it would not be able to provide fuel fast enough.

Found this old thread and wanted to add some info.

Traditional return style fuel systems have a vacuum/boost sensitive bypass regulator. The fuel pump's output is constant volume, and the regulator varies fuel pressure based on manifold vacuum/boost. Excess fuel is returned from the engine bay to the tank.

The first returnless designs eliminated the return line and hardware as a cost savings. In this design, the fuel pressure is always constant and is set by an in tank regulator. From an electrical power consumption point of view, this system has the least efficiency as the pump is always pumping enough fuel at pressure to feed the engine at maximum power.

The newer systems like the one in the Cruze use an intelligent driver to manipulate the fuel pump RPM to vary fuel pressure and flow as required. As far as I know, no pressure regulator is used so every bit of gas pumped by the fuel pump is required by the engine. It wouldn't surprise me if lots of vehicles are using this system by now.

Older systems that were less efficient due to pumping losses also heated the fuel in the tank, leading to increased evaporative emissions.

Another advantage is the fuel can absorb engine heat which improves atomization. In the return systems a lot of that heat was returned to the tank and over some time would warm it up measurably and, as previously mentioned, increase evap emissions, which are generally offset by reduced fuel delivery from the injectors.

regards
Mech

Thanks for adding that! I realized I didn't put that in there after posting and was too lazy to add it. :o

The voltage to the FP on my '90 Toyota pickup (motorhome) varies. I assume that means it has the ability to vary pump power output. I think there is a return line, but, I'm not sure. Maybe Toyota was already doing this 23 years ago?

Some data to add
 

I don't know how prevalent they are yet, but ther are coming soon.

An Electronics supplier showed me today, as an example about the power of Matlab software, a PWM ECM controlled variable speed fuel pump with feedback loop to maintain the exact pressure at all times.

On a sample Mini Cooper run through Matlab Simulink, baseline fuel pump was 95 watts constant. Variable speed was averaging in the 55 watt range. And a brushless variable speed was in the 30 watt range.

To convert to theoretical FE changes, more Matlab analysis indicated a 0.5% to 1.5% FE increase due to reduction in alternator load. They considered this low hanging fruit, even though it was small, but measurable, FE improvement.

Yep, every 746 Watts of electric "load" is another horsepower you're feeding gasoline to.

After 8 years of owning a cruze with this system it has been so so on the bubs, it eats about 1-2 headlights per year but no other bulbs. Insofar as the battery, the OEM battery lasted 6 years. I too feared that the alternator would be hard on batteries but 6 years out of a battery these days isn't bad.

Holy necro posting, batman!

If you are buying you headlights at Walmart, stop they are only rated 150 hours. Go to rockauto or similar and get some Long Life bulbs for $6 each went with Hella's for the cobalts and Impala.. I finally started tracking when I replaced them and 150 hours is about it on the last one.

The impala also drops to low 12's a lot, asked when it was in for something else and they said it was normal.