[alfon]

Of all the gasoline 4 cylinder engines that GM manufactures is the 2016-17 Volt's 1.5 engine the most fuel efficient.

It just seem to me, being that the 16-17 Volt empty weighs 3,550 lbs empty, and close to or over 4,000 lbs with luggage and passengers, its amazing that it can deliver the mpg's when running on gas compared to Civics, Corollas, etc.

Just yesterday my wife had to drive an extra trip, without charging, in our 2016 Volt, 68.9 miles total. The electric ran out at 60.1 miles with 14.0 KWH used, and the gas engine kicked in for 8.8 miles and used .15322 gal's of 87 octane Costco gas, according to voltstats.net. This equates to 57.4 mpg, when running on gas.

We also have a 2010 Prius, and thats pretty close to what the Prius would have obtained. Maybe we just lucked out
in this car with an extra fuel efficient engine.

 

[obermd]

Nope. While the Ecotec 1.5 NA engine in the Volt is efficient it also gets a lot of help from the regenerative braking system. Anytime you decelerate or go down hill the car puts power back into the batteries. The Volt then uses that power first before going back to ICE. This power is recorded against the ICE statistics, making the ICE appear to be more efficient than it really is.

The Ecotec 1.4T engine in the Cruze is slightly more efficient. The 1.6T Whisper Diesel in the Cruze Diesel returns 50 highway MPG by itself. Where the Voltec drive system outperforms both of these is in stop and go traffic and when slowing down. Most of the Volt's kinetic energy is recovered and then reused before the ICE is engaged again, actually reducing the amount of time and distance the ICE has to operate. In the Cruze none of this energy is recovered. Instead it's turned into waste heat with a smattering of brake dust.

 

[Dutch]

<snip>Where the Voltec drive system outperforms both of these is in stop and go traffic and when slowing down. Most of the Volt's kinetic energy is recovered and then reused before the ICE is engaged again, actually reducing the amount of time and distance the ICE has to operate.

I knew about regen before buying a Volt, but I sure didn't understand just how much energy it recovers.
Makes me annoyed now when I drive my Jeep and "bleed energy" with every stop.

 

[alfon]

I'm just curious how the Ecotec 1.4T can be more fuel efficient if the Volt, which the Volt weighs more than a Cruze, gets better mpg's just on gas than the Cruze per EPA, when the battery is depleted than the Cruze does? I would have to believe when the Volt's battery is depleted that the gas engine is producing the electricity either directly from the engine or regen when decending down hill, or breaking. So the electric miles from that point on, after battery depletion, should be gasoline miles.

 

[telveer]

I'm just curious how the Ecotec 1.4T can be more fuel efficient if the Volt, which the Volt weighs more than a Cruze, gets better mpg's just on gas than the Cruze per EPA, when the battery is depleted than the Cruze does? I would have to believe when the Volt's battery is depleted that the gas engine is producing the electricity either directly from the engine or regen when descending down hill, or breaking. So the electric miles from that point on, after battery depletion, should be gasoline miles.

Even with a depleted battery, the Volt is still a Hybrid -- and the battery is never truly depleted. Hybrids are more efficient (especially on local roads) because they capture some of the kinetic energy when braking/slowing down and store it in the battery. This helps increase efficiency. The Cruze is not a hybrid - when you brake, energy is lost as heat. So, while the Volt may appear to be more efficient, it may not be because it has a more efficient gasoline engine but because it is a Hybrid.

 

[z80]

I knew about regen before buying a Volt, but I sure didn't understand just how much energy it recovers.
Makes me annoyed now when I drive my Jeep and "bleed energy" with every stop.

I know the feeling. When a light turns red on me (>80% of every light, it seems), if I'm driving my truck I get frustrated. However in the Volt, I don't care.

Yeah, I guess that makes me a total regenerate.

 

[llninja]

so it's not the gas engine that is more fuel efficient, it's the whole package: the gas engine, twin electric motors/generators, battery, etc.

 

[sparks]

Yeah, I guess that makes me a total regenerate.

LOL, I see what you did there...

 

[obermd]

I'm just curious how the Ecotec 1.4T can be more fuel efficient if the Volt, which the Volt weighs more than a Cruze, gets better mpg's just on gas than the Cruze per EPA, when the battery is depleted than the Cruze does? I would have to believe when the Volt's battery is depleted that the gas engine is producing the electricity either directly from the engine or regen when decending down hill, or breaking. So the electric miles from that point on, after battery depletion, should be gasoline miles.

The Cruze LT Automatic is rated 40 MPG and it's within a hundred pounds of the Volt. The ICE engine there gets no assist from batteries. The Volt is also rated at 40 MPG but the ICE engine gets EV assist. My 4,000 mile round trip to New Hampshire and back in June returned just shy of 40 MPG in my Volt running ICE for all but 130 miles of the trip. On the six trips my 3,100 lb 2012 Cruze ECO MT made returned about 1 MPG better each time. The 1.4T engine is a more efficient ICE power plant than the 1.5 NA in the Volt.

Even with a depleted battery, the Volt is still a Hybrid -- and the battery is never truly depleted. Hybrids are more efficient (especially on local roads) because they capture some of the kinetic energy when braking/slowing down and store it in the battery. This helps increase efficiency. The Cruze is not a hybrid - when you brake, energy is lost as heat. So, while the Volt may appear to be more efficient, it may not be because it has a more efficient gasoline engine but because it is a Hybrid.

I quoted both these posts because the telveer's point about the Volt being a hybrid and regenerating power is critical. Engines are not an isolated system in the overall power train. They are the primary source of propulsion but their power gets sapped off to run every single system in the vehicle. The regenerative power system in the Volt, combined with the car's computer always using EV before ICE, makes a significant difference in the overall power train efficiency, which is why the Volt is rated at the magic 40 MPG number.

 

[Neromanceres]

Okay are we talking about the most efficient engine. Or the most efficient car. Because these can be and are very different things.

The only way to establish which engine is the most efficient is to stick them on the same engine dyno and measure their brake specific fuel consumption.

The same engine will have different fuel economies when used in different applications.

 

[freshcut]

I think the thing to keep in mind too is that it's very likely the Volt engine doesn't have to work as hard either since for the most part it's generally only applying power to a generator rather than propelling the car as the case with traditional ICE drivetrains. All driving conditions aside when it comes to how the engine may interact with the drivetrain at certain speeds/conditions I think it's probably less stressful on the ICE than having to apply all of that power through a transmission to the wheels. Less work would definitely translate into fuel savings, and the added benefit of power regeneration adds to the efficiency factor.

 

[canehdian]

If both cars weigh the same and have the same engine, you can reasonably expect them to perform about the same when cruising steady-state as both cruze and volt (2.0) offer direct-coupled gear modes for engine to power wheels directly.
However, one would expect volt to be slightly more efficient because it has the ability to provide temporary bursts of power via the electric motors to help the engine propel the vehicle.
So while the cruze may need to kick down and rev up to a less efficient spot, the volt can (in theory) retain it's highly efficient rev point and just supply momentary extra power from the electric motors. Meaning so long as the road is not perfectly flat, the volt would probably win out even on a highway cruise.

 

[jbakerjonathan]

I know the feeling. When a light turns red on me (>80% of every light, it seems), if I'm driving my truck I get frustrated. However in the Volt, I don't care.

Yeah, I guess that makes me a total regenerate.

Your choice of words is so electrifying.

 

[obermd]

If both cars weigh the same and have the same engine, you can reasonably expect them to perform about the same when cruising steady-state as both cruze and volt (2.0) offer direct-coupled gear modes for engine to power wheels directly.
However, one would expect volt to be slightly more efficient because it has the ability to provide temporary bursts of power via the electric motors to help the engine propel the vehicle.
So while the cruze may need to kick down and rev up to a less efficient spot, the volt can (in theory) retain it's highly efficient rev point and just supply momentary extra power from the electric motors. Meaning so long as the road is not perfectly flat, the volt would probably win out even on a highway cruise.

My experience shows the Cruze ECO MT is slightly more efficient on the open road. The flip side is the Gen 2 Volt is definitely cheaper to operate. I had to run 91 octane in the Cruze to avoid the ECU pulling ignition timing, thereby wasting energy. The price per gallon differential between 87 and 91 octane is nearly 70 cents across the Midwest.

Now for my day to day driving I'm able to stay pure EV, which is definitely more efficient than any ICE powered drive train.

 

[srmarti]

I think the thing to keep in mind too is that it's very likely the Volt engine doesn't have to work as hard either since for the most part it's generally only applying power to a generator rather than propelling the car as the case with traditional ICE drivetrains. All driving conditions aside when it comes to how the engine may interact with the drivetrain at certain speeds/conditions I think it's probably less stressful on the ICE than having to apply all of that power through a transmission to the wheels. Less work would definitely translate into fuel savings, and the added benefit of power regeneration adds to the efficiency factor.

Actually I think when the Volt engine is on, it's running harder than the average ICE-only application. Generally not idling and burning 0.3 gal per hour going nowhere and only running
where the specific fuel consumption is generally better.

 

[freshcut]

I've wondered on this point since I got my Volt last year. It just seems to me like turning a generator doesn't put as much strain on the actual engine as if it were having to apply that power to the ground through mechanical means. Not to say that it isn't a walk in the park for the engine since I know the generator takes a lot of power to maintain speed while under load, just that it's probably less than what it would otherwise experience in a traditional drive train.

I do agree that there is the added benefit of not idling while sitting at a stop and have actually noticed that more often than not I tend to roll the windows up at a longer signal light since the exhaust fumes of nearby cars tends to be more pronounced for me now.

 

[srmarti]

I've wondered on this point since I got my Volt last year. It just seems to me like turning a generator doesn't put as much strain on the actual engine as if it were having to apply that power to the ground through mechanical means. Not to say that it isn't a walk in the park for the engine since I know the generator takes a lot of power to maintain speed while under load, just that it's probably less than what it would otherwise experience in a traditional drive train.

I do agree that there is the added benefit of not idling while sitting at a stop and have actually noticed that more often than not I tend to roll the windows up at a longer signal light since the exhaust fumes of nearby cars tends to be more pronounced for me now.

I disagree about the engine load (strain). Perhaps you are observing the difference in inertia of accelerating the whole car vs. spinning up the motor generator. When the engine is on and the car is in motion it is usually producing more power than necessary to maintain cruising speed as it is also maintaining a battery charge. I think it runs at higher power levels, getting better s.f.c. and a different duty cycle avoiding less efficient operating conditions. It's one of the things that helps a hybrid get better fuel economy.

 

[KenC]

...
We also have a 2010 Prius, and thats pretty close to what the Prius would have obtained. Maybe we just lucked out
in this car with an extra fuel efficient engine.

I had a 2013 Lexus CT200h, a slightly more sporty version of the Prius, and I would agree. The Volt, in hybrid mode gets nearly identical mileage to my old Lexus, with better overall performance. It's a very efficient hybrid ICE. I don't know if it's the most fuel efficient GM engine, but it's pretty comparable to the engine the Prius uses, and the performance is better.

 

[saghost]

I've wondered on this point since I got my Volt last year. It just seems to me like turning a generator doesn't put as much strain on the actual engine as if it were having to apply that power to the ground through mechanical means. Not to say that it isn't a walk in the park for the engine since I know the generator takes a lot of power to maintain speed while under load, just that it's probably less than what it would otherwise experience in a traditional drive train.

I do agree that there is the added benefit of not idling while sitting at a stop and have actually noticed that more often than not I tend to roll the windows up at a longer signal light since the exhaust fumes of nearby cars tends to be more pronounced for me now.

So many different things going on in the thread in general and this post in particular - without separating out the variables you can't really give a definitive answer.

The generator runs differently than a typical ICE in a lot of ways - it pretty much always runs at wide open throttle, it seldom runs at high rpms, never sees shock loads, and always has a controlled startup, with a warm-up before heavy loading.

The last is perhaps the most important for engine wear - I've been told that on a typical ICE, something like 90% of the wear on the bearings and surfaces occurs during the startup, when the engine is spun at a few hundred rpm and combustion occurs but there's no oil pressure and hence no oil film.

That doesn't happen on the Volt and I believe most hybrids. The Volt uses raw 360V power to spin the engine straight to operating speeds, pauses for a moment to get oil pressure, and then starts combustion.

Always being at full throttle means higher cylinder pressures, which is presumably harder on the rings - until you start comparing to the turbocharged engines that are becoming more common - under boost they have much higher cylinder pressures than the Volt ever gets.

On the whole, I'd expect a lot less wear in a Volt engine with the same operating hours.

For the rest of the thread, folks really need to make a clear distinction between engine average efficiency, engine peak efficiency, and students in vehicle loads required for the same speed.

 

[srmarti]

I'm sure all the stuff saghost described is true. I figured freshcut meant load on the engine was lower in the Volt more than talking about wear and tear and engine life. Thought he was implying the Volt uses less gas because it doesn't work as hard. My thought is the engine when running is generally working harder and more efficiently than in an ICE car and not spending much if any time in less efficient operating ranges.

Of course working harder means making more power and implies using more fuel; but probably at a higher efficiency?