Actual MPG of C-Max gasoline engine (ICE): Can they do better?

[Hybrid dude]

This is my first hybrid but even with all my various issues, dead battery, etc., I can still go further on a gallon of gas than on my previous vehicle. 

 

My question: At the end of a recent trip, if one subtracts the number of EV miles from the number of total miles, then divides by the number of gallons used, the result is the true miles per gallon. So, on a ~500 mile trip, mostly highway and a few hills, my MPG was about 24. Could Ford have used a more efficient gasoline engine (ICE) in the C-Max, as 24 was my overall MPG on my previous vehicle and from looking at window stickers, several non-hybrid Ford models get better MPG.

 

If Ford sales thought there was demand for an even more efficient C-Max in exchange for a loss of performance/acceleration, could they use the engine from the Fiesta, for example or an even more efficient one?

 

I do get a good feeling when the engine shuts off when stopped and from my many short electric-only trips, however. 

[hybridbear]

It's important to remember that in a hybrid when the ICE is on it's not only driving the vehicle but is also charging the battery, so it's not really fair to calculate that way. However, the answer is YES Ford could have put a more efficient ICE in, but at what cost? Most hybrids typically don't have the most advanced ICE technology such as direct injection because it would be too expensive. The ICE in a hybrid already runs on the Atkinson cycle to sacrifice power for fuel economy and when hybrids are such a small % of Ford's overall sales they aren't going to invest a lot of money into R&D for direct injection with an Atkinson cycle engine which would only add more cost to each car. Once hybrids become mainstream and make up a significant (>15% minimum) chunk of all new vehicles sold then you'll see more manufacturers bringing advanced ICE technologies to hybrids because the cost per car will be much lower.

[Hybrid dude]

Thanks for the additional insight.

I did forget to mention the charging function of the ICE.

[Testdriver]

OTOH, the EV can also assist the ICE, inflating the ICE MPG number, especially on the highway. My guess is if you disconnected the battery components, then the C-Max would be slightly more efficient than the Escape, thanks to the Akinson cycle engine and better aerodynamics.

[fbov]

... The ICE in a hybrid already runs on the Atkinson cycle to sacrifice power for fuel economy ...

It's innacurate to say that an Atkinson cycle engine sacrifices power for fuel economy. The engineers traded off weight for efficiency, not unlike gas vs. diesel.

 

A 2.0L engine weighs more than a 1.8L engine. Letting 1.8L of fuel/air mixture do additional work expanding to 2.0L captures more energy from that 1.8L of air/fuel. Ford could as easily have upped the power by increasing the operating RPM (remember, horsepower is torque x RPM), with an associated fuel economy penalty. RPM's the only reason diesels "sacrifice power;" they have plenty of torque, just like the C-Max.

 

HAve fun,

Frank

[Adair]

Sometimes you guys just blow me away! You are so freakin' smart about all this stuff. I'm not being facetious...I'm just amazed....I mean, you understand all of this, and you talk about it like I talk about recipes, or raising birds, or gardening, and the best I can do with my car is fill up, check the oil, and drive. I am in awe.

[zhackwyatt]

Sometimes you guys just blow me away! You are so freakin' smart about all this stuff. I'm not being facetious...I'm just amazed....I mean, you understand all of this, and you talk about it like I talk about recipes, or raising birds, or gardening, and the best I can do with my car is fill up, check the oil, and drive. I am in awe.

I'm an engineer so that helps.  But to make you feel better, I burn food, my birds would fly away, and I have a brown thumb, lol.

Edited September 5, 2013 by zhackwyatt

[viajero]

As hybridbear said, you shouldn't subtract any EV miles, because all the miles are powered by gas burning in the ICE.  One exception would be if the state of charge were different at the start and end of the trip.  In that case you've borrowed some gas from or loaned some gas to your next trip.  For a long trip it shouldn't make much difference.

[hybridbear]

It's innacurate to say that an Atkinson cycle engine sacrifices power for fuel economy. The engineers traded off weight for efficiency, not unlike gas vs. diesel.

 

A 2.0L engine weighs more than a 1.8L engine. Letting 1.8L of fuel/air mixture do additional work expanding to 2.0L captures more energy from that 1.8L of air/fuel. Ford could as easily have upped the power by increasing the operating RPM (remember, horsepower is torque x RPM), with an associated fuel economy penalty. RPM's the only reason diesels "sacrifice power;" they have plenty of torque, just like the C-Max.

 

HAve fun,

Frank

I thought the point of the Atkinson cycle with its longer power stroke (compared to the shortened compression stroke by leaving the valve open) means that you can have better economy but less power (due to the lengthened power stroke) for a certain displacement.

[fbov]

Bear, I don't know your background, you've missed the key bit about horsepower: it's irrelevant. Another marketing scam to get you to buy something you don't want and can't use; a car salesman's dream!

 

ICEs produce torque, and torque x RPM = HP. Lengthening the power stroke increases torque. Getting a 2L power stroke for every 1.8L of intake displacement improves efficiency as well. Both show an advantage for Atkinson. So how does more torque result in "less power?" It doesn't. 

 

Running at lower RPM results in less power, while capturing huge efficiency advantages. Look at a BSFC (brake specific fuel consumption) chart and you'll see that high RPM requires high fuel consumption. Kind of makes it seem like horsepower is a bad thing... which it's not, its just an unimportant thing to an automotive engineer.

 

Now the added weight of an Atkinson makes a difference...

 

Have fun,

Frnak

[Jmonty]

Bear, I don't know your background, you've missed the key bit about horsepower: it's irrelevant. Another marketing scam to get you to buy something you don't want and can't use; a car salesman's dream!

 

ICEs produce torque, and torque x RPM = HP. Lengthening the power stroke increases torque. Getting a 2L power stroke for every 1.8L of intake displacement improves efficiency as well. Both show an advantage for Atkinson. So how does more torque result in "less power?" It doesn't.

 

Running at lower RPM results in less power, while capturing huge efficiency advantages. Look at a BSFC (brake specific fuel consumption) chart and you'll see that high RPM requires high fuel consumption. Kind of makes it seem like horsepower is a bad thing... which it's not, its just an unimportant thing to an automotive engineer.

 

Now the added weight of an Atkinson makes a difference...

 

Have fun,

Frnak

Interesting, thank you

[fotomoto]

Ford could make it more efficient but then it would have the output/throttle response of a prius; a common compliant.  

[nsteblay]

Good article on the Atkinson engine: http://auto.howstuffworks.com/atkinson-cycle-engine.htm

 

I do think Toyota has some pretty sophisticated engineering to achieve consistently high MPG and with what they consider appropriate tradeoffs in power and comfort.  I prefer the tradeoffs Ford has made with the C-Max.  Styling has impacted aerodynamics.  Larger ICE, EV and batteries has increased weight and requires more pure EV miles to offset ICE miles.  The results are excellent comfort, visibility and power when you need it, but greater reliance on driving technique to achieve maximum MPG.

 

I achieved 55 MPG this evening during my 21 mile commute from work - mixed driving freeway and highway - and I wasn't holding up traffic.  

[fbov]

I haven't driven a Prius, but i would welcome a reduction in throttle sensitivity at the very low end. Yes, when you put your foot into it, it should scoot. At the same time, I'd like to stay in EV mode occassionally without watching the display!

 

Have fun,

Frank

 

PS interesting article. I'll take exception to some of this comments (1.8L with 11:1 compression, 141hp and 129 torque would not be unusual today), but he did give me one insight.

 

Atkinson cycle engines don't rev well. They work best in CVT-type applications, and need EV for throttle response.

 

Balanced compression engines have more pressure in the cylinder when the exhaust valve opens. Unbalanced compression/power stroke engines will have less pressure in the cylinder due to the added expansion. As you remove intake vacuum (open the throttle), the engine gets less kick starting an exhaust/intake stroke due to the added expansion. That's where the efficiency comes from!

 

No freee lunches...

Edited September 6, 2013 by fbov

[nsteblay]

Frank you got me interested in BSFC after seeing one of your other posts.  I'm far from a mechanical engineer (software engineer) but found the Wikipedia article informative http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption.  At the end of the article there is a rating of various engine efficiencies.  The numbers show Volkswagen and Audi TDI diesel engines being more efficient.  Do you think we'll see diesel hybrids in the near future?

 

Nick

Edited September 7, 2013 by nsteblay

[Sparky]

  Do you think we'll see diesel hybrids in the near future?

 

Nick

 

The Volvo V60 Plug-In Hybrid is the first diesel plug-in hybrid vehicle.

 

http://www.greencarreports.com/news/1083037_volvo-v60-plug-in-diesel-hybrid-quick-drive-of-ny-auto-show-debut

[fbov]

One reason diesels are efficient is their lack of noxious emissions at lean burn conditions. They have no "air-fuel mixture." so fuel consumption is not tied directly to RPM as with emission-controlled gas. When you direct-inject only the fuel you need to maintain desire RPM at some load, there's less waste than pumping a constant air/fuel ratio at every RPM with no regard for load, energy required.

 

You also see economies of scale; the lowest consumption engines are megawatt generators.  I assume no one here misses the irony that the VW TDi Sportwagon actually delivers 47 mpg... my Brother-in-law has one, and gets 38MPG in the C-Max driving it like his VW... on Interstates, of course.

 

HAve fun,

Frank

[pjurek99]

Their TDCi's are ok. Combined with hybrid thing it would be an awesome power-plant. But... would the Americans be willing to spend their money on such expensive combination*? It makes sense in Europe. It would do so here in the States.

 

*AFAIK the PSA (Peugeot/Citroen) makes good-diesel hybrid cars. And Ford EU has been using the PSA TDCi's (HDi's in PSA's) so maybe there can be a successful combination applicable to C-Max.

Edited September 6, 2013 by pjurek99

[viajero]

Depending on which web site you read, diesel fuel gives 11-15% more heat per gallon than gasoline when burned.  Plus most gasoline has about 10% ethanol which knocks off another 3% heat content.  So, diesel engines are burning (roughly) 14-18% more energy-rich fuel to start with.  Then they're a bit more efficient at converting heat to mechanical energy as well.

 

Of course diesels and hybrids are both more expensive than plain old gas cars, so a diesel hybrid would be even more pricey.  I think that Volvo's around $60,000 U.S.

[PWBarrett]

I've always wondered what the MPG of the ICE would be like if charging the HV battery could be removed from the equation.

(If that's what the elusive "sweet spot" is all about, it sounds quite significant.)

It seems a bit counterproductive to be charging while accelerating, but you can often see it doing that as indicated by the up-arrow.

I'd like to have a selectable mode that would only charge by regen and by what's generally considered engine braking.

 

(Okay, you'd also have to maintain enough charge to start the engine. Running the A/C would probably have to disable this mode.)

[fotomoto]

I've always wondered what the MPG of the ICE would be like if charging the HV battery could be removed from the equation.

 

A regular 4 cylinder car.  25-30mpg.

[Jmonty]

The Volvo V60 Plug-In Hybrid is the first diesel plug-in hybrid vehicle.

 

http://www.greencarreports.com/news/1083037_volvo-v60-plug-in-diesel-hybrid-quick-drive-of-ny-auto-show-debut

 

"215-horsepower, five-cylinder turbodiesel"

 

"This Volvo is quick, sprinting to 62 mph in as little as 6.1 seconds in 'Power' mode (maximum engine and electric outputs combined), with a top speed of 143 mph. Electric-only top speed is 78 mph."

 

Very interesting!!

[fbov]

Depending on which web site you read, diesel fuel gives 11-15% more heat per gallon than gasoline when burned.  ...

Actually, its not the web site, it's the units. You need to know if it's mass (megajoules/kilogram) or volume (megajoules/liter) being compared.

 

Diesel fuel has greater mass density than gasoline, it's a lower fraction (larger molecule) in a refinery stack. You get more heat per gallon because there's more fuel there. Wiki puts it well.

"As of 2010, the density of petroleum diesel is about 0.832 kg/l (6.943 lb/US gal), about 12% more than ethanol-free petrol (gasoline), which has a density of about 0.745 kg/l (6.217 lb/US gal). About 86.1% of the fuel mass is carbon, and when burned, it offers a net heating value of 43.1 MJ/kg as opposed to 43.2 MJ/kg for gasoline. However, due to the higher density, diesel offers a higher volumetric energy density at 35.86 MJ/L (128,700 BTU/US gal) vs. 32.18 MJ/L (115,500 BTU/US gal) for gasoline, some 11% higher, which should be considered when comparing the fuel efficiency by volume."

 

While we normally do Chemistry in terms of mass of components, we sell fuel by the gallon...

 

HAve fun,

Frank

Edited September 7, 2013 by fbov

[viajero]

Actually, its not the web site, it's the units. You need to know if it's mass (megajoules/kilogram) or volume (megajoules/liter) being compared.

 

I've seen different web sites list different results per gallon.  It may actually be different from place to place and batch to batch for all I know.  Gasoline and diesel are blends of hydrocarbon chains of various lengths.  It wouldn't surprise me if the mix was somewhat different from refinery to refinery.

[MtnMarty]

What an interesting discussion!