Does EV+ Actually Help?

[fbov]

You're dancing around your assumption that we all have plug-in's, and ignoring the consequences of that assumption.

 

There's still no way to charge my HVB without using fuel. Your mileage may vary, but your statements are false. 

 

Frank

[stevedebi]

You're dancing around your assumption that we all have plug-in's, and ignoring the consequences of that assumption.

 

There's still no way to charge my HVB without using fuel. Your mileage may vary, but your statements are false. 

 

Frank

Frank,

Sorry, it did get a bit side tracked. The conventional C-Max makes it a moot point. I have read that the hybrids are more efficient when running the ICE, based on posts by larry.  I got the discussion a bit off by using the Energi to demonstrate that Ford doesn't utilize the greater capacity, indicating they agree that it isn't profitable to charge the HVB via the ICE.  Really, the hybrid is built around the Atkinson cycle concept, which has 5-7% better MPG at higher RPM, but has poor low RPM performance. Hence, the battery power to provide take off acceleration. I think Ford basically thinks of it as an ICE vehicle at speed, although they do make use of the battery when possible, to reduce engine load and to provide extra boost.

[fbov]

The thing I like most about forums is that I learn things from other posters, and from researching my replies. One of them was that "moot" didn't mean what I thought, in fact, it's quite the opposite - debatable, contentious, disputable - which is not what I think you meant, either.

 

In that vein, you may want to look deeper into Atkinson-cycle engines. It's actually a dual concept of asymetic intake and exhaust volumes (or compression and power strokes), in an engine that achieves all four strokes in a single crankshaft revolution. Atkinson was apparently trying to get around Otto's patents.

 

Only the first aspect is used here, and If anything, intake/exhaust volume assymetry improves low RPM torque over a conventional Otto-cycle engine, at the expense of high RPM performance. Torque comes from expansion during the power cycle. By allowing the expansion to continue past the original intake volume, the engine produces more torque for a given intake volume, thus better volumetric efficiency. The many BSFC charts in the link in post 13 bear this out; all show lots of output below 2000 RPM. For me, data trumps opinion....

 

As we agree there is no free lunch, there is a price to pay (two actually), and the first is in the engine's ability to accelerate, to increase engine operating speed. This is the only sense in which an Atkinson is "low torque." In conventional engines, cylinder pressure when the exhaust valve opens is much higher than when the intake valve closed. The piston approaches bottom-dead-center with greater pressure behind it, a force which is carried over to the intake stroke, and requries intake throttling to control RPM. The Atkinson is disadvantaged in this respect by the reduction in piston acceleration approaching bottom-dead-center, due to the energy extracted by the longer power stroke.

 

The second price you pay is power-to-weight ratio. The C-Max has a 2.0L engine mass, but the output of a 1.8L engine. Power density, HP/lb, is lower, so vehicle weight is higher than it might be. That's again a reasonable tradeoff, as regnerative braking negates much of the inefficiency of increased vehicle weight.

 

Ford's initial prohibition of EV above 63MPH certainly supports your last point, but I don't see Atkinson having any advantage at high RPM, and the strong negative correlation between average speed and mileage bears this out. Conventional cars (especially diesels) do better at speed due to gearing that increases engine load and reduces operating RPM, allowing them to run at wider throttle settings. At low speed, they waste energy accelerating mass, only to dump that energy into the brakes as heat.

 

You have made me curious about the Energi's regen behaviour on long, downhill runs. Hybrids quickly run out of room in the battery. I would expect an Energi to keep charging, given 5x the capacity. You ever get into the mountains?

 

HAve fun,

Frank

[stevedebi]

The thing I like most about forums is that I learn things from other posters, and from researching my replies. One of them was that "moot" didn't mean what I thought, in fact, it's quite the opposite - debatable, contentious, disputable - which is not what I think you meant, either.

 

In that vein, you may want to look deeper into Atkinson-cycle engines. It's actually a dual concept of asymetic intake and exhaust volumes (or compression and power strokes), in an engine that achieves all four strokes in a single crankshaft revolution. Atkinson was apparently trying to get around Otto's patents.

 

...

 

You have made me curious about the Energi's regen behaviour on long, downhill runs. Hybrids quickly run out of room in the battery. I would expect an Energi to keep charging, given 5x the capacity. You ever get into the mountains?

 

HAve fun,

Frank

Frank,

You are correct on "moot", but I've normally seen it used the way I did (incorrectly it appears)!

 

This is from the link you posted: "but substantially reduced torque makes it largely unsuitable in a conventional drive train". I'm pretty much standing by the concepts in my post - and they were not based on opinion, take a look:

 

http://auto.howstuffworks.com/atkinson-cycle-engine1.htm

 

I have studied the engines and powertrains, but I don't generally get technical on these posts unless it comes up. What I was saying is that the hybrid works well because the electric motors supply the get up and go at lower speeds, whereas the ICE supplies the more efficient power at higher speeds. The lack of low speed capability is why the Atkinson cycle is not used on normal cars. Once up to speed it can work well.

 

As to mountains, I recently ran into this exact scenario. I had put 24 miles of electric on my energi, at which point the car went into conventional mode. I went over a long hill, and watched the "normal" battery charge level go up and up as I went downhill. When it hit the top of the battery icon and still showed charge indicator, I let it run for a couple of minutes, and then switched back to EV Later and found that it had about 2% available capacity - the display showed 1 mile on the battery. Subsequently I was able to get that up to around 10% using the off ramp slow down and a couple of stoplights (not sure I didn't cost some gas on those lights), enough to get it to 8 miles on the return trip - so I was able to use EV to the highway, go EV Later up the hill, then add sufficient charge down the hill to again get it to 4 miles EV on the battery, which is enough to get me into EV+ range to get from the freeway to my house. Overall, it resulted in an MPG in the 50s going both ways over that big hill here in LA, wheas it would have been in the late 40's at best in all EV Later mode.

 

(EDITED: I believe it was actually late 50's MPG, not 70's).

Edited December 11, 2014 by stevedebi

[plus 3 golfer]

...Hybrids quickly run out of room in the battery. I would expect an Energi to keep charging, given 5x the capacity. You ever get into the mountains?

 

HAve fun,

Frank

Yes, the Energi keeps charging as verified by a member here. 

 

BTW, you guys are looking at the "wrong" dictionary.  Try the Urban Dictionary.   It's on the internet and has the most votes so it must be correct. :)

moot

 

useless, nothng, pointless

this is so....moot

Edited December 11, 2014 by Plus 3 Golfer

[Kelleytoons]

I think the definition of "moot" as being "contentious, debatable" in essence means it's kind of pointless and useless to keep talking about it.  IOW, trying to debate something that is "moot" isn't going to get you anywhere, as you will never get resolution.

 

So this portion of the discussion, at least, is moot. <bg>.

[stevedebi]

I think the definition of "moot" as being "contentious, debatable" in essence means it's kind of pointless and useless to keep talking about it.  IOW, trying to debate something that is "moot" isn't going to get you anywhere, as you will never get resolution.

 

So this portion of the discussion, at least, is moot. <bg>.

Good one!

[fbov]

...This is from the link you posted: "but substantially reduced torque makes it largely unsuitable in a conventional drive train". I'm pretty much standing by the concepts in my post - and they were not based on opinion, take a look:

 

http://auto.howstuffworks.com/atkinson-cycle-engine1.htm...

One must be careful when researching things on the internet. Unsubstantiated opinions get repeated until they're accepted, regardless their basis, applicability or veracity. (That's one reason I hate poliltics.)

 

I linked that site for it's animations, not it's (faulty) explanation. Your link is a great example; at least the author provides references. She also used the animation site, so I'll use her other reference to make a point about the quality of unsubstantiated opinions:

"In terms of power the Atkinson engine lag behinds the Otto cycle engine due to the amount of air it takes in; the Atkinson engine does not take in as much air as an Otto cycle engine resulting in greatly reduced power."

 

All true, until we get to a misleading use of the word "greatly" without qualification. Let's see  how "greatly" reduced an Atkinson's power output really is...

 

From 2014 Ford Focus Specifications:

Engine type 2.0L Ti-VCT GDI I-4

Horsepower (SAE net@rpm) 160 @ 6500

Torque (lb. ft. @ rpm) 146 @ 4450

Compression ratio 12.0:1

Bore x stroke (in.) 3.44 x 3.27

 

From 2015 C-Max Specifications:

Engine type 2.0L Atkinson-Cycle I-4 Hybrid Engine

Horsepower (SAE net@rpm) 141 @ 6000 rpm 

Torque (lb.-ft.@rpm) 129 @ 4000 rpm 

Compression ratio 12.3:1

Bore x stroke (in.) 3.44 x 3.27

 

I don't have a reference for the Atkinson displacement ratio of 90% (1.8L intake, 2.0L exhaust displacements)

90% of 160 HP in the Focus = 144, compared with 141 in the C-Max Atkinson

90% of 146 lb-ft in the focus = 131, compared with 129 in the C-Max Atkinson

90% of 12.3 compression ratio in the C-Max  = 11.1, compared with 12.0 in the Focus

 

(The only thing that doesn't scale closely is compression ratio, and that's not a fair comparison. This 2L has GDI, gasoline direct injection,not conventional port injection. One might expect direct injection enables higher compression ratio.)

 

I conclude that an Atkinson engine gets the same torque and power output as it's conventional brethran, when scaled for intake displacment, and at lower RPM. Output is not "greatly" reduced, it's reduced in proportion to the intake displacment reduction. If one thinks these output levels are low, keep in mind that the Porsche 944's 2.5L made 143HP@5500 RPM.

 

The true disadvantages are that an Atkinson is larger than a conventional engine of the same intake displacment, and has poor drivability in a conventional drivetrain. Power density, HP/lb. is lower than it would be in a conventional engine, and it won't rev as fast, so it's not well suited for use in conventional drivetrains.

 

Stating this Atkinson engine is somehow low on power or torque is just plain wrong, and I trust you now see why.

 

Have fun,

Frank

[stevedebi]

...

From 2014 Ford Focus Specifications:

Engine type 2.0L Ti-VCT GDI I-4

Horsepower (SAE net@rpm) 160 @ 6500

Torque (lb. ft. @ rpm) 146 @ 4450

Compression ratio 12.0:1

Bore x stroke (in.) 3.44 x 3.27

 

From 2015 C-Max Specifications:

Engine type 2.0L Atkinson-Cycle I-4 Hybrid Engine

Horsepower (SAE net@rpm) 141 @ 6000 rpm 

Torque (lb.-ft.@rpm) 129 @ 4000 rpm 

Compression ratio 12.3:1

Bore x stroke (in.) 3.44 x 3.27

 

...

 

Stating this Atkinson engine is somehow low on power or torque is just plain wrong, and I trust you now see why.

 

Have fun,

Frank

Frank,

I think you just proved my point. For the same engine displacement, the Atkinson cycle has less power. It does have better fuel economy at speed. This is the entire point of coupling it with an electric drive system for lower speeds and additional punch when needed. Otherwise they would have simply used a conventional cycle engine in the hybrids.

 

EDIT: Thanks for the information, though, it is appreciated!

Edited December 12, 2014 by stevedebi

[fbov]

If I proved you point, it's only because you missed mine... for the same engine intake displacement, the Atkinson cycle has comparable power.

 

For something I would call a signficant difference, compare the Focus' normally-aspirated specs with those for the Ecoboost turbo... 57% and 85% increases are a great improvement, especially given a 15% hit in EPA mileage!

 

Have fun,

Frank

[stevedebi]

If I proved you point, it's only because you missed mine... for the same engine intake displacement, the Atkinson cycle has comparable power.

 

For something I would call a signficant difference, compare the Focus' normally-aspirated specs with those for the Ecoboost turbo... 57% and 85% increases are a great improvement, especially given a 15% hit in EPA mileage!

 

Have fun,

Frank

Frank,

The figures you posted:

From 2014 Ford Focus Specifications:

Engine type 2.0L Ti-VCT GDI I-4

Horsepower (SAE net@rpm) 160 @ 6500

Torque (lb. ft. @ rpm) 146 @ 4450

 

From 2015 C-Max Specifications:

Engine type 2.0L Atkinson-Cycle I-4 Hybrid Engine

Horsepower (SAE net@rpm) 141 @ 6000 rpm 

Torque (lb.-ft.@rpm) 129 @ 4000 rpm

 

I'm not sure of your point, because the Atkinson engine puts out less Horsepower and less Torque. how is that "comparable power"?

[fbov]

Because...

I don't have a reference for the Atkinson displacement ratio of 90% (1.8L intake, 2.0L exhaust displacements)

90% of 160 HP in the Focus = 144, compared with 141 in the C-Max Atkinson

90% of 146 lb-ft in the focus = 131, compared with 129 in the C-Max Atkinson

 

And...

for the same engine intake displacement, the Atkinson cycle has comparable power (emphasis added)

 

Your posts display what's known as confirmation bias... when someone disagrees with you, you misrepresent the dissenting argument, so you remain apparently correct.

 

It's very common on the internet, as I said, but a fatal flaw in engineering and the natural sciences. Take GM's ignition switch problems, or Takata's position on air bag ignitors as current examples.

 

Have fun,

Frank

[stevedebi]

Because...

 

And...

 

Your posts display what's known as confirmation bias... when someone disagrees with you, you misrepresent the dissenting argument, so you remain apparently correct.

 

It's very common on the internet, as I said, but a fatal flaw in engineering and the natural sciences. Take GM's ignition switch problems, or Takata's position on air bag ignitors as current examples.

 

Have fun,

Frank

I'm not interested in being correct, I'm interested in the correct information. Rather large difference...

 

Sorry, I still don't see it. For the same engine size, the Atkinson has less power. The engine size largely determines MPG (along with how hard it is driven and etc - there is a ton of factors).

 

If there is no difference, why don't the manufacturers use Atkinson cycle on all engines?

Edited December 19, 2014 by stevedebi

[Adrian_L]

Wow.  I always thought "moot" meant "besides the point".    As in "Until we have kids, where we put the crib is a moot point."

 

I have always admired Ford engineers, who described the Prius's "power modes" as gimmicky.  That's why you don't see them on the C-max.  But inexplicably we have EV+ that comes on 4 blocks from my house and probably saves me a quarter a year in gas.  Like I said, it is so innocuous that I can't be bothered to turn it off, like that leaf on my porch I should sweep away.

 

Thanks for the lively debate.