Efficiency on longer highway trips...

[Hybrider]

My anecdotal observations are that it is traffic which has the single biggest effect on the fluctuations in my MPGs on my regular highway commute, but then again I don't have an anemometer mounted on my FFH either. :play:

Edited July 22, 2014 by Hybrider

[ptek]

I had been trying to maximize time in EV mode on my commute, and had managed an average of about 46 MPG and a best of about 51 MPG using that technique. Over the past few weeks, I've been trying the high charge, ICE on mode described in this thread. (Is this the same as the ICE-High mode described in other threads?)

 

Most of the time, the instant MPG would max out at about 40 MPG and to push the average higher, I have been doing a mini pulse-and-glide technique. Doing this, I was able to get about the same MPGs as my prior max EV technique.

 

Today, I kept the ICE on instead of doing pulse and glides and was rewarded with the instant MPG climbing into the 50 MPG range, even at 65 to 70 MPH. On my evening commute, I got my new best of 53.3! I've noticed that the engine is much quieter in this mode. With my previous maximize EV technique, when the HVB is depleted and the ICE comes on, the ICE must work hard to both propel the car and to recharge the HVB. The ICE RPM range tended to fall into an area of a lot of resonance, resulting in a loud growl or mmMMMMOOOOOO-ing sound. Now, the ICE has a light load (typically just over 1 bar) and I barely hear it. Also, when I do get to a good EV section of road, the car can enter it with a full charge and go a long way.

 

I'm going to keep using this mode for a while to see if it gets easier to use and if I can learn the light touch needed to keep the ICE on without falling into EV mode. Minnesota's rolling hills makes it hard to keep an even throttle.

[hybridbear]

We just did a highway trip this past weekend to Kansas City & back. We drove into the wind both directions and used AC both ways. We got 38 MPG going south at 65-75 MPH and 40 MPG coming home at the same speeds. Kansas City is at approximately the same elevation as Mpls. I attribute the difference to two things: the south winds were slightly stronger than the north winds & out southbound trip was made with higher ambient temps so the AC had to work harder that day.

 

Each way I drove about 2/3 of the miles trying to keep the ICE on and my wife drove about 1/3 just letting the car do its own thing using cruise control.

[acdii]

This morning I was SO close to a perfect score, then just before I reached my wife's office did a 99% and 94%. For some reason the brake feel changes in my car, where it feels like there is none then push just a touch more and hit service brakes. Anyhow, leaving the house with a full charge I got a 49+. For my driving, staying on ICE does seem to return the best. I have been doing the EV P&G all last week and yesterday and only seeing a 44 MPG tank, so it does matter.

[Texasota]

If I am understanding the "keep the ICE on" technique the ultimate goal is to keep the ICE on the entire time and ideally without it expending any energy to recharge the HVB. And using this technique it is being reported that MPG in the high 40s and low 50s can be consistently achieved.

 

If this is true, then does it logically follow that if Ford produced a gas Fusion that had the 2.0 Atkinson engine (with no hybrid componentry) we would have a mid-size car that would achieve high 40s or low 50s MPG on the highway which exceeds the EPA highway MPG of even the most efficent diesel midsize cars?

[hybridbear]

If I am understanding the "keep the ICE on" technique the ultimate goal is to keep the ICE on the entire time and ideally without it expending any energy to recharge the HVB. And using this technique it is being reported that MPG in the high 40s and low 50s can be consistently achieved.

 

If this is true, then does it logically follow that if Ford produced a gas Fusion that had the 2.0 Atkinson engine (with no hybrid componentry) we would have a mid-size car that would achieve high 40s or low 50s MPG on the highway which exceeds the EPA highway MPG of even the most efficent diesel midsize cars?

Yes, but that car would be lacking in power compared to what most Americans demand. Note that the FFH has more total horsepower (188) than the 2.5L Fusion or the 1.6L Ecoboost Fusion.

 

If you had only the 141 HP Atkinson cycle 2.0L engine it would seem underpowered. It would also need a conventional transmission which may not be as efficient.

 

While our car is in the shop the dealer gave us a 2013 Fusion SE base model as a loaner. I plugged my ScanGauge in to it and I was watching HP & Load numbers while driving. Most of the time while accelerating, etc the HP demanded was about the same as what I see in the hybrid without the generator load, about 30 HP. When accelerating onto the freeway I accelerated slightly more aggresively and the ICE quickly raced up to over 100 HP. Even at that power level the car seemed to take forever to get up to 60 MPH. I don't think our ICE would have gone anywhere near that high. I'll have to monitor data if I drive it any more to see how it compares.

 

At 60 MPH the HP demand was quite similar to what we see as described above. However, the Load numbers were quite different. The FFH reports Load numbers in the high 70s to low 80s at ~25 HP. The 2.5L Fusion reported Load numbers in the 40s. This shows the efficiency of the atkinson cycle at that power demand and in how the ICE is programmed. The FFH ICE is programmed to never really go much higher than 60 HP unless you really push it because it has the electric motor to help it out with providing power. A non-hybrid doesn't have that so its ICE must be able to provide more power.

 

Either way, I hate driving a car with a shifting transmission. And this Fusion has almost 40k miles on it and the shifting is incredibly rough. Each time the transmission shifts the car lurches. I don't know how anyone can drive a car like that...

Edited July 30, 2014 by hybridbear

[corncobs]

Speaking about underpowered.

Ford is planning to sell the European Fusion ( Mondeo ) with their 1.0l Ecoboost engine. The same 125 HP engine they have been selling in the Fiesta since last year in the US and have won engine of the year award 3 years in a row.

 

I still remember when Japanese car makers started making 1.6l with 90 HP and th German auto makers said these engines will never last.

 

How times have changed...

[mwr]

Either way, I hate driving a car with a shifting transmission. And this Fusion has almost 40k miles on it and the shifting is incredibly rough. Each time the transmission shifts the car lurches. I don't know how anyone can drive a car like that...

That must be a very poor 6-speed, either the design or that particular one. The 5-speed in my 2005 Subaru Legacy GT (2.5L, turbo, lots of power) shifts very smoothly.

[acdii]

 

 

If you had only the 141 HP Atkinson cycle 2.0L engine it would seem underpowered. It would also need a conventional transmission which may not be as efficient.

 

 

Either way, I hate driving a car with a shifting transmission. And this Fusion has almost 40k miles on it and the shifting is incredibly rough. Each time the transmission shifts the car lurches. I don't know how anyone can drive a car like that...

 

The FFH ICE would work fine with a CVT, but would be very underpowered. I also think that you are spoiled driving the Hybrids, after so many years driving one I find conventional trannies harsh too.

 

However, mating the Atkinson without the Ecvt would not make a very efficient ride, the fuel used to get up to speed would be far more than a normal ICE since it wont have the Electric assist you get from the Hybrid side. Once up to speed and cruising on level roads with low resistance, you should see good economy, but any grade would put it back into fuel sucking mode. The current ICE and ECVT is a perfect match, it just needs more tweaking in the programming. Hopefully at some point Ford will come out with new programming to lower the EV threshold at highway speeds to force more HVB charge into the pack to match what some of us are seeing doing this technique.

[Texasota]

Yes, but that car would be lacking in power compared to what most Americans demand. Note that the FFH has more total horsepower (188) than the 2.5L Fusion or the 1.6L Ecoboost Fusion.

 

If you had only the 141 HP Atkinson cycle 2.0L engine it would seem underpowered. It would also need a conventional transmission which may not be as efficient.

 

While our car is in the shop the dealer gave us a 2013 Fusion SE base model as a loaner. I plugged my ScanGauge in to it and I was watching HP & Load numbers while driving. Most of the time while accelerating, etc the HP demanded was about the same as what I see in the hybrid without the generator load, about 30 HP. When accelerating onto the freeway I accelerated slightly more aggresively and the ICE quickly raced up to over 100 HP. Even at that power level the car seemed to take forever to get up to 60 MPH. I don't think our ICE would have gone anywhere near that high. I'll have to monitor data if I drive it any more to see how it compares.

 

At 60 MPH the HP demand was quite similar to what we see as described above. However, the Load numbers were quite different. The FFH reports Load numbers in the high 70s to low 80s at ~25 HP. The 2.5L Fusion reported Load numbers in the 40s. This shows the efficiency of the atkinson cycle at that power demand and in how the ICE is programmed. The FFH ICE is programmed to never really go much higher than 60 HP unless you really push it because it has the electric motor to help it out with providing power. A non-hybrid doesn't have that so its ICE must be able to provide more power.

 

Either way, I hate driving a car with a shifting transmission. And this Fusion has almost 40k miles on it and the shifting is incredibly rough. Each time the transmission shifts the car lurches. I don't know how anyone can drive a car like that...

HB, thanks for the interesting response. I was partially motivated to pose those questions because of this article that I read recently which discusses Atkinson cycle engines that are coming in the near future for non-hybrid cars:

 

http://wot.motortrend.com/1404_toyotas_future_engines_employ_atkinson_cycle_for_max_efficiency.html

[hybridbear]

That must be a very poor 6-speed, either the design or that particular one. The 5-speed in my 2005 Subaru Legacy GT (2.5L, turbo, lots of power) shifts very smoothly.

I think it's just been abused because it's a rental and at almost 40k miles the fluid is likely very dirty & in need of replacement.

[jonessoda]

I don't know how I feel about "tricking" the car into staying on the ICE while on the freeway. It seems like that would be a poor engineering choice on Ford's part to make the car less efficient at highway speeds.

 

The last >100 mile drive I did was last year, and included going over the Grapevine (http://en.wikipedia.org/wiki/Grapevine,_California), and I still managed this:

 

 

 

 

[Brandon Satterwhite]

 

Power Efficiency

 

10 28%

 

15 32%

 

20 35%

 

25 36%

 

30 35%

 

35 35%

 

40 35%

 

45 34%

 

 

This is interesting data that Larry posted on ICE efficiencies, but can someone make it more useful for me... Are the bars on the Empower screen 10 kW each?

 

i.e. can I expect to get basically max efficiency from the ICE if I'm at 2 bars? I think that's the result I'm picking up from all my reading here... if the EV goes above 1 bar, nudge the gas pedal until the ICE kicks on and you go up to 2 bars. Accelerate/charge HVB at 2 bars until (HVB approaching full and you're say a few MPH over the speed limit), and then glide back down in speed and go EV as far as you can.

 

Note that this is the plan I'm formulating in my head for 40 to 45 mph, which is my commute. I understand the ICE-only argument for the 65 to 70 mph crowd. At that speed, you probably don't accelerate with ICE at 2 bars, so you'd never hit the EV glide phase I'm describing, I'm guessing.

[Brandon Satterwhite]

Never mind about the kW question. After I went out to the car to look at the Empower screen, I see that it looks like 1 bar = 1 kW.

 

This is great data to have. So it sounds like the general guidance would be that when possible you want to drive the ICE at > 1.5 bars on the Engage screen and (based on what I've read elsewhere) you want to use EV at <1 bar. I can definitely work with that!

[MeeLee]

On 7/18/2014 at 3:37 AM, larryh said:

Based on my observations, when the ICE is providing between 20 to 35 kW of power, efficiency is around 35%. Of the 33.705 kWh of energy released from the combustion of a gallon of gas, 35% of this energy is converted to mechanical energy used to power the car and charge the HVB. When the power provided by the ICE is less than 20 kW, efficiency starts to fall. For example, when providing 10 kW of power, the efficiency might drop to 25%. (It requires about 20 kW of power to go 65 mph and about 10 kW of power to go 50 mph.)

 

The efficiency the motor/generator in generating electricity is probably around 90%, i.e. 90% of the mechanical energy provided to the motor/generator is converted to electrical energy. The efficiency of the motor/generator in providing mechanical power is about 80%, i.e. 80% of the electrical energy provided to the motor/generator is converted to mechanical energy. This means about 90%*80% = 72% of the mechanical power provided by the ICE to charge the HVB is actually recovered in EV mode.

 

There is little advantage in having the ICE charge the HVB when it is providing 20 kW of power (around 65 mph) or more to propel the car. You are only going to recover 72% of the energy produced by the ICE when in EV mode. So 35% of the energy released from the combustion of gas is converted to mechanical power to power the motor/generator, and then 72% of the resulting electrical energy is converted back to mechanical power to propel the car later in EV mode. The overall utilization efficiency of this portion of the gas that was used to charge the HVB and later power the car later in EV mode is then 35%*72% = 25%. If you now run the car in EV mode at 65 mph using the energy from this gas, you are now effectively only getting 25% efficiency from the combustion of that gas and have lowered the overall mileage (mpg) of the car. If you had not used the gas to charge the HVB, and instead used it to propel the car, you would be getting 35% efficiency. Charging the HVB and running later in EV mode reduces mileage (mpg) at 65 mph.

 

However, if you could utilize the energy stored in the HVB at a later time when the power required drops below 10 kW and efficiency of the ICE drops below 25%, then it is advantageous to charge the HVB at 65 mph. With the gas used to charge the HVB, you are effectively getting 25% efficiency. If you had instead used the gas to power the ICE and propel the car (without charging the HVB), you would have gotten less than 25% efficiency since ICE efficiency has dropped below 25% at 10 kW of power. This can happen during downgrades on the freeway. So you might want to charge the HVB while driving 65+ mph so you can power the car later in EV mode while driving on a downgrade. (There are additional considerations, such as having the HVB assist the ICE to reduce the load and drive it into a more efficient operating region.)

 

Better yet, is to charge the HVB when the power required to propel the car is less than 20 kW. The additional power required to charge the HVB increases the overall ICE efficiency from maybe 25% to 35%--the ICE is providing 20 kW of power rather than 10 kW of power. So now you are getting 35% efficiency from the gas that is used to propel the car (rather than 25%). In addition, you are going to get at least 25% efficiency from the portion of the gas that was used to charge the HVB. So charging the HVB and running later in EV mode increases mileage (mpg) at slower speeds (around 50 mph or less).

 

The goal is to achieve maximum efficiency for all gas consumed. Don't run in EV mode when high power is required (high speeds or up hill), and don't charge the HVB. Don't run the ICE when low power is required (at low speeds or down hill), unless you can also charge the HVB to increase the load on the ICE and can run later in EV mode at low speeds.

 

There are additional considerations when deciding to charge the HVB. The HVB of the Fusion Energi is composed of 84 cells (less for the Fusion Hybrid). The cells need to all be kept balanced, i.e. maintained at the same SOC and voltage. Using power from the HVB tends to disrupt this balance--the greater the power drawn from the HVB and the lower the SOC, the greater the disruption. Charging the HVB restores the balance. The weaker cells experience greater stress than the stronger cells. If the cells are not rebalanced, the weaker cells will continue to experience more stress until they fail. See the following and subsequent posts:

 

"http://www.fordfusionenergiforum.com/topic/1683-obd-ii-data-for-hvb/?p=14915"

 

A lot of what you mention is very interesting, and I have to agree with a lot you write.

 

The later models (on my FFH 2019), the electric motor is tuned to work at higher speeds. 
So long the electric motor output doesn't exceed 20kW, you can drive on it even at 75 or 80MPH (lowering speed as 75-80MPH really need 25-30kW to sustain the speed, with a strong back wind, or downhill for instance).

On the other hand, the ICE engine, only stays on at speeds of above 65MPH. Below 65 MPH it's nearly impossible to keep the ICE running (in eco mode).

It'll run fine for a while, but as soon as the battery reaches a certain charge, it'll disengage the ICE and run on electric, switching between electric and ice.
The only solution to it, is to release the throttle, and slow down by about 5MPH, then engage the ICE to do a lengthy but very slow acceleration, slowly accelerating from 55-60MPH; during which phase the ICE won't turn off.
It's entirely possible to stretch this acceleration to a good 2 to 3 full minutes.

But keeping the ICE on in this acceleration stage, or even keeping it at 65 without engaging the electric motor, requires a VERY steady foot, because the smallest pothole might cause my throttle to move even a millimeter, and the ICE cuts off.

The engine does this, because MPG increases actually by switching between the two. 
Despite the mention of the charging being less efficient, you don't have any internal ICE friction when it's RPM is zero.
While the car runs more efficiently switching between ICE and electric (~50MPG @ 60MPH this way, vs 42MPG on ICE only, unless you hit that super efficient 52MPG at 25kW output doing ~1300-1500RPM), it does wear out the Lithium pack and ICE engine (and engine oil) much quicker. The start-stop isn't recommended on the highway. And the battery pack heats up exceedingly.
If I see the electric motor go on at 60MPH, I try to switch over quickly. 

 

Personally, I try to keep 65-80MPH on highways as standard speed (which is on the higher end of the vehicles on the highway here), but chances of the ICE to turn off is lower.
Besides on my 2019 model, doing 65 or doing 75 MPH gets me identical MPG ratings.

 

I also run my car in ECO mode, because RPMs seem to dip ~200-400 RPM lower than in normal mode, and fuel economy seems to go up on the highway.

I am a bit concerned at the charge levels with the ICE running at 2k RPM or higher (2nd line on the kW meter, which I believe is close to 44kW, since there are 5 lines, and the maximum ICE output is ~110kW; or 145HP);

Concerned, because the charge is quite high in ECO mode; and a high charge will result in quicker degradation of the cells.
Especially since the battery pack is a Lithium pack, which can suffer from dendrites forming quicker when heated (or higher currents flowing).

Since the pack is using Lithium Ion cells, it should be a lot smaller than the metal hydride packs used in the 2010 models, and thus has place for more cells to be installed, and given an increased range.
When I look behind the panel, I do see A LOT of space still that could be used for an upgraded model battery.
I wished some company could increase the capacity from 1.4kW to 1.7 or 2kW. Advances in battery technology should be able to make this possible.

In eco mode, I try to keep the RPM below 2k for accelerating, and between 1.5 to 1.8k RPM for cruising, to reduce the charge current on the batteries.
On the kW meter, that's roughly 25kW to 40kW the ICE produces.

Additionally, I prefer to use normal mode for accelerating (despite the throttle being a bit brisk/abrupt), and switch over to eco mode while cruising at RPM ranges below 2k RPM, which I think will allow the battery to last longer; as well as keep eco mode for highways. Since the battery will be nearly fully charged on any higher than 5 minute highway ride anyway, charge currents will be much lower.
 

Edited August 22, 2021 by MeeLee