C-max EV mode

[fordfan82]

My questions are how does EV mode work on the Hybrid? How long do you stay in that mode? Share your tips for staying in EV.

[ptjones]

My questions are how does EV mode work on the Hybrid? How long do you stay in that mode? Share your tips for staying in EV.

Read the wealth of info in "Hybrid driving tip and tricks"  forum :) 

 

Paul

[plus 3 golfer]

I have not seen a Ford write up on the algorithm for EV operation. You do know that you can watch the Empower Screen and observe the engine on/off load threshold. Keep the kW load under the on threshold and you stay in EV mode.

 

From my observations, the threshold changes as you drive. It appears the primary driver of the threshold (in normal operation) is the State of Charge (SOC) of the Hybrid High Voltage Battery. Typically when recording data and normal driving, the SOC runs between about 40% and 56% (not the same as the battery symbol). So, when the SOC increases, the engine on load threshold increases and EV operation will kick in when the engine on threshold excees the kW load, EV operation should kick in. As the HVB SOC diminishes from running in EV, the engine on threshold drops. When the kW load goes above the engine on threshold, the engine will come on.

 

So, by adjusting the kW load generally by slowing down, one can stay in EV longer as the engine on threshold drops. By watching the Empower Screen, knowing your route, and better controlling the SOC to match your route, you may be able to better optimize fuel economy. For example, it may be better to accelerate slightly up-hill maybe keeping the kW load at a certain level on the Empower Screen to get the SOC near maximum and use the full battery SOC in EV mode on the downhill portion of the hill. I think the issue though is that what works for one may not work the same for someone else, as driving conditions are likely not the same.

 

I very seldom try to intentionally stay in EV mode as it generally requires changes in speed and subsequently more driving time than simply using ECO cruise mode which supposedly moderates the response of the car to changes in load requirements such that one's cruise speed may fall slightly when going uphill and increase slightly going down hill which should have the effect of reducing mode changes.

Edited July 20, 2014 by Plus 3 Golfer

[Adrian_L]

Agreed. Don't "try" to keep yourself in the blue, especially when accelerating from a stop. You'll get better mpgs by letting the car do its own thing. Eco cruise helps a lot.

[fordfan82]

So if you accelerate gradually from when you're stopped at a light to stay in ev mode won't someone behind you get ticked off since it won't move like a non hybrid car?

[plus 3 golfer]

Generally, you will always use EV up to about 15 mph.  Then, It depends on your SOC as to where the engine on box is per the Empower Display and how hard you want to accelerate (kW load required to be met).  In general, if you have room to charge the HVB, you'll want ICE to operate when accelerating.  Accelerating moderately is generally adequate as to not pi$$ off the drivers behind you.and ICE to run near its efficient operating range or minimum Brake Specific Fuel Consumption (grams of fuel / joule of energy).  

 

I would think the PCM algorithm would always try to operate ICE in its efficient range of the BSFC.   If the power requirement is too high for best ICE efficiency, the PCM should hold off requiring very much additional power to charge the HVB (probably somewhat dependent on where the SOC is at  also).  If the power requirement is too low for best ICE efficiency, the PCM should increase load on engine, increase engine speed, and operate MG1 to charge the HVB providing their is room in the HVB.  This is seamless to the driver.  But, one might be able to optimize this process by anticipating conditions and adjusting load requirements by the throttle for the anticipated conditions.  The PCM does not know what's ahead (yet)!

 

Try the tips that Paul linked to and adjust such to your liking and improvements you see in FE.  As I've said before, generally one has to trade time for better fuel economy: Slow down, coast more, accelerate moderately, brake less, anticipate hills and stops, and use pulse and glide.  Many of these techniques add time to a trip and hence a lower average speed but improve fuel economy.

Edited July 20, 2014 by Plus 3 Golfer

[ptjones]

The easy way to do it is to accelerate EV to 15-20mph then ICE at 2 bars in Empower  Display Mode till you get to desired speed. This shouldn't pi$$ off drivers behind, but some people don't like Hybrid's or are in a big hurry so you can't please everyone.I'm happy to know I'm spending less at the fuel pump. :)

 

Paul

[kostby]

IF you have the patience for it, and time to, uh, invest (*or waste) in achieving higher mpg's...

 

In heavy traffic, at traffic lights, construction zones, and toll booths, follow behind a big diesel rig pulling a trailer.

 

I guarantee that no one behind you will even notice you are driving a hybrid and accelerating gently.

 

You'll stay in EV mode as long as possible, until the HVB (High Voltage Battery) is discharged far enough that the ICE (Internal Combustion Engine) comes on to re-charge, AND you won't make anyone mad at you for accelerating slowly.

 

*waste, because time is truly the only non-renewable resource for human beings.

Edited July 22, 2014 by kostby

[ScubaDadMiami]

I made a post with a link to a video clip about this subject. Check around for it.

[fbov]

Two things I'm doing differently: get rolling in EV, and stay below the discharge threashold. The first is obvious, the second perhaps not so obvious.

 

Depending how hard you accelerate, and battery state-of-charge, the car may charge or discharge the battery. ICE + motor is how Ford gives us 8-sec 0-60 times. The secret to the 2-bar acceleration limit is that you continue to charge the battery while speeding up. But 2-bar burns are close to the discharge threashold, when the drivertrain starts draiing the batter rather than the gas tank.

 

This Spring I started experimenting with the tradeoff between engine RPM and "burn" duration. A 2-bar burn from a stop would get me up to speed by a certain point while charging the battery. Switching to a 1.5-bar burn rate, it took longer (and farther) to reach the same speed, but, since the engine runs at lower RPM, the fuel usage rate is slower and the battery has more time to charge. I am getting longer glides for the same fuel investment.

 

This is the idea behind SDM's video, but without the burst of full 2-bar burn, which can be very useful in traffic. I find that the lead-foots behind me fall away because I continue accelerating after they level off. Of course, they catch up on the glide, but by then, it's time for another burn. Add in a slight downslope, and it's amazing how far you can go without using fuel. I hit 60MPG again this morning, with a roughly 30 mph average speed (15.3 miles in 30 minutes) partly due to luck (hitting green lights). It's typically more like 58mpg, maybe 56 on a bad day now that the weather's nice. Don't ask about Winter

 

HAVe fun,

Frank

[shinytop]

I made a 1 mile trip to the drug store yesterday.  Going, while the car warmed up, I got 29 MPG.  Return trip, almost all EV was 119 MPG. 

 

Today I made a 10 mile trip to the Dr.  Got 50 MPG using city streets going with AC off.  On way back I went interstate and AC on and also got 50 MPG.  I love this car.  

[Jus-A-CMax]

Time the lights and find "quiet" streetsand less traffic lights would YIELD better MPGs than a 1, 1.5 or 2 bar burn. But what do I know...

 

 

;)

Edited July 22, 2014 by Jus-A-CMax

[C-MaxSea]

My questions are how does EV mode work on the Hybrid? How long do you stay in that mode? Share your tips for staying in EV.

 

We swear by the 'blue' (EVe) & cheat !

(Purge the blue 'forever with a feather', & treat the ICE well ..... like ice, handle it with speed and minimally !)

(Oh, and avoid the 'double burn' (Ice & battery combined for acceleration (white ICE mode with the battery chevron down)) like the plague  :redcard:  - unless showing off your 0-60 time :) .  In other words, keep the chevron up (charging) when accelerating with the ICE) 

We :love_shower: :love_shower: :love_shower: our C-Max

 

http://fordcmaxhybridforum.com/topic/2962-the-force-is-with-you/

Edited July 23, 2014 by C-MaxSea

[fordfan82]

 

Do you happen to know where this Clip is? if you could post the link to it much would be appreciated.

 

 

 

Edited July 23, 2014 by fordfan82

[ScubaDadMiami]

 

 

Do you happen to know where this Clip is? if you could post the link to it much would be appreciated.

 

 

 

 

I would suggest reading this entire thread. It is well worth it. http://fordcmaxhybridforum.com/topic/3342-best-engine-rpm-for-minimal-fe-loss/page-5?  Here is the link to the video clip, which is fully discussed in the thread.

[fordfan82]

I noticed yesterday while driving, the arrow was pointing up above the battery but it displayed EV mode? How long can you be in EV mode? Until the battery drains to a certain point?

[Adrian_L]

You could be in the EV mode for a long time, if the car is going downhill.  You get out of EV mode if A) you accelerate to the point where the computer determines running on the gas engine is better or b)the high voltage battery dips to the point where recharging is needed--again the gas engine kicks in.  Basically you'll be going back and forth between gas and EV with EV being about 65% of the journey (in my experience).

 

Didn't the dealership go over this stuff with you? 

Edited July 30, 2014 by Adrian_L

[nsteblay]

There are four fundamental propulsion modes for the C-Max.  These modes differentiate how the Electric Traction Motor, Generator Motor, Internal Combustion Engine, and Planetary Gear System work together to power the car.  

 

 

Series Mode

• Used only when vehicle is not moving and the engine is running
• Engine may be running for battery charging, cabin or battery temperature control, or catalyst warm-up.

Positive Split Mode (ICE Mode)

• Engine is ON and driving the generator motor to produce electricity
• Power from the engine is split between the direct path to the road and the path through the generator motor
• Generator power can flow to the battery or to the traction motor
• The traction motor can operate as a motor or a generator to make up the difference between the engine power and the desired power
• This is the preferred mode whenever the battery needs to be charged or when at moderate loads and low vehicle speeds

Negative Split Mode

• The engine is on and the generator motor consumes electrical energy to reduce engine speed
• The traction motor can operate as a motor or a generator to make up the difference between the engine power and the desired power
• Typical highway mode
• Occurs when the engine needs to be on, the system can not be operated in parallel mode and the battery is charged near its upper limit

Electric Mode (EV Mode)

• The vehicle is propelled by stored electrical energy only
• The engine is turned off
• The tractive torque supplied from the traction motor
• Preferred mode whenever the desired power is low enough such that it can be produced more efficiently by electrical system than engine
• Preferred mode in reverse because the engine can not deliver reverse torque
• Separate electric pump maintains power assisted steering

The two modes that provide best MPG are Negative Split Mode and Electric Mode (EV on the dash).

 

What I've discovered is if you want to get really good mileage you need to spend as much time in EV mode as possible.  Personally I don't like being the one holding up traffic so I pretty much keep up with the general flow.  I've learned to optimize time in EV mode by employing what's called a Punch and Glide technique.  Using this technique I accelerate using the ICE, pull off the gas pedal a bit to get in EV mode, push again on the gas pedal and coast in EV mode as long as possible before repeating.  I pay attention to the Empower gauge when driving in EV to maintain speed as much as possible without going over the ICE threshold - this requires pulling off the gas pedal slightly and steadily until ICE needs to kick in again to maintain speed.  I don't like oscillating my speed more the a couple of MPH as its very irritating to anyone behind me.  In my most recent morning commute the traffic was 70 MPH for much of the trip.  I oscillated my speed between 68 and 72 MPH switching back and forth between ICE and EV modes.  I've averaged over 50 MPG these past 800 miles.  In my 21 mile commute yesterday I got 50 MPG.

 

I think the two biggest reasons the CMax hasn't achieved its original MPG ratings is driving technique and environment temperature.  In cold weather the ICE needs to run to keep the car warm.  When the ICE runs, gas is burned and MPG goes down.  If a P&G technique is not employed it is difficult to get really good MPG - you can get low 40's in good weather - but you'll never get upper 40's to lower 50's like the Prius.  P&G driving technique has become second nature to me now - I don't really think about it much - it just happens.  

 

If you try and run exclusively in Negative Split mode I've found the best you'll get for overall average is around 40 MPG.

 

The Prius is the master of Negative Split mode.  Toyota has engineered their cars to get very high mileage in an automated fashion.  It doesn't require much technique but there are tradeoffs.  The tradeoffs are power on demand, styling, ride comfort and noise - big issues for me and my family. 

 

For long freeway trips I use Eco Cruise and leverage Negative Split Mode.  I've take two long trips this summer - 3400 miles and 1300 miles.  For both I averaged just over 41 MPG.

 

[plus 3 golfer]

....

I think the two biggest reasons the CMax hasn't achieved its original MPG ratings is driving technique and environment temperature.  In cold weather the ICE needs to run to keep the car warm.  When the ICE runs, gas is burned and MPG goes down.  If a P&G technique is not employed it is difficult to get really good MPG - you can get low 40's in good weather - but you'll never get upper 40's to lower 50's like the Prius.  P&G driving technique has become second nature to me now - I don't really think about it much - it just happens.  

 

If you try and run exclusively in Negative Split mode I've found the best you'll get for overall average is around 40 MPG.

 

The Prius is the master of Negative Split mode.  Toyota has engineered their cars to get very high mileage in an automated fashion.  It doesn't require much technique but there are tradeoffs.  The tradeoffs are power on demand, styling, ride comfort and noise - big issues for me and my family. 

...

Just a couple of comments.  

 

The two biggest reasons C-Max drivers have a harder time achieving its original 47 mpg rating in the EPA tests are its weight and its coefficient of drag (along with a larger frontal area).  These two factors (along with frontal area) add significantly more load that has to be overcome in a C-Max than a Prius or Prius V.    The C-Max weighs 18.6% and 10.2% more than the Prius and Prius V, respectively and has a 20.0% and 3.4% higher coefficient of drag than the Prius and Prius V, respectively. It's difficult to find accurate (precise) frontal area numbers but it appears that the C-Max may have about a 14.1% and 6.2% larger frontal area than the Prius and Prius V respectively.  My drag models show that if the C-Max had the Prius or Prius V specs for C_d , frontal area, and weight, I would have no problems increasing my 41 mpg to similar FE numbers of a Prius of Prius V and not change my driving style.  Apply hypermiling driving techniques to a C-Max of lower weight and lower C_d and one should be able to achieve greater FE than the original EPA number. 

 

 

All cars take a hit on FE in cold weather and it is factored into the EPA FE calculations. The hit is more noticeable in higher FE cars than lower FE cars.  But, obviously drive more in cold weather than what's factored into the EPA numbers then FE will suffer more.  Drive in Phoenix in the winter and FE is affected very little by cold weather.  Block / oil pan heaters can mitigate this FE hit.  

 

However, hypermiling is not for everyone - eg, driving at speed limit or less, coasting to stops, P&G and so forth. But, not hypermiling and not using block / pan heaters should not be used as a justification as to why drivers have a hard time achieving the original EPA numbers.  Employing hypermiling techniques and using block heaters in any car will significantly increase FE. 

 

On running exclusively in negative split mode, one can get a lot higher FE than around 40 mpg in negative split mode.  It also depends on one's speed (load requirements).  I posted the graph below from recorded data some time ago showing about 47 mpg in eco-cruise at 55 mpg into a strong headwind in negative split mode.  Had I not had a light change on me, I think I could have ran a lot longer in negative split.  And that's the problem with negative split mode, it cannot be maintained for long periods as the road and other changes dictate changes in load requirements and the PCM algorithm will adjust power train operations.  If load requirements are increasing, one can bump the speed down to try to stay in negative split mode but then one give up time for better FE.  Same thing applies with P&G (which works for non-hybrid cars also).  If load requirements are decreasing one can try and bump the speed up to stay in negative split. But usually, the PCM will switch to EV operation (the Empower threshold).

 

I wouldn't quite characterize the Prius as the master of the negative split mode.  It's simply easier for the Prius to stay in such mode as the Prius can only run up to about 47 mph off the HVB.  So, ICE has to run above about 47 mph.  I have not found any basis that the Prius algorithm is any better than the C-Max algorithm in efficient operation.  Again, it's weight and C_d that allows the Prius to get better FE than the C-Max not the algorithm. per se.  But, like you say in comparing ease of getting higher FE in the Prius vs the C-Max -- "It doesn't require much technique but there are tradeoffs.  The tradeoffs are power on demand, styling, ride comfort and noise" - big issues for me and my family" and me too. 

 

I've said before, Ford needs to shave some weight from the C-Max and lower C_d - without sacrificing power, ride, comfort and noise (styling will probably have to change somewhat).

 

Edited July 31, 2014 by Plus 3 Golfer

[ScubaDadMiami]

Great thread, everyone!

[plus 3 golfer]

Here's a graph for demonstration purposes only.  The graph is intended to represent general relationships not precise numbers of the C-Max, Prius, and Prius V.  One can also look at the EPA dyno coefficients and should see similar relationships between the C-Max and Priis (there's another thread where I plotted the C-Max's incorrect 47 mpg coefficients vs the Prius V curve).  I'll have to look to see if the new C-Max numbers are in the EPA data base.

 

The graph shows the approximate Horse Power (HP) required to offset aerodynamic drag and the rolling resistance force at various speeds (MPH).  If one takes a look at the relationships between the C-Max and the Prius, one sees that at 70 mph, the Prius requires about 18 HP. The C-Max requires 18 HP at about 63 mph to offset the drag forces.  At 70 mph the C-Max requires about 23.5 HP.  That is about a 30% increase in HP to go 7 mph faster and hence requires significantly more fuel.   It's easy to see that the Prius will get significantly better FE at 70 mph than the C-Max assuming both are operating in virtually the same efficient area of the BSFC  

 

All energy comes from the fuel ICE burns.  My point in showing the graph is to illustrate that the primary difference in FE of similar cars is the power required to over come road drag which difference can be significant. I have seen no evidence that the power train of the C-Max or the Prius is more efficient than the other.  The same applies to the algorithms.  Most driving tips and tricks can be used on virtually any car and generally decrease average speed and hence increase FE.  But there is no magic.  Road drag reduces the C-Max FE significantly over the Prius.

 

There are three general ways to improve FE: 1) reduce the drag forces on the car - primarily reducing speed, weight, and the rolling resistance coefficient (tires and tire pressure); and improving its Cd (aero mods) and 2) finding ways to operate the power train more efficiently at a given speed and anticipated conditions keeping ICE near it's optimal point on the BSFC curve (this is where the tips and tricks come in including using engine block heaters) and 3) conserving / recapturing energy (reducing AC, heating, audio loads and so forth and regenerative braking).  IMO, the PCM algorithms do a fine job of using ICE / EV appropriately given what I have observed and recorded.  But the algorithm cannot anticipate conditions or perhaps anticipate incorectly.  For example, some believe using EV+ increases FE while others believe it hurts FE.   The answer may be it depends.

 

Edited July 31, 2014 by Plus 3 Golfer

[plus 3 golfer]

To close the loop on why "the CMax hasn't achieved its original MPG ratings", I have plotted the Road Load HP based on the EPA coefficients from coast down data.  The EPA data for the C-Max HEV has been updated in the EPA data base to reflect the latest revised C-Max HEV EPA FE numbers.  This is the data that is used to set the coefficients for road load in the dynamometer testing to get the raw data in the EPA FE test cycles.  The raw data is plugged into equations depending on the test cycles run to make further adjustments to better reflect typical driving conditions - hot conditions, cold conditions, start-ups.  For example, the coast down data is done on a dry surface, not on snow, in rain and so forth and thus reflects ideal conditions.

 

To answer the inevitable question as to but why do I get 47 mpg?.  Because you are likely driving the car using a conservative / hypermiling approach, in a milder climate mitigating the need for much heat or AC, on dry pavement virtually all the time and so forth (I don't recall the last time I drove on wet roads).  If the C-Max had RLHP like the original C-Max coefficients (red curve) which is basically the same as a Prius hatchback, ones actual 47 mpg would be significantly greater - probably in the range of 55 mpg under the same driving style and conditions.  So, beating the original 47 mpg is a moot point.  If's not the number to beat.  

 

[nsteblay]

Eyeballing fuelly.com the standard deviation is similar between the Prius and C-Max.  This could again be directly correlated to environment, predominately temperature.  This all suggests that your assertion that dyno coefficient is the major factor in mileage differences between the two cars.

 

My personal experience having driven both cars is mileage is far more variable in the C-Max and is very dependent on driving style. It would be impossible to see this in the data because it isn't measured.  It is not just the dyno coefficient but the design, configuration, and algorithms of the power split architectures that differentiate the C-Max and Prius.  I'm not saying one is better than the other, just that they were designed with different objectives in mind.  The C-Max allows for the variability to support greater acceleration if needed, and enable a physical configuration with better comfort and visibility.  If you've watched fuelly.com the average MPG has significantly improved over time for the C-Max.  I attribute this to drivers learning how to drive the car using the excellent instrumentation.  

[fordfan82]

You could be in the EV mode for a long time, if the car is going downhill. You get out of EV mode if A) you accelerate to the point where the computer determines running on the gas engine is better or b)the high voltage battery dips to the point where recharging is needed--again the gas engine kicks in. Basically you'll be going back and forth between gas and EV with EV being about 65% of the journey (in my experience).

 

Didn't the dealership go over this stuff with you?

Nope, the dealership we go to does not have too many C-max's on hand and my salesman did not know that much about the C-max. He mostly sells Fusions and Escapes.

[plus 3 golfer]

Eyeballing fuelly.com the standard deviation is similar between the Prius and C-Max.  This could again be directly correlated to environment, predominately temperature.  This all suggests that your assertion that dyno coefficient is the major factor in mileage differences between the two cars.

 

My personal experience having driven both cars is mileage is far more variable in the C-Max and is very dependent on driving style. It would be impossible to see this in the data because it isn't measured.  It is not just the dyno coefficient but the design, configuration, and algorithms of the power split architectures that differentiate the C-Max and Prius.  I'm not saying one is better than the other, just that they were designed with different objectives in mind.  The C-Max allows for the variability to support greater acceleration if needed, and enable a physical configuration with better comfort and visibility.  If you've watched fuelly.com the average MPG has significantly improved over time for the C-Max.  I attribute this to drivers learning how to drive the car using the excellent instrumentation.  

Actually the 2013 C-Max hybrid FE in fuelly hasn't improved over time. It's fallen.  You need to filter the recent fuelly data for the C-Max as Energis are now included in the overall average.  The 2013 C-Max hybrid peaked last summer at IIRC at over 40 mpg maybe around 41 mpg (I think I may have a snippet of it somewhere).  The 2013s Hybrid appear to be under 40 mpg now.  Here's a link where I downloaded the fuelly data in May 2014 and computed the standard deviation of the Hybrid at about 4 mpg (I excluded several low mileage C-Maxes that were not Hybrids but it hardly made a difference). 

 

I do agree that the characteristics (constraints) within the algorithms of the two cars have to differ based on physical characteristics of the vehicles and thus affect operations but the higher road load of the C-Max will limit the FE of the C-Max to a number significantly less than the Prius. But again there's nothing that I can find where the theory behind the algorithms differ.  I would say the C-Max  drivers have a better chance of reaching the 47 mpg in mostly city and suburban driving where year round ambient temperatures are mild.  Higher speed driving of the C-Max will have a greater affect on FE as the RLHP increases rapidly compared to the Prius. Also, air density play a significant role in FE as ambient temperatures vary. That can't be overcome but for moving to a warm climate.