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Braking best techniques

Braking techniques fuel economy

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66 replies to this topic

#21 OFFLINE   fbov

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Posted 01 May 2014 - 11:30 AM

30 mph is 44 feet per second. We tend to think 30 is slow, and it is, but it's instructive.

 

12 seconds at 44 ft. per sec. is 528 feet, 1.75 football fields. At 60 mph, it's half that distance, but still a lot farther than you think. And remember, this was an autocross technique, intended for use at speeds in the 30-70 mph range, right where we do most of our driving.

 

Have fun,

Frank









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#22 OFFLINE   Noah Harbinger

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Posted 02 May 2014 - 10:03 PM

The brake coach kind of sucks, but I assume that's intentional - they don't want you focusing on the display when you're braking because the fact that you're braking probably means there's some hazard or limit in front of you. 

 

That said, you would be surprised how hard you can brake and still capture 95-100% of energy. The catch is that the more rapidly you apply braking pressure, the more of the braking will be done by the friction brakes (i.e. WASTE!). So you have to press the peddle extremely evenly. 

 

I would love it if anyone knows more about how the braking system proportions force between the regenerative braking and the friction brakes. 



#23 OFFLINE   marshtex2

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Posted 04 May 2014 - 12:31 AM

After decades of driving so as to minimize using brakes, I have abandoned trying to change to a style that maximizes dragging the brakes and don't notice a change in actual mpg.  Anyone else have mental trouble joining the brake dragging club?



#24 OFFLINE   Jus-A-CMax

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Posted 04 May 2014 - 02:01 AM

Brake coach, acceleration coach and whatever-I-forgot-coach is useless, imo. It's not all about braking, if anything is LESS about braking as I get attrocious scores in the LUNATIC Los Angeles City driving and yet I can pull 60-65MPG driving daily in real traffic conditions as I go back and forth from home to work and wherever I care to go in my banged-up-Lemon Maxine.

 

Learn and read the roads better, if you want your MPG. Read the traffic lights, plan ahead but becareful of the red lights - not worth it. Watch the rear traffic....so a road less travelled is an MPG saver. A road with downward incline and a road with the least upward incline (at the expense of additional distance) are preferred options.

 

Remember, MPG is at the expense of time.


Edited by Jus-A-CMax, 04 May 2014 - 02:03 AM.

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#25 OFFLINE   Plus 3 Golfer

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Posted 04 May 2014 - 09:16 AM

After decades of driving so as to minimize using brakes, I have abandoned trying to change to a style that maximizes dragging the brakes and don't notice a change in actual mpg.  Anyone else have mental trouble joining the brake dragging club?

Why do you want to abandon such? Are you saying you downshifted to slow down or coasted to minimize braking? If you've got the time, coasting is better than using brakes. In the C-Max when you coast, there will be regeneration to simulate ICE engine braking as would be the case in non-hybrid cars but not in the C-Max powertrain. Using the brakes increases regeneration and slows the car down faster than coasting but there's energy losses in MG2, inverter, HVB when both storing and using the captured braking energy.
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#26 OFFLINE   ptjones

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Posted 04 May 2014 - 10:52 AM

Not using brakes gets the best MPG's, but at some point you will need to stop. LOL  I take corners faster (which bugs my wife, my grandson likes it. LOL)so I don't have to use the brakes. After a while you will get use to the seat of your pants feel to tell you if you are braking to hard. :)

 

Paul



#27 OFFLINE   ScubaDadMiami

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Posted 04 May 2014 - 01:10 PM

No question that braking is not as important as throttle control. However, with just a little additional brake control, you will also certainly get a little better fuel economy, even if it's just a little bit.


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#28 OFFLINE   fbov

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Posted 05 May 2014 - 12:00 PM

Looking at my car's data, my regen miles are about 3-5% of the total mileage, and that at 95% regen. Presumably, you'd have to try very hard to get 50%, and few of us have the test scenario to detect 1.5% change in mileage.

 

So significant? No. But still important for charging and getting the most out of gas invested in hill climbing.

 

Have fun,

Frnak



#29 OFFLINE   ptjones

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Posted 05 May 2014 - 04:11 PM

I would think you would have higher percentage of Regen miles with higher percentage of City driving. You don't normally use brakes on the FWY.  But you still can have high percentage EV miles even with 80%  HWY miles. My example is 53541mi total, 23371.6 mi. EV, 1439.4mi. Regen, life time MPG 46.2 and BS 98%. Which gives me 44% EV and .027% Regen.  I went back through most of my City Driving IPhone Pics  and found one with a 15% regen score and a few with 10% score so I guess if you only did City driving and were good at hypermiling you could end up with a impressive 10% Regen Score. :shift: 

 

Paul



#30 OFFLINE   Plus 3 Golfer

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Posted 05 May 2014 - 04:47 PM

I'm not sure I necessarily buy that a higher regen miles % is associated with city driving.  I would think that regen miles includes ALL regeneration not just using the brakes.  So when one is coasting and using grade assist one is regenerating.  My regen miles is 3.6% with a 94% brake score and my EV miles is 50.7%.  My lifetime mpg is 42.0.

 

We do a lot of freeway driving at 70+ mph and coast coming off ramps up 1/3 to 1/2 mile.  I also try to time lights by coasting and coast to stops.  We also have done many 300-400 mile trips into the mountains where I always use grade assist.  So, why is my FE about 10% lower than Paul's FE even though my EV and regen miles are a higher %?  My guess is that my average speed is considerably higher than Paul's average speed and thus I have significantly more energy available to capture via regeneration when coasting, braking, and using grade assist.

 

One other thought when applying the brakes and that is does the rear friction brakes assist for control purposes when the front wheels are in a pure regeneration mode (no friction braking).  I have read papers that have modeled and IIRC tested various control schemes.  If so, using the brakes for more regenerative braking may be lowering ones overall % regeneration vs coasting to slow down.  One anecdotal fact is that when I feel the surface of the front rotors compared to the rear rotors, the rear rotors have a slightly raised outer lip after 25k miles.  There is no perceived lip on the front rotors. Could this be friction braking wear on the rear?  Maybe others (be good to get someone with little miles on their car) could check their rotors for what appears to be the sign of rotor wear.  



#31 OFFLINE   ptjones

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Posted 05 May 2014 - 05:15 PM

I thought the Regen Score was for braking only. I thought rear braking only happens when front brakes are working. :)

 

Paul



#32 OFFLINE   Plus 3 Golfer

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Posted 05 May 2014 - 06:25 PM

I assume EV energy is all energy supplied by the battery to propel the car and thus would include all sources of energy to charge the battery.  The regen score only applies to when one depresses the foot brake and is used as a tool to help one to not use the friction brakes.  Braking to me simply means that the front wheels have a force applied to them and are slowing down via regeneration and/or friction.  The ABS / stability control algorithms know what is going on and there would be no reason that the rear brakes couldn't be applied anytime.  The ABS can do proportional braking  

 

Wiki says: "When braking or decelerating, the Fusion's hybrid system uses regenerative braking, where the electric drive motor becomes a generator, converting the vehicle's momentum back to electricity for storage in the batteries."   I've always seen discussion on "regenerative braking" to include coasting (decelerating).  Braking does not mean that one has to brake via friction brakes.  So, that's why I assume regen miles is all energy (converted to miles) generated by braking the front wheels.

 

The inverter / battery is capable of 35 kW of sustained charge.  I would think that would then be the maximum braking force that MG2 (traction motor) would apply during regen.  The question then: is 35 kW of braking force to much force to put on the front wheels while the rear end is free wheeling.  I don't know but have a feeling that the rear friction brakes may be used in assisting slow down (the rotors seem to be wearing).  Then, the question is does application of the rear friction brakes affect brake score?

 

Edit: here's the definition of regenerative braking in the owner's manual:

Regenerative Braking System
This feature is used to simulate the engine braking of an internal
combustion engine and assist the standard brake system while recovering
some of the energy of motion and storing it in the battery to improve
fuel economy.

 

 


Edited by Plus 3 Golfer, 05 May 2014 - 06:49 PM.


#33 OFFLINE   Plus 3 Golfer

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Posted 05 May 2014 - 07:54 PM

Paul, just wondering if your regen miles and EV miles are since you owned the car or from the reset of those values which should have occurred with the 13B07 update.   My dealer SO shows the mileage on my vehicle when the update was performed.  If I inadvertently used the odometer miles to calculate my % from the displayed EV and Regen miles, I would get 2.4% for regen miles and 33.9% for EV miles which is way to low.   



#34 OFFLINE   kostby

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Posted 05 May 2014 - 09:57 PM

@Plus3Golfer re: a 'low mileage car'

 
Not exactly sure what you're looking for, but here are stats:
 
Built April 10, 2013
We purchased it 03/26/2014 with 133 miles on the odometer.
Ford ETIS shows no software updates available, so apparently all applicable updates were done.
 
559.9 odometer miles on the car.
98% brake score
210.3 EV miles = 37.56% EV miles

26.7 regen miles = 4.768% regen miles

Attached File  IMG_4154med.jpg   38.08KB   0 downloads

 

Snapshots of the rotor surfaces

Attached File  IMG_4100med.jpg   80.96KB   0 downloads

Driver's side front disc

Attached File  IMG_4097med.jpg   64.42KB   0 downloads

Driver's side rear disc

 

Attached File  IMG_4108med.jpg   67.96KB   0 downloads

Passenger side front disc

 

Attached File  IMG_4105med.jpg   69.22KB   0 downloads

Passenger side rear disc


Edited by kostby, 05 May 2014 - 11:11 PM.


#35 OFFLINE   SnowStorm

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Posted 05 May 2014 - 10:22 PM

My regen miles is 3.6% with a 94% brake score and my EV miles is 50.7%.  My lifetime mpg is 42.0.

 

One anecdotal fact is that when I feel the surface of the front rotors compared to the rear rotors, the rear rotors have a slightly raised outer lip after 25k miles.  There is no perceived lip on the front rotors. Could this be friction braking wear on the rear?

My Regen is at 3.9% adding both before and after upgrade (remember Regen miles got reset).  EV is at 37.5% with lifetime miles at 31,731, 93% braking and 46.8 mpg (46.9 since upgrade - which is still biased with winter driving).  Our mileage has a lot at 55 mph and very little over 65 - using ethanol free gas.

 

My front discs are relatively smooth all the way across.  Rear ones are more uneven (slight ridges with the outer 25% looking like there was some rust there that has been mostly worn off by the pads).  There might be a tiny lip on the inside where the pads don't hit but it is almost undetectable (except for color).  Overall, front discs look a lot nicer but I don't know if it is from more use or less.



#36 OFFLINE   ptjones

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Posted 05 May 2014 - 10:29 PM

Paul, just wondering if your regen miles and EV miles are since you owned the car or from the reset of those values which should have occurred with the 13B07 update.   My dealer SO shows the mileage on my vehicle when the update was performed.  If I inadvertently used the odometer miles to calculate my % from the displayed EV and Regen miles, I would get 2.4% for regen miles and 33.9% for EV miles which is way to low.

   

It appears my LifeTime was not reset. I have 80% HWY and that is why I have the numbers I have. I coast a lot so I should have a 20% Score so that is why  I think it scores the time you have your foot on the brake and the brake coach is spinning. :)

 

Paul



#37 OFFLINE   Plus 3 Golfer

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Posted 05 May 2014 - 10:38 PM

Can you feel a raised lip on any of the flat surface rotor edges as you slide your finger across the rotor to the edge?  A new rotor is perfectly flat.  After rotors wear and since the pads don't extend to the surface, the edges will be raised slightly as the inner surface wears away.

 

med_gallery_167_32_122212.jpg



#38 OFFLINE   kostby

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Posted 05 May 2014 - 11:12 PM

At 559.9 miles, all the rotors are still perfectly flat, no raised lip.



#39 OFFLINE   Plus 3 Golfer

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Posted 05 May 2014 - 11:17 PM

My Regen is at 3.9% adding both before and after upgrade (remember Regen miles got reset).  EV is at 37.5% with lifetime miles at 31,731, 93% braking and 46.8 mpg (46.9 since upgrade - which is still biased with winter driving).  Our mileage has a lot at 55 mph and very little over 65 - using ethanol free gas.

 

My front discs are relatively smooth all the way across.  Rear ones are more uneven (slight ridges with the outer 25% looking like there was some rust there that has been mostly worn off by the pads).  There might be a tiny lip on the inside where the pads don't hit but it is almost undetectable (except for color).  Overall, front discs look a lot nicer but I don't know if it is from more use or less.

My before reset % wwere close to my after but I didn't write down the numbers.  My rear rotors feel like you describe - slight ridges across the surface not perfectly smooth. My fronts feel virtually smooth. But again my rears have a very slight ridge on the edge and no ridge on the fronts.  The brake pads would likely be a better indicator of wear. But, I doubt I will ever have to change pads or rotors.  Next time I rotate tires I'll take a better look at everything - about 4-6 months from now.

 

.



#40 OFFLINE   Zathrus

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Posted 06 May 2014 - 07:03 AM

Kostby...how do you display Lifetime Summary in instrument clustor (contained in you post above)? 

 

post-1940-0-10349900-1399344131_thumb.jp

 

If there instructions in the manual on how to do this, I have not found it. Thanks.








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