I drive over a relatively steep grade every day.

"L" definitely charges the battery faster than "D" but in my case the battery ends up fully charged in either case. Once that happens, the ICE will be spun up to use up some of that charge. The difference appears to be that in "D" it'll just come up to idle whereas in "L" it'll spin up to 4K RPM or sometimes higher. However, in "L" I'm of the belief that little or no fuel is actually being used, the motor generator is just using the ICE to pump air and use up some excess charge.

I have not seen a significant increase in FE from using "L" however.

As for tire wear, the tires don't know or care whether you're using "L" mode, engine braking with a conventional drivetrain, or the friction brakes. The amount of wear will be the same for a given vehicle of a given weight. It is true however that FWD hybrids (and the AWD Escape since it's an on-demand system) will tend to wear the rear brakes faster than the fronts because most of the regenerative braking is on the front wheels.

 

There is a good article link (I recommend highly) in a new yahoo FEH post on that board. If I'm reading it correctly, the regenerative tire is only the left front. It also says the ICE uses the right in the FWD.

I'm not sure one way or the other that a single left front tire that is used to brake the FEH in "D" and much more in "L" will ware faster than the other right front. I have notice on a car with right rear traction wore faster with a manual tranny. Maybe down shifting to slow down played a part.

Those who drive in "L" all the time may notice it first if at all a problem. I'll continue to keep an eye on it in my FEH.

Gary

 

You read it incorrectly. The paragraph in question is trying to explain the planetary gear power-split device, and uses an analogy of a conventional differential to do so.

Like the PSD, a differential has three rotating parts, and if you control two of them you can effect the third. That's the point they were trying to make.

 

Steve, your right and I kinda thought that during my post. I think a positive came out with you and many others carefully reading that great article. I read it fast because I thought in was very good. I read it again and found I stretched what I thought was the case. The only thing that was stupid was the ICE controling the right front wheel which would say there are two separate connections in the drive train.

It goes back to my racing days with my '67 GT 500 Shelby Mustang. Posi-traction was both wheel turned no matter what. Limited slip was where if one slipped, the other grabbed also. For a number of reasons, posi-traction was left just for the race track. Limited slip for the front and back of a 2WD and 4WD was a special order option for many years.

FWD and AWD on the FEH is new technology. I find it very hard to believe that both wheels in the front of the FEH have a posi-traction type connection with the generator or engine generator combination. This would combine both wheels even if there is no sign of slippage. What I would think as a matter of experience is that the right wheel or tire is the single source of the engine and generator in an AWD or FWD traction until there is slippage.

At any rate, it would be very rare that both wheels or tires are used for the energy when using "L" to charge the battery. I don't see any sharing going on till there is slippage. I believed that there is a primary tire that is used all the time from past experience. At any rate posi-traction is not happening on street cars anymore.

Gary

 

As long as the PSD works like a differential then BOTH wheels are used to transfer energy regardless of acceleration or regeneration. The only time energy would not be transferred to both wheels would be if one wheel had limited traction (such as one tire on ice). At that point the energy would take the path of least resistance. If you accelerate with one wheel on ice and apply too much power the wheel on ice will spin.

Under normal conditions both tires will have the same traction, and travel at the same speed. Power is distributed equally to both tires when accelerating. Both tires share equally when the system is in Regen.

Another way to think about it. If only one wheel was used to for Regen then every time you put the FEH in low the vehicle would pull or try to veer that direction. The fact that when I decelerate by using L and do not have to correct the steering can only mean both drive wheels are equally transferring power.

 

Whoa there...

The PSD is upstream from the final drive. In other words, the three variables on the PSD are the ICE, the motor/generator, and the final drive (with traction motor included). There is still some sort of differential downstream (two if you have a 4WD model).

This has no relation to the drive wheels and any primary dominance of one side or the other. Anyone who has driven FWD cars over the past 20 years or so knows engineers have been fighting something known as "torque steer" for quite some time due to unequal distribution of forces to the primary drive wheel. However, since most of the time the load on the left and right wheel is roughly equal this isn't much of an issue, and careful selection of half-shaft lengths has been a good solution in most cases.

High-tech drivetrains with stability control are able to actively direct torque to the wheels with best traction. AFAICT, the FEH does not have this level of control, it's "Intelligent 4WD" system can only move torque between the front and rear axles. It would in theory be possible to use the ABS system to modulate the torque further, but such systems are not always very useful for traction control (they can be effective for rollover prevention, however).

 

I think this post (stolen from another site) confirms all my thoughts about using "L" on a regular basis....I deleted some of it to save space.

Ford confirmed that it is OK to drive in the "L"
position for extended periods with no harm. They
actually found it desireable to use to slow the
vehicle all the time, but most people wouldn't go
though the effort of shifting all the time. It is not
good ( my informed opinion ) to use over the highway
because "Low" will prohibit "Neutral" coasting. It
will ALWAYS regen when your foot comes off the pedal,
slow you down, and not let you coast at constant
speed.

They said #1 There is no damage from shifting to low
at any speed, because it is only a software request,
and the software will not do anything to hurt the car.
#2 When the engine revs in "Low" to act as a
compression brake, the fuel is 100% cut off. You are
not using ANY fuel... and Steve's comments below sound
right on. However, if the engine is reving to high
RPM, it is because your request to slow down exceeds
the generator's ability to slow you down, or the
battery is already full and there is no place for the
energy to go. If you really do want to slow down
more, then do let it rev, with no mechanical harm
done. However, if you really DON'T need to slow down
faster, then you are wasting energy that could be
re-couped with more gentle slowing and longer
regeneration. This is why my personal preference is
to use low only under 40 MPH. You can do it at higher
speeds, but this tends to be more wasteful.

#3 Regenerative braking is better than we all
thought, and plays a more important role than we all
thought. 9 MPG of the city driving, or 41% of the
Hybrid benefit comes from regenerative braking.
Without regen, the city EPA rating would be about
27/24 MPG! As the saying goes, use it or loose it!
If you don't use Regen, you are loosing MPG.

 

Hi Nitramjr:
___I cannot state this any more strongly but the highest FE comes from a much longer glide w/ ICE off then with ANY use of Regen. Of course you should use regen when you have to tap or jump on the binders but if the Escape HEV would go ICE Off with a shift to N or any let off of the Accelerator below 41 mph as its HSD based competitors do with a slight reapplication of the accelerator to remove Regen afterwards (Glide), you would see even better FE results when driven for such. The problem is that the Escapes ICE-Off capability is severely curtailed without using L. Either way, a shift to L for ICE-Off below 41 mph, a glide or EV mode (I could not completely remove all regen during the ICE On to ICE Off via L transition), and a relatively swift acceleration once ICE-On re-appears w/ pack charging taking place is where the Escape HEV’s real numbers come about, not through regen. Think outside the box and your own numbers will improve mightily as well.

___Although this is not an not an apples to apples comparison by any stretch, I grabbed a screenshot off of John1701’s page showing a Prius II w/ tons of regen displayed (the little cars) and a 51.7 mpg average in 46 degree F temps per his consumption screen. He loves to promote Regen and the resulting middling at best FE results are the result.



___By contrast, here is one of many screens I have seen while behind the windscreen of a Prius II with 0 regen showing and the consumption screen maxxed out at > 99.9 mpg over the 30 minutes of 5-minute bars.



___Mary Ann, are you listening? Smooth out the ability to go ICE-Off to match your competitors below 41 mph (you have the engineers to do this!) and you can leave Regen for when someone actually needs to tap or jump on the brakes for a stop while still in D or leave the L mode alone for those that are going to grab all the regen possible in any case. Your best FE engineers are wrong about how to achieve max FE using a max or nominal regen strategy with or without using L. The Escape HEV’s D-coast is very smooth and you should keep as much of that free coast as possible. With your current almost regen-less D-coast, add max ICE-Off time and you will have little to no change to the end users feel and/or driving experience. In fact, the end user experience will be vastly improved with an ICE-Off below 41 mph with no accelerator input in D-coast vs. the hard regen transition while shifting to L to get the ****ed ICE-Off condition and then reapplication of the accelerator for either an EV propulsion or coast down Glide. D is already very smooth with its almost regen-less coast but ICE-Off in D is just about impossible until way down in the speed range when nearing an actual stop. If you don’t grab this smooth transition coast w/ ICE-Off FE boost, Toyota will and they will achieve yet another bump up in FE over and above everyone else after they figure it out for themselves. Achieving higher then 41 mph ICE-Off and no ICE spin up for MG1 protection or ICE starting torque should coincide with this regen-less ICE-Off coast design change. I know your team is working on the > 40 mph ICE-Off and no ICE spin up but if you want to see real screaming numbers while driving casually around town, model the description above and see for yourself.

___How can I put this any more bluntly. Now that your FE Engineer knows how to achieve a sustainable 50 + w/ 1,000 #’s of people in a 2WD Escape HEV since he saw it for himself, let your people take the D-coast w/ ICE-Off model one step further and remove the ugly transition from D to L with a harsh Regen before reapplication of the pedal. The FE will be that much higher.

___Another piece of anecdotal evidence for you in regards to ICE-On vs. ICE-Off over a 2.1 mile segment in a non-hybrid Accord …

Reset FCD w/ 2.1 miles total. 52 mph - 28.4 mpg initial when FAS performed at overpass sign just before a high speed off-ramp and coast into a gas station. Final 50.0 mpg.

Reset FCD w/ 2.1 miles total. 54 mph - 29.9 mpg initial when a Neutral coast was performed at overpass sign just before a high speed off-ramp and coast into a gas station. Final 41.2 mpg.

___Both of these results are while climbing 120’ in elevation from a dead stop to highway speed after a reset FCD. There is no regen in a non-hybrid Accord as you know yet the ~ 20% increase in FE while climbing from a dead stop to highway speeds and back to near 0 mph with a N-ICE-On vs. N-ICE-Off (FAS which your engineers didn’t consider) speaks volumes for a semi-lux 3,200 + # non-hybrid sedan with all the bells and whistles all the while rated at just 24/34.

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

 

A little thing I was playing with during todays errands. I used the "L" position to get the early ICE cutoff. Immediately upon the ICE shutting down, I put the shifter back into "D". Just doing this, I was able to get my FEH up to 39 mpg by the time I stopped at the dealership to have the car washed. By the time I stopped for fuel on the way home, the MFD had levelled off to 38.4 for the tank, due to the uphill trend of the drive home.

 

Hi Wayne,

With all due respect, please read my posts regarding this issue and you will see that I qualify everything I say with "in my experience" or "in my situation" or "in my opinion" or some other such disclaimer. That said, I will repeat that in my driving situation (mainly city or congested highway/collector raods), it is nearly impossible to avoid using the brakes. Instead of using the brakes, I have found (after a ton of experimenting and reading) that using low in the Escape Hybrid (I own two of them so I speak from experience) has increased my mileage greatly. Using regen, IN MY SITUATION, helps me avoid using the friction brakes (friction = heat = lost energy = decreased FE). Around here, where I drive, you either have to stop or slow down OFTEN - why not recapture as much of that energy as possible. Using L allows very good negative acceleration rates with absolutely no use of the friction brakes.

I would like to think that as an Engineer, I am perfectly capable of "thinking outside the box" and am very capable of figuring out what works for me and what doesn't. What works best for one person in one situation is not necessarily best for all in their situation. I have been experimenting since I bought my first FEH back in March and have become intimately familiar with how it works. I may not be at the top of the list (in the GH database) anymore but I am up there and my mileage lately has been better and better - I think I am doing something right. My '05 is dropping off the chart but that is because my wife drives that one.

Anyway, back on topic, my last post earlier this evening was to answer questions that have come up about whether using L has any negative effects. I posted it as information for anyone who doesn't read all the postings on the Yahoo board. The information came from someone who went to the Dearborn event this last weekend. There have been several people questioning whether L did damage or caused problems to the vehicle and according to the Ford engineers, it doesn't. Their answer appears to be similar to what I deduced from my own research several months ago.... https://www.greenhybrid.com/discuss/...l?page=2&pp=10 .