Mountain Driving Help

[fotomoto]

 I'm leaving tomorrow morning and will report back what I find.   I'll use hill assist and if the grade gets really steep I'll put it in L.  I want to see how well the car handles things with as little brake pedal as possible.  Should be a welcome diversion from traveling the straights around here!  Thanks.

[fotomoto]

Update:  grade assist work VERY well.  I rarely needed to touch the brakes and only dropped it into L twice (first time just out of curiosity).  The highest rpm I saw with grade assist activated was 4,500.   I think folks who drive through steep terrain will see economy gains with the new software update.  Since the system wants to burn off a really full battery, the higher EV speeds now available can be put to more use going up the next hill.  

 

[DaveofDurham]

I have no answer for this.  But I will tell you my experience on a mountain of a hill.  First a little about the grade I am descending.  It is on I-40 East out of Asheville, NC (near Black Mountain, NC).  Here is a note I found online about the grade:

 

By law, all trucks except pickups and vans are required to stop at the top of this hill and read the information posted about the eastbound descent ahead.  The top of the hill is near milepost 67 just east of Black Mountain.  The grade is posted as 5 miles of 6%.  It is a strong 6%.  There are three runaway truck ramps, all of which are short sand beds with sand piles at the end.  There is about a mile of grade left after the last escape ramp.   The westbound descent is about 1¼ mile of 6%.

 

I have descended this grade with hill decent on and hill decent off.  With hill descent on, when the battery gets very close to 100% (I have a scangauge to monitor this) the ICE will kick in and rev very high (as Noah Harbinger pointed out above). While the ICE is engaged, it does not use any fuel.  I left the hill descent on for the length of the grade.  The ICE does a very good job of holding back the car during the descent and I used very little brakes.  The last time I descended this mountain I did so with hill decent off.  Normal regen (foot off both the gas and brake) does NOT hold the car back at all on a hill this steep.  When I would press on the brake pedal to slow the car, the regen symbol (blue circle) would come on until the battery hit 100%.  Once the battery was at 100%, sometimes the display would show regen sometimes it would not.  But I do not think the friction brakes engaged by themselves with the hill descent off.  If they had, my brakes would have been smoking by the bottom of the grade.  I have seen where drivers have dragged their brakes the whole way to the bottom and you can smell the brakes burning by the bottom.  I could be wrong though.

 

I will point out that even with hill descent on, regen alone did not keep the car from accelerating on this grade.

 

I'm still looking forward to my first C-Max drive to Asheville and back.

 

Two weeks ago we drove from Charlottesville VA to Parkersburg WV.  This was 5+ hours of uos and downs with minimal interstate over the Skyline Drive and through two national forests.  We used grade assist on most of the 6% downhill grades.  Once the battery was full, the vacuum cleaning/sewing machine noise was interesting.

[ScubaDadMiami]

In September, I will be driving from Miami to the mountains of western North Carolina, then driving all around that area for about a week, and finally driving back to Miami.  So, I guess I will be finding out about the mountain driving, soon enough! 

 

If I understand correctly, we can put the C-MAX into L at any speed?  When do you go with L versus Grade Assist?  Would I start by using Grade Assist, and then shift to L if Grade Assist is not enough to stay within the speed limit?

[HannahWCU]

Here is a graph of the mountain of a hill I drove to get my information on how the CMax works on hills.  As you can see the total incline is just over 1300' over a distance of 5 miles.  MPG is really sucked down going uphill, but on the downhill run ...

 

 

Here is a view of my total drive (going uphill), from my house to my parents house.  Total distance is just over 103 miles and altitude gain is almost 1900' (peak to peak)

 

 

[fbov]

Is that the the fall line of the Piedmont? we're seeing in your route?

 

HAve fun,

Frank

[ScubaDadMiami]

I have been driving the mountains since arriving in western North Carolina for the past four days. Surprisingly, I find it to be very easy. There aren't many choices about where to go EV. When you are going uphill, it is too steep to do any kind of realistic EV driving. When you go downhill, EV is a no brainer.

 

Where land is flatter, you have to decide and plan for when you go ICE or EV. That has been harder to learn, especially at highway speeds (given my limited highway driving experience).

[bigalpha]

Hannah, how did you record that data?

[obob]

I recently drover a 3 mile, 800 ft ascent route straight up, followed by 3 mile 600 ft decent and the return trip.

 

On the way up I decided to go about 47 mph to keep the engine cool and the SOC was about 3/4 on the top, and was full on the decent pretty quickly.

 

On the way back I went up 2-3 pixels over two bars(about 3200 rpm) so there was no regen to keep the SOC lower before the descent, but now I am thinking it was not worth it. Once again the SOC was 100% pretty quickly.  If the car was geeked out there would be a switch to prevent regen up the hill before a long decent.

 

I was impressed with the power of the engine though.  It never seemed like it was stressing.

 

By the way, since the software update, my sense is that when in hill assist the car goes into ICE slowing on any pretty steep hill, even without a full SOC sooner than before the update.

 

I liked the idea that was presented to turn the A/C up (if it is hot) on the downhill to use up some electricity and store the energy as a cool car.

Edited September 10, 2013 by obob

[obob]

Hannah, how did you record that data?

http://fordcmaxhybridforum.com/topic/2875-tool-for-the-third-dimension-mapping-route-altitude/

[HannahWCU]

http://fordcmaxhybridforum.com/topic/2875-tool-for-the-third-dimension-mapping-route-altitude/

Yes that is what I used. And no that isn't the Piedmont. Its a mountain near Asheville. The route I mapped is actually I-40. So it is a road that ALOT of people use.

[HannahWCU]

I wanted to add a little to this discussion.  I finally remembered to take a few pictures on my mountain descent:

 

Here I have Hill Control on. I am running 55MPH, the battery is fully charged (State of Charge 100%), ICE is engaged (4296RPM), no fuel burning (0.00GPH), and a slight charge into the battery (-1.28 AMPs).

 

 

 

This is 1.5 miles later. Same conditions, but as you can see the car has accelerated to over 60MPH now (STEEP hill!  LOL)

 

 

Now where is that 1+ amps going?  Well the AMPs fluctuates from +1.?? to -1.??. My assumption is that those amps are what the car uses to keep everything running (i.e. radio, fan on HVAC, electric steering, electric brakes, charging 12v battery, etc.)

 

Anyway, just thought I would post a little more information for everyone.

[stevedebi]

I'm not sure I understand some of the questions about "L" mode. The generator is spinning the engine to bleed off the excess energy once the battery is full. That is where the "extra" energy is going.

[plus 3 golfer]

I'm not sure I understand some of the questions about "L" mode. The generator is spinning the engine to bleed off the excess energy once the battery is full. That is where the "extra" energy is going.

MG1 (the generator) is not spinning to bleed off excess energy.  It's using energy to control engine speed - in negative split to more efficiently run ICE (like up-shifting a conventional transmission to a higher gear) and when in "L" mode to increase engine speed perhaps for engine braking or because the driver wants ICE to run in an effective lower gear. 

 

Speed up MG1 and the engine slows down (assuming car speed hasn't changed).  Slow down MG1 or reverse MG1 rotation and engine speed increases - "L" mode (like downshifting to a lower gear in a conventional transmission).   De-fuel the engine (take foot off accelerator) in "L" and engine becomes a load on the drive train (engine braking) which can help in controlling / reducing vehicle speed especially going down hill.  

 

 If the battery is not full, the PCM will use MG1 as a generator to increase engine load requirements and ICE will increase rpm / fuel to meet the additional load.  ICE should be operating in an more efficient range (than without the additional load) similar to when the battery if full but at decreased load and rpm.  The PCM should control MG1 and thus rate of charge for best efficiency.

 

There is no benefit to simply bleed off energy. Once the battery reaches its threshold capacity for hybrid operation, the traction motor (MG2) can act as a generator at the same time the generator (MG1) can act as a motor. The PCM should effectively use MG1 and MG2 to minimize input energy (fuel) effectively changing the gear ratio for best overall efficiency. Sometimes, one might see the battery being charged and sometimes one might see the battery being discharged.   The net effect as I've stated before in monitoring change in battery energy in negative split was a slight increase in state of charge of 2% points over 4 miles.  Going down hill for several miles using regenerative braking can increase the state of charge up to it's limit of about 70% SOC given a long enough down grade  But there's nothing one can do about that.  Just like a convention vehicle, one may lose some of the available potential energy going down hill because there is no room to store any more energy.  

[stevedebi]

Plus 3,

Let's not get another thread off topic again. The car is causing the engine to spin because it has to slow down the vehicle, and the generator cannot store any more energy in the battery due to high SOC. It is a high level description, not an in depth discussion of the internal workings of the hybrid system.

 

I read your former posts, and watched the video. I prefer to think of it the way I do, and I don't think most folks care that much about the semantics.

[bigalpha]

Plus 3,

Let's not get another thread off topic again. The car is causing the engine to spin because it has to slow down the vehicle, and the generator cannot store any more energy in the battery due to high SOC. It is a high level description, not an in depth discussion of the internal workings of the hybrid system.

 

I read your former posts, and watched the video. I prefer to think of it the way I do, and I don't think most folks care that much about the semantics.

 

That's a pretty snotty reply.

[stevedebi]

That's a pretty snotty reply.

Sorry, I didn't mean it to be. We both got warned in another thread to get back on topic, and I didn't want this discussion to wander off again.

 

EDIT: I don't think it would be beneificial to the average reader...

Edited November 12, 2014 by stevedebi

[BIG ROCCO]

We go up and down a lot of long steep grades going to our cabin in the AZ White Mountains and so I have had a lot of practice and have tried a lot of things.  I don't like how high the engine revs in downhill assist mode...4,000+ RPM.  I try to keep the revs to no more than 3,000 RPM going uphill (or sometimes 3,500 RM at the most, if necessary), so 4.000+ seems, and sounds, really high to me.  OK, maybe I'm wrong to be concerned about that, but one thing I noticed is that if I am going downhill and I put the hill descent mode on and the engine revs up higher than I would like, turning the hill descent mode off does not actually disengage the hill descent mode.  The ICE is still engaged and revs, but not quite as high as when the hill descent mode light is on.  It's kind of like shifting to a higher gear when engine braking/decelerating...maybe like going from 3rd gear to 4th gear or 4th gear to 5th gear in a conventional car with a 6 speed automatic.  So it's like hill descent "light".  The only way to actually turn the hill descent off and disengage the ICE is to accelerate slightly by pressing on the gas pedal

[stevedebi]

We go up and down a lot of long steep grades going to our cabin in the AZ White Mountains and so I have had a lot of practice and have tried a lot of things.  I don't like how high the engine revs in downhill assist mode...4,000+ RPM.  I try to keep the revs to no more than 3,000 RPM going uphill (or sometimes 3,500 RM at the most, if necessary), so 4.000+ seems, and sounds, really high to me.  OK, maybe I'm wrong to be concerned about that, but one thing I noticed is that if I am going downhill and I put the hill descent mode on and the engine revs up higher than I would like, turning the hill descent mode off does not actually disengage the hill descent mode.  The ICE is still engaged and revs, but not quite as high as when the hill descent mode light is on.  It's kind of like shifting to a higher gear when engine braking/decelerating...maybe like going from 3rd gear to 4th gear or 4th gear to 5th gear in a conventional car with a 6 speed automatic.  So it's like hill descent "light".  The only way to actually turn the hill descent off and disengage the ICE is to accelerate slightly by pressing on the gas pedal

Well, at least the engine is not straining when it does that - there is a fuel cutoff and it is simply spinning rather than the hard work that an uphill 4K RPM would indicate.

[plus 3 golfer]

Plus 3,

Let's not get another thread off topic again. The car is causing the engine to spin because it has to slow down the vehicle, and the generator cannot store any more energy in the battery due to high SOC. It is a high level description, not an in depth discussion of the internal workings of the hybrid system.

 

I read your former posts, and watched the video. I prefer to think of it the way I do, and I don't think most folks care that much about the semantics.

Describing how L mode works in mountainous driving in not off-topic as I use it all the time descending steep, curvy mountainous roads to control speed when grade assist can't adequately control speed regardless of the SOC of the HVB so I don't have to use the friction brakes very often if at all.   

 

Your high level description above (highlighted in red) as what is happening in L mode when the battery is full (knowing full means about 70% SOC) is not technically correct except if  you mean MG2 not MG1 the generator. The traction motor MG2 provides regenerative braking slowing the car down when the battery is not full with ICE off.  This is to simulate ICE engine braking when coasting.  When regenerative braking is not sufficient to slow the car down, shifting into L aids in braking the car. L mode  causes the engine to engage and spin even if the battery is not full.  As I've said before, negative spit starts when the battery is around 56% SOC. So, positive spit mode ceases (MG1 charging the HVB). The HVB will continue to be charged via MG2, regenerative braking up to around 70% SOC

 

What I care about is that posts are representing conditions correctly and are not ambiguous.  There's a big difference between MG1, the generator and MG2 the traction motor.  Wording (semantics) is extremely important.   ;)

Edited November 13, 2014 by Plus 3 Golfer

[stevedebi]

Describing how L mode works in mountainous driving in not off-topic as I use it all the time descending steep, curvy mountainous roads to control speed when grade assist can't adequately control speed regardless of the SOC of the HVB so I don't have to use the friction brakes very often if at all.   

 

Your high level description above (highlighted in red) as what is happening in L mode when the battery is full (knowing full means about 70% SOC) is not technically correct except if  you mean MG2 not MG1 the generator. The traction motor MG2 provides regenerative braking slowing the car down when the battery is not full with ICE off.  This is to simulate ICE engine braking when coasting.  When regenerative braking is not sufficient to slow the car down, shifting into L aids in braking the car. L mode  causes the engine to engage and spin even if the battery is not full.  As I've said before, negative spit starts when the battery is around 56% SOC. So, positive spit mode ceases (MG1 charging the HVB). The HVB will continue to be charged via MG2, regenerative braking up to around 70% SOC

 

What I care about is that posts are representing conditions correctly and are not ambiguous.  There's a big difference between MG1, the generator and MG2 the traction motor.  Wording (semantics) is extremely important.   ;)

Plus 3,

I hope you didn't take offense at my other post; none was intended!

 

The engine does not always spin in L. I thought that too, at first, but someone pointed out I was wrong, and subsequently I discovered them to be right.

[stevedebi]

I need to clarify my last post - the Energi C-Max does not always spin the engine in "L". But it has a larger battery, and would have more capacity.

 

For all I know, the C-Max Hybrid, with it's smaller battery may very well always end up in the condition where "L" will spin the battery.

 

I try and make sure my posts apply to both vehicles, but in this case I thought I'd clarify a bit.

[ptjones]

When possible I try to use up the HVB before I get to the top of a hill so I can get the maximum of regen braking and use down hill assist If I need to. That way you get the most for your EV miles. :)  :shift:

 

Paul 

Edited November 14, 2014 by ptjones

[BIG ROCCO]

Well, at least the engine is not straining when it does that - there is a fuel cutoff and it is simply spinning rather than the hard work that an uphill 4K RPM would indicate.

I think you are correct...there may be some small difference between acceleration and deceleration (or I suppose more properly, negative acceleration), but even just spinning the engine at high speed does still subject all the parts to the same or similar forces as when when it is actually running.  I will admit that the Ford engineers probably decided that 4,000 or 4,500 RPM is not an unsafe speed, or they would not have programmed the car to permit that, but I like to keep my cars for >10 years/100K miles, so I try not to always push the car to the limit...sometimes, you can't help it, but I try to avoid beating on the car on a daily basis.

[plus 3 golfer]

I need to clarify my last post - the Energi C-Max does not always spin the engine in "L". But it has a larger battery, and would have more capacity.

 

For all I know, the C-Max Hybrid, with it's smaller battery may very well always end up in the condition where "L" will spin the battery.

 

I try and make sure my posts apply to both vehicles, but in this case I thought I'd clarify a bit.

Yes, I do recall there's a difference between the two using Low.  I forgot that you have an Energi. There were discussions on this in the past.  For those with Hybrids, it's easy to see that shifting to L starts ICE spinning.  Put RPM in MyView and drive shifting in and out of L.

 

I don't recall anyone who has documented / described the hybrid mode operation in the Energi.  I would think the hybrid mode algorithms are the same except perhaps threshold levels in the Energi might be increased  - but why? running ICE just to charge the big HVB (in positive split mode) even now with low gas prices would likely cost (in Phoenix with about $2.64 / gallon) over twice as much to charge the HVB with gas vs electricity.   But when descending a hill in the Energi, it makes sense to maximize regeneration whether the car in in D or L.   So, ICE should not spin in L to slow the car down like in the Hybrid. 

Edited November 14, 2014 by Plus 3 Golfer