Taken to the limits up and down grade - Kia Niro Forum
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post #1 of 15 (permalink) Old 02-18-2019, 11:57 PM Thread Starter
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Taken to the limits up and down grade

Drove up a very long grade today with cruise control set to 70 mph. PHEV in HEV mode. The battery assisted the engine and it maintained 70 until the battery reached 2%. At that point the engine, without help from the battery, would not maintain speed. I say would not because it was capable, it just wouldn't downshift. It slowed all the way to 45 before it down shifted and accelerated.

On the way back, when the battery reached 2%, I floored it and it down shifted immediately and maintained speed at something less than full throttle. (Cruise is not active with any manual throttle. It will go faster or slower than the cruise setting with any manual throttle.)

At first I thought this a rather poor way to program the car's cruise control. On second thought, however, IC engines are most efficient at relatively low RPM and high manifold pressure, just where it was climbing in cruise control until 45 mph or where I intervened.

That same grade on the way down was well controlled by the cruise control and regenerative braking. I don't think the friction brakes were used by cruise to maintain speed but I don't know for sure.

Interesting way to operate but, I suspect, quite efficient.

The trip was a bit over 200 miles most at 70 mph and produced an indicated 46.4 mpg. This after a full level 1 charge of almost exactly 9 KWH overnight. The geek in me is really enjoying this car.
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post #2 of 15 (permalink) Old 02-19-2019, 12:38 AM
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I've had a similar, but slightly different experience while driving up Cajon Summit in Southern CA. The first time I did this, my PHEV electric range was fully depleted at the outset. I recall that the car struggled to maintain 70 MPH during the steepest parts of the climb and it wandered back and forth between gears frequently. I don't recall how much of the ascent was in Cruise Control though: that road tends to get trafficy and I usually disable cruise when that happens. The second time I did it, I started with a range of maybe 16 EV miles at the bottom, but I had manually switched to HEV mode: the car performed much better, but most of my electric range was gone when I reached the top. And then a really strange thing happened: I had another 20-some-odd miles to go after reaching the summit, mostly flat and much of it highway. I switched to EV at the top and even though I was only showing about 6 miles of EV range, I drove the entire remaining distance in EV mode. Still haven't discovered the explanation for that.
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post #3 of 15 (permalink) Old 02-19-2019, 10:31 AM Thread Starter
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I wonder if the error in your EV range was caused by the system learning too much from the grade and thus underestimating what you had left.

I'm beginning to think that on a long trip it may be best to use the HEV mode until in EV range of a charge. The little 1.6 needs electric help on a grade.

My last two charges have been 9.0 and 9.4 KWH's respectively. With 10% or so left, the battery has to be 10 KVA plus whatever overhead it allows at full charge to preserve battery life. If I drive around town, I always get 26 or more miles in pure EV. REALLY refreshing to see a company fairly representing performance figures.
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post #4 of 15 (permalink) Old 02-19-2019, 12:51 PM
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Quote:
Originally Posted by Mal View Post
I wonder if the error in your EV range was caused by the system learning too much from the grade and thus underestimating what you had left.

I'm beginning to think that on a long trip it may be best to use the HEV mode until in EV range of a charge. The little 1.6 needs electric help on a grade.

My last two charges have been 9.0 and 9.4 KWH's respectively. With 10% or so left, the battery has to be 10 KVA plus whatever overhead it allows at full charge to preserve battery life. If I drive around town, I always get 26 or more miles in pure EV. REALLY refreshing to see a company fairly representing performance figures.
Yes, the 60 hp electric motor really helps going up hills when in hev mode. The ICE is 1.6 but its only ~100 hp because it is an atchison cycle engine (more efficient but less power density). The same 1.6 engine running the Otto cycle puts out ~140 hp.

FWIW

The current ICE is 100hp and the motor is 60hp. I which they were reversed. ICE 60hp and motor 100hp. More hp when in ev mode but still enough ICE for long trips.

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Last edited by charlesH; 02-19-2019 at 12:55 PM.
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post #5 of 15 (permalink) Old 02-19-2019, 08:25 PM
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The current ICE is 100hp and the motor is 60hp. I which they were reversed. ICE 60hp and motor 100hp. More hp when in ev mode but still enough ICE for long trips.
That would be great!

@Mal : you went down to 2% ??

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post #6 of 15 (permalink) Old 02-19-2019, 09:03 PM Thread Starter
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Several times during the long climbs....
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post #7 of 15 (permalink) Old 02-19-2019, 11:07 PM
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Quote:
Originally Posted by Mal View Post
I wonder if the error in your EV range was caused by the system learning too much from the grade and thus underestimating what you had left.

I'm beginning to think that on a long trip it may be best to use the HEV mode until in EV range of a charge. The little 1.6 needs electric help on a grade.

My last two charges have been 9.0 and 9.4 KWH's respectively. With 10% or so left, the battery has to be 10 KVA plus whatever overhead it allows at full charge to preserve battery life. If I drive around town, I always get 26 or more miles in pure EV. REALLY refreshing to see a company fairly representing performance figures.

I really don't know what that was about. Maybe the ICE was running in generating mode after I switched back to EV mode at the top and I just didn't hear it. I just noticed that as I continued to drive at 70 MPH for many miles, the EV range didn't budge. I parked that night with an EV range around 4 miles. When I left the next day, it was around 6 miles if I recall correctly.


When I come back down that same route, I've been disappointed at how little EV range I pick up: only a couple of miles at best, while the car is in HEV mode. I did a different mountain drive at Christmas time over "the Grapevine" headed north from LA. The EV range dropped near the summit, but I kept it in HEV mode and unlike my Cajon pass trip which levels out at the top, the trip over the Grapevine is immediately followed by a steep descent. On that trip, I recouped most of my lost EV miles on the way back down, maybe even to the point of having a couple more than what I started with. Of course, I was in HEV mode the whole time so it's not like it was "free".


Regardless of the explanation for what reads on the EV range, I no longer use up my EV miles at the outset of a long trip. I use up a few so that the battery will have room to accept charge from regenerative braking, and then I switch to HEV mode. On the way home, when I get close to home, I switch to EV mode to use up any miles I have left in the EV range. And if I get stuck in stop-and-go traffic along the way, I switch to EV mode for that too. Having that surplus capacity along the way helps when you want a little more power, or have to struggle with stop and go traffic. And it's just as easy to use it up at the end of the trip as it is to use it up at the beginning - well, almost as easy: you do have to remember to manually flip the switch.
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post #8 of 15 (permalink) Old 02-20-2019, 07:55 AM Thread Starter
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I watch the energy flow for IC operation. At speed it is hard to tell if it's running and, if running, it seems to maximize energy by driving wheels, generator or both as needed. How I haven't figured out.

I think your methods are sound. No matter how good KIA's algorithms are, they can't read your mind. I will do the same.... EV if the trip is short, otherwise EV for some battery room then HEV until in EV range of a charge. I will be really interested in what the battery does in HEV mode starting at 80+% or so.

Meanwhile, gotta buy gas soon for the 4th time in a bit over 2000 miles.

Last edited by Mal; 02-20-2019 at 08:01 AM.
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post #9 of 15 (permalink) Old 02-21-2019, 10:16 PM
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interesting thread. i thought the ice would only fire up in ev mode with hard acceleration. in a previous post someone mentioned running the tank dry to see what the electric motor could do on itís own. anybody out there ever try this?
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post #10 of 15 (permalink) Old 02-22-2019, 09:09 AM
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When you run out of gas, it goes into a limp mode and limits your speed severely. Eventually when Kia thinks you will damage your battery, it will shut off.

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