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R/T drive mode questions

11K views 8 replies 4 participants last post by  4regt4  
#1 ·
I've been studying the owner's manual - which I usually do pre-purchase on any car. The descriptions of the drive modes seem a little vague to me. So... questions:

1. Hybrid mode - I'm guessing that unless max power is needed, the gas engine stays off until the battery is depleted. Right? I realize that when more than the 120hp-ish electric motor output is required, the gas motor turns on. But, say, in normal city driving, does the gas motor ever come on?

2. Electric mode - I get the impression that the gas engine can be utilized if the throttle is pressed to WOT. Right? If so, it sounds like Electric mode isn't that much different than Hybrid mode. Both run on battery until the battery depleted. And the gas engine is fired up in either mode if full power is needed. Or what am I missing here?

3. Sport mode - Does this run the gas engine all the time? If the battery SOC is low, does it charge the battery from the gas engine up to some minimal level?

4. Any mode - Does the gas engine go through a brief warm up period before giving full output? I've always been taught not to give an engine "full beans" until sufficiently warm.

Thanks,

Hans.
 
#5 ·
I didn't mean to offend, it wasn't meant that way.

I've read the manual, and looked at some of the videos, but they don't answer a few questions. I was hoping to hear from someone who has experimented a bit with the modes and has info that goes beyond what is described from the "officially" available sources.

FWIW, I'm currently driving a Chevy Volt. From what I can tell, it appears that the Volt behaves much as the Hornet R/T does in "Electric mode" - all electric until the battery runs out. The Volt has a "Hold" mode, that keeps the battery at it's current level, running the gas motor as necessary to do so. This seems to parallel the Hornet "Esave Passive".

The Hybrid mode is not fully explained as to whether or not the gas motor is used in situations other than heavy throttle or battery depleted. And it doesn't mention whether or not the motor runs all the time in Sport mode. And motor warmup?

Hans.
 
#6 ·
Image


Unlike hybrid mode, which will use an "efficient" combination of the two power sources, electric mode will use the electric motor in any scenario except full throttle or high demand (towing, heating/cooling).

Take a look at this link and let me know if you have any more questions. I'm not especially familiar with the hybrid powertrain but I might be able to help you figure it out with what knowledge I do have.
 
#7 ·
Thanks. That does bring some clarity. It doesn't mention Sport mode, as that probably doesn't apply to the Jeep.

Do any of you know if the gas motor is always on in Sport mode? I took a brief test drive in an R/T that had the battery nearly depleted. Sport mode did turn on the gas motor, but I don't know if that behavior applies if the battery is at a higher SOC.

Hans.
 
#8 ·
Perhaps this will help. I agree that this is confusing as, um, 'hellcat', and I have been digging through all available material to get the answers. I'm a former Technical Writer, so I'm used to looking in weird places for information...

I am taking delivery -I think- today (car is with the dealer, for cable recall to be completed), and this information is in the 'Owner Support' info sent to me by my dealer:

<BEGIN QUOTE>

Hornet R/T offers drivers a choice of three driving modes with the push of a dedicated button on the steering wheel, to tailor the performance of the vehicle to suit their driving preference
Hybrid:
  • The default setting
  • Utilizes both power sources (gas engine and e-Motor) to deliver maximum performance and fuel efficiency
  • Electric use prioritized until a set minimum battery level reached
Electric:
  • Prioritizes all electric driving
  • 84 mph top speed
  • Over 30 miles of range
  • All electric, zero emissions
  • Automatically switches to Hybrid when battery is depleted or extra power requested by throttle kick-down
E-Save:
  • Prioritizes gas engine in order to maintain or recharge the high-voltage battery
  • Prioritizes gas engine to hold battery charge
  • Passive operation to maintain battery charge
  • Active operation to charge battery
<END QUOTE>
 
#9 · (Edited)
Follow up after a few weeks of ownership:

I drive the R/T mostly on short trips around town, but have done 3 trips each over 200 miles. One of those trips was on mostly flat 2 and 4 lane highways, the other 2 were on a very mountainous (6% grades common for much of the distance) freeway.

1. I was curious if the gas motor goes through any sort of warm up before having to deliver any significant power. Yes.. it does. I live on a very steep hill. Driving in Hybrid mode, the ICE turns on at the bottom of the hill. For perhaps 30 seconds, it sits on a fast idle - 1700rpm - regardless if I'm stationary or not. It does not appear to be delivering any actual power to the drivetrain while warming up, as the engine speed is constant. It also does this in eSave mode.

2. Hybrid mode - Because of my usage patterns, I haven't really experimented with Hybrid mode much. The ICE seems to have a mind of it's own, as sometimes it is helping when pulling away from an intersection, sometimes it leaves the electric motor to fend for itself under similar conditions. Certainly under heavier throttle, it will come on. I haven't driven in this mode until the battery is near depleted, so I don't know if it tries to leave some reserve that could be used in full Electric (quasi-eSave mode, I guess) or not.

3. Sport mode - I only tried this briefly on one of my mountainous trips. Didn't like it, as it basically parks the tach between 4000 and 5000 rpm, even at steady speed. If I manually upshifted, it would just downshift again. I can't see the point of turning the engine that fast if it's not needed. Perhaps it would be useful in "point and squirt" driving on twisty switch backs.

4. Electric mode - Pretty much what you would expect. Just runs off the battery. A couple of times I've seen it jump to Hybrid for what seems like no logical reason, but that was soon after taking delivery. It hasn't done that since. Be aware that the car is no power house in Electric mode. 0-25mph is decent, but 25-60mph is best described as very leisurely. There is a tach-like gauge that shows power usage level. You will peg that gauge easily and often in normal city traffic use. This may sound critical, but it's not really. The power level is very adequate for city driving, which is why I bought the thing in the first place. In situations where you will need more power, you are likely to be in Hybrid or eSave mode.

5. eSave mode - Interesting. There are 2 sub-modes, Battery Save and Battery Charge. Battery Save holds whatever charge level the battery is currently at until taken out of eSave. Battery Charge will bring a depleted battery up to a pre-set SOC. I've been using Battery Save a lot recently on my highway trips. Gas motors are least efficient in stop-go traffic, so I save some electricity for town use, and use gas on the open road. For example, I drive from my house to the freeway on Electric. Then switch to eSave until I arrive at my destination city, where I switch back to electric. That's how I also operated my Chevy Volt. A couple of times I had depleted the battery, so I used Battery Charge to bring the SOC up to a useful level for when I arrived back home. Note that it takes a considerable amount of time to charge the battery this way, even to just the 40% level.

What's interesting about eSave is the driving dynamics. When accelerating or climbing a hill (physics students among you will mention that those are the same thing....), the gas and electric motors share the load. Each will put out, say for example, 30-40% of their available power. So it's not gas motor maxed out with the electric helping, or vice versa. This sharing is quite seamless, it's not noticeable what's going on without looking at the gauges. Since hills will deplete the battery below the set eSave level, the car will slowly recharge while going downhill or on level ground. It all works quite well. This is in contrast to my Chevy Volt, which would max out the gas engine on hills before resorting to the electric motor for assist.

In eSave, the transmission will "hunt" on hills. Not uncommon, I think nearly every car I've had does this. Some worse than others. But the Hornet has the advantage of going full manual and shifting via the paddles. After observing at what speed the system prefers operating the engine at under different conditions while using cruise control, I have essentially set my own operating parameters. At highway speeds, I shoot for 2500rpm, which is 85mph in 6th (high) gear. Moderate hills get 2800-3300rpm (5th). Steep hills need in the high 3's (4th). And if there are trucks on the hills that I might need to maneuver around, I might hold it in the low 4000 range briefly. These engine speeds and gear selections mimic what the cruise control does under similar conditions, but without the up/down hunting that happens on hills. They might seem high for those of us coming from cars with bigger motors, but remember this is only a 1.3L boosted motor. 6% grades at highway speeds require quite a bit of power. Also, as previously mentioned, these engine speeds are lower than what the car does by itself in Sport mode.

Anyway, I'm still learning.

Hans.