CVT's (non-hybrid) = fewer opportunities for fuel-cut mode (DFCO) when coasting?

[cRiPpLe_rOoStEr]

Originally Posted by Ecky

Longevity could be the motivation behind this.

Since it tends to keep the engine at a steady RPM more often, it seems to be an improvement on that matter.

[MetroMPG]

This is all good info - thanks for the CVT anecdotes.


Versa: your car uses the same JATCO CVT-7 transmission as in the Mirage I drove. Though it could be programmed differently for different applications (1.6L 109 HP vs 1.2L 78 hp).


Considering pretty much the only reason for building CVT's is improved fuel economy, it sure is odd that they don't do DFCO as much as other transmission types.

I wonder if it's partly because there aren't enough DFCO opportunities built into the various fuel economy test "routes" (driving patterns).


Rooster: your experience of seeing "boosted" RPM when going downhill is interesting. Do you mean RPM goes up higher than you'd see for example with a fixed gear connection to the wheels (like a manual) as speed increases?

[roosterk0031]

Yes RPM's go way higher than would on level ground. It's normally just under 2,000 rpm at 55-60. I probably wasn't going over 70 mph down hill but reving a whole lot more, I'd crank up the AC to create more engine braking/load.

The in town spot it does it every time, I'm rolling along at 20-25 mph, it's basically idling, it will go up to 13-500 rpm to keep from picking up speed.

The Navigation does know the speed limit most of the time but I don't think it uses it to control the engine braking. I think it just sense of increase of speed with no throttle input and decides you don't want to pick up speed.

Not sure if it will do it when Cruise control is enabled (95% of time), it blinks a little warning light when exceeding the set point but don't think it's ever slowed it down. You can set a warning set point at 5 or what ever MPH above speed limit in the Nav so I don't know if it's using that same limit for that alarm. It's on the dash not the Nav screen. I turned the audio alarm in the Nav on once at 5 over, wife let me know after her first drive to turn it off.

[MetroMPG]

I think it just sense of increase of speed with no throttle input and decides you don't want to pick up speed.

Odd. That's anti-eco! CVT's are weird.

[MeteorGray]

That is weird.

Are there statistics showing how much better fuel economy a CVT achieves than a standard automatic?

When I bought my Mazda in 2015 I remember reading that they chose to stick with a conventional automatic design instead of a CVT for a couple of reasons, but I don't remember if fuel economy was in there.

[RedDevil]

FWIW, my Insight surely does DFCO on deceleration. It will even mildly regenerate, more so at higher speed. (it will regenerate harder if I press the brake pedal)
It will stay in DFCO if I feather the throttle to neutralize regeneration and prolong the 'glide'.
Regeneration aside, I see no reason why DFCO would not function in non-hybrid CVTs?

Unless you're running AC. That may keep the juice flowing even when decelerating.
The less I use the ventilation system and other power consumers, the better it DFCOs.

[MetroMPG]

Originally Posted by MeteorGray

Are there statistics showing how much better fuel economy a CVT achieves than a standard automatic?

Oh yeah, it's a big difference over an older slushbox design.

Here's a telling apples-to-apples comparison that 2016 Versa will appreciate:

For a couple of years, Nissan took the unusual step of offering 3 different transmission choices in the Versa sedan, all with the same HR16DE 109 hp 1.6L engine & as in the Versa Note hatchback:

EG. for 2013...

• 4-speed automatic (w/lock-up torque converter) = 26 city / 35 hwy / 30 combined
• 5-speed manual = 27 city / 35 hwy / 30 combined
• CVT = 31 city / 40 hwy / 35 combined

https://fueleconomy.gov/feg/bymodel/...an_Versa.shtml


(Of course, ecodriving the 5-speed, you would still match or beat the CVT numbers in the same real world conditions. No pulse & glide shenannigans required: just upshifting to the highest gear as soon as practical, and with smart use of neutral coasting and DFCO.)

[roosterk0031]

I haven't driven the Elantra (6 spd auto) a lot, I drove it 2 days to work just to see how it compares to the Cobalt. Running with Cruise on, it would down shift going down hills to avoid over running the cruise set point. 49 mpg calculated, 53.7 indicated on a short tank.

On the 15 Rogue the Eco button is normally pushed, seems to only deaden throttle input though.

[2016 Versa]

The Versa on downhill coasts also increases the RPM's by several hundred but in just over 1 year of driving the car with and without a/c use and on some pretty long steep hills I've never seen the Ultra Gauge indicate DFCO. There's pretty significant engine braking, just the opposite of what I want it to do. I read somewhere that there was a way to go into the ECU and make adjustments to the amount of engine braking. There were 3 different settings but only 1 was recommended by Nissan. I suspect maybe one either has minimal engine braking or none at all, one has moderate engine braking and one is probably like they have it set from the factory. I'd thought about trying to find someone who could go into the ECU and make the changes but again with the problems Nissan has had with their CVT's I decided maybe that wasn't the best choice.

Metro MPG-My '16 Versa has an EPA rating of 31 city, 39 highway, and 34 combined. I don't remember the automatic and standard transmission numbers but, I do remember the CVT has the best ratings. As you can see from my fuel log I can easily beat the highway EPA rating with probably somewhere between 80-90% of my driving being on rural 2 and 4 lane roads with speeds in the 45-55 MPH range. If all my driving were city I'm not even sure I could maintain the 31 MPG rating. According to the Ultra Gauge this car doesn't care for extremely low speeds. It seems that right around 45 MPH may be the sweet spot. Since I'm usually in no hurry to get to my destination a large portion of my driving on secondary roads is around 45 MPH and on the better roads 50 MPH. With the c/c set at 50 MPH on flat sections of the highway even this time of year when the temps are cooler I can sometimes maintain MPG numbers in 60-70 MPG range for up to a mile or more.

[cRiPpLe_rOoStEr]

Sure the usually wider gear-spread on a CVT compared to a more traditional AT or MT might also be accountable for the MPG improvements.