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

[CVTCivic]

Here you can watch how relatively low the RPMs are with a CVT of the 1,5 liter Civic at different velocities.
Still I think the RPMs would be slightly lower with a manual transmission in the same car:

https://youtu.be/F1dXjiuT6JM

[MeteorGray]

Thanks for that video. The Civic was achieving 88KPH at about 1500RPM and those proportions were roughly the same at other speeds but with some variation.

This about what I see with my Mazda3 automatic: 55MPH (88KPH) at 1530RPM.

However, the Forester cited above was making 100KPH at 1200RPM, which is amazing to me.

[alcom]

Originally Posted by MeteorGray

Wow: 100KPH / 62MPH at 1200RPM is amazing for a gasoline engine.

That's in heavy diesel truck territory.

Correction: 1,800-2,000 RPM at 100 KPH -- I was in a hurry and had 60 KPH on my mind when I wrote that.

The Forester's CVT seems to always have the engine in the 50-80 percent LOD range, and you can get 99 percent LOD at 30 percent throttle. I accelerate at 17-20 percent throttle and that usually gives 60-70 percent LOD.

What's interesting is that LPH does not vary between D or N when stopped. Turning the AC on will increase it 30-40 percent at idle.

I installed Subaru rain guards on all the doors and keep the windows cracked 1-2 cm on the highway. This gives ample air flow through the cabin with zero buffeting or wind noise. I only use the AC when the humidex is impossible.

[MeteorGray]

OK alcom, thanks for that.

Darn, I was hoping the Forester's CVT enabled the lower RPMs as earlier reported. I have always been a fan of slow-turning engines to reduce internal friction and increase longevity and efficiency, but I guess it was too much.

Oh well, c'est la vie.

[alcom]

Originally Posted by MeteorGray

OK alcom, thanks for that.

Darn, I was hoping the Forester's CVT enabled the lower RPMs as earlier reported. I have always been a fan of slow-turning engines to reduce internal friction and increase longevity and efficiency, but I guess it was too much.

Oh well, c'est la vie.

There's a sweet spot in LOD for maximum efficiency, and Subaru's CVT has its eye on that. The engine has variable valve timing, but 1,800 RPM is still near the bottom of the torque curve.

I've been limiting my highway speed to 90 KPH whenever possible. We used to do that in the 70's, and it's time to have a good, hard look at it again. No matter what your rig, your fuel efficiency goes up by 30 percent compared to 120 KPH.

[MeteorGray]

I agree with the speed limit reduction point!

However, the oil-production war currently going on between Saudi Arabia and Russia is sinking the price of oil and thus its products. This makes it more difficult to get the general public behind any idea of reducing speed llimits to reduce consumption.

Alas, my 50-year-old son-in-law showed me Saturday night his brand new 2020 Ford Mustang...a GP something-or-other. It features a 760HP V8 that makes 17 MPG on the highway. I attribute it to his mid-life crisis. I doubt he drives any slower in his new ride.

He showed me his new car not long after I was complimenting my Mazda3 on its highway mileage potential.

[alcom]

Originally Posted by MeteorGray

I agree with the speed limit reduction point!

However, the oil-production war currently going on between Saudi Arabia and Russia is sinking the price of oil and thus its products. This makes it more difficult to get the general public behind any idea of reducing speed llimits to reduce consumption.

Alas, my 50-year-old son-in-law showed me Saturday night his brand new 2020 Ford Mustang...a GP something-or-other. It features a 760HP V8 that makes 17 MPG on the highway. I attribute it to his mid-life crisis. I doubt he drives any slower in his new ride.

He showed me his new car not long after I was complimenting my Mazda3 on its highway mileage potential.

In two years of big city (Toronto) driving, the Forester has averaged 10.5 L/100KM or 22 MPG. On a long highway drive at 90 KPH I can consistently get 7.0 L/100KM or 33 MPG. That's from fuel and odometer records, using Fuelio for Android.

My ScanGauge II is so accurate, when I fill up the pump shows within 0.1 L of what the ScanGauge had predicted. When ScanGauge upgraded their circuit board a few years ago, they sent me the new board with install instructions for about $15. That's very good for customer loyalty. I have a custom gauge (ScanGauge gives you the code) for transmission temperature (TFT), so I can monitor the CVT temperature. I have BlueDriver for diagnostics, but nothing can replace the ScanGauge for everyday real-time feedback.

[MeteorGray]

I agree. The ScanGauge is a magnificent tool, and its management has a reputation for being very customer-oriented. I've been using a ScanGauge for a few years now, and it has paid for itself and then some by helping me achieve significantly better fuel economy.

I recently read that a competitor product with a larger and more modern-looking screen and readout was having problems, and some users report fading screens that could no longer be read. My old ScanGauge keeps right on working as good as ever.

[Tahoe_Hybrid]

Originally Posted by MeteorGray

Thanks for that video. The Civic was achieving 88KPH at about 1500RPM and those proportions were roughly the same at other speeds but with some variation.

This about what I see with my Mazda3 automatic: 55MPH (88KPH) at 1530RPM.

However, the Forester cited above was making 100KPH at 1200RPM, which is amazing to me.

1800RPM @ 85mph 136KPH V4 mode 4 speed auto

(technically it's a inline v4 since it's bank 1 only)

[alcom]

Originally Posted by alcom

Correction: 1,800-2,000 RPM at 100 KPH -- I was in a hurry and had 60 KPH on my mind when I wrote that.

I did a controlled run to map RPM against speed -- 100 kph on the expressway going out and 40 and 60 kph on city streets coming back -- light traffic, roads visibly flat no strong wind. Here's what I found.

Forester CTV -- 40 km x2 on cruise control
100 kph 1750-1800 rpm - expressway, going out
40 kph 1250-1350 rpm - city streets, coming back
60 kph 1250-1500 rpm - city streets, coming back

The bottom end for the CVT is just 500 rpm above idle. The wider variance at 60 kph is likely due to variations in road pitch. Engine torque curve is a factor. Even with variable valve timing, the sweet spot is likely 1500-2500 rpm. Maintaining momentum and keeping airspeed (i.e. resistance) down are at least as important as low rpm. The CVT will deliver lowest rpm for torque needs.