CVT in 2018 CRV - Fuel Economy, Hypermiling, EcoModding News and Forum

Joggernot · 09-08-2018, 07:05 AM

I just bought a new "economical" 2018 Honda CRV 1.5L turbo that has a continuously variable transmission. This doesn't do well for hypermiling.
1. The transmission doesn't allow the engine to go to fuel cutoff (9999 on Scangage II) except for about 1 second. Then the CVT matches the output and the engine again gets fuel.
2. The engine can't be shut off if the car is moving above 1 mph. Can't even coast into the driveway. I have a keyless entry system.
3. Eco mode does work for my lead-footed wife. Her mpg has improved to close to EPA estimate.
4. I am able to coast in neutral, so engine-on pulse-n-glide can be done.
5. The Active Cruise Control (ACC) is very nice in heavy traffic for keeping my following distance under control. It is good in Eco mode because it allows for +5 to -5 mph from the setpoint when traffic permits. In normal mode it only allows about +2 to -2 mph.
6. The instant mpg readout really does help us keep economy in mind while driving. This is the first time we've had this.

I'm still learning about the CVT. I hope to improve. If you have any "simple" driving tips that will work with the CVT, please let me know about them.

Ecky · 09-08-2018, 07:53 AM

A lot of the point of pulse and glide is removed with a sufficiently good CVT. With a manual or conventional auto, the engine is invariably at less than 100% load most of the time. By pulsing with 100% load, then shutting the engine off and gliding, you can maintain a roughly constant average speed while getting the benefits of 100% load. A CVT with a sufficiently tall final drive on the other hand can always keep the engine fully loaded, by microscopically adjusting RPM to get the correct power output, rather than throttling the engine.

The G1 Insight had a 5MT and a CVT option. The 5MT offered considerably better economy, but I speculate two major reasons for this:
1) The CVT did not have lean burn. Those who have swapped lean burn ECUs into their CVTs have seen significantly improved economy.
2) The Insight's CVT was a very early one, and did not have a wide enough gear ratio range, resulting in the engine running at lower than optimal load on the highway - the CVT's tallest ratio was only slightly taller than 4th gear in the 5MT. Most new CVTs have much wider ratio spreads than conventional autos or manuals.

The best way to drive with a CVT is to just let it do its thing. Accelerate gently, giving the engine no reason to rev up.

I think very highly of CVTs and their potential for great fuel economy. I had a rental CVT Corolla not long ago in which I was getting near 60mpg on the highway with door placard tire pressure... during winter. My reason for avoiding them is entirely do to my perception of their long-term reliability.

19bonestock88 · 09-08-2018, 08:32 AM

I agree with Ecky on this one, the CVTs are great for keeping low RPM (my Altima turned 2500 at 80mph), but they’re still flawed in that they’re usually programmed to hold back on hills, and don’t allow normal pulse and glide cycles, or even DFCO in some instances... however, for the average driver, a modern CVT is great for efficiency... I could usually beat the EPA rating for my Altima by 25-30% without any sort of heroic effort...

ProDigit · 09-08-2018, 10:16 AM

Cvts are for the city. They're not good for higher speeds, as they rob more power from the engine than an automatic transmission.
They're also not very flexible. You can manually operate them, but only like 5 or 6 gears. Not ten or twelve, or twenty. CVT has 'infinite' gear ratios, but you can't shift in them.

Manual is still the best for Hypermiling, and highway cruising, provided the final gear drive is well chosen (2-2.5k rpm at 80mph is unbeatable).
On my Subaru's CVT, when I put it in neutral, the engine automatically starts revving at 2-2.75k Rpm, and gas mileage is worse than coasting in gear.
It gets a meager 24MPGs, while my manual car gets 32.5. Both we're jamming the pedals to 100mph regularly.

cRiPpLe_rOoStEr · 09-08-2018, 09:01 PM

Quote:

Originally Posted by Ecky

The best way to drive with a CVT is to just let it do its thing. Accelerate gently, giving the engine no reason to rev up.

I have no first-hand experience with a CVT, but both my dad and my stepmother's eldest son told me the Nissan Sentra was set to preferably retain a constant RPM. Which maybe wouldn't be so easy without the electronic throttle pedals which become mainstream nowadays.

teoman · 09-09-2018, 04:58 PM

The cvt’s imitation of gears is a handicap (as far as it has been discussed in this forum).

I wonder now that electric cars are becoming more popular, they will try to imitate those and make them infinite gears again?

cRiPpLe_rOoStEr · 09-10-2018, 10:13 PM

Quote:

Originally Posted by teoman

I wonder now that electric cars are becoming more popular, they will try to imitate those and make them infinite gears again?

Just look at the Prius and other hybrids, which imitate a CVT. I have already wondered why they tend to not feature some gear emulator, even though it may seem quite obvious due to their purpose not being some spirited driving.

ProDigit · 09-11-2018, 05:08 AM

Quote:

Originally Posted by cRiPpLe_rOoStEr

Just look at the Prius and other hybrids, which imitate a CVT. I have already wondered why they tend to not feature some gear emulator, even though it may seem quite obvious due to their purpose not being some spirited driving.

Because a gear emulator, would totally defeat their purpose.
Cvts strength lies in:
Cheap,
Lightweight,
Simple,
And keeping the car in optimum balance of acceleration and MPG when needed.
Cheap cvts just read their gearing from the position of the accelerator pedal.
More expensive ones, count in load as well.
The most efficient CVT, keeps RPM static, when acceleration and load is static, even if the car is accelerating, and keeps it as low as possible when cruising.

A CVT using gear shifts defeats this purpose as it jumps to different RPM ranges, which is what you don't want power, or mpg wise.

Joggernot · 09-11-2018, 08:36 AM

I have learned how to accelerate. Press the accelerator down until I get 2000 rpm. It then will accelerate evenly up to 45 mph when I set the "active cruise control". It then drops rpm down to around 1500 rpm to cruise. I can't beat EPA so far; mostly town (not city) driving.

I am able to coast with engine on, but wonder if that will hurt the CVT. I now have the tires pumped to 48 psi (max sidewall is 51 psi). This made a 1-2 mpg improvement for the last tank. We'll see if it continues.

General impression is that the CVT is nice to drive, but takes some getting use to.

cRiPpLe_rOoStEr · 09-16-2018, 01:07 AM

Quote:

Originally Posted by ProDigit

The most efficient CVT, keeps RPM static, when acceleration and load is static, even if the car is accelerating, and keeps it as low as possible when cruising.

That's why my stepmother's eldest son didn't really wanted another car with a CVT. He claimed the car felt quite "lazy" because it kept RPM constant.