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MPGs with 2023 Hybrids

8160 Views 136 Replies 32 Participants Last post by  MartyV6
As I've gotten used to driving a hybrid, I've found it quite interesting how driving habits seem to impact fuel economy in ways I didn't initially expect. I likely will not change my driving style in the interest of maximizing fuel economy over time, but in the past week or two have paid a bit more attention to check if my 23 touring model is in the expected MPG range. So far it definitely is with my average in the 42-44 range with mixed city and highway miles. But with some caveats ...

If you truly push the car non-stop very aggressively, yes fuel economy suffers and you'll be lucky to be in the 30s especially if you're in a hilly area. No surprise there. But ... on the flip side if you drive the car very conservatively as if you were trying to conserve gas (as I would in any other traditional ICE), fuel economy also seems to suffer. That is, If I gently accelerate to desired speed with light pressure on the accelerator, the engine is on the entire time fueling either the battery or the drive motor, and the direct drive clutch is not engaged until you get to desired speed. Fuel economy suffers this entire time. However, if I accelerate more briskly to desired speed - whether it's 40, 50, 60, 70, whatever - then settle into that speed, the engine turns off and you're EV, or the direct drive clutch engages for higher MPGs. Maybe this is old news for hybrid owners, but I found it quite interesting. And I've found it very useful to use regenerative breaking to both charge the battery and save the brakes. In a few short weeks, driving a different car that doesn't have this feature is suddenly odd! I really like that feature. Regardless, it's been refreshing that in my limited experience more aggressive driving actually seems to yield better MPGs!

Curious if others have noticed this?
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Accelerating more rapidly to desired speed increased MPGs in my experience.
Time to pull out my old 10G plots. I know there are minor updates in 11G, but the basic ideas are the same. This is the efficiency map for my 2018 HAH engine:
Colorfulness Rectangle Slope Font Parallel

There is a lot going on here, so let me explain. Engine speed and torque should be self explanatory. Since RPM*TORQUE=POWER, we can determine the power being generated at any point here. Which is the more important number. It is labeled on the right side in horsepower, and follows the gray curves thru the plot. (Sorry for the mixed systems of measurement.)

The colors in the center indicate how much gas is used to make that power. The best is 208.1 grams for each kiloWatt-hour, which is 40.6% efficiency. It happens at 2000 RPM (or 54 mph in Engine Drive) and 34 HP. This is where we would like the engine to operate all the time. The blue line represents the best efficiency at each RPM value.

The disadvantage of gasoline cars is that, for the car to have enough power for acceleration, this "sweet spot" has to be in between the power needed to maintain speed on a flat road, and the power needed for acceleration. Cruising power is shown by the black dotted line, for the gear ratio we have in Engine Drive. A conventional car, with a shiftable transmission, would move that line right or left so that it crosses the blue line near the power requirement.

And that's the problem. To cruise at 45 mph, the black line says that our car needs a little under 10 HP. That crosses the blue line (the last blue dot on the left) at about 230 g/kWh, or 35% efficiency. In a gas-only car, this would be lower since the engine has to be bigger. It would operate at about 30% efficiency. I'll return to this number.

But in our hybrid, the system will move along the blue line to one of the purple dots, as indicated by the yellow arrow. The extra power generated will be used to charge the battery. This will be used later, either in EV Drive or to move back to the purple dots (from either the right-side blue dots of the higher yellow dots). That will also improve efficiency. The down-side, is that using the battery to save, and recover, this extra energy has maybe a 25% loss. So, while the power you use directly is 40% efficient, the power you use indirectly is 30% efficient. I've gone on too long, but the yellow dots do something similar in Engine Drive.

And this finally gets to your implies question. When accelerating, the absolute best thing to do is to accelerate at a rate where you are neither charging, or discharging, the battery. This way, you get it all at 40% efficiency, and none at 30%. I've never tried to watch that, but my guess is that you come close to it with what you describe. But it can only apply easily at the slower ranges of speed.

And yes use regen paddles if you care about efficiency - brakes do some regen but i believe less than paddles.Hope you see improvements!
They do the same thing. When you press the brake pedal, the computer uses what is called "blended braking." It will apply as much regen braking as is both possible and safe, then add friction braking. If you use just the paddles, the system relies on you to determine when to add the friction brakes. You can train yourself for how much room is needed to slow down most efficiently with the paddles; but once you master that, the pedals are just as efficient. (I really do feel like Dr. Seuss when I talks about pressing pedals vs. pulling paddles.)

It sounds to me like you're just doing the "pulse and glide" technique which will give you better fuel efficiency in a hybrid. It's not very good for people around you though as you're constantly speeding up to go over the speed limit, then coasting down under the speed limit, and repeating.
Pulse-and-glide is essentially doing the same thing as moving the dots around as I described above. The exception is that our hybrid, unllike some others, does not have to speed up and slow down to accomplish it.
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Good lord. That is quite the detailed explanation. Why does hybrid system do worse on highway than city driving?
The better question is "Why do non-hybrids do better on highway than city driving, when less power is needed to accelerate and overcome drag in the city?"

Two reasons:
  1. There is less stopping and starting on the highway.
  2. Highway cruising operates much closer to the "sett spot" than city cruising.
Since a hybrid takes advantage of both of these factors, it gains less on the highway than in the city. But it still gains in both. Comparing the 1.5L Turbo Accord to the base Hybrid:
  • City mileage improves from 29 mpg to 51 mpg.
  • Highway mileage improves form 37 mpg to 44 mpg.
Of course, if Honda hadn't mucked with the system to please the people who want to hear shifts, it would probably get 50 mpg on the highway. But I can't prove that.
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This explanation will use some words slightly differently than what is normal. I find it helps to understand the complete process.
  • Slowing is any process that forces a reduction in the car's speed.
    • Friction slowing uses the brake pads in the wheels.
    • Regen slowing uses the 181 HP electric motor as a generator.
    • There actually is a third kind, that applies only when the battery is full, called Engine slowing. It still uses the 181 HP motor as a generator, but that drives the generator as motor to spin the engine. This works just like engine braking in a conventional car going down long hills. I can't say about the Gen11, but in a Gen10 you have to have selected at least level 2 with the paddles to get it.
  • Coasting is when you let up on, or completely release, the accelerator pedal to activate slowing.
    • Coasting uses only regen slowing.
    • The regen paddles set the maximum amount of regen slowing, when you release the pedal.
    • You can moderate the amount, up to that level, with slight pressure on the accelerator. This is called "One Pedal Driving," and it does not use energy to counter-balance the slowing. It just regenerates less. You won't "waste fuel" unless you press so hard that you actually accelerate.
  • Braking is when you press the brake pedal to activate slowing.
    • Braking uses what is called "blended" slowing.
    • A computer will determine how much slowing you want, above what the paddles indicate, from the pressure on the brake pedal. It will apply as much regen as is possible, and then whatever mix of front- and back-wheel friction is safe to make up the difference.
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One question though....let's say I was coming down Pikes Peak and so in a normal car I would shift down to a low gear to avoid burning up the brakes and use engine braking to my advantage. Is that an application of the manual regen paddles here?
That is, indeed, one of the the best ways to use them. Think of each click as a downshift, with less jerking.

But they do have another positive use. While the paddles don't accomplish anything that the pedal (this is where I feel like I am quoting Dr. Seuss) can't, they do so more smoothly and with the certainty that all of your slowing is dome by regeneration. You can use them to train yourself for how to gradually approach a red light for maximum benefit.
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Yes, you need to fully empty the tank and fill up from scratch to know exactly the amount you are putting in to base your calculations from. If you don’t, you will never know the most accurate figure.
But how much pedantic accuracy do you think is needed?
  1. Fill the tank at your favorite pump, at your favorite gas station. Stop when the fuel pump stops. You now have P+ΔP0 gallons in your tank.
    1. P is the theorectical "fill" level when this pump shuts off.
    2. ΔP0 is the error in matching that theoretical level for this fillup.
  2. Drive for as many tanks as you want to keep track of. Except for the last tank, it does not matter where you fill up or how many miles you drive. Just keep a log of:
    1. The number of gallons in each fillup; G1, G2, G3, ..., Gn
    2. The number of miles driven between each; M1, M2, M3, ..., Mn.
  3. For the last tank - that is, the one where you put in Gn gallons, fill it at the same pump as the zeroth tank. And let the pump shut itself off the same way. You now have P+ΔPn gallons in your tank.
The number of gallons you have used is G1+G2+G3+...+Gn+ΔPn-ΔP0. This is an exact number; well, exact except for the fact that we don't know for sure what ΔPn and ΔP0 are. So let's over-estimate it: say each can be +/-0.5 gallons, so the difference cab be 1 gallon.

We can now estimate MPG, and the possible error:
  • MPG = (M1+M2+M3+ ... +Mn) / (G1+G2+G3+...+Gn)
  • Possible error is ±1/(G1+G2+G3+...+Gn)
So, in a 50 mpg hybrid if we average 10 gallons a fillup, the number of miles is 500n and the number of gallons is 10n. This means that the error is ±1/(10n). After one fillup, that's 0.1 mpg, which is really to low to be of concern. Unless you really want to be picky. After 10 fillups, it is 0.01 mpg.

Now this might take a bit of work. That is, unless you have an app.

Then again, why would you want to do that. You want to believe the higher skewed numbers which supports your narrative.
What makes you think it is "skewed higher" ?
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Wow! The Hybrid owners are now going in full tilt in their responses to support their beliefs. LOL! I’m impressed, but until we get a verified test from empty, it‘s all just conjecture.
And.... you obviously don't understand measurement error. That was not conjecture, that was how it is done. If you feel differently please tell us what was wrong with it.
Because you made an assertion of fact, but provided no reason to support it.

Since it is incorrect, I'm curious as to why you believe so strongly in it. And providing a reason why is what makes the "rational argument" you seem to say you can't get. Yet you are the only one who refuses to try.

No matter what I could say would change the beliefs of some Hybrid owners on here
And it seems that no matter what I say, it won't change your beliefs. I don't claim 0-60 in under 6 seconds, 55 mpg, or $10k batteries, based on my beliefs. But I don't doubt them based on belief, either. All I'm doubting is your claim of how the measurement of mpg needs to be done.
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