So I've been driving my 2007 Civic Hybrid for about a month now. After going through a bad tank of gas, I'm consistently getting between 38-45 MPG on highway travel. I'm wondering about how mileage plays out when you take into account the gas and battery power used in coasting vs cruise control.
It seems like I get better MPG when I coast up hill and bleed off a few MPH, and then pick up my speed on the down hill than I do using cruise control to keep my speed perfectly set all the time. Unfortunately, most highways in my area have long stretches of up-hill climbs, with few down-hills, so there is almost a constant use of the IMA assist. However, I also find that it is very difficult to meter the pressure on the gas pedal so that I am getting at least 1 bar of charge while maintaining my speed. Seemingly the cruise control is able to adjust the flow of fuel better than I can, so the batteries at least get 1 bar of charge when I am driving highway on a level surface. The 1 bar gained in using the cruise control isn't such a big deal, until I find that when I don't use cruise control, the batteries tend to do a re-calibration and for a while, I lose all IMA assistance which shoots my MPG to hell really quickly.(Like trying to enter the freeway with no IMA assistance at 4000 RPMs.)
So my question is, how do you balance battery re-charge while driving and is it unwise to use cruise control often?

 

Your comments raise several issues. I would avoid cruise control except for very level roads and light traffic. You are wise to let the speed drop as you climb any grade. A technique called "drive with load - DWL" has you hold a steady gas pedal position as you climb a hill. This should reduce the IMA boost and battery pack drain. Be sure to maximize the regen function on downgrades by lifting right off the gas. If you really need to slow down, try using the "S" position and notice how much more regen you get.

Another technique to practice is "gliding", meaning that you apply very light pressure to the gas pedal to eliminate both assist and regen. This can do wonders on level or slight downgrades. Just for practice, try using the metric fuel consumption setting where 1 bar means no gas is being used. The HCHII has a very sophisticated valve control system which closes all valves under these conditions to reduce engine drag and extend the car's momentum.

Driving these cars to their best advantage takes some practice but it's an interesting challenge and results can be noticed very quickly. It's really too bad that Honda doesn't do more to explain the methods many owners have "discovered" or learned from others on this site or over at CleanMPG.

Cheers,

Roger

 

How fast are you driving? I would think you would do better than 38-45mpg on the highway unless the trips are really short, or you're driving 75+mph.

Personally, I don't care fore the cruise control much since it tries so hard to maintain speed on the hills, and therefore costs you mpg. When I drive, I've gotten into the habit of frequenly letting up on the gas so that I'm using only enough to maintain speed. I've stopped worrying about the charge/assist because trying to make the car not assist wasn't working--especially with the TSB-058 software revision.

How often are you experiencing recalibrations? You think that cruise control diminishes the frequency of the recalibrations? I used to get them several times a week, but I've only had 1 in the last 4 months (huge improvement). Despite a few other annoyances with the TSB, I think it is the main reason why I don't have as many recalibrations.

The other thing that might have helped with recalibrations are that I use "S" for braking most of the time which only generates about 3/4 of the maximum regen. I have a theory that the battery control module thinks it's storing more juice at 100% regen than the batteries are actually capable of banking so with time the calculated SoC becomes different than the actual SoC--leading to a recalibration. I have no proof of this, but it seems to have helped in my case.

 

Thanks for the replies. You both are knowledgable it seems about your experiences with what I'm asking about. I'm a bit confused about a few points though.
Kristian, yes these are short highway trips. Less than 8 miles. And they are mostly through interchanges, bridges and above-ground on and exit ramps.

Braking with "S"? This sounds awefully dangerous on the CVT. You expect me to shift from Drive into S at 60 MPH when exiting from the highway?
I thought that in ANY car, shifting into low gear was only safe at slower speeds (30 MPH or less).

Seemingly here is what I noticed on today's re-cal! ARGH!

I have been operating at 40-50 MPG and 7 Bars of Battery charge for a week. It hasn't dipped below 7 Bars because I was being careful to maximize charges on braking, and trying not to use too much assist bars when accelerating. Then today, the car just decides to do a re-cal and tosses me down to 2 Bars of Battery Charge and hardly no assistance at all, using up gas. After driving at lunch and this evening, and the car getting some green-bar charge time with the re-cal, the car remembers the battery is actually charged and this time gives me 8 Bars of Battery Charge, once again affording me excellent mileage per gallon.
What the heck?
This is my 2nd re-cal in a week. I thought I was doing good to "baby" the charge and make sure I use assistance sparingly. Apparently, good hypermiling is being rewarded with punishing re-cals that are stealing my gas mileage.

Dream'R, you recommend driving with 1 Bar, are you referring to 1 Bar of Charging or 1 Bar of Assist? 1 Bar of Assist is nearly impossible for my foot to meter on the gas pedal. I'm just not that tactile.

To both of you, I've gotta road trip coming up in 1st week of march that should put some heavy miles on the car over a multi-hour higway trek. I guess I will find out how well I am doing by how well that trip goes. Maybe my minimal experience with these short 8 mile or so highway trips is clouding the MPG at it's best. The car is obviously spending some of that time with the engine warming up, everytime I get on the road. I also run my A/C at 69 Auto right now, since I thought that perhaps the batteries weren't getting cooled enough with the cabin temp set at 70. Any thoughts on that?

 

A couple of thoughts:

Shifting to S (for Sport?) just raises the rev's a bit, makes it more aggresive. I find it great for winding and hilly stretches. Not moderately windy/hilly, but very w/h, where you're contantly jumping from gas to brake, and back. You can bring your speed up quicker, and don't need to brake as much. The stretch of road that defines w/h for me is between Port Alberni and the west coast of Vancouver island. It was little more than a dirt logging road 40 years back, it's been paved since, and slightly straightened/levelled, but not by much.

BTW, the west coast of the island is a very interesting destination if you're ever in the neighbourhood

Regarding bars of charge, recalibration, etc: the operative word is recalibration, ie: the computer has lost track of state-of-charge and is re-assessing things. When it displays one bar, that doesn't necessarily mean your battery's near discharged, just that the computer is wiping the slate, starting a fresh calibration. If it's happening a lot, it might be a harbinger of ailing battery, but I would cross that bridge when it arrives.

 

When my SoC gets down to 4 bars and I know I'm not going to have a good opportunity to use the regenerative braking, I flip on my headlights. This induces a hidden regen until the battery is at 7 bars of charge. When the SoC is back up to 6 I flip them off.

I can't remember the last time I had a battery recal and this is coming from someone that used to experience them every other day.

Jess

 

I'll try that Jess. So it is not bad to try and keep SoC at 6 or 7 Bars? That won't cause a Re-cal after a while at those levels?

I noticed the batteries charge when idling, if you rev the engine up to 2500 RPMs. Is it stupid with a cold engine to warm it up by doing that for a few minutes before driving? Is it just wasting gas?
Should I pay whatever fees Honda charges to get the latest TSBs installed?
Also, as a completely unrelated quick question: Why is the Select Vehicle drop-down box on the greenhybrid Add A Tank form empty? I can't add a tank.

 

Um, yes. You're just wasting your gas and hurting your emissions systems. You're better off driving off as soon as you start the car.

If you're speaking of the Software Updates, you could "complain" of the symptoms the updates are for and see if they will do it under good will. My dealer was able to do it under the "powertrain warranty" which is good for 60k miles.

Forget the mileage database here. It used to work and now it doesn't. You can track your mileage better at cleanmpg.com or fuelly.com.

Jess

 

A couple of things to remember about the hchII, it is a cvt, there are no "gears" per-se, so you are not downshifting to a lower gear, the S, as someone else mentioned is sport mode, it reves the engine higher, and disables the auto stop...makes the car peppier but burns gas...conversly, because it revs the engine produces a lot more regen, who knows, maybe Honda figured if you are driving in S, you will need more regen.

I seldom have regens, maybe 3-4 a year, I drive consertivaly keeping my rpm at 2,000 or less unless there is a need...I never see the "rubber band" effect that so many car reviewers complain about with the cvt. I try to keep my battery between 4-6 bars, the reason is, above 6 and the car goes assist happy, under 4 and well, it is a bit sluggish :-)...running your a/c at 69, no really? the batterys are happy at about the same temps as people so low 70-80...if you are using 69 to cool the car off quickly, that isn't going to happen....try setting it for about 10-15 below the outside temp, once that is reached, decrease it 3 or 4 degrees at time....I think you will see better results.

 

For a CVT, that's fine. I've done "S" as high as 80mph and "L" as high as 65mph without any problems--it's not like a traditional automatic where "2" refers to a fixed ratio second gear, and risk over-reving your engine.

I used to get recals a lot (2x weekly average, daily in the summer). After the dealer upgraded the software to TSB-058, I have only had a few recals--maybe 5 in the last 6-7 months. I would say that it was successful based on my experience, but there were a few annoyances with the upgrade too. My CVT feels like it's on valium now. If I come to a dead stop on a hill, I really need to goose it to get the revs up. I can't say if the mileage is better before or after though since I had the upgrade done shortly after buying a new house (my new commute is a lot worse mpg-wise than my old one since it's only 5 miles).

The assist affinity has also increased measurablely when the SoC is 4 bars or above and decreased affinity below 4 bars. It seems like my car is ALWAYS assisting 1-2 bars now, and usually it would be better from an mpg standpoint if it only used assist on the larger hills. I've given up trying to reduce the assist though, and just let it do whatever it wants to. Again, it's hard to say how this has impacted my mileage because the overall mileage has gone down vs. a year ago due to the new commute.

Your road trip will be a good chance to get your mpgs up a little. Don't forget to check your tire pressure before you start. If you're comfortable, 73 degrees of A/C should be plenty to keep the battery cool, and make sure to drive around with the windows open at first to let the hot air out.