In answering another thread, I got to thinking. We HAHers have another unique twist to the vehicle. We're the only (I think?) ones with a standard automatic transmission.

We don't get the infinite optimization of a CVT, nor can we ride 5th gear down real low for cruising at any speed.

With that, I've noticed that 5th gear is selected around 43mph, and the torque converter locks up at 48ish. It seems to stay locked on the way down until ~45. Soooo- the most efficient point for 'normal' operation should be right there, at the lockup point, about 48mph or 1500rpm. Seems that should be true for any AT, and is true for the analagous conditions in CVTs and MTs as well. Nice spot for the engine itself too, from a loading condition and thermodynamically.

Has anyone driven a substantial distance at 45-50mph and recall their mpg? Most of my driving is at 60-65, so not much experience to fall back on here.

Perhaps it would be enlightening and a wakeup to the consumer if 'nominal' efficiency vs speed curves were pasted on the window next to EPA in the showroom.

GoNavy,
Some anecdotal evidence: a couple of 30 mile stretches in construction zones early in my HAH mileage supports your 45-50 miles per hour sweet spot hypothesis for the HAH; I saw an incredible (at the time) 48 mpg over 30 miles of the 45 miles per hour limited zone (some tailwind, also, as I recall). I might lower your sweet spot to that 42-3 miles per hour 5th gear shift zone when the rpm drops noticeably but will still run the car on even some moderate rolling hills in the 40-45 miles per hour range. I have a couple of steeper hills on my commute, and I've experimented with pedal pressure to call IMA assist up the hill, vs. driving to load, trying to keep ECO on, slowing down to 40 miles per hour, but trying to avoid a downshift. Tho I don't have Navi, I've zeroed trip B on these hill tries, and I see better FE from squeezing the 42-48 miles per hour window rather than using faster speeds and/or IMA assist.
Lewis

Hi GoNavy:

___Same experience … As long as you can maintain a locked OD w/ ECO at 42 - 50 miles per hour with just the basics of DWL and DWB in heavy traffic, you are good for 50 + just driving! I saw this in Chicago’s relatively heavy and congested traffic earlier this year in G&B’s over a week I had his. Add in a few more tricks and the AH is good for a daily 55 mpg in my experience. I was running 56 #’s in the Michelin’s but other then that, it was almost brand new and still on its break in oil. A distance-draft at 60 + was good for the same.

___I was a bit disappointed with the AH when performing FAS’s that did not finish below 10 miles per hour before start-up and tranny re-engagement. His Auto would re-engage smoothly but OD was disabled about 75% of the time afterwards unless I took her all the way down. Going to < 10 miles per hour after a long FAS was not always available in heavy traffic as it would lighten up with a re-acceleration needed at the most inopportune times

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

thanks. I'll have to check out the sweet spot one night when I'm not tired, in a hurry, or stuck in traffic.

Wayne,

OD = overdrive?
DWL = driving with load?
DWB = ???
FAS = ???

Hi Weyus:

___Sorry …

DWL: “Driving w/ Load”, yep.
DWB: “Driving w/out Brakes”
FAS: “Forced Autostop”
OD: “Overdrive”, yep too

___GoNavy, you must learn to stay away from her “go” pedal

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

Driving with load means that you drive with weight? Why does that help?

How does driving without brakes help?

What's a forced autostop?

If there's any more jargon, we're gonna need a glossary.

Hi Weyus:

___DWL is driving at a given load on the ICE, not to a given miles per hour or speed.

___DWB is for heavy city congestion for the most part. Imagine you were in a bumper to bumper crawling nightmare. 0 to 10 to 5 to 20 to 5 to 30 to 10 to 50 to 10 … How would your driving technique instantly change if you did not have any brakes? How would anyone’s technique change in that condition without brakes? Now you get the picture

___FAS … Just look it up in the link below.

___There is a glossary! The direct link below is a great help for the new hybrid pilots. You can click on the direct link from the upper left hand side of this Forums page - labeled “Glossary”.

GH’s Glossary

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

So does driving with a given load on the ICE mean "maintaining a constant speed"?

Also, to the original point of this post, I just lifted this from a Houston Chronicle article on 22 Aug.

"When calculating a car's fuel economy, the EPA keeps the air conditioning turned off, the radio silent, and assumes it's traveling 48 miles per hour on the highway."

Apparently 48 is the magic number!

Hi Weyus:

___DWL - real quick … Imagine driving up to an overpass on the highway. Most just leave their cruise on, the ICE revs up a bit, they climb at absolutely terrible mileage, they crest, the ICE RPM drops off, they descend, possibly receive some ICE braking at very high FE, arrive at the backside of the overpass at the same speed they began … You can only receive a maximum 2X the climb rate over a given equal distance so your FE is screwed even with a full blown FAS on the downhill side! DWL on the other hand over the same overpass works as follows: Let the automobile climb bleeding off some speed while trying to keep the instantaneous exactly where it was before the climb. Maintain the lower speed at the crest while still maintaining the instantaneous as steady as possible. On the backside, you slowly accelerate back down the descent to your initial target speed before you hit the overpass in the first place all the while still maintaining the instantaneous where it was initially. Just like a roller coaster. You gave away some kinetic for potential on the ascent and you received the kinetic back giving away the potential on the descent while on your way back to the initial target speed. You lost maybe 10 seconds depending on how high the overpass was but more importantly, you received slightly higher FE through the transition

___If you do not have a game gauge in your other automobiles, you can semi-simulate the technique by locking the accelerator pedal to a particular angle and leave it there while climbing, cresting, and descending. I alter this a bit in the non-game gauged equipped automobiles knowing what an instantaneous would ~ act like. Hopefully you have an idea as to how this works with the above. Some have equated the technique to “Coasting up hill” if that helps you. Now its time to practice, practice, and practice some more …

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net