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Old 05-18-2008, 08:02 PM   #57
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Quote:
Originally Posted by richinny
two different vehicles, two different drivers @ 45 mph, they need to go back to school.
I've run this experiment a couple of times that I can recall. Not scientifically, but enough to satisfy myself as to what was essentially going on.

Best: No A/C, windows closed
#2: No A/C, windows open
#3: windows closed, A/C on

Then I looked it up and found numbers ranging from 7-20 hp going to the compressor. If we use the old formula of 0.43 lb/hr/hp for gasoline engine fuel efficiency, we could calculate a theoretical fuel economy hit of the AC at any given speed.
I'm not going to. At least not until I get really bored.

For a small, aerodynamically clean car, say in the .33 cd range, I could envision the windows having a pretty big impact. But for a brick towing a bigger brick? With big honkin mirrors? Not so sure.

One thing for sure, the two rightmost pedals have a LOT to do with it. Everytime you brake, you're turning gasoline into heat. And careful accelerations make a big difference too.
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Old 05-18-2008, 08:47 PM   #58
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Quote:
Originally Posted by RedSHED
I've run this experiment a couple of times that I can recall. Not scientifically, but enough to satisfy myself as to what was essentially going on.

Best: No A/C, windows closed
#2: No A/C, windows open
#3: windows closed, A/C on

Then I looked it up and found numbers ranging from 7-20 hp going to the compressor. If we use the old formula of 0.43 lb/hr/hp for gasoline engine fuel efficiency, we could calculate a theoretical fuel economy hit of the AC at any given speed.
I'm not going to. At least not until I get really bored.

For a small, aerodynamically clean car, say in the .33 cd range, I could envision the windows having a pretty big impact. But for a brick towing a bigger brick? With big honkin mirrors? Not so sure.

One thing for sure, the two rightmost pedals have a LOT to do with it. Everytime you brake, you're turning gasoline into heat. And careful accelerations make a big difference too.
thank you sir,you made my day.seriously however ,aint too many gonna roll down the windows......that includes me too.old school stuff still works.airstreams still roll and are inherintly fuel efficient.maybe we all can't turn off the ac and roll down the windows but pulling a streamer still gives us a leg up on the sob's.go slow,that's cool too.slowwwwww rideeeeee take it easy.
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Old 05-18-2008, 09:13 PM   #59
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You Are On A 70mph Interstate Running 55,you May Be Saving A Little Gas,but You Are A Traffic Hazard To The Other People Out There.the Semitrailers Are Paid By The Mile,they Come Up On You And Must Slow Or Switch Lanes,When They Are Boxed Behind You , Then Finally Get Out In Traffic ,then Everyone Is Braking ,Seen A Few Rear Enders Caused By Slow Movers,and The Slow Movers Goes On Down The Road Like Nothing Happened. If You Insist On Running 55 To Save A Few Bucks,please Do It On A State Rd.or Save It 6 Lane Interstates.I`ve Had Too Many Close Calls Caused By Slow Movers
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Old 05-18-2008, 10:43 PM   #60
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Quote:
Originally Posted by easyride
You Are On A 70mph Interstate Running 55,you May Be Saving A Little Gas,but You Are A Traffic Hazard To The Other People Out There.the Semitrailers Are Paid By The Mile,they Come Up On You And Must Slow Or Switch Lanes,When They Are Boxed Behind You , Then Finally Get Out In Traffic ,then Everyone Is Braking ,Seen A Few Rear Enders Caused By Slow Movers,and The Slow Movers Goes On Down The Road Like Nothing Happened. If You Insist On Running 55 To Save A Few Bucks,please Do It On A State Rd.or Save It 6 Lane Interstates.I`ve Had Too Many Close Calls Caused By Slow Movers
Dave
you are absoluley correct about slow drivers on the interstate.when i hook up i travel secondary roads with speed limits between 45-55.the pace is slower,the scenery more pleasing.after all ,i am on a pleasure trip.lower fuel consumption happens to be a by-product,a plus if you will of my particular driving habits.also at these speeds on a nice day,rolling down the windows and turning off the ac is quite likely.planning ahead,checking the weather forecast to do exactly that.no ac on,less fuel useage again.i'm not running a marathon ,don't get paid by the mile nor do i need to. so i enjoy the ride and use less in the prosess.now doesn't that sound appealing? i can think of a few secondary roads that run clear north from florida to upstate ny.
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Old 05-19-2008, 06:05 AM   #61
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The pro's know.

Schneider reduces speed governors to 60 mph. Story here.

And they aren't alone. Con-way's gone to 62.
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Old 05-19-2008, 09:22 AM   #62
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It's all about gallons-per-hour and reducing required stops in my book.

70mph seventy miles at 10mpg = 7 gallons x $3.65 is $25.55 per hour...

55mph seventy miles at 14mpg = 5.2 gallons x $3.65 is $18.25 per hour...

$7.30 an hour is a humble payback; increasing a tank of fuels range by 30% and keeping my exposure at fueling stops to a minimum is worth a lot too.

What I will do is try and keep off your roads at peak travel times... And happily lead or follow a string of vehicles doing the same!
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Old 05-19-2008, 11:30 AM   #63
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you meet the nicest people in an airstream,or so the ad goes.if you choose to drive 70mph and cost ,responsibility or risk do not factor in your mind please let others who care be privy to your location.i like meeting those nice people,but i may never get that chance if i'm in your realm of highway or state of mind.the topic is fuel savings,but thank you for injecting your thoughts on traffic flow.
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Old 05-19-2008, 09:26 PM   #64
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Quote:
Originally Posted by easyride
I`ve Had Too Many Close Calls Caused By Slow Movers
One must assume that around any curve, over any hill, etc, that there may be a vehicle stopped dead in the road. People dazed and injured. On this problem I have happened twice, and it was scary bringing 78,000-lbs to a full, fast stop. But I was already below my governed speed of 68 mph and anticipating such a problem.

There is always someone out there moving slowly on the Interstate, for whatever reason they deem appropriate. So long as they are within the posted limits, then they have the same rights as all others. There is NO obligation to "get out of the way" "go with the flow" or other inane rationalizations people come up with (unless the overtaking vehicle is an official police or emergency vehicle to whom all traffic must yield).

For the non-Interstate highways, in most states, one is required to move out of the way of traffic when it is safe to do so. I have only rarely encountered drivers who lacked the courtesy, when driving slowly, to stay out of the way on such roads. And, so what?

I agree that 55 is slower than I like, thus I choose 62-63 as it gives me a good blend of fuel mileage & perceived speed (not just actual) . . BUT I can drop a gear and just touch the brakes and I am below 50 mph at which I have verified is a speed where I can do double lane changes all day with my rig.

I have no idea what problems the other (slower) driver is dealing with, it may be a cluster of minor problems or a serious one. I do know that we share the road, and that speeding drivers (too fast for conditions) are the drivers most likely to be the cause of an accident.

"Close calls" are not caused by slow-movers, they are, as above, caused by those traveling too fast for their ability, their skill and the common sense rules we are all to abide by.
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Old 05-22-2008, 08:59 AM   #65
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Thought I'd add another observation to this discussion: transmission slip. I suspect that most of us have automatic transmissions that complicate the fuel economy equation. On my recent trip to northern Michigan I noticed a bit of change in tachometer RPM at a constant road speed in high gear. It seems that the transmission "unlocks" when more power is required as in going uphill. This tendency is more common at 50 than 60 mph with my current setup: 86 25 foot A/S (6100 lbs loaded) & 2003 Chevy K2500HD with 6.6 diesel. (It is also my impression that the older 75 Trade Wind was much lighter - but I never put it on the scale - and this "problem" was not as noticeable.)

My next trip I'm going to try and run a little faster and see how it effects fuel consumption. That is, if traffic conditions permit. On busy highways I prefer to get behind a truck in the right lane and stay there - a good safe distance back. It makes driving easy and everyone can see the truck and pass him at the same time.

Whit Nash
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Old 05-22-2008, 10:32 PM   #66
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[quote=rwnash] On my recent trip to northern Michigan I noticed a bit of change in tachometer RPM at a constant road speed in high gear. It seems that the transmission "unlocks" when more power is required as in going uphill. This tendency is more common at 50 than 60 mph with my current setup: 86 25 foot A/S (6100 lbs loaded) & 2003 Chevy K2500HD with 6.6 diesel.

Hi, rwnash. I can't speak for newer Chevrolets, but Fords will unlock the torque converter when ever you back off of the throttle; This will momentarily raise the RPMs about 500 and slowly return to the locked converter mode.
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Old 05-22-2008, 10:54 PM   #67
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Better MPG's

Dug this back up per a request on this tool. This is a high horsepower modified truck (poor mileage compared to mine). Much of the info quoted is from CUMMINS in re Class 8 trucks, but this man has revised it nicely for our little 'uns.

Diesel men, note the graph at bottom on EGT versus fuel consumption.
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Old 05-23-2008, 06:57 PM   #68
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Yesterday driving north through the Colorado high plains I found the best natural MPG improvement. 60mph cruise and a 35mph tail wind. 180 miles and the MPG-O-Meter showed almost 20 (calculated was 17.4)
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