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Old 03-05-2010, 11:52 PM   #11
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Re: MPG of diesel 4X4 van

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Well, there you have it. I'm guessing their lawyers forced them to insist it is insane to be inside of 150 ft. Could someone please tell me where in the continental United States you can maintain 150 feet without someone pulling in front of you?

My guess is that I was hanging in the 75-100 ft range. I think the key point (from a safety perspective) is being able to see the trucker's mirror so you are not in his "blind" spot (where you will apparently spontaneously combust from stupidity) and staying focused on the task at hand.

I'll spare you all the lecture on terrain clearance tasks and "the bucket". But, suffice it to say that if you can stay focused enough to hold steady at 75', you likely will have plenty of reaction time. If you find yourself drifting closer and farther away, it is due to some sort of distraction and it would probably be in your best interest to pull over until such time you can focus on driving...

Of course the real test will be when the family jumps in the van (one member in particular). Much like Jage's sexy "inclinometer", my sexy "your-driving-too-close-ometer" will start ringing in my right ear if I pop the safety "bubble".

Finally, although the fuel savings is nice, I'm guessing the saved wear and tear on the engine and drivetrain are where the really big gains are. AND I can say I'm doing my part to save the planet!
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Old 03-06-2010, 06:31 AM   #12
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Re: MPG of diesel 4X4 van

What's "the bucket"?
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Old 03-06-2010, 09:38 AM   #13
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Re: MPG of diesel 4X4 van

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What's "the bucket"?
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Old 03-06-2010, 10:15 AM   #14
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Re: MPG of diesel 4X4 van

Unless you are on a super flat Hwy you are going to use more fuel trying to keep the same distance from a big truck. When they are carrying a full load (any where from 40k to 52k) their speed will change constantly. There is another consideration to keep in mind and that is that most Semi Trailers use recap tires and they can end your trip in a heart beat. I owned a small trucking company many years ago and I will never put my life on the line to save a couple a miles a gallon at best.

Sorry about the rant Ive just seen really bad things from avoidable circumstances.




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Old 03-06-2010, 11:48 AM   #15
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Re: MPG of diesel 4X4 van

Ron,

It's a great rant! I am constantly re-evaluating my decisions. How far back would you say is enough? Right now I feel pretty comfortable at 100'.

From my 2,500 mile road test, it appears to be significant. 16 mpg on my own. 21 mpg 100' back.
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Old 03-06-2010, 12:08 PM   #16
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Re: MPG of diesel 4X4 van

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How far back would you say is enough? Right now I feel pretty comfortable at 100'.


Each situation is different. My van does not stop fast. But I also drive class A vehicles at work so I'm used to it. I don't worry about drafting for fuel savings. The best advise in a situation is to leave enough room for an escape route. It depends on what you're hauling (how heavy your rig is) and if you even have a place to go. You might want to hit a country road and try to do an emergency stop...get the feel of your rig. I had a guy pull out in front of me one time and I just barely missed him. After that I had the Brakeman upgrade done. I can't say that the short hard braking changed that much, but brake fade improved. When the guy pulled out in front of me, I was on a long downhill grade and by the time I was getting close I lost most of my stopping power and ended up off the road to miss his long ass trailer. Almost rolled. If I could have got to my gun I'd probably be in jail
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Old 03-06-2010, 02:38 PM   #17
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Re: MPG of diesel 4X4 van

Reposted from Jessenej with permission:

The bucket represents everything you are capable of doing while (in this case driving) without hitting something. Here's how the analogy works:

1st thing in the bucket (and last thing out) are all the tasks you need to accomplish to avoid hitting something. These are called clearance tasks. These tasks would include things like scanning the road ahead, looking before you turn, checking your mirrors before you change lanes, etc.

2nd in the bucket is the stuff that needs to get done or you won't make it to your destination. These are called critical tasks. These tasks would include things like checking your navigation, checking your fuel gauge, etc.

Last in the bucket are things you would like to get done, but at the moment will not affect whether or not you will make it where you are going. These are called non-critical tasks. Think of these things as stuff that will help raise your awareness of the world around you, but don't necessarily need to get done right now.

The relationship between critical and non-critical tasks can flow back and forth. For instance, when your gas tank is full, checking the gauge would be considered an non-critical task. However, eventually you need to check it or you will run out of gas. At the point where if you don't check it you will not have enough gas to make it to a gas station, it just became a critical task. Make sense?

Here's how you apply the concept: Let's say your goal is to "draft" at 75'. For argument's sake, let's say that gives you 2 seconds of reaction time to catch a change in the vehicle ahead of you. That is your cross-check time. You can look away for up to 2 seconds to check something else (say your fuel gauge). Then you need to get back to the vehicle ahead of your to catch and correct any deviations to your 75'.

Now, if you can do everything you need to do in 2 second intervals without dropping any critical or non-critical tasks that need to get done AND not get closer than 75' than you are at your "comfort level"

If however, today you're not quite on your game. Let's say it takes you longer than 2 seconds to scan other stuff and while looking away you find yourself drifting inside of 75'. Than your "bucket" runninth over. Critical or non-critical tasks have taken priority over clearance tasks. Otherwise, you would have seen the deviation and corrected to keep yourself outside of 75' before it happened. You need to back off until you can manage to ALWAYS keep yourself outside of 75'.
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Old 03-06-2010, 02:49 PM   #18
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Ok, I admit, I'm over-simplifying the various techniques I'm using. But, here's the deal, 2,500 miles with nothing to do put pay attention to my new van.

I started out doing what I always do, aim about 5-10 over the posted limit and go. First day was rural driving which gave me about 19 mpg. Then I started interstate driving and noticed it drop to about 16.

Worried it was due to the drag and weight of my new PH top, I slowed down to replicate the speeds I had been driving and it jumped back up.

So, I started paying close attention. I slowed down a bit (max of 65) when ony own. And started running with other vehicles where it made sense to do so. I've been getting over 20 mpg ever since (Tulsa, OK to Fresno).

Fuel savings is nice, but I'm thinking about getting the van to 500,000 miles and beyond. My take-away from the trip is that by backing off a bit when going it alone and running in a pack when the conditions seem to allow for it safely, I'm probably doing a lot to help myself reach the goal of getting to hundreds of thousands of miles. AND saving on both fuel AND costly repairs along the way.

Just thought I would pass it along if, like me, you had never given much thought to longevity vice simply time when going from A to B.

Oh, and I made it home to my wife, four kids, dog, and all the crazieness that comes with daily life. So now my rant is complete...
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Old 03-06-2010, 03:24 PM   #19
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Re: MPG of diesel 4X4 van

I believe proper maintainance has more to do with longevity than driving slower does. Speed extracts a cost, but primarily in fuel and nerves.

Trucks that always carry a load seem to last as long as others. While poor maintainance always shortens the life of a vehicle.

I won't argue that driving at full throttle will have no effect on engine life, but normal use won't shorten it either. The 6.0 is used by International in alot of trucks that constantly carry 25K# and more and still go 3-500,000 miles. So should ours.

If you want it to last, change oil regularly, use OEM filters, don't drive short trips, don't idle more than you have to, baby a cold engine, after a long hard pull let the engine cool before shutdown. I'm sure there are more, but that is a good start.

Mike
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Old 03-06-2010, 09:05 PM   #20
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Re: MPG of diesel 4X4 van

Quote:
Originally Posted by daveb
Quote:
Originally Posted by jessenej
How far back would you say is enough? Right now I feel pretty comfortable at 100'.


Quote:
Each situation is different. My van does not stop fast. But I also drive class A vehicles at work so I'm used to it. I don't worry about drafting for fuel savings. The best advise in a situation is to leave enough room for an escape route. It depends on what you're hauling (how heavy your rig is) and if you even have a place to go. You might want to hit a country road and try to do an emergency stop...get the feel of your rig. I had a guy pull out in front of me one time and I just barely missed him. After that I had the Brakeman upgrade done. I can't say that the short hard braking changed that much, but brake fade improved. When the guy pulled out in front of me, I was on a long downhill grade and by the time I was getting close I lost most of my stopping power and ended up off the road to miss his long ass trailer. Almost rolled. If I could have got to my gun I'd probably be in jail [/q uote]
Yep, none of our SMBs stop fast, and they have a relatively high COG. The words "draft" and "SMB" don't mix for me, regardless of the MPG improvement. Unexpected stuff happens and I want the biggest margin of error possible.
R
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