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garygid
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Re: 100 miles?

Thu May 13, 2010 6:50 pm

Actually, being in the truck's dead zone (drafting), you IMPROVE his mpg.

But, watch out for the rocks, road debris, etc. that will crack your windshield, or worse. Here, our freeways, especially the "truck" lane(s) are often not in good repair.
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evnow
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Re: 100 miles?

Thu May 13, 2010 6:51 pm

LTLFTcomposite wrote:
soareyes wrote:Frequently I will tuck in behind a semi in the slow lane and go 55-60 mph when I need to get max range.


Doesn't doing that reduce the fuel economy of the truck, resulting in greater CO2 emissions into the atmosphere?


No - the slower you go, the better the mileage. See Tesla's graphs. The air resistence is proportionaly to the square (!) of the velocity.
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drees
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Re: 100 miles?

Fri May 14, 2010 11:26 am

garygid wrote:Actually, being in the truck's dead zone (drafting), you IMPROVE his mpg.

But, watch out for the rocks, road debris, etc. that will crack your windshield, or worse. Here, our freeways, especially the "truck" lane(s) are often not in good repair.

What Gary said here - if you've ever watched Nascar (not that I recommend it!) you'll notice that on high speed ovals when two cars draft closely they can go faster than one car alone.

The 2nd car fills in the low pressure zone behind the first car so there is less drag on the 1st car and the 1st car is pushing air around the 2nd car - end result - less drag on both vehicles and both can go faster.
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palmermd
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Re: 100 miles?

Fri May 14, 2010 11:32 am

soareyes wrote:
LTLFTcomposite wrote:
soareyes wrote:Frequently I will tuck in behind a semi in the slow lane and go 55-60 mph when I need to get max range.


Doesn't doing that reduce the fuel economy of the truck, resulting in greater CO2 emissions into the atmosphere?


No, the dead air zone behind the truck is there whether I'm taking advantage of it or not. I have no effect on his mpg.


Actually by filling in this area with your car you may actually be improving his mileage. Best case you can slightly improve his mileage, but usually it will have zero effect on it.

edit: whoops...I did not see that there were more responses on an additional page to the thread.
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LTLFTcomposite
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Re: 100 miles?

Fri May 14, 2010 11:40 am

garygid wrote:Actually, being in the truck's dead zone (drafting), you IMPROVE his mpg.

But, watch out for the rocks, road debris, etc. that will crack your windshield, or worse. Here, our freeways, especially the "truck" lane(s) are often not in good repair.


The other thing to watch out for is decapitation if the truck stops fast. All those air brakes can be surprisingly effective, and having your car sheared off at the belt line can be a real inconvenience.
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garygid
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Re: 100 miles?

Fri May 14, 2010 11:44 am

Yes, the closely-following vehicle (usually too close to do safely on the public highway) essentially streamlines the leading vehicle, by filling in the "suction" area that occurs behind most "solo" vehicles.

With a large truck, the "suction" zone is a lot bigger, but to take maximum advantage of it, one might still need to follow dangerously close.

When following the truck a bit further back, the truck can still provide some wind-braking benefit to the following car, but the truck is less likely to experience any significant benefit.
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Re: 100 miles?

Fri May 14, 2010 11:49 am

More than the drag effects - I think following a truck gives you "cover" for not going fast. Noone from behind will act funny / tailgate / harass you for going slow.
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palmermd
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Re: 100 miles?

Fri May 14, 2010 11:56 am

garygid wrote:Yes, the closely-following vehicle (usually too close to do safely on the public highway) essentially streamlines the leading vehicle, by filling in the "suction" area that occurs behind most "solo" vehicles.

With a large truck, the "suction" zone is a lot bigger, but to take maximum advantage of it, one might still need to follow dangerously close.

When following the truck a bit further back, the truck can still provide some wind-braking benefit to the following car, but the truck is less likely to experience any significant benefit.


Interestingly, using the mpg gauges in a Prius and Accord Hybrid and Civic Hybrid (assuming they are reasonably accurate), I've found that the long flatbed trailers provide a better increase to my mileage than the large box trailers, when following at about 1 second behind the truck which is close, but not too close. I was quite surprised by this result, and I have tried repeating this test several times in each of the cars, and it always seems to favor following an empty flatbed trailer.
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Re: 100 miles?

Fri May 14, 2010 12:21 pm

You know what would be really cool for long trips is more "auto trains". Load the car on to the train (which has charging capability of course) then kick back to the dulcet tones of Nick Rails in the lounge car while you knock back a few and watch the miles go by.
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Re: 100 miles?

Fri May 14, 2010 12:41 pm

As an ex-math major I understand the fascination with the numbers, much like sports fans do pre-season, analyzing all the stats. That's good fun, so go at it if you like, but like sports, I find it all irrelevant when the season starts. Some star gets injured. The top recruit isn't so good when he gets to tough competition. Weird things like weather and home field advantage, a coaching change, and dozens of unforeseeable things change the picture. In the EV world that means we just won't know until we get the car and use it in our everyday driving. I suspect that even the Tesla owners get a huge variety of range statistics depending on when, where, and how they drive, so even if we could map the Leaf accurately to some Tesla curve it wouldn't do us any good. As they say YMMV.

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