Removing Tailgate

[aerohead]

Originally Posted by JETZcorp

I know that what I'm seeing here is no very scientific, but given that my commute is 90% highway at least, and therefore more biased toward aero than weight, that leads me to believe that the noticeable improvement in range (and coast-down) is due to the aero, the weather, or likely a combination of both. I don't see weather adding this much on its own; it certainly didn't last summer.

But, obviously the Ecomodder community is very difficult to sway, and that's great! So I tell you what, when I get another tailgate (gotta have one for ice chests, chainsaws, etc) I'll do some actual ABA testing. If the ~2mpg gain that the gauge seems to be predicting is related to the tailgate, it should be pretty obvious in an ABA, considering how many percent that comes out to.

As for safety, my rear brakes would struggle to stop a tricycle, so I don't see the rears locking. And if they try, I have ABS back there, which has never been called on. The fronts, which don't have ABS, most decidedly have locked up before. Big smoke, very scary.

When Texas Tech did their pickup truck research back in 1988 the difference between tailgate up/down meant only a 1% change in drag on average,which would translate to only a 1/2% change in fuel economy,measured under extremely controlled conditions.
With all the variables of real world driving it would be very difficult to discern such a small difference given the signal-to-noise ratio.

[JETZcorp]

FE for that tank is in, and we scored 19.24mpg. This is a new full-tank record for the Dakota, and by about a full mpg. It's also about 1.5mpg over the record for a pure commuting tank.

Now, possible alternative explanations. The weather, as I was saying earlier, is getting really nice lately. In removing the tailgate, my ruined bumper and the sandbags went with it, shaving probably close to 200lbs. One of my tires is having issues with air, so it fluctuated between 45psi, and 8psi during the tank. Average was probably 30psi but the truck pulled noticeably to that side when it was on the lower end.

This tank did include a road trip into the desert (evening trip so it was cool). Without the pressure of having to get to work, I was able to hold more economical speeds (averaged 50 or so, commuting usually 55 or so). I burned a huge amount of gas going over Mt Hood, but coasted in Neutral coming back, so I don't know how that changes the average.

This was also a compound-tank (went to the gas station once to top off for the desert trip.). This shouldn't affect anything because I added both fills together to the third decimal before dividing by total miles.

My next tank will suck because I'm driving really inefficiently and that tire is getting worse. When I get me new tires on (same type and size as before) we'll get another tank. Oh, and I'm due for an oil change, if that matters.

[aerohead]

Originally Posted by JETZcorp

FE for that tank is in, and we scored 19.24mpg. This is a new full-tank record for the Dakota, and by about a full mpg. It's also about 1.5mpg over the record for a pure commuting tank.

Now, possible alternative explanations. The weather, as I was saying earlier, is getting really nice lately. In removing the tailgate, my ruined bumper and the sandbags went with it, shaving probably close to 200lbs. One of my tires is having issues with air, so it fluctuated between 45psi, and 8psi during the tank. Average was probably 30psi but the truck pulled noticeably to that side when it was on the lower end.

This tank did include a road trip into the desert (evening trip so it was cool). Without the pressure of having to get to work, I was able to hold more economical speeds (averaged 50 or so, commuting usually 55 or so). I burned a huge amount of gas going over Mt Hood, but coasted in Neutral coming back, so I don't know how that changes the average.

This was also a compound-tank (went to the gas station once to top off for the desert trip.). This shouldn't affect anything because I added both fills together to the third decimal before dividing by total miles.

My next tank will suck because I'm driving really inefficiently and that tire is getting worse. When I get me new tires on (same type and size as before) we'll get another tank. Oh, and I'm due for an oil change, if that matters.

Just thinking out loud.When you removed the weight,is it possible that the 'rake' of the truck was altered ie.the tail went up a bit,giving it a relative 'nose-down' stance?

[cRiPpLe_rOoStEr]

Originally Posted by aerohead

Just thinking out loud.When you removed the weight,is it possible that the 'rake' of the truck was altered ie.the tail went up a bit,giving it a relative 'nose-down' stance?

If this can be considered, the effect might be very low altough can be credited alongside the weight reduction and the resulting aerodynamic profile of the bed without the tailgate. Many small effects leading to a bigger result.

[JETZcorp]

The rake did change a bit, but the rear only went up by roughly one inch, if that.

The next tank is in (I've been neglecting my log, so pay no attention to that). MPG for this one was 17.89mpg. That puts in in third-best ever for a commuting tank. First place at 19.25 is the one above with commuting and a bit road trip, and second place was 18-point-something with commuting and a 30mi hypermiling run. With the tailgate and full weight in place, at one point I tried to get maximum economy on pure commuting and got about 17.2, although that was with noticeably worse weather. Given that this tank had a LOT of driving like an idiot, I'd say that's pretty okay. The tire continues to plague me, and at least 50mi of the 320mi tank were done with one tire at 10psi or less.

When I get the new tire on, I'll start a new tank and we'll see where that goes. So far, the Dakota has set two top-three-ever tanks with the current setup.

[wdb]

200 pounds is a lot of weight. Dropping 200 lbs. could yield 1MPG all by itself. And one inch difference in rake can be a lot of difference, as its effect varies exponentially with speed.

[Cd]

This thread looks like a good place to dump this image :



If you look below the image there are additional thumbnails that you can open.

Now why isn't the image showing up ??? I am seeing a little blue box with a question mark in it. Using Safari.

Here is a direct link to the image : http://www.autoblog.com/photos/2014-...#photo-5885423

[freebeard]

It looks OK

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    <div id="post_message_379761">This thread looks like a good place to dump this image : <br />
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<img src="http://www.autoblog.com/photos/2014-gmc-sierra-regular-cab/full/#photo-5885423" border="0" alt="" onload="NcodeImageResizer.createOn(this);" /><br />
<br />
If you look below the image there are additional thumbnails that you can open.<br />
<br />
Now why isn't the image showing up ??? I am seeing a little blue box with a question mark in it. Using Safari.<br />
<br />
Here is a direct link to the image : <a href="http://www.autoblog.com/photos/2014-gmc-sierra-regular-cab/full/#photo-5885423" target="_blank">http://www.autoblog.com/photos/2014-...#photo-5885423</a></div>

In Opera I see the <br />, but no placeholder icon.

If the pickup had a slant chop, even a stock height windshield, with the back lowered 2-3" the point where Templating begins would move forward 2-3'. The curve might touch the top of the tailgate.