To draft or slow down?

[palemelanesian]

I saw a study done with 2 computer-controlled semi trucks. At a 10-ft following distance, the trailing truck got a 15% boost in mileage, and the leading truck got a 10% boost. At no point did the leading truck actually lose mileage.

And as I said earlier on, you get a benefit even at a legal, safe 3-second following distance. 70mph distant-drafting beats 65mph driving solo.

Update: I got the numbers wrong, but the concept is accurate. Here is the study: http://gcep.stanford.edu/pdfs/ChEHeX...0_11_trans.pdf

[Snax]

I think the problem with benefiting the truck is that the following vehicle has to be really close, otherwise the effect drops off very quickly, and is likely nil at a distance that a normal person might consider safe to follow at.

[theholycow]

Originally Posted by Snax

I think the problem with benefiting the truck is that the following vehicle has to be really close, otherwise the effect drops off very quickly, and is likely nil at a distance that a normal person might consider safe to follow at.

Nil is acceptable. The question was whether it causes the puller any detriment, which it does not.

[racertim]

Wow.... I haven't checked the thread in a few days and there are million posts!

I supposed I had a good first question!

Anyways, I updated my mileage log with my tests between drafting and slowing down. I managed to get a couple MPG better by slowing down. I think I will do another test to see if the results are confirmed.

[palemelanesian]

Originally Posted by Snax

I think the problem with benefiting the truck is that the following vehicle has to be really close, otherwise the effect drops off very quickly, and is likely nil at a distance that a normal person might consider safe to follow at.

Originally Posted by PaleMelanesian

And as I said earlier on, you get a benefit even at a legal, safe 3-second following distance. 70mph distant-drafting beats 65mph driving solo.

This is a test I did in my minivan.

[racertim]

Originally Posted by PaleMelanesian

This is a test I did in my minivan.

Your minivan has different characteristics than my civic. I noticed a drop in economy and was following much closer than 3 sec.

[palemelanesian]

The Civic has TERRIBLE highway gearing. But I've done some great numbers using Pulse&Glide combined with a 2-3 sec draft - upper 50's mpg at 70mph average. The aerodynamic benefit is still there, it's just that the high gearing masks it.

[racertim]

Originally Posted by PaleMelanesian

The Civic has TERRIBLE highway gearing. But I've done some great numbers using Pulse&Glide combined with a 2-3 sec draft - upper 50's mpg at 70mph average. The aerodynamic benefit is still there, it's just that the high gearing masks it.

What do you recommend that I try differently then? I was cruising steady behind the trucks at 1 sec at 70mph on average.

[Hateful]

Originally Posted by PaleMelanesian

The Civic has TERRIBLE highway gearing. But I've done some great numbers using Pulse&Glide combined with a 2-3 sec draft - upper 50's mpg at 70mph average. The aerodynamic benefit is still there, it's just that the high gearing masks it.

I do the same with my Cavalier with good results.The pulse and glide seems more of a benefit for my MPG's,but if I can get both I will.

[palemelanesian]

I suggest you work on Pulse & Glide. Running the RPM that high is a KILLER to mileage. Pulse & Glide is a good way to overcome that. I've run that same highway trip several times.

57 mpg - 70mph drafting P&G
43 mpg - 65mph cruise-control
75mpg - 50-60mph P&G