getting a tow
 

I was able to replicate my mileage this weekend while going to and from the shack, which is getting in a group of cars and drive with them. This didn't work until I put the side skirts and the rest of the air dam on Stinker.


At 65 mph, driving by myself, I get 25-26 mpg. In a group of cars going 80-90 mph I get 24-25 mpg. Apparently, with the new aero stuff, I'm getting a pretty good tow off of other vehicles. When I started trying this, I figured I'd be killing the mileage and use 14 gallons on the 250 mile trip. I used 10.5. Obviously, the type of vehicle you're traveling with makes a difference. I'll have more details and some video later.

Now I gotta figure out what to call this technique.

Good deal !

At 80-90 mph ? Technique ? Nascar Baaaaaabeeeeee ! :p


It's a form of drafting fwiw . Group drafting ?

NASCAR lost me when everyone started driving plastic cars. SCCA, Formula 1 all the way for me baby, hence the tow reference instead of drafting. Gotta stay out of the klag too. We'll see who gets that term.

Well, I was coming back the same week I put the stuff on the truck (before I modded the bed cover) and had to speed up to get around a National Guard convoy. While I was in traffic, I noticed I lost just a tiny bit of mileage and thus my hyper-speed-mileage idea was born.

What I noticed is that it doesn't work until you're over 75 or so. Any slower and I go down to 21-22 mpg. And the group should be 4-5 cars at least but with the right vehicle in front, it worked just as well. With 4-5 vehicles, it don't matter what they are, I get the mileage. With just one, it's a crapshoot but my list is growing. As with following a semi, I go until I feel the wake affecting Stinker and back off a bit. Now, with a single vehicle you have to be closer than a nervous person would like. With a pack, you can be back 10 car lengths and still get the tow.

But, now I have to dig out my radar detector again. :cool: See, while I was videoing this little deal, I fell behind the pack of cars and...accelerated...to catch up. There's this one ramp in northern Michigan, North Down River Road that has a very long ramp through the pines. Well, as I was catching up and pretty much cracking the century mark, I spied a State Trooper. Of course, I backed off and slid with everyone else into the slow lane and started to pull over for him. Just as he gets past the last of the trees this Silverado, red, 4x4, diesel, big tires, long bed, crew cab, roll bar, etc.. blew by us like we're standing still. Needless to say, I got the free pass.

Here's my list so far:

by myself, 65 mph, 25-26 mpg, 21% engine load
by myself, 75-80 mph, 16-19 mpg, 35% engine load

All speeds, 75-85 mph
behind:
Dodge Dakota, 22-23 mpg, 25% load
Chevy Silverado (long box), 24-25 mpg, 22% load
Dodge Durango, 23-24 mpg, 23% load
Ford F-150, 23-24 mpg, 23% load
Chevy Trailblazer, 24-25 mpg, 22% load
Ford Taurus, 23-24 mpg, 23% load
Chevy Impala, 23-24, mpg, 23% load
Ford F-350, crew cab, 24-25 mpg, 22% load

Now I gotta get some of that coroplast or whatever the heck it's called for my belly pan. But with as much air as I've cut off from the underside, I just don't think it's going to work.

Drafting - definitely works. Good that you documented it.
What's your usual following distance?

And -
What's the size of vertical gap below your air dam and side skirts? My air dam on Volvo wagon is about 7" from the ground (oem air dam = 11"). I hope to do side skirts to match the 7".

Okay. Air dam and side skirts. Measured them for you. Front air dam is 2 inches from ground. Side skirts are 3.25 inches from ground. Now, I also added an air dam on the inside of the front wheel wells that is 3 inches from the ground. In my humble opinion if you don't hear "SSSCCRRAAAACCHHH" at least once a day your mods aren't low enough.

If I were to add the lower portion of the air dam that I had last summer, the dam would be 1 inch from the ground for driveway scraping fun. :eek:

You know Bruce, it seriously hadn't occurred to me that I could actually get benefits from "drafting" - I prefer the term "Tow" that they use in Formula 1 - at such low speeds. My big "surprise" (although nothing surprises me any more) is that the difference between the air dam and adding the side skirts added that much mpg performance to the vehicle under these conditions. Maybe it's the fact that it's a truck. I would really really hope that this would work with any vehicle. We Americans like to go fast.

My deal is to get the stuff as low to the ground without scraping a "lot". Now I'm wondering if adding fences to the rear quarters would help too.

Drafting in a group? That is easy! The flying V from the Mighty Ducks!!

I am serious too btw.

What I was getting at is that this did not work before the aero mods. Now I'm trying to find wind tunnel stats for the vehicles that get me the best effect to see what their wake looks like so I can tweak my plastic panels. I'm thinking that they split the air in such a way as to minimize the turbulence from my wheel wells. From what I remember, the bed cover wasn't doing anything different than normal so I'm thinking it's not the flow over the vehicles rather on the sides.

You know whats better than drafting an 18 wheeler semi?

A coach bus! I found one on my way home for the weekend. It sits lower to the ground than the semi.
Fuel mileage was awesome!

If you can find one that's going a decent speed. A lot of them things here in Michigan go 55, which is way too slow. I've been behind a couple that were driving like maniacs too.

I like to follow the motor homes but most of them just poke along.

2 to 3 inches from the ground - yikes. I scraped mine a few times already and it's 7" from the ground. I'm in New England and we have hills here. OK, you must have some too out your way. The driveways are the issue. People and businesses have driveways on hills; you turn into it and you go SCRAPE!! if things are too low.

Hmm. I probably could build the air dam + side skirts to go lower as you move away from the very front. Because if the nose just barely clears, the side of air dam a foot further back, towards wheel cutout, will have more clearance, and so will the side skirts. Just have to measure some speed bumps for height.