Removing Tailgate

[JETZcorp]

First, I just want to say I already know this has been discussed to death here. Now, moving on.

I've always driven the Dakota with the tailgate installed and up. All indications showed that at highway speeds, that was the way to go. I knew that every vehicle reacts differently to it, but I'd never seen anyone show a statistically significant increase.

Then, a week ago I was on my way home (night time and raining) and noticed a gorgeous red first-gen Insight sitting in what looked like a dealership lot. I turned around to check it out. Turns out it wasn't for sale, and had a CVT anyway. I go to back out the way I came in, in neutral letting the Dakota roll back at sub-walking pace. Then it stops mysteriously. Whet the hell? I couldn't see anything out the back, I hadn't hit any of the other cars... I got out and discovered that a light pole (with lights off) had located itself INSIDE my rear bumper and folded my tailgate like a banana! It was about 2" around and almost entirely solid. If someone hit it at 15 it'd cut the car in half. Obviously, I was pissed.

A few nights later I decided to take the tailgate off, because it was so hideous. I also took the opportunity to remove my pair of 50lb sand bags, which hadn't noticeably affected mileage when I added them, and allowed the Dakota to drive at normal speeds without doing big burnouts and snap oversteer (only small burnouts and controlled oversteer). Now that it's June, they're not necessary anymore unless I want to drag race on the street, which I don't. I've been driving it like this for about a week now. Now, normally I get to half-tank at about 150-160mi in normal commuting. I was expecting about the same now, but I just crossed half-tank at 195mi. I've never seen that before. Now, the weather is getting better here lately, although still happens, so that's going to improve things as well. But, I've also got a tire that's leaking pressure and is almost always low.

We'll see how the full tank comes out, but so far I'm very surprised at what I'm seeing.

[KamperBob]

Yes a full tank (ideally more) would be more statistically sound. Meanwhile, a couple thoughts. Less weight could improve FE city. Different gas. Others?

Originally Posted by JETZcorp

First, I just want to say I already know this has been discussed to death here. Now, moving on.

I've always driven the Dakota with the tailgate installed and up. All indications showed that at highway speeds, that was the way to go. I knew that every vehicle reacts differently to it, but I'd never seen anyone show a statistically significant increase.

Then, a week ago I was on my way home (night time and raining) and noticed a gorgeous red first-gen Insight sitting in what looked like a dealership lot. I turned around to check it out. Turns out it wasn't for sale, and had a CVT anyway. I go to back out the way I came in, in neutral letting the Dakota roll back at sub-walking pace. Then it stops mysteriously. Whet the hell? I couldn't see anything out the back, I hadn't hit any of the other cars... I got out and discovered that a light pole (with lights off) had located itself INSIDE my rear bumper and folded my tailgate like a banana! It was about 2" around and almost entirely solid. If someone hit it at 15 it'd cut the car in half. Obviously, I was pissed.

A few nights later I decided to take the tailgate off, because it was so hideous. I also took the opportunity to remove my pair of 50lb sand bags, which hadn't noticeably affected mileage when I added them, and allowed the Dakota to drive at normal speeds without doing big burnouts and snap oversteer (only small burnouts and controlled oversteer). Now that it's June, they're not necessary anymore unless I want to drag race on the street, which I don't. I've been driving it like this for about a week now. Now, normally I get to half-tank at about 150-160mi in normal commuting. I was expecting about the same now, but I just crossed half-tank at 195mi. I've never seen that before. Now, the weather is getting better here lately, although still happens, so that's going to improve things as well. But, I've also got a tire that's leaking pressure and is almost always low.

We'll see how the full tank comes out, but so far I'm very surprised at what I'm seeing.

[freebeard]

Just go easy on the brakes. An unladen pickup truck can lose the rear wheels in a panic stop, through loss of traction. Or at least one '54 International would.

[MetroMPG]

Cannot... resist... urge... to ... post... link:

http://ecomodder.com/forum/showthrea...ery-11445.html

[t vago]

Originally Posted by MetroMPG

Cannot... resist... urge... to ... post... link:

Resistance is futile.

[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.

[MetroMPG]

Originally Posted by JETZcorp

But, obviously the Ecomodder community is very difficult to sway, and that's great!

Merci, monsieur, for posting that. Best thing I've read so far today.

By the way, when I posted that thread link, I wasn't implying that it's outside of the realm of possibility that for your particular truck/cab/bed combination, a missing tailgate might benefit. I'm not up on the exceptions to the rule of the tailgate up being better for aero.

I'd just hate to see someone draw a conclusion about a mod and decide it's "good" when the effect might have been the result of some other uncontrolled factor.

[t vago]

Originally Posted by MetroMPG

I'd just hate to see someone draw a conclusion about a mod and decide it's "good" when the effect might have been the result of some other uncontrolled factor.

And that's the exact point, right there. Eco-tuning a gasoline-powered vehicle is tricky, to say the least. I've seen in my experimentation things that just don't make sense - for instance, highway commutes with A/C using the same amount of fuel as without A/C (the Karen-mobile), or slightly less (the Fiat Dakota).

I'm pretty convinced it has a lot to do with the fact, that gasoline engines in general have to use fuel solely for the purpose of creating and maintaining intake manifold vacuum. This is why, for instance, it's possible to get awful gas mileage while driving steadily at either 25 MPH or 75 MPH. It's possible to make a vehicle more aerodynamic, for instance, only to see the expected fuel savings go away because the engine now has less of a load to push forward -> intake manifold vacuum goes up in order to compensate for the lesser amount of demand -> engine now has to work at maintaining this higher vacuum -> total fuel burned paradoxically goes up.

The converse is true, and I've seen this, too. Load a vehicle with more weight (like I did with the Fiat Dakota) -> engine loading goes up -> engine vacuum goes down to compensate -> paradoxically, slightly less fuel is used. The same could be said for inducing drag via removing the tailgate.

The worst part about all of that is that all of this is so wildly dependent on speed and engine loading and the power output of said engine, that it's next to impossible to exactly quantify the benefits of a given eco-mod for a gasoline-powered vehicle.

Now, for highway commutes, adding eco-mods generally gives the desired result. However, the old saying applies - Your Mileage May Vary. So, good luck and have fun with experimenting.

[freebeard]

The fronts, which don't have ABS, most decidedly have locked up before. Big smoke, very scary.

[cRiPpLe_rOoStEr]

No wonder race trucks usually have either a tonneau or the tailgate removed...

BTW is your Dakota fitted with regular ABS or just an LSPV valve on the rear brake lines? I remember Chevy used to advertise the LSPV as an ABS in some of its Brazilian and Argentinian trucks...