Thor Forums

[FW28z]

After 500 miles, I have noticed some pretty interesting results. I drove in various conditions, rain, sunshine, cool, and warm temperatures, secondary highways and freeways.

First, there is a phenomenon called "Station Wagon Effect" which is essentially a low pressure that is present at the rear of "boxy" vehicles, such as SUVs, motorhomes, and semi trailers. This low pressure is detrimental to fuel mileage, and is what Air Tabs aim to remedy.

I noticed on a rainy day that the rear-view camera was much cleaner. Previously, the camera got all dirty and water spots on it, so much so that it was not useable in the rain. This time though, I did notice the camera was much more viewable. In fact, it was interesting that I could see the vortexes coming off the ends of the vehicle by observing the visible water vapor in the air while raining. I never noticed this before, because... for one thing, the camera would always get water spots on it in the rain.

I cannot make any conclusion to this other than it was interesting to watch.

Over the 500 miles, I noticed that my combined fuel mileage (city + highway) increased by around 6%. This was observed by the Scangauge as well as confirmed by calculating fuel used vs. miles driven at fuel stops.

Of course, I filled the tank to the brim each time. Still, there could be variations here, so the more I repeat this, the more accurate results I will have.

At highway speeds (55~60mph), the mileage increased 12~15%, and I consistently saw over 10MPG average. This makes sense as the air tabs are only effective at speeds above 45mph or so, and when averaged over the overall driving pattern, the tabs won't change the lower speed fuel mileage at all, so the only fuel savings is at higher speeds.

I also noticed that at highway speeds, my tachometer dropped about 100RPM from before. I was seeing around 2,150RPM at 60MPH (reading from the ScanGauge).

I also purposely drove as close (safely) to the center line as I could on secondary (2 lane) highways so I could feel the effect of semis passing. I felt some push at times, but nothing scary. The push felt about like it does when in a passenger car.

The RV definitely handled much better in winds. Yesterday we drove through a thunderstorm, and the winds were pretty strong at times. I was able to maintain 55~60mph with a bit of steering correction, but not bad at all. I was even passing other RVs during this time.

Previously, this would have been a white-knuckle experience.

Now, a month before adding the Air Tabs, I added aftermarket Hellwig sway bars, so I am not sure which of these additions was the most help to remedy this, or if they both helped. Regardless, the handling is so much better.

While it may be a stretch, the break-up of low pressure in the back could - and I mean could - be causing more weight to remain on the front axles, improving steering. I cannot quantify this in any form, so call it speculation, but it could be happening. If indeed there is less suction in the rear, it makes sense.

So while I am going to do some more testing, I feel pretty confident that I am observing a 5% increase in overall (combined) fuel economy (it would be more if the air tabs were effective at low speed), up to 1MPG increased economy at highway speeds, improved handling in certain situations, and perhaps a bit less grime on the back.

A cleaner camera is encouraging, but I won't know for sure until I tow the toad in the rain.

I'll have to admit though that we had our bicycles attached to a hitch-mounted bicycle carrier (we didn't take the toad on this trip). They seemed dirtier after driving through the rain, which was surprising.

The only conclusion I can make is I also tied streamers to the back of the RV (not on the rainy day though), and again, from the rear-view camera - I saw that the streamers on the bicycles at the center of the RV were horizontally pointed to the left/right of the coach, while the streamers on the ends were going straight back.

This kind of suggests airflow from the center towards the outer edges on the back of the RV, and perhaps that was happening with the gunk on the bikes. The more air flow, the dirtier they became I suppose.

In all honesty, I am not sure why, as the camera was cleaner (but it is a lot higher too). I am not sure what to make of it, and it could either be further evidence of loss of low pressure in the back, or something else. One thing for sure, the bikes never got that dirty before.

Again, the one definite conclusion - things have changed, but the what and why is not fully determined.