Learn me: tiny box trailer aero improvements and the law of diminishing returns

mad_machine wrote: looking at the miata airflow pics.. could you make a small "spoiler" bubble on the front of the trailer that overhung the trunk on the miata to take advantage of the air flow off of the convertable/hard tops?

I was thinking more in terms of modifying the car.

How about a rear spoiler, or a small adjustable wing that could be removed? Seems more likely to redirect the airflow appropriately.

novaderrik wrote:

SVreX wrote: I agree, however don't forget that the big boys are really happy when they can gain 0.25 mpg. Most cars can't even measure that. We are doing diesel fuel additives. Our target is 10% improvement, but the starting point is 6 mpg. That's only 0.6 mpg improvement. The difference is that we can prove it on a dyno and long term steady over-the-road tracking. You'll never drive a Miata a million miles. How much of a reduction in fuel economy are you currently seeing when towing?

they must be seeing quite a bit of improvement, given that i see more and more of them on the interstate every week..

Oh they see plenty of improvement. Don't misunderstand me.

But my point was the specific type of improvement they get for the specific type of driving they do.

OTR trucks drive an average of 130,000 miles per year per truck. That means they burn over 21,000 gallons of fuel per year. They do this driving almost entirely at highway speed with full loads. The maximum load for them is punching that big whole through the air.

They average between 4 and 9 mpg. Assuming 6 mpg and $4 per gallon, a .25 mpg increase for a small fleet of 100 trucks equates to nearly $350,000 in savings over the course of a year. A 10% increase is almost $800,000.

That buys a lot of aero improvements. If they spend $1000 per truck, they still gain $250K.

But note that you don't see those aero mods on the trucks that are used for local runs. Only the OTR trucks. That's because there is no payoff. When the vehicle is moving slower, makes lots of turns, stop and go, etc, the improvement is too small to measure, so they don't do it.

That's why I said I don't the the mods on a tiny trailer behind a Miata driving under local driving conditions would be able to be measured.