The art of the lawn edging air dam

[kach22i]

Originally Posted by Frank Lee

The aluminum was supposed to be "backing" and I was all "what purpose does a lawn-edging cladding serve?"

I was there, and agreed with you but perhaps silently.

In any case the mystery was solved, and in the future perhaps we can ask more questions of the poster first.

There was certainly misleading and confusing information presented. However I'm sure it was not intentional.

[oil pan 4]

Sorry about the confusion, I expected there to be more over lap of the aluminum and lawn edging, I knew the 5'' or so the lawn edging offered wasn't going to be enough so I was shooting for between 7'' and 9''. Once I started mocking it up with the actual parts I realized 9'' of air dam was going to work a lot better than I expected.

And boy does it work.
I ran the air dam hard on a 6 hour drive taking it up to 90mph on several occasions with a strong cross wind. I tried to break it for hours. Got 18mpg and at the speeds I was going I expected a lot less than that.

[kach22i]

Originally Posted by oil pan 4

And boy does it work.
I ran the air dam hard on a 6 hour drive taking it up to 90mph on several occasions with a strong cross wind. I tried to break it for hours. Got 18mpg and at the speeds I was going I expected a lot less than that.

The biggest difference I've seen on vans and trucks I've put large chin spoilers on has been highway stability at speed, especially in heavy cross winds.

The slight MPG improvement is just a bonus, like a cherry on top.

[oil pan 4]

I noticed the front end is less twitchy when driving in a cross wind.
Also seemed like the suburban was holding speed with less effort than before the air dam went on.

[oil pan 4]

Last 3 fill ups were pretty good.
The 18mpg fill up I would have expected 16 to 17mpg due to the speeds I was driving.
The last 2 fillups would normally be around 19 to 20 mpg on the road and in the direction I was driving, this time it was 21.1 and 21.5MPG. That beats the normal fuel economy for this drive by 1 to 2 MPG.
EDIT: I had a small fuel leak on the #8 injector, I hope its just a return line.

[kach22i]

That matches my results in the past, a 3-mpg improvement.

I went a little off course on my current truck to achieve down-force and a off-road stance, so it's been a wash mpg wise with much improved safety at speed and on wet roads.

My lawn edging chin spoiler now has a large cut in it and deflects easily. It's held together with foil tape. I hope to get a conveyor belt on there soon.

[Otto]

The lawn edging with the PVC pipe insertion may be adequate stiffness. By heating the PVC pipe with a heat gun, you can bend it around a radius to match the bumper. That way, you'd have both a cheap and light application, but also the aero advantage of the radiused ends of the air dam. Maybe an elliptical shape would be attractive, as well as efficient.

Further, the arc-shaped device could be hinged at its tips (sides), such that it could be raised and lowered, up high for parking lot and driveway clearance, and down low on the highway, or anyplace in between for measuring optimal height. (Imagine the hinges on a motorcycle helmet visor, which it would somewhat resemble.) This thing could be retracted behind the stock bumper.

Use the same PVC pipe-in-edging idea to make side skirts between front and back wheels. That should use up the whole roll, more or less.

Another idea you could easily incorporate, is Hatchtastic's air dam/undertray mod, see his post on that.

Just add a sheet of Coroplast to the bottom edge of the air dam chin, extended back to, say, the oil pan.

[TheOutdoorAdventure]

Quick question. Assuming that we're channeling the air around the car, would it be best to have the rounded edge of the lawn edging at the bottom to catch the wind?

[aerohead]

Originally Posted by TheOutdoorAdventure

Quick question. Assuming that we're channeling the air around the car, would it be best to have the rounded edge of the lawn edging at the bottom to catch the wind?

I'm inclined to believe that it would,acting in a minor way like a flow fence/chine/micro-splitter.Added strength down there as well.

[TheOutdoorAdventure]

Great thanks!