TJ: Bug Shield testing

[GasSavers_Red]

For starters, while I know adding a bug shield should be a given MPG penalty on any kind of vehicle, but considering the aerodynamics of a TJ (two completely vertical/flat surfaces; the grill and the windshield) I figured it might just help. So I had a bug shield I had bought a while back and I figured why not.

I used the route from my house to school as my test route. Tests were performed over 3 days. Run A is going to school, B is heading back, a trip distance of 12.3 miles. Engine was cold for all runs. I go in around 10, leave around 7. Run A temps were 64F-66F, Run B temps were around 66F-68F Cruise control was set at 65 mph.

Run A
Shield on: 19.6
Shield off: 20.3
Shield on: 19.8

Run B
Shield on: 17.9
Shield off: 16.2
Shield on: 17.3

Now my question is that, going in, there appears to be a small hit in FE but it could be almost neglibile, but going back there is a descent gain in FE with it on, why is that? I'd have figured a penalty on both trips

[2TonJellyBean]

Look at differences between runs... you'd need more samples to conclude anything that small.

[trebuchet03]

^^ ditto

Your environment factors are too large to easily see a result

Do you have consistent wind conditions - that is, do all run B tests have a headwind (explaining lower overall results and potentially increasing an mpg/aero change).

If you're going to collect data over time... Collect a lot more, but also record all of the temp/wind conditions for every test. That's what sucks about long term testing - it's more difficult to control variables :/

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Can you experiment with different attack angles? Or is it a molded one-shape only type of thing?

[GasSavers_Red]

Kewl, I'll keep on going.

treb, I'll double check the wind info I have, don't recall the direction. B is worse, FE wise since its mostly uphill, while A is mostly down hill.

It is a molded one piece thing, I was hoping that the collected data would be bad enough to warrent me chopping it up some. I'll post up a picture of it tomorrow.

[DRW]

I wonder if the bug shield could be mounted at the base of the windshield? I was thinking of doing something similar to my car. It should reduce the high pressure area that builds up at the hood/ windshield junction.

[Danronian]

Originally Posted by DRW

I wonder if the bug shield could be mounted at the base of the windshield? I was thinking of doing something similar to my car. It should reduce the high pressure area that builds up at the hood/ windshield junction.

I?ve seen cowl covers for sale in JC Whitney before for trucks that would basically do the same thing you are looking for I believe.

[GasSavers_Red]

So some pics of what it looks like





And some simulated "air flow" testing with a hose.







I've got next Friday off so I am going to try another set of runs inside a smaller time frame.

[soda_pop503]

Originally Posted by Red

So some pics of what it looks like





And some simulated "air flow" testing with a hose.







I've got next Friday off so I am going to try another set of runs inside a smaller time frame.

judging from the way the water jets up so harshly, I would think it might help get some air up and over that big flat wind shield. maybe if you can find one that has a less harsh angle and maybe a little bigger, it could actually help get the air around that wind shield, rather than taking it off all together.

[trebuchet03]

Man, that's a steep angle of attack - I'll bet it has to be to change the velocity of flow above it

The best question as far as overall performance of it is... Does it actually work? If it doesn't do a decent job - and decreases mileage... Sell it on fleaBay

[GasSavers_Red]

It pretty much sends anything small to the moon

Honestly when I ran it way back when I didn't notice much of a change. Tried selling it then, no takers, figured I'd try to quantify what it exactly did before I try to sell it again.