Lexan headlight cover how-to

[MechEngVT]

Originally Posted by lunarhighway

why did these metro's have these silly straight lamps to begin with in the us, Clearly the car was not designed to have them, so i can only assume some old regulation or cost considerations could be at the heart of this.

I vote for the regulation. Until sometime in the early 1990s US FMVSS code 108 restricted manufacturers to 7" round lamps as standard-beam from 1940 until the 1970s when it also allowed two sizes of rectangular lamps. The aerodynamic "Euro" headlamps were not legal until the 1984 model year, but this meant that they were not practical on vehicle designs that were undertaken until sometime after 1984. Still the replaceable-bulb lamps we all have today weren't common in the US as many companies continued using the old-spec sealed beam lamps (I have the larger rectangular style on my 1988 Dodge truck (not in EM garage). GM kept using the old sealed beams and may have insisted on keeping them on the Metro as par of their original "design language."

[stant01]

Has anyone done before and after testing to see what effect these headlight covers have? I'm tempted to make a pair, but I'd like to know how effective they are.

[cfg83]

stant01 -

Originally Posted by stant01

Has anyone done before and after testing to see what effect these headlight covers have? I'm tempted to make a pair, but I'd like to know how effective they are.

Welcome to EM!

When you are driving, can you "see" where the top edge of your headlight meets the front of your hood? If yes, then maybe you could do a tuft test. Cover one headlight with masking tape, tight so it won't "wobble" in the wind. Then tape yarn tufts right behind the headlights and maybe for a few "rows" of tufts back. With one headlight covered, you should be able to watch the tufts and compare the benefit.

Does that make sense?

CarloSW2

[stant01]

Actually that won't work for me, because I am considering trying it on the fog lights on my Subaru, which are inset low into the front bumper. They are at the far outside edge of the bumper so I suspect they disturb airflow around the sides of the car.

In any case, if it won't make a measurable difference in FE, I am not interested. There is a FE gauge built into the car, so I may try an a-b-a test on a stretch of highway, using cardboard covers taped into place. The hangup may be that the smallest FE increment the meter will show is 0.3 mpg, or about 1%. I don't know if the covers will make that big a difference. Their total surface area is about 0.5 sq feet, and the Subie's effective frontal area (Cd X area) is about 7.5 sq ft.

[MetroMPG]

Nobody here has tested this mod. The difference is probably minimal - small enough that it's not detectable at the gas pump or on the MPG gauge.

That's not to say it's not worth doing - many effective but individually unmeasurable mods will add up.

[frostyfreeze]

Anyone have experience with using the adhesion promoter on a painted surface? If the paint is really clean (alcohol, etc.) can I get away with not using it?

[bbjsw10]

Originally Posted by frostyfreeze

Anyone have experience with using the adhesion promoter on a painted surface? If the paint is really clean (alcohol, etc.) can I get away with not using it?

Alcohol would be fine on painted surfaces, only need promoter for plastics(has a mold release agent in it)

[EXPIOWA]

Nice write-up. Have you determined if it has made any difference yet?

[White118]

Can this mod be done with out preheating the lexan? This will be my first mod but I'm short a heat gun.

[ATaylorRacing]

Hey guys, I did this last year and did the grill block at the same time. I used wood screws at 4 places to hold mine on. The grill block was made by trimming a piece of plastic that used to be located on the inside of thwe rear hatch and it too is held on with wood screws. I have not been able to test the FE benefits yet but the top speed with these mods went from 81 up to a nice 87 mph! The main benefit is a LOT less buffeting on the hiway, almost likie I am drafting. Here are a couple of pics:

Even the 3 cylinder Geo gets action
UMTR Nationals at Edgewater - 9/26/09 - Hyper-Performance Motorsports Inc. Photography
The White Gnat strikes again
UMTR Nationals at Edgewater - 9/26/09 - Hyper-Performance Motorsports Inc. Photography