7" retrofit (GDAA WRX)

[satrya]

Okay, now I'm torn...

How so? About whether a foglight trim makes sense? Or whether completing this retrofit makes sense?

[csjoh]

No, the foglight trim makes sense, I'm torn between wanting to see the finished result and wanting updates and new ideas being tried out

The screws in the trim, I assume they are for securing the trim to the car? How about plastic welding or epoxying something to the back of the trim that can be secured from the back?

..and as I wrote that I realized that might not be possible at all... oh well

[satrya]

No, the foglight trim makes sense, I'm torn between wanting to see the finished result and wanting updates and new ideas being tried out

I see. There's retrofit for the taillights coming up next.

It won't be HID of course. I used to have a pair that had an aux 35W halogen reverse light, wired to the oem reverse light but with a switch. In one position, the oem reverse light (which serves to inform others of your intent to go on reverse) turns on. In another position, both the oem and the 35W aux turn on (which serves to help the driver see objects around). I plan to make a new version; maybe I'll try new tricks.

The screws in the trim, I assume they are for securing the trim to the car? How about plastic welding or epoxying something to the back of the trim that can be secured from the back?

..and as I wrote that I realized that might not be possible at all... oh well

There's an OEM foglight cover, that completely covers the foglight opening, as well as an OEM foglight mesh, that has a mesh opening to let light pass through. Both of these options use a single screw via an extension bracket, and 2 tabs on top that insert themselves into slots on the bumper cover.

My aging foglight trim borrows exactly the same approach. A piece of galvanized steel mimics the bracket like so:


And then, on the top of the foglight trim, are 2 metal tabs:

, which are secured via the 4 screws like so from the back:

, in order to take advantage of the 2 aforementioned slots:


So, the foglight trim is mounted by first inserting the 2 tabs into the slots:

, and then securing the bottom using the lone screw mounted onto the custom extension bracket:

, which takes away some of the square-ness of the foglight area (excuse the 13 year old picture):


I like metal because the amount of shear & bending stresses experienced by the 2 tabs can be great. So, I'd rather not epoxy anything that will later become the weak point or source of stress concentration because of incompatible stiffness.

If possible, I'd rather not go with the 4 screw approach again for the 2 tabs, to reduce the amount of unintended visual features. This might sound odd given the somewhat busy look of the foglight retrofit.

[Fstrsn]

I see. There's retrofit for the taillights coming up next.

It won't be HID of course. I used to have a pair that had an aux 35W halogen reverse light, wired to the oem reverse light but with a switch. In one position, the oem reverse light (which serves to inform others of your intent to go on reverse) turns on. In another position, both the oem and the 35W aux turn on (which serves to help the driver see objects around). I plan to make a new version; maybe I'll try new tricks.


There's an OEM foglight cover, that completely covers the foglight opening, as well as an OEM foglight mesh, that has a mesh opening to let light pass through. Both of these options use a single screw via an extension bracket, and 2 tabs on top that insert themselves into slots on the bumper cover.

My aging foglight trim borrows exactly the same approach. A piece of galvanized steel mimics the bracket like so:


And then, on the top of the foglight trim, are 2 metal tabs:

, which are secured via the 4 screws like so from the back:

, in order to take advantage of the 2 aforementioned slots:


So, the foglight trim is mounted by first inserting the 2 tabs into the slots:

, and then securing the bottom using the lone screw mounted onto the custom extension bracket:

, which takes away some of the square-ness of the foglight area (excuse the 13 year old picture):


I like metal because the amount of shear & bending stresses experienced by the 2 tabs can be great. So, I'd rather not epoxy anything that will later become the weak point or source of stress concentration because of incompatible stiffness.

If possible, I'd rather not go with the 4 screw approach again for the 2 tabs, to reduce the amount of unintended visual features. This might sound odd given the somewhat busy look of the foglight retrofit.

Why not fiberglass the metal brackets to the backside of the fog trim?

[satrya]

Why not fiberglass the metal brackets to the backside of the fog trim?

Same reason why I avoid epoxying them. Metal and the flexible trim have quite different stiffness. If I lay fiberglass around the metal tab, it might provide some transition in terms of the stiffness, hence reduce the stress concentration (which is good). But I still have to rely on the resin to keep the fiberglass from delaminating against the flexible trim and against the metal tab.

The way I see it, that moves it from one failure mode to another, whose probability is not necessarily smaller. Maybe I can do a finite element analysis on it, but I don't know how to properly model resin and fiberglass and the adhesion among the different materials. (not that I remember how to run an FEA tool, but that's not an impossible task)

Barring that, the spreading of stress concentration using metal washer around screw+nut combo is my preferred method. Making them inconspicuous is the trick here. The approach I took a decade or so ago with the exposed 4 screws is what I'd like to avoid. That and making the retrofit splash resistant are the next challenges.

[Fstrsn]

Same reason why I avoid epoxying them. Metal and the flexible trim have quite different stiffness. If I lay fiberglass around the metal tab, it might provide some transition in terms of the stiffness, hence reduce the stress concentration (which is good). But I still have to rely on the resin to keep the fiberglass from delaminating against the flexible trim and against the metal tab.

The way I see it, that moves it from one failure mode to another, whose probability is not necessarily smaller. Maybe I can do a finite element analysis on it, but I don't know how to properly model resin and fiberglass and the adhesion among the different materials. (not that I remember how to run an FEA tool, but that's not an impossible task)

Barring that, the spreading of stress concentration using metal washer around screw+nut combo is my preferred method. Making them inconspicuous is the trick here. The approach I took a decade or so ago with the exposed 4 screws is what I'd like to avoid. That and making the retrofit splash resistant are the next challenges.

Could you make a cap of some sort to attach to the screw head?

[satrya]

Setting aside the issue of splash proofing the housing and the fog trim tabs (for more brainstorming)...

I've reserved some of the corners of the housing skin (from sheet aluminum) to jut out relative to the 7" lens.

I wanted to keep them available for either a replacement mounting point in lieu of the extension bracket (as shown below), or additional mount to help keep the fog trim secure.


A proper sized rubber hose can be made to snugly fit into the corner openings like so, and then trimmed off almost flush with the edge of the opening:


Then, a long pin with ribbed texture (e.g. a long screw's thread) can be held in place by a combination of compression + friction. I may stay with the extension bracket approach, but it doesn't hurt to affix these rubber hose segments into the corner openings just in case.

We'll see. Maybe they won't be needed. In that case, the top one can be extended as one of the breathing tubes of the housing.

[satrya]

Could you make a cap of some sort to attach to the screw head?

That's possible. I was hoping for something where the screws don't have to be in that visible location, but I'm not sure where yet. If the fog trim were to be made entirely of metal, then the trim itself can have a tab shape. But I don't have the tools nor experience to form metal plates into complex shapes (other than flat or straight bends).

[satrya]

Bending the back panel's extra material to wrap around the box..

[satrya]

Functional test

Confirming that the connectors & new wiring does as intended.

Aux LED DRL:


Aux LED turn signal, in conjunction with the amber incandescent turn signal in the headlights:


Catching the turn signal lighting with the aux DRL also turned on.

[Fstrsn]

Any plans to have the turn signals be color matched?

[satrya]

Any plans to have the turn signals be color matched?

I considered that. Thanks for bringing that up.

From observing other vehicles in daytime, night time, and inclement weather, I'm leaning towards amber turn signals for both the main and the aux units. Amber seems more conspicuous than white in most conditions.

If I put an amber filter ahead of the white LED, I wouldn't be surprised that the available intensity in the amber spectra from the "white" LED is very minimal. That would mean a very dim amber output from the relatively decent white LED's intensity.

On the other hand, having the aux turn signal left at "white" with the main turn signal amber could hedge against weather / road conditions where one may be more visible than the other. To my knowledge, amber and white are both allowed as turn signal colors in north america.



Maybe I should take out the LEDs in the aux turn signal units and replace them with amber incandescent bulbs...

My main motivation for using LEDs for the aux turn signal is because I didn't want to draw too much additional current from the existing turn signal wiring. But I can always add a relay+harness just like the biXenons or the halogen fogs.

[Fstrsn]

I believe for front turn signals they can be either amber or white. I prefer amber though. Can you just swap out the AUX LED for an amber one?

[satrya]

I believe for front turn signals they can be either amber or white. I prefer amber though. Can you just swap out the AUX LED for an amber one?

The LEDs mount into the aux turn signal unit like so:


I'd have to find one that is compatible with that mounting fixture if I want to avoid having to refabricate the aux turn signal unit. When I compared similar sized LEDs, the white LEDs typically are brighter than the amber equivalent, so finding an amber replacement didn't seem like a promising option.

[Fstrsn]

Ah, fair enough then.

In that case if you wanted to color match them I would just grab some clear orange hobby paint and paint the lens that they shine through. This would however give you an orange appearance in the fog lights that is not there in the headlights.

Would you be opposed to running a white turn signal?