Mazda MX-5 RF Louvres -: Draft of an article I intend to submit to a club.
Louvres on the rear windshield of a car can be a divisive subject among motoring enthusiasts. Some people don’t like the way that they make a car look at all, and that’s okay because I think it is perfectly fair to say that louvres are anachronistic. But for me, that retro aspect is exactly the appeal.
There is a company in Mexico called ideaen3d that custom make rear louvres for the Mazda MX-5 RF, and their website is here. I’ve lived with their louvres installed in my daily driver MX-5 RF for about a year now and I would like to share some of the things I’ve learned so far, and some of the things that I'd like to try in the future.
So ignoring the objections of the people who simply don't like the way that the rear louvres look on a car (this article is obviously not for you), the second most common complaint that I hear from people is something to the effect of: “Don’t they block your rear vision?”
And the answer to that question is: not really. If the louvres are installed correctly, then there are only three thin, horizontal, black lines across your rear vision mirror. There is no significant impact on seeing out of the car as I hope this photo from the driver seat shows:
Given how the louvres usually appear in all the glamour photographs, and how high we are above them when looking at the car in person, I can understand how people assume that vision out of the vehicle might be limited. However, to everyone not familiar with how louvres work, I assure you that this design makes very little difference to rear vision; it all comes down to what angle you look at them from. I hope that this photo further illustrates that when your head is at the same height as the driver's, vision straight through the car is largely unaffected.
The Company:
To acquire the louvres, I contacted ideaen3D via Facebook Messenger as they requested on their site, and they responded quite promptly, answered all my questions immediately, and even offered free shipping if I paid for them through PayPal right away. Which I did. However, shipping was to take a very, very long time. Although they promised two week delivery, and I ordered the louvres mid February, they did not arrive until mid June. I typically left it three weeks between contacting them for shipping information and I don't know what to believe of all the reasons for delays they kept telling me, but at the beginning of June when I started asking for a refund due to non-delivery they were suddenly able to provide shipping details and the louvres arrived quickly. It was the first, but not the last, aftermarket parts company that seemed to drag their heels excessively until threatened with providing a refund.
The Product:
The louvres cost me $590 USD back then, and the quality is to my eye, extremely good. Aluminium coated in a semi-matte black finish, perfectly cut and shaped, holes pre-drilled and pre-threaded for ease of installation. The kit also provided instructions, a template, a drill bit, a thread tap, bolts, an Alan key; and although it was nerve-wracking to irreversibly drill into the retractable fastback, the actual installation process was one of the quickest and simplest of all the modifications I've made to my car. ideaen3D provided an excellent product in a well-thought-out, easy-to-use kit.
Benefits of Louvres:
In all honestly, the practical benefits of adding these louvres to an RF are I think, very, very small. In all my previous cars the louvres served a real purpose as an alternative to window tint, a way of stopping the sun from shining through the large, sloped, convex rear windshield of my fastback car and turning it into an oven. However, the RF only has a small and vertical rear windshield, so I can't pretend that the louvres are really keeping any sun off the glass. It might be argued that they provide a modicum of privacy from the rear as few cars are low enough to see in, but the prime benefit of these louvres is their aesthetic appeal; the cosmetic change that they make to the profile of the car. I personally like the way that it resembles something like a classic C3 Corvette.
Downsides of Louvres:
These particular louvres come with a definite downside that there's just no getting around which is particularly egregious if you happen to be an ex-car detailer like myself; it makes cleaning the void behind the rear windshield quite inconvenient. Technically, it's not hard to remove the louvres, 16 fairly simple bolts that can only be reached by hand, but removing, storing and reinstalling is a bit time-consuming for an ordinary weekly wash. I save it for the 6 monthly polishes. I have, on several occasions, flooded the interior of the car's cabin by probing that space too vigorously with the pressure washer to make up for my lack of reach, but I have since reached a compromise of treating the areas under the louvres with my best hydrophobic coatings, and cleaning it with only a light spray of water and gentle sponge.
The Real Problem with the Louvres
I had been driving with the louvres installed for about two months, and they'd made no difference to wind noise in the cabin with the roof open or closed, when I noticed that the top slat in particular had developed a loud and quite irritating rattle, and this was to become a recurring problem for reasons that we will go into. In defense of the product I will say that I had taken the car to a track day, and had been pushing the car (and my nerve) to the upper speed limits to see what they could do. Later when I contacted ideanen3D about my issue they told me, and I quote: "Louvers are more for the city, aesthetics. I recommend you not use them for races.", so it could reasonably be argued that I was not using them as intended. The cause of the problem is that the material of the fastback (I think it's fibreglass?) had basically disintegrated around the thread of the bolts and no longer held them snug. The slat was essentially floating, only held in place by the length of the bolts, and as the slat flexed and moved during regular driving the threads were acting like the teeth of a saw, slowly enlarging the hole in the fastback material. The following photo is what greeted me when I removed the top slat, and the dust and debris from the "sawing" can clearly be seen.
Ideaen3D suggested that I get wider diameter bolts and enlarge the holes on the louvres and in the fastback. I ignored their suggestion though as that sounded like a lot of work (drill out and retap a total of 32 holes without damaging the finish on the louvres), and to me it didn't address the core issue; that the thread on the bolts was extremely fine and was clearly meant to be inserted into a corresponding metal thread. I believe the fibreglass of the fastback is too brittle for such fine thread, and would merely slowly break apart again.
For my first fix, I mixed up some 5-minute quick-setting two-part epoxy glue from the hardware store, pushed it into the holes whose thread had failed, and re-drilled and re-tapped the holes. The louvres went on fine, but about three months later, they had broken loose again.
For my second fix, I obtained some strong, slow-drying, clear two-part epoxy glue, mixed it up and pushed about a teaspoon's worth into each of the holes in the fastback, and using a piece of wire with a small right-angled bend on the end smooshed the glue all the way around the back of each hole to reinforce it. When the epoxy was almost cured I re-drilled the holes, but did not tap them, instead I screwed the bolts straight into the not-entirely-hard glue. That was four months ago, and so far there have been no more issues.
The cause is something that I have put a great deal of thought into; there is obviously a lot of wind force being applied to primarily the top slat of the louvres. I know nothing about aerodynamics really, but I read a few papers and tried to get my head around it. I began to wonder if the top slat is just a sliver too high; that some of the air coming over the top of the MX-5 roof is going under the center of the uppermost slat, while the air coming over the sides of the roof is passing over the top of the sides of the uppermost slat, causing it to lift in the middle and pull away from both sides simultaneously. Rather than re-drill all the holes to lower the slat (and further weaken/damage the fastback material) I wondered if I could add some turbulence over the roof to break up the forces acting on it. So as an experiment, I purchased some cheap vortex generators off the internet and attached them, making sure there was one in the exact centre, and trying to duplicate how various other aftermarket aerodynamic kits are with spacings.
Unfortunately, since I added the vortex generators to the roof at the time as I added glue to all the bolt holes, I do not know which of the modifications has most contributed to the current stability of the slats, but together they are working well.
Next time, and I will add them again if I ever get another RF, I will make a few changes to the installation procedure so that I can be more confident of them lasting. Firstly I will lower the template provided by ideaen3D for the top slat by about 5mm, I will leave the lowest slat where the template suggests, and I will lower the two middle ones ever so slightly so that the spacing between them all remains equal. Secondly, rather than attempt to thread the bolts directly into the retractable fastback material, I will instead look into the feasibility of installing rivnuts for the bolts to screw into. Thirdly, I will adjust the angle of the slats ever so slightly. If you look in the rearview mirror photograph near the top of this article, I believe I can see the underside of slats two and three, and that they can be made even less visible by tweaking the angle ever so slightly. I'd do this by first drilling the frontmost hole of each louvre and attaching them, then sitting in the driver's seat and having someone lower and raise the angle of the slat and mark the point at which they are least visible.
Although there have been complications along the way I really do love the look of these louvres and have no buyer's regret.