I like the trunk mechanism on the Audi A3 2015 car. The trunk opens all the way up by remote. When you’re carrying groceries it is very convenient. I usually carry two bags for my work commute and the MX-5 trunk will only open an inch or so, causing me to have to put my bags down to open the lid all the way. After a closer look at the current mechanism, I thought it would be easy to add a couple of torsion springs, to help the trunk lid open-up all the way, by remote.
I found on the McMaster good size torsion springs and designed simple brackets to attach them; I 3D printed the brackets from ABS plastic and they seem to do a good job!
Parts from McMaster-Carr (updated):
- 9271K125 – 180 Degree Music-Wire Steel Torsion Spring Left-Hand Wound
- 9271K124 – 180 Degree Music-Wire Steel Torsion Spring Right-Hand Wound
- 94850A129 – No-Slip Clip-On Barrel Nut 1/4″-20 Thread Size – 2
- 8863T23 – Vibration-Damping Loop Clamp, 3/16″ ID, 1-1/8″ Long – 2 (to attach spring to the lid)
- 94779A840 – Head Screws, Black-Oxide, 1/4″-20 Thread Size, 3/4″ Long -2
Updated 3D printed parts are here .
Bracket attached to the hinge with one screw. Spring need to be cut on one sde for 2″
Of course closing the lid now requires a little more push, but not much. This modification is simple. I really like this new feature in my car.
The latest design does not require you to install a loop clamp on the lid, just a plastic pad on top of the screws.
Updated on 10/1/2017
MX-5 2017 RF has slightly different hinges, to make my design work in both car versions I have designed new plastic parts.
In the RF model this design works very well, however the Soft Top version still has some cosmetic issue. The soft top trunk lid is lifted 0.5-2 mm above the body line, the RF seems to not have this problem.