"In this Product Series, I document the unboxing and test fit of the E92 Superlight Carbon Trunk. The E90 LCI variant is also available here. They are ideal lightweight trunk options for those seeking to retain original aesthetics with much lighter weight.

In this entry, I go back to my roots and DIY the test fit of the E92 Superlight Carbon Trunk in the driveway. I further compare fitment to my previous CSL replica trunk."
- Matt

Back to the driveway. 

Ah - yes, the sight of my father's interlock driveways. It can only mean one thing: we're DYI'ng this one for better or for worse. Proud of his new power tools, he lent a hand or two to fit uninstall, install, uninstall, re-install the trunks, while he fitted side skirts to his car. 

He's retired now - he sold the BMW motorcycles, skipped on getting back into a Porsche and bought what is the logical answer to everything car related: a Miata. 

As with most DIYs I take on, I set unrealistic expectations. I wanted do test fit the trunk and the widened front fender kit within the afternoon. Lofty goals aren't the problem, it's usually been accepting you won't reach them. 

I'm glad to say I learnt a thing or two today, including accepting the slowness of this process: I didn't even try fitting the fenders. 

It's an easier way down. 

The first step to test fitting the OE+ Superlight carbon trunk was evidently to remove the replica CSL trunk. It fit starts with removing the pop in clips from the liner. Most were easy, except the two at the top right corner. 

The holes were slightly misaligned and creating to tight of a fit. It made the removal process laborious with trim tool tools. I had to pull out metal tab removers to get it done. 

The great thing about having a liner on most aftermarket trunks is hiding the riff-raff hacks needed to make some accessories fit. 

To fully remove the liner, you also need to remove the emergency handle in the middle. It's fairly easy to remove. 

The next step is removing the trunk's struts. It's a straight forward process: pop the metal tabs and gently pull. 

The trunk won't fall off on you - it will instead slightly tilt forward. 

I did not fully remove the accessories off the replica CSL trunk as some were a one way street for a few reasons. 

Unlike the E46 M3 that uses threaded rubber stoppers, the M3 V8 a metal and plastic stopper that is riveted into the trunk. 

The trunk came off as he unbolted the hinges. These use a 11mm / torx 30 bolt head.

My replica trunk is made in fiberglass: it's heavy.

Taking the trunk off was a shoulder and back workout, probably adding another 4kg / 10 lbs to the the trunk. 

Zooming in on the inner taillights, you'll immediately notice the weird fitment. We decided on this when originally fitting the trunk to atleast achieve a proper fitment on the outer lights.

It required us to glue them using urethane. I chose not to remove them as I needed a functioning trunk later that evening. I will source used inner taillights to test fit the OE+ carbon trunk later this week. 

The test fitment. 

Below you'll find my test fitment notes and the little things that will be corrected for production of the OE+ carbon trunk. 

The liner. 

The obvious first test fit was the trunk liner. It aligned perfectly well with the lower trunk's holes. I also got to test fit push pins and they went in and out easily. 

The liner completely hides away any sight of carbon. I'm unsure if I would personally fit the liner if the black gelt coat was satin.  

The trunk liner cut outs are there on the lower section.

Here was the first "Motorsport" fitment feature I noticed: the upper section of the trunk did not have the cut outs required for the liner. 

This does give you the option to run without the liner with holes for cleaner aesthetics. If you want to run the liner, you will have to drill. It's relatively easy, align the liner and drill.

Don't punch through the topside carbon though (!). 

Inner accessories fitment. 

This part of the test fitment is limited in details as I chose not to remove most accessories from my current trunk. With the liner test fit done, we moved to bolt the trunk on the hinges.

We did not re-use the dual washers. No issues with the threaded inserts. 

The trunk being this light, we only fitted a single strut. If you fit both, watch for your chin (!).  

With everything bolted up, there was an obvious oversight in the trunk's production. The cut-out to fish through the wiring harness and clip in the rubber grommet was missing by the bottom right corner of the trunk. 

This cut out will be present on all production trunks - no exceptions. 

Notes on wing reinforcements. 

A few of you asked on whether this trunk can support a wing. This specific one, no, but wing reinforcements are available on the Superlight trunks for a small extra fee. 

There would be added layers of carbon at the spots below where the inner section is bonded to the outer section. 

Panel gaps.  

Beyond the little details above, panel gaps are what matters most to me. It's what has been most disappointing in the replica CSL unit I am currently sporting and motivated me to source and develop a better fitting unit. 

I'm glad to report this fits very, very well. It's in line with my original BMW trunk. 

As a reminder, this is how an OEM trunk fits. Somewhat tight but not too tight, and straight, everywhere. 

Before you dash in the comments saying I lost my eye sight. I did not fit the trunk latch mechanism. It explains why it sits higher. 

As such, evaluating fitment was done while pressing down on the trunk. The trunk is perfectly level with the quarter panels. 

The corners by the back window are your first guide to aligning the trunk correctly. The adjustments are entirely done by the bolts on the hinge: there is surprisingly a lot of play.

This is an example showing the corners as misaligned. It will take you a few tries to get it visually perfect. 

That is a sharp corner, unlike the rounded off corners on my current replica CSL trunk. 

The lines are parallel to the quarter panel. From experience, the white primer emphasizes the gaps. It's only going to get visually better from here on out. 

We adjusted the upper right corner fitment by pulling the trunk outwards. The inner lights' upper tip end up aligning with the quarter panel gaps.

This was with the corner perfectly aligned. The mold is straight!

The driver side aligns as well. In this view, you could see the hinges with the replica CSL trunk. We were able to push it slightly further left by a millimetre or two to get a balance between both sides. 

Seeing my car in a quasi-Touring Spec again had me questioning my decisions to go for a wing. It's undeniably a great design from BMW M.

A reminder why. 

Fitting the CSL trunk again was a PITA: taking close to 2 hours of fiddling around, it  reminded me why I'm doing this.

I struggled to plug in connectors to the glued in inner lights and the trunk latch's handle, along with clipping in the plastic bracket for the emergency trunk latch wire. 

I thought I was done [...] until I closed the trunk and the license plate lights popped out.   

We had previously also used a dab of urethane to get them to stick. I used a 3M double sided tape at first but it wasn't enough. I pulled out the gasket maker instead. 

Things you don't see won't hurt - but things you know [..] AH!

 

I did not fully paint the OE+ Superlight trunk. It was sold as a demo unit to a customer in New York. 

I chose to focus my efforts on the development of a new CSL carbon trunk with Vorsteiner.