Friday, March 6, 2015

Project 981 Cayman S - Installing A 981 GTS Rear Diffuser

Looking to give the rear of your 981 Boxster or Cayman a little more flash?

When the 981 Boxster and Cayman GTS were introduced, they brought with them some new styling cues, most notably a new bumper design, and a rear diffuser that works in conjunction with the front bumper to change how the air flows underneath the car vs the non-GTS models.

Putting on the GTS rear diffuser may not give you the same benefits that you would get on an actual GTS, it will however, make things a little more interesting looking for everyone you show your taillights to (whether in traffic, or on the track).

While changing the front bumper is an expensive and time consuming process, putting the GTS' diffuser on your non-GTS 981 is a fairly simple and quick process.

This is what the rear diffuser looks like on a non-GTS 981 Cayman or Boxster.

Before you begin, here's a quick rundown of things to watch out for:
  1. Don't do this right after you've been driving the car around. You are going to be very close to the exhaust, and the last thing you want to do is burn yourself. Give your car time to cool off before tackling this project.
  2. Wear eye protection. If you drive your car often, you're going to find a nice collection of dirt and rocks trapped in your rear bumper waiting to drop into your face. If you're doing this on a lift, or otherwise other elevated working space, your eyes will probably be at the right angle to be a catcher's mitt for all the detritus that comes along with a street-driven car (no matter how well you clean it).
  3. You're going to have a hard time unclipping the stock diffuser from the center trim that surrounds the exhaust pipes. That's normal, and has been the point of frustration for nearly everyone doing this same mod. While you might be tempted to try and unclip the center trim piece and remove the diffuser as a single unit, the tabs they use for that specific piece are unusually long, and it would be very easy to damage it when trying to free it from the corresponding slots. Just have patience and remove the diffusers individually.
Other than those things to keep in mind, the process requires minimal tools - there are only 6 Torx head screws to remove (3 per side, with two obvious ones at the bottom edge, and one hidden behind the diffuser near the center, all T25), and beyond that, it's just all clips, so a small panel clip removal tool, or even a thin flat-head screwdriver with tape wrapped around the tip (to prevent marring of the plastic) will be fine. A flashlight would also be helpful to see the location of the hidden screw.

Location of all the top edge tabs.

Location of all the bottom edge tabs.

Location of all the middle top edge tabs.

Location of all the middle bottom edge slots.

These are the side tabs/slots that connect the to center trim piece around the exhaust tips.
The parking sensors are fitted into these openings, and secured via two tabs. It will only fit in one orientation.

These instructions apply to both sides, so we'll only cover the removal of one end.

The first step is to remove the 3 screws. Removing these screws allow the bumper and retaining frame under the diffuser to move around, making the removal process easier. 1 of the screws (the one nearest the fenderwell) doesn't actually attach to the diffuser, but removing it will allow you to move that edge of the bumper around to make alignment of the new diffuser easier. The hidden screw is near the center opening facing inwards.

This screw is located behind the diffuser  near the exhaust opening/center trim.

With the screws removed, we opted to free the top edge of the diffuser from the bumper. There are tabs on the diffuser that go into slots on the bumper, and some persuasion with your panel removal tool/screwdriver and a few firm tugs will release them. If your vehicle comes installed with parking sensors, make sure to reach behind the diffuser once the top edge is freed, and pop the sensors out. They are only held in place by weak plastic tabs, so it should take minimal effort to release the sensors.

With the sensors out of the way (if so equipped), and the top edge free, all that is left is to release the remaining tabs and slots on the retaining frame attached to the car from the tabs slots on the diffuser.

There are tabs on the bottom edge of the diffuser that clip into slots on the bottom edge of the retaining frame, as well as tabs and slots along the top and bottom of the middle opening of the diffusers. Use your panel removal tool or padded screwdriver to gently release the tabs.

With the diffuser released from those, all that is left are the tabs that connect the diffuser to the center trim piece.

This is the part that people find difficult, because of the three tabs that attach the diffuser to the center trim piece, the top two are both tabs and slots, so you will have to play around to find a method to release the tabs from the slots on the tabs. Once you figure out one, the rest will be far easier.
Unfortunately, there is no easy way to free the diffuser from the center piece.

These are the slots with tabs that the diffuser hooks into.

Once you finally get the diffuser unclipped, it can be removed altogether, and the new diffuser installed.

We opted to install the sensors into the new diffuser first. They will push in and seat easily, and they will only insert into the diffuser in one position.

With the sensors in place (if so equipped), you can then install the diffuser the rest of the way. 

As the new diffuser does not have a middle opening, you only have to worry about the top and bottom tabs of the new diffuser, as well as the tabs on the side that attach it to the center trim piece.

You can start with the top or bottom tabs first, and in our case, we started with the top tabs, pushing the new diffuser into place so that it's tabs engage the slots on the bumper. Once the diffuser attached to the top slots, we attached the bottom tabs, making sure everything clicked into place. After that, we attached the diffuser to the center trim piece. While the top and bottom tabs should click in fairly easy, it took a little more force to get the side tabs to properly engage.

Once you have the center tabs in place, double check to make sure the top and bottom tabs are fully engaged, and everything looks like it's seated correctly.

With everything seated properly, reinstall the screw nearest the fenderwell. You may have to move the bumper edge around to get the tabs to align again, but it shouldn't take too much effort for that either.

Reinstall the two remaining screws in the same locations they were removed from, and you're done!

This is the end result: a 981 with an extra little oomph in the rear styling department.


  1. Hi,
    I'm interested in doing this conversion. My first concern is that since there are no openings in this diffuser to allow heat to exit, is heat build up a concern? Then I see that Suncoast offers this item 2 ways: Either just the 2 side panels, or a kit that adds heat shielding and new center trim. So I contact them to inquire, and they respond with, well yes, possibly, that is why the kit with heat shield is offered.

    Can you offer any comments? I would prefer to just swap the 2 side panels only, but don't want to introduce heat buildup issues, if it is even a true concern.

    Thanks, Greg

  2. Would have been nice to see an answer to this question. Clearly there seems to be some hard venting behind the diffuser. If this openings gets blocked then I can see possibly some melting after hard drive.