How to (better) install your cheap knock-off BRZ Diffuser
 

I bought a knock-off BRZ diffuser from a vendor on this forum. They are less than $200 and the quality is OK, not great, just OK. But hey, it's not the $700 Subaru part.

I don't know about the fasteners that come with the factory stuff, but if they are anything like what comes with these kits, they are not up to the task.

I did not have desire to take the bumper off, I think all those plastic clips wear out every time you remove them. The goal here was to not remove the bumper but make a strong installation.

I will leave the five middle 5mm bolt/clip installation to the factory instructions, they are OK. I will deal with the outer fasteners.

Instead of push-in fasteners, I used some 10mm OD plastic spacers around a 6mm bolt. These are much sturdier then the push in fasteners. Outward from there is where a u-clip with a threaded insert is provided. This U-clip squeezes the the two diffuser halves against the stock bumper. This adds a surprising amount of solidity to the installation. Here I used a metal 1/1-20 u-clip with a 1/2" long phillips head stainless bolt. You must drill out the plastic hole already in the diffuser to 1/4". The clips in the chinese kit are not up to this task and will strip.

Lastly, is the outer bracket that attaches the edge of the diffuser to the bottom of the bumper. I didn't like the looks of the included bracket and to make it work you really should take the bumper off. Yes, there may be a way to un-do some clips and get in there, but I didn't want to go down that road. Instead I made my own bracket. A 6mm button head bolts and a nyloc nut take care of the diffuser end of the bracket. On the other end I used 10/32 "Well Nut". This is a blind fastener. Meaning you just need to drill a hole, you don't need to have access to the back side. There is a black plastic box structure behind the rear wheel where a drilled a hole to the OD of the Well Nut. You just push the Well Nut in the hole, thread a bolt through the bracket and start tightening. Turning the bolt compresses the rubber you push in the hole and acts like a rivet.

Ignore the 3m tape in these pictures. It won't do anything where I placed it. I was very happy how the metal U-clip tightened everything up.

With the way you named the thread I half expected you to say:

Throw it away...lol

Good write up on how to mod it for extra hold.

I was in a bit of a hurry to write this, I should have waited until I had more time.

A couple things. The placement of the U-clip that is near the exhaust tip is a little confusing. The clip really needs to snap over both the layers of the diffuser. It pinches them together to sandwich a section of the rear bumper. The threaded part of the u-clip should point towards the ground and you will have to tap on with a hammer. You can tap it on and partially thread the bolt. before you install it The plastic u-clips included in these kits will probably break if you tried to do this. The factory stuff may be better.

Replacing the u-clips with metal ones and using bolts instead of the push in fasteners are mandatory in my view. It really firms up the structure.

Well Nuts are available at US Lowes stores in their specialty hardware bins, but their inventory control of this stuff is poor. I used some "inch" fasteners, but used phillips button head screws so you don't need to go find your "inch" tools.

I've never looked at the factory BRZ diffuser that close, but if it close to this construction it certainly wouldn't be worth $700. If it was carbon, maybe, but not plastic.

Now my next problem is the diffuser makes the stock FRS exhaust tips look tiny.

Any pictures of it installed?

or even a link to the vendors thread would be much appreciated.

EDITS: nvm found it http://www.ft86club.com/forums/showt...light=diffuser

Some picks, so now I have an FRS with the BRZ diffuser.

The bracket shown is the right rear corner.

Now all you need is some:

1. Better looking tips
or
2. Catback exhaust
or
3. Header with better exhaust tips
or
4. Header with Catback exhaust

Nice job! The only issue with making such a solid connection is the bumper is going to rip to shreds if you hang the diffuser on anything. The entire point of the cheap plastic rivets is they give way before the part they're holding breaks.

True, but I don't need it flapping around either. There are five bolted connections that I did not modify. Unfortunately, they are all in the center of the diffuser and the outer connections are all very weak. Two of the supplied clips are just too weak to work properly. I can deal with my errors if I tear it off doing something stupid.

I really have to get an exhaust now to fill out the space in the diffuser.

Nice write up. I've seen a couple of these floating around for about $70 bucks or so.

yes i seen them on ebay for like 69 bucks free shipping

Did your kit come with those brackets? If not, where'd you get them?

I went to a local body shop and got 3 big Body panel clips and 4 small body panel clips the plastic screw-in type that expand when you screw it in. This worked prefect, looks OEM and mounted like Subaru would have.