DIY: Single exit exhaust diffuser for less than $10
 

So I've had my FR-S for a little under a month, and already I felt the need to start tinkering with it. I'm going for weight saving mods first, and high on the list was a single exit exhaust. I picked up a Nameless muffled track pipe with tip from @PantsDants on Saturday and got to work.

After talking to PantsDants and @Decay107 about swapping to a single exit, both of them mentioned concerns about the aerodynamic impact removing the stock exhaust can have. The idea that it basically turns the bumper into a parachute when you have a single exit exhaust was a little concerning...

Well, as soon as I got under the car to look at removing the stock muffler, I realized there was a big heat shield directly above it that was held on by 4 evenly spaced out bolts. I had the crazy idea that maybe I could make some brackets to move the heat shield down into the airstream to use it as a diffuser. Even better, the heat shield already had the right shape of bend in it to lead the air up to the bumper in a semi-smooth fashion. The heat shield is a bit flimsy, but after making the brackets and bolting it down, it's really secure.

Anyways to do this you need:

• The stock heat shield
• The 4 stock bolts that hold the heat shield on
• 4 extra 10mm nuts/washers/bolts (I rummaged around in my garage for ones with big built in washers)
• A strip of Zinc-Plated Punched Steel Flat Bar from home depot (http://www.homedepot.com/p/Everbilt-...2067/204225777)
• Something to cut it / bend it with to make brackets (I used a Dremel and a Vice with a sledge hammer).
• A measuring tape

Of course you could use something else to make the brackets, although I wouldn't recommend aluminum, as in my experience - bending aluminum to make right angle brackets usually results in it cracking / breaking. I've never had a bent steel bracket break on me (and I've made a lot of these in the past for various car things). If you're worried about rust, rattle bomb them after you've verified they're the right length/shape. :shrug:

First, flip the heat shield over so the bend is going the right direction.

I had a friend hold up the heat shield while I measured the spacing I needed to make it sit at the angle I wanted. I made the rear brackets 4" from the L bend, and the front brackets 4.5" from the L bend.

Ideally it would probably sit a little farther down, but I didn't want it to hit the exhaust piping. If you cut the heat shield a bit, you could probably put it lower so it was a smoother transition from the bottom of the car.

I then bent my L into the brackets, measured the length from the L that I needed and cut them off the bar. Pretty straightforward.

Bolted them up loosely so I could maneuver the shield a bit - the large holes in the punched bar allow you some play to move it up/down at each corner to get it just right. And then tightened it down. Stepped back and lol'd at how easy it was.

Questions / Comments / Concerns? Too ghetto? lol :burnrubber: I took her out and took the car up to roughly 90mph and didn't feel the rear end get light at all... so yeah - hopefully it's doing it's job. Looking forward to someone that tracks more frequently to try this out and see if it makes a tangible difference for them.

Pictures:

http://becausehonda.com/system/files...DSC_0030-2.jpg

http://becausehonda.com/system/files...C_0046-2_0.jpg

http://becausehonda.com/system/files...DSC_0011_0.jpg

http://becausehonda.com/system/files...DSC_0013-2.jpg

http://becausehonda.com/system/files...DSC_0016-2.jpg

http://becausehonda.com/system/files...DSC_0019_2.jpg

http://becausehonda.com/system/files...DSC_0021_0.jpg


And just to show that you can't see it from any normal height - here is a picture of the car at rest.

http://becausehonda.com/system/files...DSC_0051_0.jpg

Now that's cool and creative! :w00t::thumbsup:

Several of us have done something similar though not to the same level with brackets and things as you have done

http://www.ft86club.com/forums/showthread.php?t=66581

I like this though. You could go get a big piece of sheet metal, pop a few holes in it and the stock heat shield, then attach another piece of cardboard to it to cut a form to fill in all the open area - then use that as a pattern to cut the metal. Just a few more $$ than what you've already spent and it would really fill in the openings in the bottom. Might have something to go do this weekend now.

Also be careful at Home Depot, they just got hacked like Target did...

Sweet - glad to see others have tried this. As for filling more of the space, not worried about the space on the passenger side for now since there is that natural opening in the bumper there. I do plan to fill that in with the piece from ft86speedfactory though and when I do, I planned to get additional sheet metal to fill the void as you said. :thumbup:

Very nice!!! Thx for the write up!!


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Looks good!

Ingenious! Not sure if it's sturdy enough for track use (the thin, flexible heatshield material and minimal spot welds at the heat shield mounting locations), but I really like the idea! At a minimum I'd beef up the mounting locations with some type of bonding epoxy to act like a weld joint. Might not be ideal for laminar flow, but better than not having one and catching air with the rear bumper "diffusor" section! Wonder how it would work and look with the "diffusor" part of the bumper cut out - I'd be curious to try it but unfortunately my SRT exhaust is in the way...

I imagine it'd look a lot like this:

http://www.ft86club.com/forums/attac...1&d=1393455610

http://www.ft86club.com/forums/showthread.php?t=42284

Brilliant!
A little off topic but could I ask you to post a sound clip of the muffled track pipe?
Is that the 4" or 5"?

It is the 5". I bought it brand new last weekend. In a former life, I was a sound engineer, so I'm generally disappointed in sound clips for exhaust. Was thinking about trying to make some sound bytes with some of my pro audio equipment...

I don't see the heat shield used as a diverter/"diffusor" on Anthony's car? I have the rear factory bumper "diffusor" section removed on mine... so I know what that looks like.

So what you're saying is that I asked the right guy ;)

Now just add some fins and paint it black.. :respekt:

http://i40.photobucket.com/albums/e2...psad20e2c8.jpg

Anthony deleted the heat shield for weight savings.

We'll see. Will have to get some help to handle the audio equipment. Also don't have much in the way of video equipment. So I could end up with crappy video and good sound... The opposite of how it normally goes I guess.

Haha photoshop. I actually got under the car yesterday and mused about how I could make it better. Have some ideas, just have to have the time to execute them.