Unsatisfied with ANY of the exhaust options available for a 996TT, I decided to combine the best attributes of certain available products and have an exhaust made for me. My primary goal was to minimize back pressure/resistance, minimize turbo lag, and maximize power. That being said, I wanted something quieter than straight pipes.

With one or two exceptions (most notably Fabspeed), all exhausts made for the 996TT use a chamber muffler. The benefit of a chamber muffler is increased sound attenuation. However, a chamber muffler creates back pressure/resistance, which decreases power and delays spooling of the turbos. For minimizing back pressure/resistance and increasing power, the far better option is a straight through muffler. Race cars that are required to use a muffler (certain race circuits require mufflers) use straight through mufflers, rather than chamber mufflers, and most of the major muffler manufacturers produce straight through mufflers for race applications. See e.g., http://www.borla.com/products/xr-1_racing_exhaust.aspx (Borla racing mufflers); http://www.magnaflow.com/02product/02race.asp (Magnaflow racing mufflers); and http://www.burnsstainless.com/Ultral...temuffler.html (Burns Stainless).

I presume that most of the companies manufacturing exhaust systems for the 996TT elected not to use straight through mufflers for sound attenuation purposes. Fabspeed is the exception. Fabspeed uses straight through mufflers. Thus, it is no surprise that Fabspeed produced the most power on Stephen’s independent test of many different 996TT exhaust systems. From a power standpoint, Fabspeed uses a far superior design to those incorporating chamber mufflers. Fabspeed’s straight through mufflers are clearly louder than chamber muffler exhaust systems and, therefore, not appropriate for everyone. However, if increased power and quicker turbo spool are your goals, a straight through muffler is the way to go.

My only gripe with Fabspeed’s exhaust system is the size of their tubing. Fabspeed uses 63.5mm tubing. For most lower to mid-power 996TTs, 63.5mm tubing should not create meaningful resistance, nor reduce power. However, for higher HP applications, it is my belief, based upon my research, that 63.5mm tubing is too small, will create back pressure/resistance, and will reduce power. Again, higher HP race cars use far larger tubing than 63.5mm (the vast majority of straight through race mufflers are larger than 63.5mm ID – see above links). Europipe uses 70mm piping for precisely this reason . . . to reduce back pressure/resistance. However, Europipe uses a power sapping chamber muffler.

Based on the foregoing, if I wanted an exhaust with a straight through muffer AND larger than 63.5mm tubing, I had to have it custom made. I approached a local exhaust shop that specializes in custom exhausts for race cars (this shop had previously made the race pipe for my Ruf exhaust when I removed the cats). We discussed many different design concepts. I initially wanted a straight run from the muffler to the tip (a slight bend would be required), with a 9-10 inch straight through muffer (the muffler would have had to be custom made). My exhaust shop convinced me that this would be nearly as loud as straight pipes. Therefore, we instead went with 17 inch Burns Stainless Ultralight racing mufflers stacked underneath the rear bumper (these mufflers are incredibly light). We choose 3 inch inside diameter mufflers (76.2 mm) and three inch tubing because that is diameter of the turbo exhaust housing. We used T-304 stainless for the tubing. We choose Tubi tips because they appeared the best able to accept a 76.2mm tube without reducing the diameter at the tip (I picked up a used set of tips).

Manufacturing the exhaust with 76.2mm T-304 tubing turned out to be a Herculean task. It was VERY difficult to accomplish the short radius turns with the large diameter tubing. However, after several days of work, my exhaust guy was ultimately able to squeeze everything in. Here it is:












The Tubi tips looks amazing from behind (The attached photos do not capture it – Ill take some more photos soon). The exhaust is a mere 20 pounds total weight (does anyone know the weight of the OEM exhaust – I think it is over 60 pounds).

Initial driving impressions: The turbos definitely spool quicker . . . the reduced lag was immediately apparent. The tone is much deeper and throatier than my Ruf. Predictably, it is louder than my Ruf, but no louder than a Fabspeed.

This exhaust should create less back pressure and more power than anything else currently available for the 996TT.

Craig

 

nice... hows the sound?

 

I had SCARGO fab up an exhaust for my 993tt using 4 small bullet type mufflers (two 6" long 6" round & two 10" long 4" round) They had perforated core for maximum flow. Spool up on K24's was amazing! Problem was that the resonance when loading the motor at lower RPM's made me crazy. Hope yours works out better than mine did. I think a balance tube may have helped.

Anyone want to try active noise cancellation???

 

Alright Craig... when are we gonna hook up?! You gotta let me help you spread the cost of stuff like this over a couple of units! Woodland Hills close enough, lol! I've gotta come check out the beast... better yet, PM me next time you're at SG... I live just down the street from there!

Congrats... nice look'n exhaust! Too bad my ECU needs to see a cat... otherwise, I'd be game!

 

heya craig... put me down for one or pm me about it bud

 

so what did it end up costing?

 

Looks great Craig. Are you going to coat it or leave it as is?

 

Craig,

Will they make more and what will they cost?

 

What about the fact that there are no cats on your system? That has got to be a factor is less lag.

 

Looks like a great project. So....where are the before/after dyno sheets? Let's see the resultant fruits of your labor!

 

Very nice Craig! Even more reason for us to hook up and go for a drive...let's set something up with the local So Cal guys.

 

Craig,

Killer exhaust, I was having the same idea with some Borla XR-1s. Sign me up for one if you are gonna start having them built.

Cleve

 

great job craig do u have a closer pic of the welds? fromt he looks of it the welds look killer.. thats hand welded right not robotic.. great job... ive been thinking of doing something liek this for a whiel now custom exhaust.... i too have a guy in santa ana that professionally does a lot of race applications liek custome manifolds etc.. if u can giev me soem of the specs of your exhaust id appraicte it .. maybe even the cost of the parts fromt he exhaust etc.. thanks

joe u can pm me the details if u want to..

 

great job. Looks good!

 

Do you think you need heat shields? Is there less heat because there is less pressure?

Did you dyno the car before and will you after the install?