New Birkin Exhaust

[Davemk1]

So I made myself a new side exit exhaust system for my Birkin a few weeks ago. The stock system went from a 2.5" collector down to a 2" pipe that went all the way out the back. The exit out the back caused exhaust fumes to come back up into the cabin too often and the 2" pipe seemed to be choking the engine at high RPM's.

 

So this new system is 2.5" all the way and much shorter exiting on the side. This has stopped the fumes issue and really opened up the top end of the RPM range. It used to fade when getting toward redline and not pull as hard and now it pulls with urgency all the way up. It's noticeably quicker now.

 

And it sounds like a Seven should.

 

This weekend the car finally gets it's lightweight aluminum flywheel and undersize crank pulley. Should be good for another boost of power and more smiles.

 

Thanks for looking,

 

Dave

 

 

 

http://www.usa7s.com/aspnetforum/upload/1686905587_DSC_7337.jpg

[Automoda]

Thats a DNA muffler isnt it.

 

Do you like the sound? I'm still assembling my Birkin but eventually I may go with something like what you've got there. I know some of the guys on the Birkin list are talking about that muffler.

 

I've thought about extending the 4 tubes further back before collecting them, though.

 

I dont see an O2 sensor on there...

[Davemk1]

It is a DNA truck muffler. It's the longest and supposedly the quietest DNA offers. The sounds is good with a nice bark to it. Overall it's a bit loud for residential use so I made up a slip on SuperTrapp exhaust tip for it. It just slips over the end and secures with a clamp. Now I can drive out of my neighborhood at 6AM for an autocross and not feel like a criminal. I get to the event and undo the clamp and throw the tip- into my tool box. Seems to work out very well. The added tip seems to take the edge off but still flows very well. If you'd like I can post a picture of it.

 

I wonder what the most effective length of the collector tubes would be? Mine are as Birkin supplied. It would be interesting to know.

 

The is no O2 sensor. The car runs on Webers.

 

Dave

 

 

[soareyes]

If you'd like I can post a picture of it.

 

Yes please! This will be one of my winter projects for my Birkin. Can you also take a pic of how you mounted the muffler to the chassis? Thanks!

 

 

[Davemk1]

It's a bit hard to take photos right now as it's a bit dark inside and it looks like snow outside. But I think you'll get the idea.

 

The SuperTrapp thing came with a 2.5" O.D. flange which wouldn't fit over the 2.5" O.D. exhaust so I made a new flange for it so it just slips over. The flange has hacksaw slots to allow it to compress and grab the exhaust when clamped with a stainless hose clamp.

 

The bracket is a bit harder to show. It's a 3/4" square steel tube. I attached it to the seat belt bolts that protrude from the bottom of the car using pieces of angle steel bolted to the 3/4" square tube. The 3/4" stuff runs across the bottom of the car so it picks up both seat belt bolts. The part that sticks out is pretty easy to see I think. There is a stainless exhaust clamp that bolts through holes drilled in the 3/4" tube.

 

It seems to work very well with no funny vibrations or rattles and was very simple to make and pretty darn cheap too.

 

Does that help??

 

Dave

 

http://www.usa7s.com/aspnetforum/upload/111564468_DSC_7400.jpghttp://www.usa7s.com/aspnetforum/upload/1330146691_DSC_7401.jpghttp://www.usa7s.com/aspnetforum/upload/1809254526_DSC_7403.jpg

[soareyes]

Thanks Dave, your install looks great, simple and effective. I'll get to work on mine!

 

82 degrees and sunny here