So I am a bit of a stubborn person. I refused to think I would have to deal with rasp when adding test pipes to a stock exhaust, so I started thinking for a solution. I went with ehh quality Megan resonated test pipes and a M2 HR design Y pipe that is 2.5" merging to 3". Oh boy did it sound nice under very light load, but 1/3 throttle and beyond was rasp city. I immediately removed it and put the stock DE Y pipe on. Rasp was reduced but still there, obviously from the 2.5" test pipe hitting the 2.25" stock y pipe flange. Also the non HR design merge point made the tone not as sexy. So what to do, what to do??? I had my friend fabricate a 8" gradual reducer inside the 3" merge of the HR y pipe to a 2.5" end.

Here are the pics.




So now I have a 2.5" all the way through exhaust!!!!!!!
Here is a video of the STOCK Y PIPE with resonated test pipes





I will be making a video tomorrow of the results with the new y pipe installed. I also will be installing V2.22222 ART pipes also for more power in a few weeks when they come in.

So why all this trouble? Well I drive 3-4k miles a month, I want no drone/audible hwy exhaust, no cop attention, and I am supercharging the motor so squeezing every N/A hp out is not my goal.


>>>>Fabricator said if this works well he will weld a 1/4" flange with the reducer on it, so people can slip this into their existing 3" y pipe on a stock exhaust it is a very tight snug that requires the last 1.5" to be hammered in.<<<<<<

 

Perfect. It's amazing what universal piping diameters will do.

Correct me if I'm wrong, but aren't ART pipes 2.25in as well? It may create more rasp, but the hemholtz resonators should get rid of it.

 

From what I read art pipes, HFCs, test pipes are all 2.5" and the stock y pipes are 2.25" inlet merging to a 2.5" all the way back to the muffler.

 

wow thats amazing! My HFCs definately give me some rasp at full throttle and on the rev down at around 2k rpm

 

My big aggravation is that I keep killing flexible couplings (both sides) My car is by no means slammed and I have killed at least 10 sets since May '10.

I just ordered another set and am going to have my exhaust shop do whatever it takes to sinch the exhaust up so it no longer hits speed bumps.

 

nice work...what a coincedence - I was researching the same issue --- since I'm running the MD xyz pipe(3" outlet) which bolts to my Megan mid pipe(2.5" inlet) I felt as if I was 'hurting' performance and getting unusual sound... Today I had my exhaust guy install a stock G35 Ypipe while I figure out options...I was also thinking of putting in a reducer or also swapping out the MD resonator and fabricating a 2.5" reso to a new flange....

let me know if your friend will ship to Cali...I'd be interested.

 

I've got the megan HR style y-pipe on stock cats and exhaust. Just ordered some M2 test pipes that will probably go on next weekend. I'm sure I'll get some rasp, but hopefully wont have the whistle/hiss with the bigger y-pipe. I'll be bumping up the exhaust to 3" soon to hopefully eliminate any rasp caused by different pipe size. I plan on putting a bigger resonator on to help eliminate it all together.