Just installed a Mynes V2 header in my 2006 JCW along with a 17% pulley and WMW street cam. Car is a beast now, but the header is damn loud. This is coming from a guy who rides Harleys, so I am no stranger to loud exhausts. I deleted the CAT but kept the resonator. Any way to take the edge off the exhaust sound level, or is my only option going back to the stock header?

 

Put a cat back into it. That's what I had to do with my old STI, put in a high flow cat.

 

I read that the CAT doesn't effect the overall exhaust sound level. It changes the tone but not how loud it is.

 

You are decreasing a restriction so it will absolutely make it louder as well as changing the tone. Can you post the source to see if maybe they aren't the most credible?

 

I was checking several gen1 posts on headers and read it there. Not sure of which member it was. I know it wasn't Way or Jan or the like.

 

How much louder it gets also depends on how much of a restriction it was in the first place, so a stock setup won't see the same decibel gain as your setup that is pushing much more exhaust gas through

 

Well my stock CAT only has 46k miles on it. So it's still very usable. As far as I have read, the stock CAT for R53's is still one of the best all around CAT's. The Mynes has a CAT delete bolt on section. So the stock CAT can be cut and modified to fit.

Again don't mind it louder, just not this freaking loud.

 

That's not what I was referring to - increasing the volume of exhaust gas flowing through (a sure consequence of making more power by most means) will mean the cat, though unchanged, is restricting the exhaust more than it was before the modifications.

 

The Mynes is similar to the OBX relative to how the header mates up to the cat/exhaust. I have a 200 high flow on my car. I also found a used manifold on ebay for $30. At inspection time I am not going too chance a EML light so making a similar 13" section up that I can just remove the 200 cell and put the OEM Cat in its place. The donuts for the Mynes and OBX are odd ***** as you can get the 2 5/8" inner opening but most that size do not have a 3 1/8" outer diameter.

I have my header and high flow mated to my JCW exhaust. Great results and sound. I also have my stock manifold/cat that has only 55k miles on it. Going to keep it for now.

 

Of course. My big question is what will be the net effect of adding the stock CAT in relation to overall sound levels. Am I spending money and cutting up my stock header for a 10% reduction, or 20%, etc.

 

Based upon a friend that tracks, header/no cat/jcw exhaust will be close to 100db. With a cat, at idle you will not even really know but at WOT thinking in the 70/80 db range.

 

I was finally able to contact the original owner of the Mynes header, and he stated the deleted CAT is my problem. He had it on his modified R53 with the stock CAT. He said it was only louder at WOT and even then it wasn't obnoxious. Seems that cyow5 is correct. So will try that.

 

Lol...like I originally said, the cat will definitely quiet down that header. I have real applicable experience on my STI where a highflow cat quieted down the car. I am guessing where ever you read that it wouldn't was somebody just regurgitating something they heard one time from some random person and now its become fact to them with no actual experience.

 

Forums have some great info and some not so great info. I win way more than I lose though. The support from this site via members and vendors is helpful beyond measure.

I am getting an appointment today for an estimate on inserting the stock CAT. Will follow up once it's installed. Looking to prove you right, 1FSTREX!

Jim

 

Just got the CAT installed. Major improvement! The myth about the CAT not effecting overall exhaust sound levels has been BUSTED!

 

Think about it, you have a coffee can that has a mesh system with square holes about 1/16" that go from front to back. Each on of those holes has a material that will impede the flow of air via friction on the walls of the hole.

I am no engineer and do not need to be one to accept that the air flow and therefore the harmonics of the engine will be impacted.

 

Glad to hear you're happier.