I am going to put a JDM 4-1 header and test pipe on my 98 R with otherwise stock exhaust, how loud is it going to be? Obviously I didn't buy an R cause I want Caddy like quiteness but I don't want it to be too obnoxious either, so how much louder than stock will it be? thanks.

 

I am doing the same and am very interested in this as well.

 

At one point in time i had AEM CAI with JDM 4-1 and high flow cat..i know its not a test pipe but cats really dont quiet things down in the exhuast system..anyway...after adding the header and HF cat the only difference i noticed was a little more raspiness at low RPM's..once u hit VTEC with the header there is a noticeable difference in sound..the stock exhuast does a GOOD job of keeping things quiet on the outside. With the header, intake and cat i could REALLY TELL that my car wanted to push more air out but was having a hard time cuz of the restrictions in the stock exhuast..when i took my stock exhuast off and noticed the bottlenecks at beginning of B pipe i could see why. By the way...if u get a 2.5" test pipe it will NOT correctly seal with the stock B pipe. i had a small pin hole leak in mine.

 

With stock exhaust I noticed no increased noise other than a bit of wooshing from underneath the car due to no cat. Exhaust noise was unaffected. You can use a standard 3 bolt gasket to seal up the test pipe with the stock B-Pipe.