Does it really make that much of a difference? I hear a lot of commotion about 2.25 and bottlenecks lately in the TYPE R forum...I mean is there going to be enough difference in power gains for both cases: 1) mildly tuned vehicle (i/h/e/fuel/cam gear tuning)

2) heavily modified motor (headwork/cams)

I mean how much HP are we talkin going from a 2.25" catback system versus a 2.5" because I'm having so much trouble finding mainstream exhaust manufacturers such as Greddy or HKS supplying those diamaters...the only ones carrying large diameters are Type One and Spoon and Kakimoto right now..in 63mm variety... I wonder if the extra $$$ and hassle are worth it..especially the noise levels going up when stepping up to a larger diamater. I"m running a Jdm 2.5" header going to a 2.5" carsound cat or 2.5" Type one racing convertor..and right now need to know what B-pipe/midpipe i should go for....please give me your input and REAL world data for backing...thanks.

 

2.5" vs 2.25" is all relevant to how much whp you are producing. If all you have is I/E/H than 2.5" prolly isn't gonna help you much.

Regarding bottlenecking:
going from 2.5" --> 2.25" is pretty significant. A difference of .25" or .125" around in diameter. I would not recommend this type of bottlenecking for a motor making good power.

however going from 2.5" --> 2.375" (equivalent to 60mm) is not quite that drastic. A difference of .125" or .0625" in diameter. Although bottlenecking is not desireable...I feel the pressure drop across the different diameter piping is insignificant that the power loss (if any) are minimal.

I have thought this through alot considering I wanted to go 2.5" all the way from header to muffler but was unable to find a catback system that I liked that were 2.5" or 63.5mm. I decided to go with the RS*R catback and sacrifice the .0625" (or 1/16") in diameter bottleneck for a sound I really like.

I apologize if any of this doesn't make any sense. I am in a hurry to get this done so I can go eat.

 

https://honda-tech.com/zerothread?id=380727

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IN2VTEC &raquo;</TD></TR><TR><TD CLASS="quote">because I'm having so much trouble finding mainstream exhaust manufacturers such as Greddy or HKS supplying those diamaters...</TD></TR></TABLE>

Why does your exhaust need to be from a "mainstream" manufacturer?