i would like to build a 2.75inch exhaust but cant find any mandrel pipes for a good price. i usually buy from columbia river mandrel bends but they dont have 2.75. so my question is since 70mm is the best diameter for the s2k would 3 inch hurt me. i have intake 70mm test pipe and custom 2.5inch exhaust. put down 219whp and 150trq untuned soon to buy a header and maybe k-pro. has anyone used 3 inch n/a.

 

if you're gonna tune, I'd say go for it, although, and I will have to say this- I would not really recommend it unless u plan on going FI...good luck to you though!!

 

Supposedly, T1R or A&J Racing did some testing and found that 70mm was ideal...larger lost power for NA. If you are planning to go FI, then 3" might be ok.

 

earlier discussion here

btw ... I switch between a 3" dual and the stock exhaust and do not notice any power loss. Never had it dyno'd nor have I tried a 70mm exhaust while NA. Bought the 3" when my car was FI ... it's now NA.

 

3in will be fine tuned on hondata just use a single insted of duel exhause i used a custum 3in exhaust on my all motor ls/vtec hatch and saw good gains and the shop that bult the motor for my also uses 3in on qll there all motor raace cars as with everything get a good tune and you will be good to go

 

If you go N/A i would just go 70mm

 

If you tune the engine, 3" is fine and will make more HP in VTEC...

 

Another 3 in. thread?

 

its for the most part agreed on that 3" is too much without boost

 

3" is huge for NA. Hell 2.5" was plenty good for a 400 whp DSM. 3" is for some big power numbers! Just go 70mm as other have said if your going to stay NA. Plan to go FI shortly then sure go 3"