I am building a b20vtec with 84.5mm 11.5:1 compression with Toda b cams and many more. BUt my question is:

Would a 3" catback system be a disadvantage or advantage? I am planning to go with 2.5" but wanted to ask before I purchase the 2.5" system. Please state your reason too.

Thanks---

 

2.5" will still restrict your flow... It adds a bit more back pressure to a CRVTEC motor due to displacement... If it were me I would go with 3" as we do on all of our turbo cars... I personally hate mufflers tho and would just run it straight back ducting it down before your gas tank... If you want it quieter on the street then go with 2.5" and drop your exhaust when racing... This is just my opinion too but I would reconsider those cams... My friend's CRVTEC/EK which you've probably heard of, running 84.25mm JE 12.0:1 slugs, stock rods, ARP rod bolts, Portflow P72 cylinder head, CTR IN cam (GSR EX), SK2 IN manifold & sprockets, RC 310's, AEM FPR, ITR ECU, and VAFC (tuned by feel) ran a 12.62@107 last season... Anyways we put some Toda B's in it ~2 months ago just for the hell of it and it ran like ****... Tossed it on the dyno and the baseline run with 12 degrees of ignition timing was 179whp and 125wtq... After pulling like 15 runs it made 190whp and 140wtq at 18 degrees... Later that night he ran a best of 13.31@101... We just pulled those cams Saturday night, put the CTR IN cam and GSR EX back in... Left the VAFC on the Toda settings and he ran a 12.7@106... I'll put his car on the dyno sometime with the R cam to see what we're making... We're gonna pull the head in a few weeks, install a new valvetrain then put in the new cams... Either JUN3's which I know will work awesome in his CRVTEC since my other friend had the exact same setup... JUN Killers or *SK2st3's (*which I'm trying to talk him out of) Sorry I turned your whole exhaust post into some **** about cams but I just wanted to add my $0.02... Good Luck

 

Thanks for the insight.

 

anymore opinions?