What size cats?
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
What size cats?
Running a 2.5 inch dual exhaust system. Should I get 2.5 inch cats or 3 inch cats?
My thinking is that the 3 inch cats will be less restrictive.
What should I get?
My thinking is that the 3 inch cats will be less restrictive.
What should I get?
Racer
Joined: Feb 2006
Posts: 462
Likes: 0
From: green valley az
cats
Originally Posted by 4Ever21
It all depends, since you have an L98 I wouldnt go any bigger than 3" pipes. I have an '85 and I put 2.5" pipes on mine with 3.5" tips.
Team Owner
Joined: Sep 2001
Posts: 62,140
Likes: 1,729
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Originally Posted by black_89_vette
So when people say cats are restrictive, there wouldn't be any difference between a 2.5 " and a 3" on my system?
In that sense 3" might be more restrictive.
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Racer
Joined: Jan 2005
Posts: 476
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From: Tucson, AZ. L98-85 AUTO COUPE: 120k MILES: daily driver. SOUND OFF IF YOU'VE BEEN THERE. Ex-Jumpin' Junky-82nd Airborne-2/505 PIR: 1st ID-1/16th Inf: Recon Marine Retread. GOD BLESS GRUNTS.
as far as i've read, the closer you are to the 3" collectors, the more you need the 3" tubing. the reasoning is that the hotter the gasses are, the more volume they need.
i say this because i am mentally planning an exhaust system and my research has me putting dual baby cats immediately after the collectors. in this case, i will put 3" tubing there. personally, i will not put anything less than 3 untill after i pass the tranny. if i go to 21/2, it may be after the x pipe.
from what i have gleaned it is a good idea to reduce pipe size after the collector to maintain some back-pressure--logically as the gas shrinks due to heat loss, a smaller diameter pipe is needed to maintain velocity. the only problem is where do you start the smaller pipe? as always with any type of flow--transitions should be a smooth as possible: turbulence kills flow. if i just had $5,000 to do the research. any sponsors?
just my opinion.
i say this because i am mentally planning an exhaust system and my research has me putting dual baby cats immediately after the collectors. in this case, i will put 3" tubing there. personally, i will not put anything less than 3 untill after i pass the tranny. if i go to 21/2, it may be after the x pipe.
from what i have gleaned it is a good idea to reduce pipe size after the collector to maintain some back-pressure--logically as the gas shrinks due to heat loss, a smaller diameter pipe is needed to maintain velocity. the only problem is where do you start the smaller pipe? as always with any type of flow--transitions should be a smooth as possible: turbulence kills flow. if i just had $5,000 to do the research. any sponsors?
just my opinion.
Last edited by parafrog; Mar 17, 2006 at 07:44 PM.