With basic bolt ons does a 3 inch cat back cost horsepower/torque?

[desertg8]

I always hear it costs horsepower/torque due to the exhaust gases exiting slower. But with a ported intake, ported throttle body, cai intake, kooks 1 7/8 shorties along with a few other goodies does the 3 inch cat back slow down the car verses a 2 1/2 inch catback?

Any one with dyno numbers or seat of the pants feel or track time?

[G8 GT V8]

With the bolt ons that you described, I'd be very surprised if you saw much of a difference in performance between a 2.5 and 3 inch catback.

[Fatdaddy]

^This. 2.5 inch pipes are good to almost 600hp wot. Bolt ons won't get you anywhere near that. The larger pipes will degrade your part throttle and mid-range response. The car will feel sluggish on the street versus the smaller pipe.

[GRRRR8]

Unless you were planning on a TT system you wont see a gain with 3inch unless you had big cubes and HP.

[desertg8]

I will keep my setup then. I am running freakishly fast for the mods I have. Better than alot of gxps.

I have a rotofab in which I opened up the bottom of the splash pan real well, a ported t.b., a ported intake, kooks 1 7/8s mids, 2.5 inch pipe back to a 3 inch x pipe, and a custom made 3 inch axle back with dynoflow turbos on them. Suspension wise I have bmr lower control arms. Oh, I have an underdrive pulley and a superchips tuner which I have set to the 91 rotofab tune. It does not even tune for headers.

With a 2.03 sixty foot at Firebird in literally over 100 degree heat with a DA of close to 4800 feet I ran a 13.075 at 107.5. I was faster than srts by 8 tenths and gxps by a few tenths.

I just ordered some spohn chrome molley toe rods and hoosier 275/40/17 drag radials for my 17 inch knock off corvette rims which I bought on this forum. The nitto nt555rs almost acted like street tires no matter what method I used to get them hot. It should be fun after I get the hoosiers on and down the track. They each weigh 8 pounds less than the nittos.