Originally Posted by
MightyMaxGS-T
ok it's an 1/8 of an inch so approximately 5mm? ok so when some one goes from a 60mm tb to a 65mm (approximately 2.5") throttle body are there no gains or minimal increase in flow? absolutely not, when you increase the diameter by 1/8 of an inch what you are increasing is the volume of your piping throughout the entire system not so much just the diameter in one area. so for an entire system it would equate to a lot less volume in the exhaust system. also, i wasnt saying to use a fart can, mufflers with a good packing material have a tendency to be quieter than those without. i'm not saying yours was not quiet, but for the most part if you buy a muffler (same style as the thrush) with ceramic/stainless packing it is usually a lot less. the dynomax ultraflo oval mufflers are usually pretty quiet and quite durable. it is definitely a much better built muffler than the thrush, hence, the reason it costs more. in addition to that the ultraflo flows a much higher cfm of air than the turbo style because of its internal straight through design. now don't take what im saying as offensive because im not saying that ur thrush is no good, but there are better mufflers out there that offer a much better sound and flow design than it, in my opinion of course. lol i didnt just post up here because i felt like talking, i have built a lot of exhaust systems, and i have actually used the thrush. i dont know what motor you had it on, what size piping you used, or if you had any other resonators (or cats) on there, but i have built a system with that muffler alone and it is not a pleasant sound. and as for those cars with the 60mm piping making 200+ all day, i'll bet they would make more power with a 2.5" system rather than the 60mm.
simply put, youre going to get more power from a 5mm bigger tb than a 5mm bigger exhaust. ive been thru calc class and yes i understand what your saying about the system being collectively bigger in volume over the entire area. however, it is harder for a motor to take in air/fuel mixture than it is to expell it. hence the reason you gain more power from just a bigger intake cam than just a bigger exhaust cam. ill give you a prime example: installing a ctr intake cam on a b16 is likely to give you 7-8 hp. installing both will get you maybe an extra 2-3 over just the intake side depending on mods and tuning and such. why? because once the mixture is burnt its easier to release because there is less to it. most has been used in the reaction inside the chamber to create the combustion engergy driving the motor, and the rest is then expelled thru the exhaust. thus meaning that you dont need the biggest possible exhaust to get the most power. if it were a larger displacement motor that moves more air, i would agree that the 5mm extra makes a difference. but were talking about a b16 and not an h22. thats a large difference to say the least.
as for my setup: its an ls vtec. and when i upgraded headers, my exhaust got really loud bc of the fart can i WAS using, and because i had to cut out a resonator to install my header. i then cut the fart can off and clamped to my shitty 2.5" exhaust shop specual exhaust a thrush turbo muffler, and instantly the car was quiet. it sounded stock immediately. and the 20 dollar thrush muffler made more power over a borader range on my setup because of the tiny extra bit of back preassure it made with the chambers. hence the reason when i switched from that system to my 60mm mandrel bent greddy system, nothing really happened except i gained throttle response. which makes sense considering the bends were mandrel instead of crush bent.
no offense taken. i guess there are two different oppinions on the same topic. i still advise using a jdm r header over anyother header besides a high dollar hytech, the hytech rep, or something equivalnt with a 2.5" collector such as a buddy club, smsp, toda, etc... even the ebay knock offs with a 2.5" collector make great power for what they are.