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Ask me any day of the week and I'll tell you I love the B&B system as far as looks are concerned. But tell me that the bends in the exhaust "don't matter" and I'll respectfully disagree. I completely understand that to some people the looks are worth sacrificing some performance/response but after seeing all the dyno testing Greg has done and how nearly all the truly quick cars on both coasts run some sort of straighter pipe, I feel it's a bit more than "negligible". But that's me...I want the absolute best I can get so I got a performance exhaust not just something that looked shiny. Greg's post:
On a street car like a Z, The exhaust is about 10 feet long on each side and when the exhaust is this long and you start putting bends in the exhaust system, exhaust speed or velocity starts to become very important. Backpressure in an exhaust can be caused by turbulence and slow exit speed, just as easy as it can by size restriction. If the exhaust gas remains in the pipe without exiting from the pipe size being too large in a long exhaust system, it causes back pressure from the slow exhaust flow. I have been told by NASA engineers that one 90 degree bend has the same exhaust restriction as adding 25 feet of straight pipe. This means if you have two 90 degree bends in each side of your exhaust it has the same effect as adding 100 feet of straight pipe to your Z (or 50' with one bend on each)! Turbulence can cause a large amount of backpressure. Some of the things that cause turbulence are bends, sudden pipe size changes, rough pipe ends, etc. Something that use to be common was gutting cats. This gained top end power and higher peak numbers on a dyno, but at a huge sacrifice in low end power due to the turbulence caused by the sudden inner pipe size change. The reason this hurts low and mid range power is because the turbulence causes the velocity of the exhaust gas to slow and even though the area is larger it causes backpressure from the turbulent slow exhaust speed and thus the turbo spools up slower. At higher RPM’s the exhaust speed is higher and less restriction from the cats being gutted still net a gain on top, Although it is possible to have a net loss in power because it can hurt the low end enough.
"If I'm an asshole it's only because I've been turned into one by the sheer
amount of stupid people and stupid logic that dominate Twinturbo.net today."
My Zs: www.zheaven.com - Pics and information about both of my 300ZXs - Down for now
Member: www.SoCalZCrew.com - Come find out how we do it in the West! |
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12:56:53 04/19/06
