vvega wrote:LEV_101 wrote:na cars need back pressure. if it was turbo then thats a different story.
sorry mate thats a comon falacy
providing you can attually tune your car to take advantage backpresure is just a restriction
v
Unless you have a 2stroke car! (I had one afew years ago)lol.
Essentially, (but not in totalaty) back pressure is part of the exhaust system which is not flowing efficently.
theres even an equation to measure power reduction 'due solely to back pressure induced pumping losses' (rererenced from David Vizzard)
HP Lost = BP (in psi) x Stroke x Piston Area (of all 4 cylinders) x RPM /(all divided by) 792,000.
With a system with back pressure, the engine is producing power (or wasting it) simply to expell the back pressure from the cylinders.
Of corse, that is going off topic a little as it is not including the exhaust design, or loss through scavenging, or cam design. But, in generaly, represents the minimum loss you will get from backpressure on a given engine.
Its quite an indepth topic really, and im sure there are others on here who can explain it better than myself.
Using the term sports or bigbore is really using terms people take/understand differently, as can be seen throughout the post. I guess, technically, you can say you have a big bore sports exhaust- but then one has to ask, going by the pictures above, do you view a big bore simply as a 'large exit' cannon, or if the whole system is enlarged?
Although not the best around, this is a useful link for more exhaust reading:
http://www.nsxprime.com/FAQ/Miscellaneo ... theory.htm
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