Weird phsyics question, about exhaust


so we all know that high speed air creates a low pressure region (bernoulli effect) right? this creates lift in wings, and likewise creates pull in other similar situations.

i just thought of something wierd that i thught id mention - so with exhaust systems, supposedly a loss of backpressure is bad for torque… and at very high rpms, the free flowing exhasut is good… so, imagine (dont laugh) if exhaust pipes faced straight up…(or down, or sideways…). what would theoretically happen, if the pipes were good for backpressure, is that at lower speeds, pressure would be normal, and at high speed, a vacuum effect would occur, creating a low pressure zone outside the exhaust pipes, which would draw gases out at a faster rate… sort of like a ‘automatic variable backpressure adjustment’

i dont know why i just typed that, since in retrospect it seems ridiculous, but whatever… I = :tard



I’ve never though that much into it, but if you did think about it you’d also have to consider the heat of the exhaust and its fluctiuations which would also affect pressure, and the scavanging effect your referring to I believe comes from the low pressure area created at the exhaust ports between cylinder firings, not at the tailpipe.


MD is almost dead on. The scavenging happens more efficiently with a properly set up pair of headers (i.e. equal length and a well designed collector). This is why the better headers are long tubes with equal length tubes.


and thats why front wheel drive cars sound like crap sometimes, because the exhaust has to take a 90* turn to leave the car… unless they (the driver) ports it out onto one of the front wheel brakes… which isnt smart, but is isnt smart to buy an import now is it?

nah, just kidding about that last statement… v8’s are now more exspenive (thanks corporate america, and those damn tree-huggers!!)… stupid gas prices…

um, i should be asleep, but i couldnt sleep… sorry :smiley: :smiley:


And speaking of gas prices… I hear you peeps in the states are getting butt-raped on the ol’ gasoline prices. Here I pay $1.83 for mid-grade (which is the only option… no premium dangit). Just thought I would rub that in.


??? i paid yesterday 2.29 for 87…


2.44 for premium now!


it was 2.49 in bk…

the prices at the station i was at were 229, 239, 249…


Man that sucks. Can’t imagine how much it’ll be when I roll back to the states.