Hey CRM, I'm not sure if someone answered this question for you yet, but I
couldn't find a reply to it. So here goes nothing:
Scavenging 101
When your exhaust leaves your manifold (or header) it comes out in a
'pulse'. This is due to the piston moving up and forcing the exhaust out,
then the exhaust valve slamming shut. Basically what this pulse is, is a
high pressure node in your exhaust 'wave'. If you remember back to high
school physics (and I know, its tough) recall the experiment with the
slinky. If you held the slinky tight, and gave it a flick at one end, you'd
see a pulse travel down the end and back. Now suppose this slinky is your
exhaust piping. As the pulse travels down, there is a low pressure area
just behind it. The whole concept of scavenging is for the 'pulse' from the
OTHER header to be 'sucked' along by the low pressure pocket just behind the
first pulse. The only way to do this is to connect the two headers (via an
'h' or 'x' pipe). This allows pressure communication between the two
systems. The 'x' pipe is preffered over the 'h' pipe because it has less
flow impedence. Scavenging is only effective at low RPMs when the exhaust
is still being sent in pulses ... at high RPMs the exhaust flow is
essentially uniform and not affected by the pulsing affect (i.e. the pulses
are so close together they might as well be a continuous flow).
I hope that explains it a bit better ... now Tuned Length exhaust is a
different story ... let me know if you want to know about that. :)
-- Canuck -------------------------------------------- Y2K 4.7L 2wd 5spd""crm"" <tb.crm@verizon.net> wrote in message news:005d01c207e6$1fb84e00$7c6445a1@vatican2... > > hey guys, some thoughts... > > > If you are planning for modded truck then go with the 3-inch to the rear > for > > a single exhaust and 2.25inch sounds good but add a 'X' pipe (Gibson > design) > > for a cross-over between the exhaust for back scavenging and a balance > > exhaust flow. > > Okay, pardon the ignorance, but what exactly is "back scavenging"? I've seen > that term tossed around but dont really understand what it is. Also, since > this is just a dual exit, not a true dual from the headers, would I really > need an X or H pipe? > > > Look for the least bends/kinks or turns in the pipe as possible for any > > added flow restriction. > > > The guy I plan on going with for the catback is supposedly well-known for > very clean bends, so I should be okay in that aspect. > > > Flowmaster 40, talk to Chris Lambert (Dakota USA) on this subject. He can > > testify the noise level and amount car alarms he setoff when coming in the > > local neighborhood. Hehehehehe > > > > The Flowmaster 50 is much quieter than the 40 series. > > Definitely gonna go with a 50 series. Anything louder and the neighbors will > be bitchin... One question though - Which is going to be louder in the > cab - a Flowmaster 50 or a Magnaflow XL Turbo? > > TIA... > > -adam > > > >
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:04:37 EDT