Exhaust design question
Thread Starter
Evolved Member
iTrader: (17)
Joined: Apr 2004
Posts: 6,224
Likes: 0
From: 41° 59' N, 87° 54' W
Exhaust design question
I know we've still got to have some engineers floating around this forum, so I'm hoping someone will have the answer to my questions, specifically:
- How much larger piping would I need to negate the effects of two 90 degree bends vs. a straight 3" exhaust pipe? I.e., if I run a 3.5" or 4" pipe with two 90 degree bends, how does that stack up to a straight-through 3" pipe?
- What, if any impact would two 90 degree bends have on reducing sound volume? The theory being that some sound waves should be reflected back up the exhaust pipe - but that may not happen with a bend, which brings me to my final question...
- What if I were to take an HVAC approach and terminate a large straight exhaust pipe with a flat cap, and continue the exhaust path by tapping into the pipe with one or two smaller perpendicular pipes? Maybe something like a 4" pipe with a pair of 3" pipes coming out of it?
l8r)
- How much larger piping would I need to negate the effects of two 90 degree bends vs. a straight 3" exhaust pipe? I.e., if I run a 3.5" or 4" pipe with two 90 degree bends, how does that stack up to a straight-through 3" pipe?
- What, if any impact would two 90 degree bends have on reducing sound volume? The theory being that some sound waves should be reflected back up the exhaust pipe - but that may not happen with a bend, which brings me to my final question...
- What if I were to take an HVAC approach and terminate a large straight exhaust pipe with a flat cap, and continue the exhaust path by tapping into the pipe with one or two smaller perpendicular pipes? Maybe something like a 4" pipe with a pair of 3" pipes coming out of it?
l8r)
the size of the pipe it would take to equal 2 90* bends with 3" straight pipe would be huge, probably over 5". I do'nt think there's anywhere in the exhaust you could run 5" or bigger without hitting stuff on the car or scraping the ground.
That HVAC idea might be able to drop sound significantly, but I think it would be a huge liability to power as it would do exactly the opposite thing a good header would do. ( I don't know what the opposite word for scavenging would be, but that word.)
A baffled muffler would probably be more effective at damping sound and be less detrimental to power.
Almost anything that reduces sound will reduce power, but I think there's a reason neither of those ideas have been used on OEM cars.
That HVAC idea might be able to drop sound significantly, but I think it would be a huge liability to power as it would do exactly the opposite thing a good header would do. ( I don't know what the opposite word for scavenging would be, but that word.)
A baffled muffler would probably be more effective at damping sound and be less detrimental to power.
Almost anything that reduces sound will reduce power, but I think there's a reason neither of those ideas have been used on OEM cars.
to be honest nothing will beat a straight tube right out of the turbo towards the fender. as with any ordinary exhaust u already have two 90* bends. the o2 housing and the downpipe as well as some wiggle in the downpipe as its not straight to clear the acd.
its hard to give a good answer as you need to know the flow rate of the exhaust gases coming out of the control setup. control is the o2 housing and downpipe left unchanged. from there on you change the setup by varying whatever.
from what others have seen 3" is sufficient up to 600whp.
https://www.evolutionm.net/forums/ev...4-exhaust.html
from fluids class u cant beat a straight pipe with one that has bends. but u have to understand with the larger diameter pipe, the exhaust gases expand faster and end up just slowly moving in the pipe and with the constant pressure behind it from the motor its going to become turbulent. then it has to hit the bends in the pipe which will disrupt the flow more. with the 3" straight pipe the exhaust gases are still HOT and flowing fast through an optimal size pipe with no disruption in the pipe. im not saying a 3" straight pipe is better than a 3.5 or 4" im just going with what you gave as the criteria. the only way to know for sure is to run a test on the dyno with egt sensors along the exhaust to get the readings, and to log your pulls with each setup.
bends in pipes will disrupt the flow causing it to be turbulent, so it does in a sense reduce noise. as for how much that depends on flow rate and bend design.
you hvac approach does not seem optimal. as the flow instantly hits a wall which is not good. this will cause back pressure. what you want is what muscle cars have. the " Y " pipes as you split instead of the " T "
take it for what its worth. if your not making GOBS of power then most of these are not going to help. your slowing your car down by adding weight. but of course Ti is out there but comes at a pretty penny.
its hard to give a good answer as you need to know the flow rate of the exhaust gases coming out of the control setup. control is the o2 housing and downpipe left unchanged. from there on you change the setup by varying whatever.
from what others have seen 3" is sufficient up to 600whp.
https://www.evolutionm.net/forums/ev...4-exhaust.html
from fluids class u cant beat a straight pipe with one that has bends. but u have to understand with the larger diameter pipe, the exhaust gases expand faster and end up just slowly moving in the pipe and with the constant pressure behind it from the motor its going to become turbulent. then it has to hit the bends in the pipe which will disrupt the flow more. with the 3" straight pipe the exhaust gases are still HOT and flowing fast through an optimal size pipe with no disruption in the pipe. im not saying a 3" straight pipe is better than a 3.5 or 4" im just going with what you gave as the criteria. the only way to know for sure is to run a test on the dyno with egt sensors along the exhaust to get the readings, and to log your pulls with each setup.
bends in pipes will disrupt the flow causing it to be turbulent, so it does in a sense reduce noise. as for how much that depends on flow rate and bend design.
you hvac approach does not seem optimal. as the flow instantly hits a wall which is not good. this will cause back pressure. what you want is what muscle cars have. the " Y " pipes as you split instead of the " T "
take it for what its worth. if your not making GOBS of power then most of these are not going to help. your slowing your car down by adding weight. but of course Ti is out there but comes at a pretty penny.
I know we've still got to have some engineers floating around this forum, so I'm hoping someone will have the answer to my questions, specifically:
- How much larger piping would I need to negate the effects of two 90 degree bends vs. a straight 3" exhaust pipe? I.e., if I run a 3.5" or 4" pipe with two 90 degree bends, how does that stack up to a straight-through 3" pipe?
- What, if any impact would two 90 degree bends have on reducing sound volume? The theory being that some sound waves should be reflected back up the exhaust pipe - but that may not happen with a bend, which brings me to my final question...
- What if I were to take an HVAC approach and terminate a large straight exhaust pipe with a flat cap, and continue the exhaust path by tapping into the pipe with one or two smaller perpendicular pipes? Maybe something like a 4" pipe with a pair of 3" pipes coming out of it?
l8r)
- How much larger piping would I need to negate the effects of two 90 degree bends vs. a straight 3" exhaust pipe? I.e., if I run a 3.5" or 4" pipe with two 90 degree bends, how does that stack up to a straight-through 3" pipe?
- What, if any impact would two 90 degree bends have on reducing sound volume? The theory being that some sound waves should be reflected back up the exhaust pipe - but that may not happen with a bend, which brings me to my final question...
- What if I were to take an HVAC approach and terminate a large straight exhaust pipe with a flat cap, and continue the exhaust path by tapping into the pipe with one or two smaller perpendicular pipes? Maybe something like a 4" pipe with a pair of 3" pipes coming out of it?
l8r)
