exhaust efficiency and noise levels

[grumpyvette]

noise levels depend on the engines compression,displacement, cam timing and length of the exhaust pipes from the header collectors to the (x) or (H) or pipe and length past the mufflers, where the exhaust exits the car, the placement of the (X) pipe in relation to the header collectors and the mufflers used, plus the vibration transmission or insulation levels of the exhaust system hangers or attachments, more than simply the diam. of the pipes alone.
there are usually compromises between back pressure and noise levels, but there are generally modifications that can be made that will minimize the back pressure yet allow except able noise levels, like
adding a second balance pipe or (X) or (H) pipe or a resonator ,can also change the frequency and level of the noise.
the first (X) or (H) pipe in an exhaust system is generally most effective at blending exhaust pulses, mellowing the exhaust tone and increasing the cylinder scavaging if its located as close to the header collector exit as possible, a second (X) or(H) pipe, is sometimes located closer to the mufflers intake pipe location, as it can also lower sound levels noticeably, remember the idea is effective noise cancellation or reduction without restrictive back pressure

yes reading thru the sub linked info leads to most of the usable info

http://www.autocarepronews.com/Article/ ... _much.aspx

viewtopic.php?f=79&t=497

viewtopic.php?f=79&t=1068

http://www.walkerexhaust.com/support/ex ... Design.asp

http://www.nsxprime.com/FAQ/Miscellaneo ... theory.htm

http://auto.howstuffworks.com/muffler5.htm

http://www.pontiacstreetperformance.com ... haust.html

viewtopic.php?f=79&t=1068&p=4047#p4047

viewtopic.php?f=56&t=1503

viewtopic.php?f=56&t=496

http://www.jcwhitney.com/jcwhitney/prod ... map=12966G

http://www.mustangmonthly.com/techartic ... index.html

http://www.holley.com/types/Maximum%20Flow.asp

 

[grumpyvette]

I can,t IMAGINE why anyone replacing their stock 1985-86 exhaust , with its well known restrictions,that was willing to spend a large chunk of cash on a stainless exhaust and mufflers would not have a 3" dual exhaust with an (X) pipe and full length headers installed, if you can weld and fabricate its a total no-brainer, but even if you must buy a decent system for a 1996 LT1 and adapt it to the L98 its still both doable and a far better system once its installed, its not like there's no options

summit and JEGS have a wide selection of affordable exhaust components, having a welder, and the skills to use it will pay for it self in very short order

ok, basics
your noise level will tend to increase with larger diameter exhaust pipes but thats only ONE of MANY factors in the exhaust design and its not necessarily true that you can,t build a reasonably quiet performance exhaust.
glass packs tend to mellow the tone frequency but don,t tend to reduce the DB (noise levels a great deal)
noise is basically vibration strength,thats transmitted to outside the exhaust system. having rubber insulators or exhaust hangers helps,placing glass packs between the (X) pipe and the (H) pipe helps and having quality mufflers helps.
your exhaust noise level is dependent on several factors that you can control,but clearances and finances will effect your choices, basically the idea is to reduce the exhaust pulse strength , you can blend pulses with an (X) as close to the header collectors as clearances allow and placing a secondary (H) pipe before the muffler entrance points tends to further reduce the exhaust pulse strength, but the length of the pipes and muffler design also play a huge role.

everything's going to be a compromise in some area, the object is to maintain a low restriction to flow (low back pressure) system, that effectively allows the headers to scavenge the cylinders, to promote high volumetric efficiency levels with tolerable noise levels
and/or you can insert baffles that will break up the pulse strength,

a set of these in the collectors helps

read thru these links

http://www.pontiacstreetperformance.com ... haust.html

http://www.mustangmonthly.com/techartic ... index.html

viewtopic.php?f=56&t=1507&p=5456#p5456

http://garage.grumpysperformance.co...-descriptions-dont-tell-you.12357/#post-61139

viewtopic.php?f=56&t=1507&p=3448&hilit=backpressure#p34

 

[grumpyvette]

DYNOMAX

http://www.summitracing.com/search/?keyword=exhaust cones&dds=1

IF your trying to reduce noise levels, you can buy or fabricate these cones that tend to break up and reduce exhaust noise, once installed in the exhaust, without producing much of a restriction since the total surface area of the mini holes is greater the the pipes cross sectional area
the tabs can be tack welded or sheet metal screw attached, and adding an (X) pipe near the collectors and an additional (H) near the muffler entrance point tends to mellow the tone

http://www.a-1performance.com/race_magnum/index.htm

http://www.pypesexhaust.com/mufflers.html

http://www.pypesexhaust.com/xpipes.html

http://www.flowmastermufflers.com/

http://www.holley.com/types/Maximum%20F ... 0Steel.asp

http://www.holley.com/types/Aero%20Cham ... 0Steel.asp

http://www.edelbrock.com/automotive_new ... ntro.shtml

http://www.summitracing.com/parts/SUM-630430/

http://www.summitracing.com/parts/FLO-842546/

http://www.summitracing.com/parts/WLK-17221/

http://www.spiralturbobaffles.com/

http://www.summitracing.com/parts/BOR-40659/

http://www.summitracing.com/parts/PYE-M ... mage=large

a few muffler options
generally I try to use stainless steel and 3" exhaust components, simply because that a decent compromise on cost vs value and they last a long time

BLUE66 POSTED THIS PHOTO of a nice chevelle exhaust

 

[grumpyvette]

some interesting exhaust data I ran across