Muffler Tech

[chris r]

4 hours ago, HumberSS said:

Would you recommend one or two different reso's per bank (and are the M&H ok)? And what about pipe size? My collector is 63mm, should I step down to 2" or 2.25" through the resos and stick with that all the way, or go up to 2.5" through the muffler? Remembering this thing is likely around 125hp per bank at a guess.. And do I need a balance pipe before muffler or would that be sufficient for the balancing aspect (will be above diff). Im open to sticking with a twin system right the way through but am trying to keep it packaged pretty tightly hence the 2 into 1. I also dont have heaps of room for a tail pipe so might side exit behind the wheel. Thanks man

I've used a couple of m&h resonators and was quite disappointed with them tbh. Didn't take any of the rasp out of the exhaust note (honda) 

I've used one of these Xlerator Enforcer Glass pack along with a turbo flow from the same company on my wagon and am really happy with it's note 

 

[kpr]

I havent done any v8 stuff. but on  4 cylinder 1.6L  making around 175hp at engine.  this is close to ideal setup ,   after the collector its 2"  then tapers up after the vband to  3" into a   glass pack.   after that you can get away with more sins.  

 

 

So yeah if you want to get fancy with it, carry on tapering down your collector to 2",  run 2" for for a  bit,  then chuck in a 2" - 2.5"  exducer cone  with  2.5 inch reso's directly after that, bigger they are the better.  some of the small ones dont really do much.    think of the reso as the exhaust ending.      after that do what you like really. merge into a single 2.5 or 3" and add mufflers till its quiet enough. 

 

you might grab a little bit of power off the bottom and in the middle doing it that way.     otherwise your original plan will probably work fine

 

 

 

[yetchh]

What was the consensus for good flow low noise/drone? Res then large barrel straight through or chambered muffler? I don't mind some noise just don't want droning.. For a zephyr 6.

[87creepin]

Wats better, 1.6mm or 2.00mm wall tube? 

[Rhyscar]

5 hours ago, 87creepin said:

Wats better, 1.6mm or 2.00mm wall tube? 

Whats the context here? It’s most commonly determine by availability in given size. 2mm wall is pretty thick but might work for certain situations where there’s high heat/cracking issues. 

[87creepin]

I’ve just seen two options available and wondered why. 
It’s for a not fast 4 cylinder. 

[87creepin]

also a dumb q perhaps but why use a megaphone @Rhyscar as opposed to straight 3” after the collector? 

[kpr]

if done correctly. choke point and diverging cone,  will make more power  than a big pipe straight on the end of the merge.  esp off the bottom and midrange.      diminishing returns the bigger you go with the diverging cone / megaphone. 

[Rhyscar]

@87creepin 1.6mm wall is fine for most typical applications. 
 

Exactly what @kpr said. But worth noting the Venturi collector and the megaphone you are trying to achieve 2x seperate things, on mine I’ve just happened to butt them up to each other - diverging straight up to 3” is fine in most cases. 
 

Lots of unproven theory has gone into my design so it will be interesting to see the results (although I’m unsure I’ve got the patience to cut it up multiple times to get it 100%!) 

[kpr]

@Rhyscar   what angle are you using on your diverging cone?

[87creepin]

I’m going to use the spreadsheet this guy has in This video

making it will be fun though, I’m not gonna pie cut it like what he did. 

[kpr]

 

 

 

[xsspeed]

more header tech, but after looking at @Romandayfs thred re stepped headers, wondered if youd done any real world testing on them for performance @kpr?

[Rhyscar]

13 hours ago, kpr said:

@Rhyscar   what angle are you using on your diverging cone?

14deg on way up, 24deg on backside.  

 

Can’t remember how I worked it out to be honest. Was so long ago. 

[Rhyscar]

This is super interesting regarding megaphones. 

https://victorylibrary.com/brit/mega-c.htm

[kpr]

17 hours ago, xsspeed said:

more header tech, but after looking at @Romandayfs thred re stepped headers, wondered if youd done any real world testing on them for performance @kpr?

Have done a little bit.   my headers have a step about 120mm out from head.      When i originally built  my big headers they were 44.5mm od primarys all the way.    This was pre dyno,  but i always checked for afr change when changing anything.   which 99% of the time  leaner = power gain.      so vs the 38mm primarys there was zero gain up top  and losses below 6000rpm.      i modified them with  the said 120mm section. using 38mm tube out of the head that flairs (not a step) up to the 44.5mm tubes.   It gained power from 6000rpm onward, with same losses down low.     which indicates the transition between the 2 pipes is where the gain come from.

Its one of those things thats a whole lot of work to fab and test. so haven't done a whole lot more on it.    But,  I can says  post merge collector, a diverging cone always beats a step.   Is it the same thing in the header primary's? i dont know.   ive never seen it done like that before.  maybe because its too hard basket to to fab the tapered transition, no one has really tried it

 

 

[Rhyscar]

Yeah I’ve also got a step at around the 120mm which was a bit of a best guess. Which works out to be 8” from the valve, as I’ve got quite short primaries at around 21”. 
 

Book I based my design on said you’ll normally find a step beneficial in the 8-12” range from the valve, but is related to overall length of primaries so is very variable exactly where this step is and how much impact it has.
 

But, exactly as you said lots of testing and fabrication to find the exact answer here. 

I think it’s important to be ‘not wrong’ more so than ‘100% right’ when it comes to header design. Especially with modern ECU and vvti technology having a larger impact on performance than exhaust tuning.

There are so many facets to the header design to test all possible iterations and find the 1 best solution would be painful. 

[xsspeed]

14 minutes ago, Rhyscar said:

Yeah I’ve also got a step at around the 120mm which was a bit of a best guess

i eyed yours up on instagram today haha

[Truenotch]

Has anyone here played with 1/4 wave resonators? They aren't a racecar thing, but it sounds like a really effective way to get rid of drone for a road car. 

They're basically a dead-end branch that comes off the main system. Pretty simple to fabricate and there's a few calculations you can do to work out volume and length. 

Apparently Darren at Pitstop in Hastings has been nerding out on them and installed one on a friends supercharged Vitz. It went from a painful drone to perfectly pleasant. 

I know @Roman is keen to experiment with them. Sounds like it'll be a fun thing to try. 

 

I haven't read these yet, but for safe keeping: 

https://wilhelmraceworks.com/blog/drone-reduction

https://grassrootsmotorsports.com/forum/grm/problem-exhaust-drone-solution-side-branch-aka-14-wave-resonator-or-helmholtz-resonator/129212/page1/

[shrike]

Is200/altezza had a jdm exhaust which had one 

https://www.rhdjapan.com/hks-silent-hi-power-exhaust-system-sxe10.html