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Posted

Ahh yeah! 

HKS does quite a few with that design:

NCP91 Vitz RS 1NZ-FE HKS Hi-Power 409 high power muffler NCP131: Real Yahoo  auction salling


Something else interesting that HKS does, is they make 4-1 manifold for the Altezza that links the pipes together into pairs.
Not sure if this is some sort of tuned length thing, perhaps it makes it behave more like a 4-2-1. 

But interestingly it's linking the cylinders which are not 360 degree separated. (should be 1&4 and 2&3 if evenly spaced)

HKS 4-1 — готовимся к МКПП — Toyota Altezza, 2 л, 1999 года | тюнинг |  DRIVE2


Then even further off topic, but the S1000RR bike has exhaust valves that open or close based on rpm, that link pairs of cyls together.

image.png.6a2f34afd780e14cd662bc7c6a803401.png


It seems that HKS is the biggest mainstream sort of company that has experimented with this kind of stuff. Might be interesting to have a dig through their back catalogue. Seems the "HKS hi power" ones usually have that design.

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Posted

Another interesting one is the Mugen loop muffler for DC5 Integras. This passes through the chamber twice, so is a cheat code for getting extra exhaust length and muffler length in one hit. 

image.thumb.png.fb22e7dda31d4e9ad5f5dc1c76f6a5cb.png

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Posted

https://www.hks-power.co.jp/en/product_db/muffler/db/3889

maybe to cut the notorious 3s drone?

For certain applications, HKS has introduced the "Silent Chamber" which removes a lot of the lower frequency noise that can often be heard into the cabin even when cruising. The silent chamber removes this uncomfortable noise but due to its closed end design, only a minimal amount of exhaust gas flows into it, meaning that the disruption to exhaust gas flow through the entire system is minimized and there is no harm to performance.

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Posted
On 21/08/2024 at 10:36, Truenotch said:

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/

@kpr doesnt your truck have somthing like this on the downpipe?

Posted

Yep,     I never got around to adjusting the length  to dial it in though.   

my trueno with same engine and pretty similar muffler setup  was quiet and no drone.  (3" with 2 straight through mufflers)   I think  the plumb back wastegate pipe just happened to be the correct length size.   since its just a pipe with a blanked off end untill the gate opens

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Posted

Anyone got a good recipe for v8 exhaust? @cletus @Valiant maybe? 

Kinda over the ponti sounding like a hairdryer.  

Current has a wee resonator just before the crossover then a big stainless muffler before the axle and then another resonator before the tailpipes. 

It's small pipe like 2.25" spec

If I just whip the middle muffler out will it go droney? 

Posted
3 hours ago, JustHarry said:

Anyone got a good recipe for v8 exhaust? @cletus @Valiant maybe? 

Kinda over the ponti sounding like a hairdryer.  

Current has a wee resonator just before the crossover then a big stainless muffler before the axle and then another resonator before the tailpipes. 

It's small pipe like 2.25" spec

If I just whip the middle muffler out will it go droney? 

Is it mild steel or stainless? 

Posted
1 hour ago, shrike said:

Is it mild steel or stainless? 

The bulk is just steel.

For some reason the middle muffler is stainless steel lol.

The rear resinaor is just a normal one 

Posted
On 23/08/2024 at 10:57, 87creepin said:

It could be threaded and then locked in place with screws. Or no thread required. I haven’t seen any on YouTube that are adjustable. 

Some 2T expansion chambers have a trombone center section.  Changes tuned length to give better off peak torque.

Small Hydro would be good example.  Long pipe to get the boat up and almost planing then shorten to get in the powerband.

Posted

what cube is the pontiac? 
2.25" is probably an OK size unless its getting over 355, especially if the bends are just normal not mandrel. 
What style is the large muffler, straight thru, centre in side out or side in and opposing side out?   or flick up a pic?  doubtful taking the smaller reso's out will make it droney at 2.25.  especially if the tips go to the very end of the car - not just past the roll pan,

Posted
On 21/08/2024 at 10:36, Truenotch said:

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/

This is something that has been suggested by a few folks for my drone (which I'm learning to drive around the 'drone zone') 

Not really any room for me to attach any unsightly proboscis (probosci?) off my secondary pipes. But maybe off the box itself? 

 

images.jpeg

Posted
On 21/08/2024 at 11:53, Alfashark said:

Nicely packaged Helmholtz chambers!

My Pug had a small one tucked under the inlet plenum for intake runner gains allegedly

Since id been shown them by a mate ages ago on his 20v carib thing I have since noticed lots of cars have them on the Inlet box. We had a serena in for work the other day and it had two on the inlet tract, different sizes I guess to cancel out different frequencies. 

Mate reckoned he'd removed the one on his 20v but it affected the smoothness of the engine enough that he put it back on. I think on those engines it's possibly fitted to create extra plenum volume before the itbs rather than just than a sound thing?

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Posted
27 minutes ago, 440bbm said:

what cube is the pontiac? 
2.25" is probably an OK size unless its getting over 355, especially if the bends are just normal not mandrel. 
What style is the large muffler, straight thru, centre in side out or side in and opposing side out?   or flick up a pic?  doubtful taking the smaller reso's out will make it droney at 2.25.  especially if the tips go to the very end of the car - not just past the roll pan,

389ci. It's not big power lol 225 at the wheels.

The stainless muffler is baffled.  Centre in side out from memory. 

Would I be better taking the resonators out the very back and leaving the mufflers in? Or taking both resonators out ?

Posted
11 minutes ago, JustHarry said:

389ci. It's not big power lol 225 at the wheels.

The stainless muffler is baffled.  Centre in side out from memory. 

Would I be better taking the resonators out the very back and leaving the mufflers in? Or taking both resonators out ?

still reasonable size cubes. stock as a rock?

is it twin all th way through? 

yes i would try taking the resonators out.

but you might find  the rear resos will help with tone. try take the front resos out first, since resonators help with pulsing not volume, they may be assisting with the stainless muffler note, ( personalli hate s/s mufflers are they typically give higher pitch dumb sound as they resonate too much),   if its easy enough to try, whip them all out, if its too loud ( cant imagine ) then stick the rear back in. 

i think the tube diameter is causing the larger issue for you.  shortening it up will help gain more sound if thats an option, but you will need to retune it - will likely need  going up a size or two in the jets. 

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Posted
14 hours ago, JustHarry said:

Anyone got a good recipe for v8 exhaust? @cletus @Valiant maybe? 

Kinda over the ponti sounding like a hairdryer.  

Current has a wee resonator just before the crossover then a big stainless muffler before the axle and then another resonator before the tailpipes. 

It's small pipe like 2.25" spec

If I just whip the middle muffler out will it go droney? 

Like @440bbm said , try taking the front resonator out first, if it's got long tail pipes the rear ones will help get rid of any rasp/ thong slap 

If you're making a new exhaust, it's down to personal preference on how you want it to sound, something like yours I'd do mild steel, twin 2.5 into a pair of decent mufflers before the diff, h pipe up the front and some small resonators in the tail pipes

 

 

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