Exhaust sound advice

[Riceburner]

I'd like to try and change the sound of my exhaust a little, some more 'rasp n crackle' would be nice but nothing too silly. I have 6-2 headers with twin 60mm secondaries, then into a 3" full mandrel system with a 14'' resonator that is 3" straight through with a 5"body (pic1) under the gearbox, I then have the Reinhard twin 60mm stainless muffler in the rear (pic2). The centre resonator is straight through and has a double chamber with an open section in the middle.

 

I was thinking maybe a long hot dog in the centre in the centre might be the way to go, something around 20-24" long? Obviously it needs to be legal and not too loud for the track, currently I feel mine is pretty quiet compared to some, but it's hard to tell with a helmet on 

 

Here's a rough video with the current system, it was done with my old 74degree cam in.

 

 

 

 

 

[Zedman240®]

If you fit a smaller but same style resonator in the middle, it should make it a tad raspier, but if you were to install a hotdog, you'd be better off and cheaper to replace it with a straight through pipe. Hotdogs to me do nothing and just add expense to the system. 

[Riceburner]

It's hard due to limited space, I can only fit a 5" dia muffler body in the trans tunnel. Anything bigger will have to sit lower and not give enough ground clearance.

 

I've seen the same style I have in 12" instead of 14" long but I didn't think that would change much  :-\

[Scoota G]

I would look in the collector area. Is there anyway you can fabricate of have something fabricated like a 6 into 1 collector. I know the V8's that have the 4 into 1 collector have more rasp than the 4-2-1 type.

[Whittie]

Mine is setup 6-2-1 equal length extractors, 2.5" mandrel exhaust and it's got a hot dog next to the gearbox and a canon on the back.

 

The induction is still louder than the exhaust and it sounds mint in my opinion. However, I highly doubt it's legal, but really is that all that much of a concern?!!

 

[d3c0y]

The centre resonator is the thing that will make the difference. I got a couple removed from cars and they starting making the sound you are talking about.

[Riceburner]

Mark, I think you're spot on the RS start/power craft systems sound epic and they are 6-1. My headers are stainless so it's too hard to modify them. I also have the wings on the baffled sump reducing clearance further.

 

Whittie, that sounds good and seems to have a bit crackle on deceleration. Do you guys have noise limits at the track? Over here they are fairly strict.

 

Jake, I'll be too loud with only the rear can its straight through and only about 350mm long.

 

That's why I was kinda leaning towards a long 20-24" hot dog thinking it wouldn't be too loud but also give a better sound.

[Riceburner]

Here's that RS Start/Power craft video. Crazy sounds, but obviously not allowed on the road here! Lol.

 

 

Dimitri, Regarding hotdogs, i follow what you mean. I've never had one fitted to any of my vehicles so I'm not sure of the sound attenuation they provide.

 

Here's my thinking, the current resonator is 3" straight through and has a 5" body O.D. So that's 2" of sound deadening. The hot dog is 3" straight through and 4" body O.D. Giving a 1" of sound deadening. So if I got a long hot dog at double the current resonator length I should get a very similar sound to the current setup as the amount of sound deadening should be the same. A shorter one at say 18-20" long should give a slightly more sporty note?

 

 

[d3c0y]

I was only running a straight through muffler (albeit on a 2.25" system) and it wasn't that bad. What dB are you running currently?

[Riceburner]

I can't recall exactly as i measured it quite a while ago, maybe 89, it was under 96 though.

[dat2kman]

All you blokes, mucking around with hotdogs/resonators, and mufflers, all packed with fibreglass, or splashed out and get stainless steel rovings packed mufflers!

 

GONZO units utilise a large screw bit like an earth auger/kole borer, with a central smaller straight through tube, wrapped in a large can.

Theory is it "knocks" the sound waves and quietens the output, without causing backpressure issues.

 

You need gas flow to scavenge exhausts out f each port, backpressure ( too much) stuffs the gas flow rate.

 

Google up GONZO mufflers. Improves power figures on most 4x4's a fair bit.

[Riceburner]

All you blokes, mucking around with hotdogs/resonators, and mufflers, all packed with fibreglass, or splashed out and get stainless steel rovings packed mufflers!

 

GONZO units utilise a large screw bit like an earth auger/kole borer, with a central smaller straight through tube, wrapped in a large can.

Theory is it "knocks" the sound waves and quietens the output, without causing backpressure issues.

 

You need gas flow to scavenge exhausts out f each port, backpressure ( too much) stuffs the gas flow rate.

 

Google up GONZO mufflers. Improves power figures on most 4x4's a fair bit.

 

Does this look the same style Jason? Gonzo was hard to find info/pics of. According to the specs it only drops 5-7dB over open collectors    Is that similar to a hot dog or resonator?

[KatoKid]

Sounds good to me as it is Gareth.

 

I take it you are happy with the "volume" aka loudness of the system and you just want to change the tone? It sounds surprisingly quiet?

[dat2kman]

Thats it, the Gonzo units use a continuos gaint type "screw" rather than the short segments of the Moroso.

He makes to order.

Operates out of a shop called "Aussie Auto and Mechanical" in Pickering st Enoggera, Qld.

He will post

 

Not heard if anyone else in Aus is making them, or similar.

[Riceburner]

Yeah Dave the volume is fine, It does seem quiet but maybe I'm slowly going deaf. You can hear the FCR's whistle at part throttle in that video, very surprising considering the camera location!

 

Jason, Do you run one of these? Thanks, I'll look into them more. It's an interesting concept.

 

 

[dat2kman]

Run on two cars, very happy, certainly knocks sound down, we have one track here, Lakeside, they are hard on sound, my old system, ( single long packed can next to box, and side pipe exit in front of wheel, blew meter off the tripid.

Replaced from header flange back, same diam pipes, but Gonzo, at same dimensions, it got me down under, with no HP at wheels drop.

 

You could get away with twin pipes right back to in front f diff, into a Y, then single under, the two bends, and as long and as large diam as they make, that will fit.

Single inlet, single outlet, if want twin, weld on a made up twin tip.

 

My thoughts fwiw.

[Zedman240®]

Its all about trying to let the hot gasses expand and cool rapidly before they exit the pipe out the back. I've always had a large resonator near the headers and that has always substantially lowered the "volume" of my exhaust...even to a point when I proved an so called "expert" wrong at an exhaust place. After insisting on a particular setup against his recommendations, he couldn't believe the results.

I'm no expert either, but I have a fair idea on what works.

I'd be trying a smaller resonator than the on you have, but not a hotdog, something in between what you have now. If you can, visit "Supercat" in Dandenong, (bring cash though  )and you will be able to pick something out and get it real cheap. 

[acf321]

Gareth,

 

just my bit for what its worth. I dod a heck of a lot of research into matching length extractors, and firing order and so on, as used on many early lotus's and of course the magnificent GT40's, ie real spaghetti stuff. I ended up with SWR's extractors in ceramic coating, and followed Peter Mac's advise to go for magnaflow rear 2.5" muffler and mid resonator. The sound of my car is perfect in my view, ie a low down mumble on idle and then a seriously raucous shriek on wide open throttle. It really does sound good, and I can suggest that for the price (bought on Summit racing) the whole thing is worth considering. I had James make a 2.5" stainless pipe, with madrel bends, and it works a treat.

 

Adam

[nat0_240_chevZ]

The best noise I have ever heard from a six, is with a titanium exhaust & rear muffler.

I bought an r34 with a turbo back steel dumper, into a de-cat pipe also MS, then titanium there back, made the most throatiest noise you have ever heard, albeit turbo, but 'everyone' who knew me, knew they had just past me, even when not gassing it hard.

Its a very distinct note whic is pure Sex, when it comes to exhaust notes, nothing like it.

the rolling growl it makes as it wonds up, you think it about to stop, then keeps on screaming......

 

What can I say, but gues what exhaust im building for all my future cars.....yup going to be expensive!!!!

Nat0

[Riceburner]

All very helpful advice, thanks gents.

[Six_Shooter]

Does this look the same style Jason? Gonzo was hard to find info/pics of. According to the specs it only drops 5-7dB over open collectors    Is that similar to a hot dog or resonator?

 

FWIW, I have this exact muffler on my car. I really like it. Easy to fit, sounds good, and noticed a difference in power between open tube and this muffler, that was before I added the turbo.

 

I have a video of my car idling with the muffler, but remember, my car is turbocharged so that will change the sound over an N/A car.

 

This was about 4 years ago, when I first got the DIS swap up and running.

 

These videos were taken about a month and a half ago. The car was not tuned to run in temperatures this cold, so it's a bit rich and sloppy when revving, it did improve once the engine temp rose a bit.

 

[Whittie]

Whittie, that sounds good and seems to have a bit crackle on deceleration. Do you guys have noise limits at the track? Over here they are fairly strict.

.

 

LOTS of crackle on over-run. There are no noise limits at the track but I ran the same exhaust at Sanddown, Bathurst, Philip Island and Eastern Creek all without any issues.

 

The car sounds louder in that photo due to resonance off the walls and the fact it was the only car on the track, it's actually rather quite, certainly the quietest car on the day.

[Riceburner]

Whittie, it sounds great especially the crackle! You guys are lucky, we have a 75dB(at 30 meters) most of the time and the occasional 95dB day a few times a year. I believe most of the historic events are 95 but if it's just a sprints it's usually 75.

 

Chris, How have you found it volume wise and do you run any other muffler?

 

Cheers, Gareth.

[Six_Shooter]

I forgot I had this video as well.

 

L28, Weber downdrafts, stock exhaust manifold, with 1.75" or 1.875" exhaust (it's been a long time) from the manifold to the rear axle, where it stepped up to 3" to fit the muffler.

 

 

Gareth, if that question was for me (I'm a "Chris") no, the only muffler I'm running is the Sprioflow. It can be kinda loud at speed, but I find teh road noise is worse, on the highway.

[Riceburner]

Yeah it was, thanks for the extra video. I'm considering trying one of those ATM, they seem pretty cheap and shouldn't burn out.