Exhaust note tuning

A bunch of us were sitting around a table drinking beer . . . doesn't that sound like the beginning to a lot of horror stories? I think it ranks right up there with "Hey watch me!"

Anyway we were talking about how some cars had such a pleasing exhaust note and others were just ratty sounding with the Harley being the worst offender.

We'd all seen articles about the engineers tuning the exhaust sound and decided that the tuning had much to do with having the exhaust pulses sound almost like they overlap or maybe a better way to say it is to have a more continuous sound.

You can't really do anything about firing order, but this brought the idea of equal length headers into question. Maybe they weren't the absolute ne plus ultra we thought, from a sound point of view.

Crossover tubes were discussed as the older Vipers w/o the crossover tubes were always said to have a raucous sound.

Anywho this led us into thinking that if you presumed a single exhaust like from a 2-3-4 cylinder and you re-split the exhaust, using unequal length pipes & then rejoined them we thought you'd be able to tune the exhaust sound.

There was just enough knowledge amongst us to say we'd need to work in halves or thirds (for the life of me I can't remember why now). In other words in the re-split section one pipe would be twice as long as the other or 1/3, 2/3 the length of the other one. The idea was to change the natural frequency of the engine exhaust pulses.

Was this the beer talking or could there be something to this?

There could be something to this but I will have to go get a beer and let you know for sure.

Better yet, have a few!

There are dual outlet exhausts that basically what you are talking about. There is one inlet to the muffler but the paths are slightly different and one exit is bigger than the other. I guess you could say helmholtz (sp?) resonators do this also

carguy123 wrote: You can't really do anything about firing order, but this brought the idea of equal length headers into question.

You can't change the firing order, but you CAN change the order in which the tubes enter the collector, which effectively changes the firing order (from the exhaust tone perspective). The scavenging headers Andrew Nelson has been building for the last few years for his SBC powered $200X Challenge cars have RADICALLY changed the exhaust tone (AND performance). Of course, it takes a heck of an effort to wrap 8 different tubes around the engine, make them all equal (correct) length, and gather them into the collector IN FIRING ORDER. But Andrew's kind of good with magic beans and fairy dust.

One of the finest sounds I can think of is 180-degree headers on a V8. That uses tubes that cross over to the other collector so the pulses not only enter the collector in even pulses, but they give even pulses on each side.

I really think the vette in this first video could almost be mistaken for a couple of 4-cyl CB750s

https://www.youtube.com/watch?v=MSZTbR6C6Lw

curtis73 wrote: One of the finest sounds I can think of is 180-degree headers on a V8. That uses tubes that cross over to the other collector so the pulses not only enter the collector in even pulses, but they give even pulses on each side. I really think the vette in this first video could almost be mistaken for a couple of 4-cyl CB750s https://www.youtube.com/watch?v=MSZTbR6C6Lw

That sound right there single-handedly makes up for the millions of trucks I have to hear with straight pipes.

Unless I'm misunderstanding things, putting the tubes in the proper order in the collectors is de rigueur on 4 cylinders. It helps scavenging which was making us look beyond just collector magic, but if there's something to be had there then I'd like to know it.

The engines we were discussing were fewer cylinders than 8. It seems 10-12 cylinders have a magic sound all on their own but lesser creatures take some massaging.

The video posted a while back on an engineer orchestrating the sound on a McClaren, Zonda or something is what sparked our conversation in the first place.

We were raggin on Harleys and wondering about the new Ford 3 cylinder plus the older Geo 3 cylinder. That was more our focus, but wondering if some of that would translate over to a 4 cylinder too.

I was just watching a video on a Locost with the Mazda V6 in it and it sounded awesome. Like an older GP car. I guess I could ask her what she does different.

Yeah, the order is normal in a 4 cyl. The proper sizing, and length is not. I keep remembering Andrew explaining his headers to a googley eyed bunch of groupies (including me). One guy asked if they were "long tube headers". Andy shot back, "They are right length tube headers. Every tube is 32 5/8" long". Do you know how hard that is to do on 8 cylinders? It's easier on a 4 cylinder, but rarely done. Once you start factoring in limited engine bay space, all bets are off.

We had a guy on shoforum make his v6 sound like a ferrari......most think it was due the ypipe, but I still believe it was his resonator and muffler choices. He did painstakingly craft an equal length though.

Its not just making the tubes equal length. Like Nelson said, the tubes need to be the right length also. Even on a turbo car there is a right way to do an equal length header. There are only maybe a couple good headers for Subarus and those only work if you have a single scroll turbo. Nobody, that I know of, makes a good production Subaru header for double scroll turbos.

I'm not just talking the most power, I'm talking a pleasing note to the ear which goes way beyond muffler choice since certain families of motors make similar noises no matter the muffler choice.

There's a site that tells you the proper length for your runners, I think possibly it's Burns, but nothing I can find that talks about sound production.

carguy123 wrote: I'm not just talking the most power, I'm talking a pleasing note to the ear which goes way beyond muffler choice since certain families of motors make similar noises no matter the muffler choice. There's a site that tells you the proper length for your runners, I think possibly it's Burns, **but nothing I can find that talks about sound production.**

Please don't start them doing this........then all the stance fanboys will do that instead

I'd much rather they try to get a pleasing exhaust note than running around on the side of their tires.

Aside from the volume of space necessary to accomplish this, you would also have to accept the limitations of using single tuned length secondary tubes. Namely that they will each inherently have certain rpm ranges where they work to your advantage, and others where they work to your disadvantage. This means that your sound quality will likely not be very consistent across the full rpm range either. In order to do that you would probably need some type of continuously variable length system, similar to that of a trombone slide.

carguy123 wrote: I'd much rather they try to get a pleasing exhaust note than running around on the side of their tires.

IDK, they'd probably make it as loud as possible.......a guy that lives just down the road from me had a straight piped last gen Prelude(This was exceptionally loud, but didn't sound absolutely horrible), now he has a newer wrx with some crappy catback that the masses told him to buy, its just as loud and sounds like ass(IMHO, they all do)......I'd rather have the honda streak past at 5am waking me up than the scooby.

Granted I used to drive the bmw with header + turndown at night to fill up with gas. I had a friend who claimed he could hear it about 6mi away on the one stretch I went WOT. I grew out of that a bit.

Reviving an old post here, found it while googling this very thing. Does anyone here know what Maserati does to make their cars sound the way they do. Is it mostly in the design of the engine or the electronic tuning... or the exhaust system?

dunruhroy said:

Reviving an old post here, found it while googling this very thing. Does anyone here know what Maserati does to make their cars sound the way they do. Is it mostly in the design of the engine or the electronic tuning... or the exhaust system?

Flat plane crank and equal length headers. Helps that some of the engines are jut slightly modified F430 units.

I find the sound of the modern Maserati's a little to high pitched for my taste. You can ignore the Ghibli. I havte just about everything the Ghibli does.

An inline six has to be one of the easiest engines to get a cool sound out of. The evenly spaced pulses (1 every 120°) helps a lot. With the right length header, they sound amazing. A v-8 with an 8 into 1 header sounds pretty cool, too, followed by 180° headers on a v-8, followed by an x-piped v-8, etc. 

wearymicrobe said:

dunruhroy said:

Reviving an old post here, found it while googling this very thing. Does anyone here know what Maserati does to make their cars sound the way they do. Is it mostly in the design of the engine or the electronic tuning... or the exhaust system?

Flat plane crank and equal length headers. Helps that some of the engines are jut slightly modified F430 units.

 

I find the sound of the modern Maserati's a little to high pitched for my taste. You can ignore the Ghibli. I havte just about everything the Ghibli does.

The Maserati version of the F136 engine uses a crossplane crank instead of the flat plane that is in the Ferrari version.  The sound must come from the exhaust and FI tuning to get the crackle on the overrun.

The VR6 in the VW GTI sounds awesome... a shame I watched what they did in the documentary "Dirty Money" though.

Titan4 said:

wearymicrobe said:

dunruhroy said:

Reviving an old post here, found it while googling this very thing. Does anyone here know what Maserati does to make their cars sound the way they do. Is it mostly in the design of the engine or the electronic tuning... or the exhaust system?

Flat plane crank and equal length headers. Helps that some of the engines are jut slightly modified F430 units.

 

I find the sound of the modern Maserati's a little to high pitched for my taste. You can ignore the Ghibli. I havte just about everything the Ghibli does.

The Maserati version of the F136 engine uses a crossplane crank instead of the flat plane that is in the Ferrari version.  The sound must come from the exhaust and FI tuning to get the crackle on the overrun.

I would like to have my car crackle on decel, but I haven't been able to figure out what part of the tune makes it happen. My bone stock '96 F-150 does it (quietly) and I don't know why.

Isn’t over run just un burnt fuel in the exhaust igniting?  

dean1484 said:

Isn’t over run just un burnt fuel in the exhaust igniting?  

Yup.  It's just the right combination of extra fuel, air for it to burn with, late spark and an exhaust that doesn't muffle the noises from it too heavily. 

As a musician and a car freak, exhaust sounds always fascinated me.

For instance, why does a V6 sound different than an inline 6?  they both have pulses every 120 degrees.

And let's say you have two 4-cylinders linked together phased 90 degrees off so you had exhaust pulses every 90 degrees.  It sounds like two 4 cylinders, not one I-8.

And how does Nissan get that sweet note from the 3.5L?

Why do old Subarus sound like they have a misfire?

Too many questions.