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Can someone explain how exhaust headers work in regards to the exhaust note? by kawana
Started on: 09-16-2014 11:40 PM
Replies: 13 (314 views)
Last post by: dobey on 09-18-2014 10:06 AM
kawana
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Report this Post09-16-2014 11:40 PM Click Here to See the Profile for kawanaClick Here to visit kawana's HomePageClick Here to Email kawanaSend a Private Message to kawanaEdit/Delete MessageReply w/QuoteDirect Link to This Post
I've read that Fbody 3.8L heads help L67's sound better by changing the how the firing order is heard or something to that effect. If I were to make a set of custom headers, how should you set put the tube lengths so that the firing order sounds right?
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Fierobsessed
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Report this Post09-17-2014 12:18 AM Click Here to See the Profile for FierobsessedClick Here to Email FierobsessedSend a Private Message to FierobsessedEdit/Delete MessageReply w/QuoteDirect Link to This Post
The 3800 has a naturally balanced left to right firing order. For performance, just equal length is best. But, It sounds like an angry garbage truck at 7:00am.

From what I gather, two short runners with one long, changes the sound to more of a euro-tone.

This example had 3 primaries that were different in length roughly equal to the exhaust port spacing. Also sounds very euro-ish.


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Report this Post09-17-2014 04:57 AM Click Here to See the Profile for bmwguruClick Here to visit bmwguru's HomePageClick Here to Email bmwguruSend a Private Message to bmwguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
We spent weeks and weeks designing headers that made the 3800s/c sound great. I'm sure that there is a small power loss compared to equal length headers, but we were aiming for a balance of flow and sound over max power. They did use unequal length runners.

Dave

------------------

www.hausofguru.com

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kawana
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Report this Post09-17-2014 08:17 AM Click Here to See the Profile for kawanaClick Here to visit kawana's HomePageClick Here to Email kawanaSend a Private Message to kawanaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Fierobsessed:



That sounds great! I'd be ok with a small power loss if it sounded like that.
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mental floss
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Report this Post09-17-2014 08:51 AM Click Here to See the Profile for mental flossSend a Private Message to mental flossEdit/Delete MessageReply w/QuoteDirect Link to This Post
Wonder which Borla system that is?
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Report this Post09-17-2014 09:24 AM Click Here to See the Profile for mental flossSend a Private Message to mental flossEdit/Delete MessageReply w/QuoteDirect Link to This Post
Wonder which Borla system that is?
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Report this Post09-17-2014 12:13 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by kawana:
That sounds great! I'd be ok with a small power loss if it sounded like that.


That car has a turbo, so a naturally aspirated car will sound different.

 
quote
Originally posted by mental floss:
Wonder which Borla system that is?


It was custom made by Fierobsessed

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Report this Post09-17-2014 02:47 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
Perhaps I've misunderstood the title, but the question is very difficult to answer for several reasons. The most important being the subjective nature of what sounds good. For example, your first hurdle will be to describe the sounds you want in a manner that other people will understand precisely what you want. The second will be to actually find someone to understand what you mean who also has enough experience to know what to do to your engine's exhaust note to turn it into what you want, if it's even possible. The third problem will be to package the design in the space you have available.

Check out this newspaper article on what Jaguar went through to design an exhaust system for a specific sound on their latest car... despite all the engineers and experienced techies at their disposal, the design was born from trial and error of about 50 different major and minor system modifications. The point is that every car will be different and there is no magic formula.

http://thechronicleherald.c...aust-notes-explained
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dobey
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Report this Post09-17-2014 03:59 PM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Bloozberry:
Perhaps I've misunderstood the title, but the question is very difficult to answer for several reasons. The most important being the subjective nature of what sounds good. For example, your first hurdle will be to describe the sounds you want in a manner that other people will understand precisely what you want. The second will be to actually find someone to understand what you mean who also has enough experience to know what to do to your engine's exhaust note to turn it into what you want, if it's even possible. The third problem will be to package the design in the space you have available.


Well, how headers affect the exhaust note isn't all that difficult to answer. Taking the knowledge and tuning to get the sound you want out of a specific engine, is a completely different thing entirely though.

Headers affect the exhaust note in the same way that the rest of the exhaust system does. Pipe diameter and length of the primaries. How the gas expands and flows through the system alters the sound. Material of the exhaust tubing also alters the sound, as the vibration of titanium is slightly different than stainless steel, which is different from inconel. If you want a higher pitched sound, then going with smaller diameter pipe will do that. Larger diameter will give a deeper sound. The trick is finding the balance between what the engine needs to flow in its current state, the sound you want, and any planned upgrades.
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2.5
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Report this Post09-17-2014 04:03 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
I would describe how headers affect the sound as differentiating each cylinder pop more than a stock manifold would. Also in my experience you get to hear some of that pop resonate thru each cylinder's steel header tube as well, all of this sounds sweet.
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Report this Post09-17-2014 04:38 PM Click Here to See the Profile for mental flossSend a Private Message to mental flossEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:


It was custom made by Fierobsessed


I like it a lot.
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kawana
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Report this Post09-17-2014 10:17 PM Click Here to See the Profile for kawanaClick Here to visit kawana's HomePageClick Here to Email kawanaSend a Private Message to kawanaEdit/Delete MessageReply w/QuoteDirect Link to This Post
The sound i'm looking for is pretty much exactly what that video was. I want the exhaust tone to sound "Smoother", more even than the stock exhaust.
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Report this Post09-18-2014 08:54 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by kawana:

The sound i'm looking for is pretty much exactly what that video was. I want the exhaust tone to sound "Smoother", more even than the stock exhaust.


Smoother and more even would be the opposite of headers in my opinion. But alot of that smoothness would be farther down the pipe than headers. Two or three high flow tube mufflers in the line perhaps.

On a dual exhaust rear wheel front engine car an x pipe evens out the sound of the flow too.

[This message has been edited by 2.5 (edited 09-18-2014).]

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dobey
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Report this Post09-18-2014 10:06 AM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 2.5:
Smoother and more even would be the opposite of headers in my opinion. But alot of that smoothness would be farther down the pipe than headers. Two or three high flow tube mufflers in the line perhaps.

On a dual exhaust rear wheel front engine car an x pipe evens out the sound of the flow too.


Headers make a surprisingly large difference to the "smoother and more even" part of the sound than one might initially imagine. One of the big problems with exhaust sound for engine swaps in Fieros, is that the exhaust tends to get the short end of the stick, literally, as headers designed for FWD cars tend to get used, and that places the exhaust collector right where the stock Fiero muffler is. The stock Fiero exhaust routing is about equal to the length of the exhaust on the F-body though, so there's more room to fit pieces in like cat, resonator, and muffler, without incredibly tight bends in the exhaust.

The image posted above of the exhaust by fierobsessed is one of the better setups, but still has a few spots I'd change to improve the sound even further (the T at the muffler exit for example results in uneven flow after the muffler).
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