Exhaust Notes

[Brad R.]

My friend is looking into building a GT40.
We were talking about exhaust notes because, on top of being one hell of a fast sunday cruiser, he wants it to sound very sweet too. He's looking at NA, 350ci, 5/6spd, 450hp.

What are the main contributors to the exhaust note, firing order?
I heard cylinder angle, bore/stroke dimensions, and displacement were all major contributors.

Since he's looking at a cross-plane crank V8 (LSx or SBF) I suggested getting 180 degree headers (which also stays true to GT40 tradition).

Would that, no cats, into a Corsa muffler put him in a mix between exotic and muscle (exhaust)? How would a massive cam alter this? In person, how do these bundle of snake headers alter the exhaust note?

Does anyone have videos of motors running 180 degree headers?

Thanks for all the help!

 

[Brian Mc]

Exhaust is a complicated topic. The correct x-pipe along with equal-length headers will sound similar to 180-degree headers. As a rule of thumb, smaller headers and pipes will tend to sound higher pitched and vice-versa. Dr. Gas has released a muffler called a Freq Mod Muffler. He explained the concept to me and it made sense. I have ordered a pair and can follow up with a video if you like.

I have converted a 289 into a Windsor which produces a short stroke (2.75 inches), allowing it to rev to 7,500 RPM's all day. Converting it to a Windsor allows us to run the Mustang EFI for tuneability, but has the lousy sounding firing order (like a Chevy :-( .

So, the most important factors in making an engine sound more exotic are:

short stroke for high revs
180-degree headers
x-pipe
4-2-1-2-4-2 headers-collectors-xpipe-mufflers-tailpipes-tips pipe configuration
correct muffler - large inlet/small outlet
high compression
small tailpipe tips

 

[Jac Mac]

If you want it to sound really exotic make the headers 8 into 1 with the individual cylinder tubes entering the ( circular ) collector as per the firing order of the cam in use.

I would like to know more about how you converted your 289 into a Windsor... but I have a funny feeling that I read about someone else doing that a while back.......
& yes, I agree that 289's & chevs have the same firing order..

 

[Keith]

Original car, 289 CI, Webers & 180 degree headers....

YouTube - GT40 spin

What's not to like?

 

[Brian Mc]

I would like to know more about how you converted your 289 into a Windsor... but I have a funny feeling that I read about someone else doing that a while back.......
& yes, I agree that 289's & chevs have the same firing order..

You need to change the cam and distributor to the different firing order. It is a pretty common conversion. There are retrofit cams with the small base circle (289 block) with the windsor firing order. I think Comp Cams makes one. I can get you all the part numbers if you like. If you are doing all this, be sure to upgrade the valve train.

Actually, the Windsors, not the 289's, are the same as Chevs. When you renumber the cylinders so they are the same, the firing order is the same.

 

[Howard Jones]

Jac, Have you ever done a SBC ( ya ya I know) with 4 into 1 on each side and then each side 2 into 1. Lets say 1 3/4 primaries into 3 inch collectors then each 3 inch into a 4 inch tail pipe about 2 feet long and straight out the back. All of this into the back of my SLC. No muffler.

Would this be as loud as 4 into 1 on each side and straight out (no mufflers)?

The motor is a 6.8K rpm 355ci at 10.5 to 1 with a lot of cam in it. Over 300 duration on both and a bit more than 580 lift. 110 lobe center. Hyd roller, Brodix alum heads (IK200)

I would like to run a crossover 180 but it would get really complicated. I could run a X pipe I think instead of the single big pipe if that would work better.

What do you think. I am going for unusual/cool sound not the very last HP. This will be plenty of motor without the final .5%. This will be a track exhaust for as long as I can get away with it then I have some mufflers to hang on the end of the 4 to 1 collectors.

Merry Christmas by the way. Howard

 

[Brad R.]

The correct x-pipe along with equal-length headers will sound similar to 180-degree headers. As a rule of thumb, smaller headers and pipes will tend to sound higher pitched and vice-versa. Dr. Gas has released a muffler called a Freq Mod Muffler. He explained the concept to me and it made sense. I have ordered a pair and can follow up with a video if you like.

I have converted a 289 into a Windsor which produces a short stroke (2.75 inches), allowing it to rev to 7,500 RPM's all day. Converting it to a Windsor allows us to run the Mustang EFI for tuneability, but has the lousy sounding firing order (like a Chevy :-( .

So, the most important factors in making an engine sound more exotic are:

short stroke for high revs
180-degree headers
x-pipe
4-2-1-2-4-2 headers-collectors-xpipe-mufflers-tailpipes-tips pipe configuration
correct muffler - large inlet/small outlet
high compression
small tailpipe tips

An properly sized x-pipe can sound similar!? I had been under the impression that such headers dramatically changed the exhaust dynamics (including note) over all alternatives. Would this simply render 180 degree headers a mere more expensive plumbing job?

I assume the smaller pipes increase the velocity of the gas traveled thus making pitch heighten.

Would resonators and cat.'s lower exhaust pitches because they are obstructions?

Does exhaust length in general effect the exhaust note (i.e. front mounted engines vs. mid mount)

Being High comp., low ci, higher rev. what kind of power does your motor make?

I found this video of a GT40 with a 289 Windsor - skip to 1:38. Revs like a flate-plane crank V8 to me!

And ya, I'm interested in seeing.hearing a video of the Freq. Mod muffler. How does it work?

 

[Jac Mac]

Hi Howard, yep Ive done a couple of chevs- sorta have to with Fords being sooo reliable & it doesnt hurt to keep an eye on the other guy ...
What you describe is essentially the setup we run on Jack Ondracks TVR ( see attached dwg ) but use a muffler ( Kiwi DIY ) to act as the point where it goes 8 into 1. It is quiet with this setup.. under 90 dba at full power... I doubt it would be under 95/98 without the muffler, though thats pure speculation since its never run open pipes.. Russ Nobles car runs a similar muffler setup, but with the tailpipes still in 180° configuration... Ive never heard it run in person , But I am led to believe its even quieter

It should be quieter than the 'normal' 4 into 1 each side setup, those guys always seem to be struggling to conform with the noise meter... I put this down to the uneven exh note beat of these. X- Pipes, I hate them, they are what I would call a crutch in the system, yes they often show more power over a non- balance pipe or even some balance (H) pies, but the science behind them is a bit vague.

The Sound.. In the case of the TVR, I like it, we get many comments from others along the lines of... delicious, grouse, cool etc, None of the Porsche guys like it.. & they probably get to here it more often than they would likeI did start in the shop one day without the muffler (when it was a simple 4 into 1 each bank ... thought it sounded bloody awful.) Looking at the SLC you should be able to accomodate a similar setup, might have to extend the tailpipe of each of the 4 into 1 sets a bit further inside the muffler though.
Give me a dimension of how much room you have for the muffler ( LxWxH ) & I'll draw up a plan & post it on your build thread ( If I can find it this week ).

Best wishes & Merry Xmas to all you guys while Im at it.

Jac, Have you ever done a SBC ( ya ya I know) with 4 into 1 on each side and then each side 2 into 1. Lets say 1 3/4 primaries into 3 inch collectors then each 3 inch into a 4 inch tail pipe about 2 feet long and straight out the back. All of this into the back of my SLC. No muffler.

Would this be as loud as 4 into 1 on each side and straight out (no mufflers)?

The motor is a 6.8K rpm 355ci at 10.5 to 1 with a lot of cam in it. Over 300 duration on both and a bit more than 580 lift. 110 lobe center. Hyd roller, Brodix alum heads (IK200)

I would like to run a crossover 180 but it would get really complicated. I could run a X pipe I think instead of the single big pipe if that would work better.

What do you think. I am going for unusual/cool sound not the very last HP. This will be plenty of motor without the final .5%. This will be a track exhaust for as long as I can get away with it then I have some mufflers to hang on the end of the 4 to 1 collectors.

Merry Christmas by the way. Howard

 

[Brian Mc]

Ryeno,
Great questions all. I can generalize by saying that this exhaust note subject is verrrrry complicated. The sound is affected by literally every bend, pipe size, muffler, collector, splitter, resonator, and even the exhaust tip. Sometimes smaller pipes (higher velocity) sound great, while other time they sound tinny and other times they sound blatty (as in blaaaaat) when installed on 1954 Chebbies or Harleys.

I don't know the HP of my motor because it also has an intercooled supercharger. I will dyno it some day.

 

[Keith]

An properly sized x-pipe can sound similar!? I had been under the impression that such headers dramatically changed the exhaust dynamics (including note) over all alternatives. Would this simply render 180 degree headers a mere more expensive plumbing job?

I assume the smaller pipes increase the velocity of the gas traveled thus making pitch heighten.

Would resonators and cat.'s lower exhaust pitches because they are obstructions?

Does exhaust length in general effect the exhaust note (i.e. front mounted engines vs. mid mount)

Being High comp., low ci, higher rev. what kind of power does your motor make?

I found this video of a GT40 with a 289 Windsor - skip to 1:38. Revs like a flate-plane crank V8 to me!

And ya, I'm interested in seeing.hearing a video of the Freq. Mod muffler. How does it work?

Hey Ryeno, did you not check the vid in post #4? I believe that to be the definitive SBF 289 180 degree exhaust sound in action. The Weber induction also makes a big difference in the overall sound experience, based on my personal observations from the '60's.

Flat plane crank? Why on earth would you...

 

[Brad R.]

Ryeno,
Great questions all. I can generalize by saying that this exhaust note subject is verrrrry complicated. The sound is affected by literally every bend, pipe size, muffler, collector, splitter, resonator, and even the exhaust tip. Sometimes smaller pipes (higher velocity) sound great, while other time they sound tinny and other times they sound blatty (as in blaaaaat) when installed on 1954 Chebbies or Harleys.

I don't know the HP of my motor because it also has an intercooled supercharger. I will dyno it some day.

Gotchya.
Centrifugal by chance? Haha, if your getting that freq. mod muffler for your setup then you sure most be going for beyond an exotic exhaust note, more like unheard of!

Hey Ryeno, did you not check the vid in post #4? I believe that to be the definitive SBF 289 180 degree exhaust sound in action. The Weber induction also makes a big difference in the overall sound experience, based on my personal observations from the '60's.

Flat plane crank? Why on earth would you...

I just did, sounds beautiful!
You're right, who would want evenly spaced exhaust pulses, less reciprocating mass allowing revving to be less strenuous, and a unique exhuast note?

Not me... :thumbsup:

 

[Keith]

Or me. Check John Horsmanns experience using the Ford/Cosworth DVF (flat plane crank) in the Mirages....

If you are looking at the ultimate experience with unlimited budget, maybe, but to convert a stock block to flat crank?

Good luck and may the vibes be with you!

 

[Howard Jones]

Jac, thanks for the offer but there is no way to mount a single muffler above the gearbox in the center. Just not enough vertical clearance. If (when) I do use mufflers (2) I will need to mount them along side the gearbox.

My interest is to try a single big exhaust and see how it sounds. If I do this it will require a cross over for one side and then a Y connection. From there out the back will be about 2 feet.

BUT.......... I need to finish a lot of other stuff before I get it running.

Merry Christmas. BAAAAaaaaaa!!!!!!!!!!! Humbug (thats a sheep joke)

 

[Brad R.]

Or me. Check John Horsmanns experience using the Ford/Cosworth DVF (flat plane crank) in the Mirages....

If you are looking at the ultimate experience with unlimited budget, maybe, but to convert a stock block to flat crank?

Good luck and may the vibes be with you!

Im playing devil's advocate.
To convert a perfectly good cross-plane V8 into flate, on top of being blasphemous, strikes me as quite foolish. :thumbsup:

 

[Graeme Stebbing]

Hi Ryeno, I think i might have posted this before but could not find it on the site, but it might come in handy for the new members out there it's a old article from hot rod mag from the 80's, yer i'm that old. Maybe it will give you some ideas about x pipes and their effects etc. There is also a section with dyno results.

Best regards
Lambo

 

[Brad R.]

Hi Ryeno, I think i might have posted this before but could not find it on the site, but it might come in handy for the new members out there it's a old article from hot rod mag from the 80's, yer i'm that old. Maybe it will give you some ideas about x pipes and their effects etc. There is also a section with dyno results.

Best regards
Lambo

Thank you!
Haha, people (like wine) grow sweeter with age :thumbsup:

 

[J. Salmon]

I have become an exhaust sound junkie. I cannot get enough. I cannot explain the fascination. I feel I have become a bit of a connoisseur, with as much appreciation for the nuances as some I know that consider themselves experts on wine.

If you want exotic, it has to be unique, unusual, and have some out standing quality that makes it just a bit... more. V12s are probably the best example - the sound is unique, they are rare, and the harmonics give the sound a depth of character - almost like a chord instead of a single note. V10s are different, but I don't find the character as universally pleasing (the new Lamborginis make a helluva nice noise though).

A flat plane crank V8 is also meets the criteria, but it's not nearly as complex and sophisticated a sound as the V12. To most, it sounds like a 4 cylinder sportbike. In contrast, no one is going to mistake a Lamborghini V12 for a motorcycle.

I would argue that a crossover exhaust on a 90 degree crank V8 may be on par with a V12. It is even more unique - almost exclusive to the GT40. And it has a subtle difference in the sound that makes it a bit more complex. It won't make a normal person scratch their head like a V12 will, but an enthusiast will recognize that there is something different, something special about the sound.

My favorite example of the sound is in the clip from Bullit. It also lets you compare 180 headers (the Mustang sound is overdubbed GT40) to a standard exhaust (the charger).
YouTube - Bullitt - Steve McQueen Famous Car Chase

That's a hard sound not to like. It's playing even as I type

 

[Dimi Terleckyj]

Thank you!
Haha, people (like wine) grow sweeter with age :thumbsup:

Trouble is some people become like sour grapes with age.

Dimi

 

[Brad R.]

Talked to Boyd from Dr. Gas and am quite sold on their Freq. Mod. Mufflers.

They just posted a video on youtube of sound clips of this muffler (along with their Xscream).
Freq. Mod.'s can be heard starting at 3:00.

He explained that these mufflers (along with good downdraft 4 into 1 headers and x pipe) will create great a very unique/exotic exhaust note. In the muffler, the single exhaust pulse is split into 3 waves (each with a different duration of interval). One direct, one delayed, and one delayed even longer.

 

[Jack Dunn]

Howard,
I and several friends race Shelby Can Am racecars in SCCA and HSR. Two of the SCAs in our group have Chev V8s with the exhaust you asked about: dual 4 into 1 headers leading into a single exhaust with race muffler. They always pass the trackside noise meter tests even though one V8 is putting out more than 600hp. And they sound GREAT!
I was at the GTP race at Road Atlanta in the late 80s and one of the factory Corvtte GTPs sounded particularly awesome in practice. I tracked it down in the pits, and it had the setup we are talking about(Chev V8 with 4 into 1 to 1 exhaust). I spoke with the team's engine man Ryan Falconer, and he agreed that it sounded wonderful. He told me that the 4 into 1 to 1 setup sounds virtually identical to a V8 with an 8 into 1 collector exhaust, and I agree.
Of course, the higher the rpm the better the wail, so your 6.8K engine should sound impressive.
There are a lot of good youtube videos with examples of these exhausts. Here's one you'll like with the V8 4 into 1 to 1 exhaust:

YouTube - DeTomaso Pantera with BMW V8

Jack