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# Exhaust and engine accoustics for asthetics and performance

## Exhaust and engine accoustics for asthetics and performance

(OP)
I wasn't sure where to post this.

This is all in relation to a 90 degree v8
I am looking for the highest frequency/note/tone/pitch I can get. I very much enjoy the higher, crisper, cleaner sound the european v8 makes. I hate with a passion the rumble of the harley/dumptruck American v8. I have heard flowmasters on these cars. I don't know if it was the particular flowmaster series or what. But that m3 was a dumptruck. I am trying to avoid that.

I do not need to be informed about flatplane cranks vs crossplane.

I am lost in design at this point. I have a few options as I see it, x pipe, headers, and muffler designs.

Maserati has used ferrari engines since they were bought out by fiat. They use a cross plane crankshaft instead of a flat plane. They also use tri-y headers factory and an x pipe further back toward the mufflers.

[url=http://en.wikipedia.org/wiki/Ferrari/Maserati_engi...]http://en.wikipedia.org/wiki/F...ons]Ferrari/Maserati[/url] engine - Wikipedia, the free encyclopedia
[url=http://cars-database.com/data_images/models/masera...]http://cars-database.com/data_...8/maserati-v8-03....[/url]
a similar snarl that the Corsa gives the Domestic V8
[url=http://www.atzonline.com/index.php;do=show/site=a4...]http://www.atzonline.com/index...2a814fd6b31677645...]A[/url] New V8 Engine Powers the Maserati GranTurismo S - ATZ online
x pipe
http://www.ebay.com/itm/08-Maserati-Gran-Turismo-4...]08 Maserati Gran Turismo 4.2 complete exhaust mufflers silencers | eBay
The illustration shows Exh mani as a 4 into 1 design, shorty, primaries appear to be equal length. X pipe is a ways downstream
http://www.maseratispares.com/1998-heden/images/ca...
same 136 engine only the tipo f136 has a flat plane.

the alfa uses the same cross plane motor as the maserati. very similar. I am sure the slight differences of video quality and the bends in the exhaust that differ between the two can attest to the very slight difference in sound.- still sounds like a domestic with corsa's and an x pipe.

How about we turn to something that takes a traditional 90 degree motor (with itbs, dohc heads, and di) that uses tri-y headers and an x pipe factory.

The s65 bmw motor is a lovely motor.
sounds like a small block chev on the dyno to me, buts its the bmw m3 s65 v8.

compare that to this full exhaust system by ipe f1

compare that to this

and lastly compare those to this

there really has to be more to it than the natural sound of the motor... I would agree that it is more than JUST one thing.

"The crank pin offset is 90°, and for design reasons, a cylinder firing order of 1-5-4-8-7-2-6-3 was chosen
for the S65, instead of the typical 1-5-4-8-6-3-7-2 firing order more commonly employed in other BMW V8 engines."
if you can make some sense of that- its odd "Cylinder numbering is 1 through 4 on passenger (right) side and 5 through 8 on driver (left) side. numbers 1 and 5 are at the front, 4 and 8 are at the rear."

Apparently, the fireing order is the same as the BMW Sauber F1 team v8.

check out this s65 header. looks like a tri-y to me.
http://img364.imageshack.us/img364/3289/dscn0632nb...

http://www.billswebspace.com/DinanE90-92ExhaustDes...
The x pipe from the above video.
http://maxcdn.nexternal.com/aaw/images/Large252.jp...

I think the only reason that the ipe f1 exhaust is higher has to be that x pipe design. which is shown in the following link
http://i244.photobucket.com/albums/gg16/dannyeatwo...
http://i.imgur.com/batEA.jpg
(not to scale dims) Note the taper of the x pipe and the hole that makes the air pass through a smaller opening on two ends. If you look very close at the x pipe design, its ALMOST as if its two x pipes in one.
http://i17.photobucket.com/albums/b81/BRAAPZ/BMW/X...

Now one thing to consider is the are resonators that cancel out particular noise. this is what Corsa mufflers do. The have chambers in the mufflers (which is more like an instrument than a traditional muffler) that are helmholtz resonators that are VERY small. They shoot for 3 particular resonate frequencies to cancel out. Now one thing about frequency is that it peaks, there is a range at the peak. The range will depend on many things and without actual testing it is not possible to know the range with math (that i am aware of to date).

http://en.wikipedia.org/wiki/Helmholtz_resonance

In use on an exhaust system

Now if you actually understand the above link you will see that they are utilizing a Helmholtz Resonator and then packing around it with fiberglass to bring down the vibration(vibration of any kind will bring the volume of the devise up- so this muffles it).

the purpous of a "muffler" is to MUFFLE sound not change the actual tone.

the corsa i wouldn't even call a muffler per say. I would say it is more similar to the dr. gas freq mod, but a better design.
http://freqmod.drgas.com/%5DFreqMod]http://freqmod.drgas.com/]FreqMod Mufflers
corsa cut away
http://s938.beta.photobucket.com/user/faytmorgan/m...]http://s938.beta.photobucket.c....jpg.html?sort=3&...

I should also note that ferrari motors that have a 180 crankshaft do not require an x pipe to merge the exhaust pules efficiently because they already do that naturally with the design of the crankshaft (and firing order of course that goes along with it).

oh as for the 180 header. I suppose I should post this- one of many, videos of a sbc with 180s sounding exotic as they do. The kelmarks, grant gts, and many other cars use these headers as well (gt40s too).

I did forget to mention that (as far as i know) all inline 4s use a flat plane crankshaft.

The complete setup of the engine.
4.060 bore (3.25 stroke) inches
team g intake single plane manifold
jegs 195cc intake port, 64cc chamber heads aluminum strait plug
Superflow sf 600 flow com
air speed: 380-100FT, 375-410SC

Intake;
(.1)66
(.2)141
(.3)200
(.4)242
(.5)270
(.6)265
(.7)268

Exhaust;
(.1)55
(.2)107
(.3)139
(.4)167
(.5)192
(.6)209
the cam will be setup for the intake/heads/headers that are selected in the end result. The cam will put the engine in the 3000rpm-7000rpm range and a redline of 7500, albeit will be designed around the intake/heads/headers flow etc.
The compression will be at 10.5:1, so as to utilize pump gas.
Forged crankshaft (small journal block, two bolt) cross plane style crank shaft I am not going to swap in a 180 crank (flat plane) as per Ferrari spec much too much work and  to do such a thing.
I have decided I should pony up for 6" rods
the rockers are at a 1.6 ratio.

The engine is designed around the fact that I wanted a specific rpm range, the car is very light and tires are very limited. The max tread width I could find in the max rim size available was 8.5 inches. The section width of the tires are 245mm. The rim itself when measured end to end was 240mm. The car will weigh in at about 2800lbs. The donor car is a 1978 Datsun 280z five speed which is going through a sbc v8 conversion. The drivetrain (axles, transmission, and differential) that are available can hold to the hp (which I realize is tq(rpm)/5252). So the rpm of the motor has been raised to the 7000rpm mark to best match the transmission ratios and differential ratio as well as to produce more peak hp than low end tq. Too much tq will just cause the tires to spin and cause premature part failure.
---------------------------------------------------------------------

http://forums.corral.net/forums/general-mustang-te...

Here is a copy of the post I made that I was told to start a new thread about.
SO, after reading all of this. I have some questions, some of them I am aware that they were already answered- though to me, they were not 100% clear.

1. "the whole idea is to have the sound wave bounce off the end of the tube and come back 180 degrees out of phase with the original wave thus canceling the resonance. A "1/2 wave tube" would reinforce the resonance - exactly the opposite of the effect being sought. " This statement was made by Michael Y.

I get this statement. One thing for me in particular, I DO NOT care about drone. I care to eliminate particular frequencies, and I care about reinforcing the frequencies that I want. That being said if I had one quarter wave resonator for canceling out the frequency undesired, and then a "half wave resonator" to reinforce the frequencies I want- would they somehow negatively affect each other?

2. It was stated that the frequency canceled (in hz) will not only be canceled at "X" rpm but at higher rpms as well. To me this sounds like what happens when increasing the cfm that, like an instrument, will cause the over-blow effect bringing the frequency up in octaves which then will cancel out out the frequency in higher octaves as well.

Is this statement correct? As I don't care about drone, which is rpm specific, and I care about the actual frequencies that end up coming out of the exhaust tip, no matter the rpm. For esthetic purposes alone for my personal application

3. People appear to be using phone "apps" to measure the DB and the HTZ of the sound of the exhaust. Is there another device (not a phone) I could purchase that does this same thing? If so what is said device called so I can run and go get one?

4. How do I tell which frequencies I do or do not want once they have been analyzed seeing that for me I, again, don't care about drone and this is not rpm specific?

5. Did we ever really have an answer for the heat problem to determine the speed of sound in the device? One thing to note. All engines are different because of the tune, the octane level and many other factors. These will all effect the engine exhaust temperature to a varying degree. Although I think there maybe a close average of what the exhaust temperature could be assumed to be for a performance engine running on pump gas (87-93 octane) that has been warmed up to operating temp and assuming a 65-70 degrees Fahrenheit ambient temperature. That temp was picked because most of us drive fast cars in the summer and we live in America where we do not use Celsius terribly often. Also on a personal note I live in Mn. Daily average summer temperatures in Minnesota range from the low 70s (22 °C) in the south to the mid 60s °F (19 °C) in the north.

6.What is the agreed upon SIMPLE formula (regardless of the final end cap tuning needed) to determine the dimensions of this device? Also I found very little information in the thread in regards to the diameter. As in if and how it makes a difference in the final product of the device. Ie:2 inch dia vs a 3 inch dia vs a 1/4 inch dia.

"That is simply a low-frequency tuning element which has no flow passing through it. Corsa is attenuating frequencies in the sub-200 Hz range to keep its claim to fame of no cabin drone. The simplest possiblity is that it's a Helmholtz tuner with relatively broad tuning due to a short, large diameter throat. The more complicated possibility is it incorporates the convoluted Corsa quarter-wave tuner maze-like device inside the oval shell. Either way, it's a high-pass filter for the purposes of eliminating drone and an "exotic" sound.

The Dinan E92 M3 mufflers that you posted the tech writeup for go one step further with absorptive tuning after the Helmholtz tuning. If you want a more civilized sound, the absorptive tuning will hit the 500+ Hz range. But, after watching FFT plots on my phone during v8 Ferrari clips on youtube, this is exactly the frequency range you seem to desire more of."

He claims that the 500+ range is what I am after.

Can I get rid of everything under the 500 plus range? Also, from my understanding of how frequency signal works- it peaks. At that peak it s not just one frequency it is a slight range. Is there a way to calculate that range?

He goes further into saying this;

"As for the calculations surround the quarter-wave tuner, you're in luck because it's simply an open-closed duct. Peak transmission loss will occur at the duct resonance frequencies, f=nc/4L, where c=speed of sound, L=length, n=1,3,5 (odd numbers). This only leaves you to figure out the exhaust gas temperature where you plan to install the tuner and the frequencies that you desire to attenuate.

For instance, at a local gas temperature of 350 deg C, the local speed of sound will be 500 m/s. For a length of 1 m, the lowest transmission loss peak frequency will be (1*500)/(4*1)=125 Hz. The next peak will be at (3*500/4*1)=375 Hz.

If Corsa claims they're only targeting 3 frequencies, that would mean there's only one quarter-wave tuner in the maze device that hides inside their flow-through mufflers. I have reason to believe they're targeting the 210-240, 630-720 Hz, and 1050-1200 Hz ranges. This lets you hear lots of 4th and 8th order content at mid-high rpm (350-500 Hz and 800-950 Hz)."

"n=1,3,5 (odd numbers)"
what is n? and why is it only odd numbers?

"If Corsa claims they're only targeting 3 frequencies"
based on what is he coming up with this?

"This lets you hear lots of 4th and 8th order content"

what does he mean by the "order content" and 4th? 8th?

8. Lastly- How could this device be used with performance in mind as mentioned in this thread on the intake side? I would like to see how this could be helped whilst using a single plane intake and a single carburetor setup. As you could postulate, that is what my engine has. Also I have seen threads in regarding g35s using "VHR Advanced Resonance Tuning Test Pipes " and apparently seeing a difference in tq (and seeing that hp is a function of tq...), minimal but still. The same can be said for the Ferrari F1 team, they are using a Helmholtz res on their exhaust. This tells me that perhaps the resonance is affecting the engine harmonics in a way that is positive in nature?

### RE: Exhaust and engine accoustics for asthetics and performance

faytmorgan, That is quite a post. I'll just throw this in for your consideration and hope my math and logic are correct. The low frequency drone of "American" V8s seems to come basically from the missing pulse on each side of the engine where the pulse spacing on each side is something like this: 0, 180, 90, 270, 180. Contrastingly, a flat plane crank produces only 180 degree intervals on each side. At 6,000 rpm, the 180 degree interval corresponds to a 400 Hz tone. But the missing pulse sounds like a pulse at 1500rpm. Then, the selection of 270 degree, 180 degree and 90 degree intervals on each side of the dual plane crank corresponds to a missing 2,000 rpm, 133 Hz fundamental tone plus a 4,000 rpm 267 Hz 2nd harmonic, a 6,000 rpm, 400 Hz 3rd harmonic and a 12,000 rpm, 800 Hz 6th harmonic. The harmonic structure infers the missing 2,000 rpm, 133Hz fundamental which the brain may then reconstruct. So, one side of the dual plane V8 at 6,000 rpm may sound like contributions from something that is running at 1,500 rpm plus something at 2,000 rpm. A dual plane V8 racing car with open headers on each side has a "drone".
H-pipes and all into one exhaust systems may not completely cancel the drone.

Lou Gigliotti made headers for the Corvette that had cross over pipes to even out the pulse intervals on each side. With these, a Corvette sounds like it is turning much higher rpms (and sounds really sweet) than a car with the same engine, but with normal headers that vent each side independently. It is quite a startling contrast. Your first impression is that there is a Ferrari engine in the car.

BTW, the "bundle of snakes" exhaust systems on F1 V8s in the '60s was all about being able to use a dual plane crank which gives a mechanically smoother engine while avoiding the uneven pulses in the header collectors which loses power. For this they turned the engine around to have the exhaust ports in the V where the crossover tubes are not long and then to not have the intake ports underneath, they put them through between the cams in what they called a "down draft port" configuration.

### RE: Exhaust and engine accoustics for asthetics and performance

What you want is an X-pipe somewhere upstream of the mufflers.

What you're trying to eliminate is the occasions where adjacent cylinders in the firing order empty into the same bank, which tends to generate heavier pulses in each exhaust pipe consistent with half engine rpm (it's where the "missing" pulse went). If you listen carefully from straight behind, you can even distinguish these pulses alternating between the two pipes.

An X is the most efficient means of getting the pulses "evened out" for a smoother perhaps snarlier exhaust note. You could perhaps accomplish something similar with a cross-around or a cross-under header design, but that seems like way too much extra work (never mind satisfying things like space and ground clearance requirements).

Here's a plot that I put together some time ago. Normally it gets used where people prefer the rumble but don't understand why you can't get it out of a 6-cylinder engine. The "bank delay" is something I threw in there for the situation I was working with on one of my own cars (where the "X" was not symmetrically situated with respect to the two banks). I hope the plot link works.

Norm

### RE: Exhaust and engine accoustics for asthetics and performance

Trying again . . .

Norm

### RE: Exhaust and engine accoustics for asthetics and performance

(OP)
I am avoiding 180 degree headers. I am thinking that I could use a set of 1/4 wave resonators to cancel out the sounds I don't want.

" The low frequency drone of "American" V8s seems to come basically from the missing pulse on each side of the engine where the pulse spacing on each side is something like this: 0, 180, 90, 270, 180. Contrastingly, a flat plane crank produces only 180 degree intervals on each side. At 6,000 rpm, the 180 degree interval corresponds to a 400 Hz tone. But the missing pulse sounds like a pulse at 1500rpm. Then, the selection of 270 degree, 180 degree and 90 degree intervals on each side of the dual plane crank corresponds to a missing 2,000 rpm, 133 Hz fundamental tone plus a 4,000 rpm 267 Hz 2nd harmonic, a 6,000 rpm, 400 Hz 3rd harmonic and a 12,000 rpm, 800 Hz 6th harmonic. The harmonic structure infers the missing 2,000 rpm, 133Hz fundamental which the brain may then reconstruct. So, one side of the dual plane V8 at 6,000 rpm may sound like contributions from something that is running at 1,500 rpm plus something at 2,000 rpm. A dual plane V8 racing car with open headers on each side has a "drone"."

This is the formula I have found to create a 1/4 wave resonator 180 degree out of phase.
"The speed of sound in feet per second (say, 1072feet/second)
divided by
The frequency you wish to eliminate (say, 128cycles/second)
equals
8.375feet/cycle (numbers divide/seconds cancel out)
This is the length of a full wave form; much too big to work with under a vehicle.
To get a quarter-wave length, divide 8.373feet/cycle by 4 to get 2.09373feet/quarter-wave length.
Multiply 2.09373feet/quarter-wave by 12inches/foot to get the chamber length of 25.125".

Tube diameter does not affect frequency, only the amount of attenuation."

That being said what length should I be after?

also would a half wave resonator promote particular frequencies? If so could use one to promote the frequencies I do want?

### RE: Exhaust and engine accoustics for asthetics and performance

I can't imagine a more subjective or less scientific topic than "acoustic aesthetics"! Fingernails scraping a blackboard is probably music to SOMEONE'S ears...

### RE: Exhaust and engine accoustics for asthetics and performance

(OP)
its about achieving whatever the person prefers bub. someone may actually enjoy that sound. The frequency of the sound could be picked up analyzed and recreated. That is the point here. Please do not post if you don't have any information. I would like to keep this discussion technical.

### RE: Exhaust and engine accoustics for asthetics and performance

The operating range of an engine where significant power is being demanded covers rpms over at least 3:1, so I doubt that resonance tuning will give you what you want under all likely conditions.

You really need to start your solution by making the exhaust pulsing in each separate bank NOT look anything like the plot below, which again is rpm and frequency independent . . . I stripped the odd numbered cylinders from the earlier plot, which should make the low frequency content that you're trying to get rid of more apparent. Hint: try visualizing a best-fit sine curve.

I do have a little practical exhaust system fabrication experience to go along with this.

BTW, your thread title does include the word "aesthetics", which opened the door to discussion concerning the subjective side of this.

Norm

### RE: Exhaust and engine accoustics for asthetics and performance

(OP)
"BTW, your thread title does include the word "aesthetics", which opened the door to discussion concerning the subjective side of this."
Yes it was to find information on making exhaust the way one prefers regardless of a preference debate.

Also, NormPeterson, I am not finding a "pm" option on this forum. Would you perhaps like to communicate about this topic outside this forum? I would be interested in listening to things you have to say. You appear to be quite knowledgeable beyond me on the subject.

dupontlm@ gdnmail. net

### RE: Exhaust and engine accoustics for asthetics and performance

A muffler design is similar to designing an Audio Filter.
You want to reject bass and boost treble and then multiply frequency with harmonic distortion from small eddy currents.

All straight pipes become Helmholtz resonators, so avoid this method.
But the shorter the straight pipe the higher the RPM that will resonate at 1/4 wave.

Minimize high frequency (HF) attenuation with short pipes and eliminate low freq (LF) with a resonator style muffler..

I'd suggest high flow 3" or 4" (ID) diameter pipes in stereo with staggered distances for each pipe and use 12"L * 3"ID resonators using stainless pipe with rough interior straight pipes that create the turbulent harmonics.

You could put a bunch o 12" resonators on each header pipe alternating 12" straight and 12" resonator pipe and have them staggered on each of two pipes.

Closest match to my idea was here. http://www.lextreme.com/Exhaust-3-resonsator.jpg

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