|Dec30-12, 11:34 AM||#1|
Exhaust and engine accoustics for asthetics and performance
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.
http://en.wikipedia.org/wiki/F...ons]Ferrari/Maserati engine - Wikipedia, the free encyclopedia
a similar snarl that the Corsa gives the Domestic V8
http://www.youtube.com/watch?v=Un_sQtJA2iA]Maserati GranTurismo Exhaust Note! - YouTube
http://www.atzonline.com/index...2a814fd6b316776454]A New V8 Engine Powers the Maserati GranTurismo S - ATZ online
http://www.ebay.com/itm/08-Maserati-...#vi-content]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
same 136 engine only the tipo f136 has a flat plane.
http://www.youtube.com/watch?v=gwVlc...O0A]Ferrari458 Italia Exhaust Sound!! Lovely Downshifts! - 1080p HD - YouTube
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.
http://www.youtube.com/watch?v=0siqv...iqvB_7Sco]Alfa Romeo 8C Competizione Sound!! - 1080p HD - YouTube
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.
http://www.youtube.com/watch?v=Y-mGG...-mGGf5Ncx8]s65 BMW Engine Dyno - YouTube
compare that to this full exhaust system by ipe f1
compare that to this
http://www.youtube.com/watch?v=Bzvpg...re=related]E92 M3 Exhaust Compilation - YouTube
and lastly compare those to this
http://www.youtube.com/watch?v=MIsc_...re=related]E92 M3 - Megan exhaust - YouTube
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.
The x pipe from the above video.
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
(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.
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).
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.
corsa cut away
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.
http://www.youtube.com/watch?v=MSZTb...6C6Lw]Corvette with 180 Degree Headers - YouTube
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
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.
Now- I just read this entire thread.
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.
7. If you go back to the thread that i posted (and now that i understand way more about this because there is some actual genius in this thread) these statements were made.
"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?
|Jan3-13, 03:33 PM||#2|
Wow...that's a lot to digest.... I've only skimmed it but here are a few comments....
To understand order content.... think of the pulses coming from each exhaust valve. If all pipes are same diameter and same length, the pulses all line up evenly distributed & sequential at the termination, so you hear a frequency that is a multiple of the # of cylinders you have. If you want only high frequency sound, this is the ideal case. If you make just one pipe a different length, you get a pulse that is out of sequence with the others.... it introduces a new, lower frequency, since it repeats itself only once for the the entire pulse train. Achieving exhaust headers with identical acoustic lengths is not easy given packaging & manufacturing realities. We work with the same issues on the intake side...same principles (although easier, since we don't have the thermal gradients which cause additional complexities...)
The quarter wave tuner only works for odd multiples of quarter wave lengths... if you have even numbers for n, you have a half wave, not a quarter wave, and you don't get the cancellation effect.
|Jan4-13, 03:22 AM||#3|
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