1989GTA

It might if it is to close to the header. So move it back some. Most of them I have seen installed are towards the rear of the car. Probably because there is more room for the installation. Also most people install them with a frequency to cancel out the drone during a highway cruising speed. For most that would be around 2000 rpm. If you have a lower ratio rear gear and a higher rpm at cruising speed you want to up the RPM range.

aknovaman

iTrader: (7)

Wood,

I can see how installing the resonator near the collector (bad idea) would provide some reversion back into the individual port pipes. I see you are educated so all the resonator does is reduce the reflected wave and minimize the standing wave.

I dont recommend placing the resoanator near the header colector. It needs at a point where there is just a constant flow of pressure pulses. Space constraints normally dictate they be installed near the mufflers, either right before or after.

PM me your phone if you want to discuss.

This is nothing new as Mr Helmholtz mathamaticly calculated all theis over 100 years ago. I brought this up just to educate readers.

smitty2919

It works. I did this on my 04 GTO:

gofastwclass

iTrader: (2)

I remember this conversation several months ago. Nice write up Aknovaman, now the nerd in me has something else to play with on an indoor day.

bluezq8

iTrader: (6)

Possible dumb question. Do you want to measure the frequency from the inside or the outside of the car?

aknovaman

iTrader: (7)

I would record the sound inside the car at cruise speeds or what ever rpm it resonates. I cant run fast engough to keep up with any car. :-0


Just use your phone's voice recorder. Download a free audio analysis program like 'Audaciy' and import the recorded file. Audacity has a very accurate spectrum analyzer built into it that has good frequency resolution for you to easily see the actual frequency that the exhaust resonates. It will tell you what frequency YOUR vehicle resonates at. Then plug in the frequency in my spreadsheet and build the resoantor to the calculated length.

smitty2919

I was able to use calculations using the RPM my car droned at to figure out the length I needed.

I then confirmed that by using a iPhone app to find the frequency. this was close enough because the values you use in calculations are assumptions of speed of sound based on exhaust gas temperature which is a guesstimate.

A lot of people will frown upon this because it's so radical of an idea they won't attempt it. It has been around a LONG time and even aftermarket 5th Gen Camaro exhaust come with these adjustable "j pipes". I believe the company is called Solo

Fry_

I say put a cutout on the end of the resonator tube then it would serve 2 purposes.

tonypaul

iTrader: (2)

heres another post with some additional info/samples- https://ls1tech.com/forums/cadillac-...ltz-tubes.html

sprech

iTrader: (1)

This is all quite cool. My thought is to make it tunable with a J pipe off the main that went past the bend with a coupler, then another pieced capped off that's maybe 3 or 4" at the end, and then vary the tube size in between the two couplers. Maybe a little extra work, but allows you to get it exactly where you want it?

The idea about a cut out is interesting, but would it work since the resonator is coming off the side, not the end?

aknovaman

iTrader: (7)

If you measure the actual drone frequency, there is no need to make its length adjustable. Plus this is not a notch filter that's only attenuated at one freq. variations of over an inch are acceptable. Think of it as a attenuators with a bell curve shape.

S10xGN

iTrader: (11)

What's at the end of the "J" pipe? Capped off or another muffler?

aknovaman

iTrader: (7)

Capped end. J pipe is slightly bent for under chassis clearance

sprech

iTrader: (1)

I guess my thought on that is if you know you can regularly cruise at 50 on your way to work, say it's all streets and no prolonged highway, then that would be one setting. If you know you are going on the power tour or some other long distance drive where you may see 80, on a regular basis, you'd want to tune it for that. That's my thought at least. Or is the drone only at a specific speed an that typically tends to be cruising speed? I might have missed this portion of the lecture.

Tanus

ok I understand this, comprehend may be better word, way differently, a exhaust (no h or x pipe or muffler) is an open chamber resonance pipe, which has those soundwaves (traveling ONE direction) that alternate from far apart (high pressure/low press, LOUD) to both with medium pressure after they bouced off the pipe and are in the center,quiet. so if that wave exits at that high/low pressure wave lenghth its loud, if you change the lenght of tube it exits at a differnt wavelength BUT it'll still exit at the high/low pressure (loud)waves but now at a different pulse/rpm, so adding shortening will change the rpm it drones at. and aslong as it doest drone at cruise rpm thats all most care about, so if possible just adding or shortening will change what rpm it drones

. the j-pipe/hpipes/xpipes and mufflers are trying to make that open pipe that will always have loud waves exiting at certain rpms to be like closed pipes that can have waves going both directions so that (set to correct length, ONLY is corect length at a certain pulse/rpm) (same as the dude used a hertz/decmil speaker in his demenstration, so change the hertz/rpm and your whole equation changes) the loud waves going one direction pass the quiet ones going oppisite way canceling each other out but still only at a certain pulse rate.
so the j pipe in some of those pics is backwards and not sending the soundwaves toward the engine, cancelling out the combustion sounds, the GTO exhaust is the correct way.

this is just a guess but i think in the gto pictured because there is 8 pulses(16 if you count the ones from jpipe once they reach the end and bounce back) all coming one way and 8 going other way making that pulse rate super super fast, figuring out that exact lenght as op is attempting i doubt really matters much cause so many pulses are coming/going that the majority are being cancelled, but thats only a guess.

but what i am sure about is to figure that length you have to know the other 2 variables, the pulse rate which i think would change alot by just a 100 rpm would add 800ppm, plus the speed of sound that even in that youtube the instructor said changes in the classroom temp changes the answer by a point so i see no easy way to measure that, id guess its nonlinear aswell cause the temp drops quickly as its gets farther from combustion chamber and from your graph drop of 1deg c slows the speed by 60 cm/s

smitty2919

The "whale *****" as I call it is capped off at the end. It is the same diameter as the "main" pipe.

You typically won't have drone at 50mph and then at 80mph. Drone is RPM dependent so every time you come up to 2000rpm (just an example) your exhaust system will reach the natural frequency and "drone".

You lost me...there is no "direction" of the resonator pipe...the simple explanation is that the the rpm which has drone has a specific sound wavelength...literally in feet, inches, meters (however you want to measure it). What you are doing is allowing that wavelength to pass down a capped tube that is 1/4 the length of the full drone wavelength. It will go to the end of the pipe, and bounce back 180* out of phase and "cancel out" the drone wavelength. No exhaust has "flows" into this pipe, only sound waves, so this has no impact on performance.

Think of it as blowing over a coke bottle with it being full, 3/4 full, 1/2 full and 1/4 full. As the fluid goes down (your capped pipe length gets longer) you generate a "deeper" tone. Same as the car...the lower the RPM you have drone, the longer the pipe will need to be. Then becomes the issue of fitting such a pipe in the car. You could run a simple single 3" pipe up over the axle and exit out the passenger side under the rear bumper. Then "T" a pipe horizontally between the axle and gas tank much like where the muffler on a FBody would be at the length you need. Done. Could probably run a single 3" or 3.5" with a glasspack style muffler and have minimal drone but have a bitchin' sounding car outside.

The only thing that you need to maintain is that 1) the resonator pipe is the same or close to the same diameter as the pipe you are branching off of 2) you need to "T" off the main exhaust pipe at 90* or as close to it as you can.

Follow the chart on post #7. The equation is simple and have a couple of variables which you will make assumed values for. Values like the exhaust gas temperature and thus the speed of sound at that temp. It's a guesstimate because the value used for the speed of sound is in AIR. Exhaust gas is not simple AIR....it is exhaust fumes. BUT the resonator pipe is not ONLY good for 2000rpm. Meaning it may start to kill drone around 1950 and end about 2050 or so.

This is a thread I started on LS1GTO:
http://www.ls1gto.com/forums/showthread.php?t=449416

A snip from one of my responses:
"Using Excel for all it's glory, I came up with the following: My drone in bold.

RPM / Tube length (in)

1500/ 33.75
1550/ 32.66129032
1600/ 31.640625
1650/ 30.68181818
1700/ 29.77941176
1750/ 28.92857143
1800/ 28.125
1850/ 27.36486486
1900/ 26.64473684
1950/ 25.96153846
2000/ 25.3125"


You can see how the pipe length is dependent on what RPM your system will drone. The one on my GTO I made 29" long and it worked VERY well. When shifting normally though the gears you could tell when the drone would normally come on but with the resonator pipe added you would expect it, but the cabin noise would decrease, then as you pass over the drone rpm, the cabin noise would sound normal again. It was strange but in a good way. I had a huge smile the first time I drove after I added it.

Also...there are TONS of other forums with this same idea...Tundra's, BMW's, 5Gen Camaros, Mustangs, Nissan 350Z's....you name it.

Tanus

by "direction" i was reffering to the fact that a exhaust, just pipe, no muffler or resonator or h/x pipe is an open chamber (as described in first vid) with soundwaves flowing(never said exhaust gas's) one way only, by adding chambered mufflers or resonators and, though id guess to less effect h/x pipes manufacter's are gaining the benifits of a closed chamber where soundwaves go down and up the pipe makeing the noise cancellation possible.

and if you take your equation that you calculated the length and you slightly change the variable that you simply gave your best guess on, the speed of sound, you'll see your answer for lenght in now different.


Also I had said above that rpm was the same variable as as the hertz tone the instructor was doing but thats wrong. hertz is same as the decmal frequincy, your trying to figure the lenght of each pulse which is impossible without knowing 2 of the 3 variables, db frequency you have but speed of sound is just your best guess.
i think the j tube does have some real benifits but i see no mathmatical equation being simple enough to acuratly calculate the pulse lengths BUT the way the dude figured out the lenght when he showed how to figure speed of sound seems pretty straight forward, and given the right parts on hand would be pretty doable

smitty2919

by "direction" i was reffering to the fact that a exhaust, just pipe, no muffler or resonator or h/x pipe is an open chamber (as described in first vid) with soundwaves flowing(never said exhaust gas's) one way only, by adding chambered mufflers or resonators and, though id guess to less effect h/x pipes manufacter's are gaining the benifits of a closed chamber where soundwaves go down and up the pipe makeing the noise cancellation possible.

Your typing is confusing me with no capitalization or complete sentences here.

and if you take your equation that you calculated the length and you slightly change the variable that you simply gave your best guess on, the speed of sound, you'll see your answer for lenght in now different.

Correct, you can only make an assumption. Unless you have the equipment to determine the exact exhaust gas composition and a thermocouple placed in the exhaust pipe at the same location you plan to put your resonator pipe, you can ONLY guess at the SOS value.

Also I had said above that rpm was the same variable as as the hertz tone the instructor was doing but thats wrong. hertz is same as the decmal frequincy, your trying to figure the lenght of each pulse which is impossible without knowing 2 of the 3 variables, db frequency you have but speed of sound is just your best guess.
i think the j tube does have some real benifits but i see no mathmatical equation being simple enough to acuratly calculate the pulse lengths BUT the way the dude figured out the lenght when he showed how to figure speed of sound seems pretty straight forward, and given the right parts on hand would be pretty doable

Again, you don't have the equipment to get any more accurate. Do your own research online and you will find that ALL the SOS values are a guess and people have had great results. There is enough "wiggle room" in the real life application on your car that a SOS guesstimate based on a Temp (that you can measure the exhaust pipe temp) in AIR (assumed because I haven't found a SOS value in exhaust gas) that the resonator pipe +-1/2" won't matter.

Sometimes you can only start with assumptions then experiment and go from there.

BTW...here is were I found out about this...16 pages of fun.
http://forums.corral.net/forums/gene...tely-gone.html

aknovaman

iTrader: (7)

Smithy, Good point, 16 pages of some substance and hypothesizing. I found the same thing with the mopar guys.

Most corral people have not scientifically analyzed it mathematically using sound physics calculations, only physical experimentation with much discussion and debate. Accept the fact that physics properties and their calculation all never change, only the variables change.

My original intent was and is to educate folks so they don't waste time guessing. I never guess, or wonder. I measure, analyze and calculate to come to real world conclusions

reedld

iTrader: (7)

I think this forum topic is a very interesting one. While my magnaflow system is not real loud...I do have some drone at highway cruising. I don't have my A/C finished yet, so my windows are always down. I may try adding a pipe before my mufflers, it's the only place I have any space. Thanks for posting!