What the inside of the resonator looks like

[EODguy]

What you have there is a good example of an expansion chamber as designed by Hiram Maxim. It allows the gas to expand slowing down the flow. I've attached a gif but just imagine that each bullet is the pulse from each cylinder, the slow down causes back pressure helping to control/slow the next pulse in turn. The bleed over is just accidental in the resonator or the baffle plates would have specific holes for the gas and not just pass through holes for the exhaust pipes.

H/T: silencerco for the gif

Sent from my SM-A730F using Tapatalk

[PropellerHead]

Originally Posted by mr_robot

I will add the water leaked very easily. I used a 20oz cup and could pour it all without over flowing.

This is surely an engineered resonator not just muffle sound but provide something they wanted to achieve.

Exactly!

Found another excellent nerd article here:

https://www.rodauthority.com/tech-st...on-strategies/


This resonator is designed to eliminate sound with the insulation around the holes. The engineer's (well, BMW marketing folks) unwanted sounds are absorbed into the insulation while the waves mix with each other and cancel one another out. This isn't a great picture since it shows only one inlet, but if you consider that this happens inside the unit, you have a clear idea of the design purpose. One set of sound comes in from the motor (blue) and hits the insulation as it flows through the holes. If we add another inlet doing the same thing and removing the noises from that bank, you get two inlets with different sound being filtered.

The audible result is the yellow arrows representing the desired sound.

Absorptive mufflers are designed so that the sound entering the muffler interacts with packing material and is converted to heat by the frictional process. This muffler’s performance relies on absorption by the packing material for performance.

Absorptive type mufflers gained serious recognition in the late 50s by hot rodders and have continued to thrive with enthusiasts that want a very aggressive high performance sound. These straight-through designed mufflers produce a tantalizing sound and are sought after by many enthusiasts.

Enthusiasts wanting an absorptive style muffler should look to choose one from a reputable manufacturer like the ones that we have listed here. “Certain mufflers can burn out because the packing material is in contact with perforated tubes and the hot exhaust gases,” said Benty. If the packing material burns out or is blown out of the muffler, it’s ability to provide any noise control is reduced.


Absorptive type mufflers tend to be a straight-through style core wrapped with a packing material for sound absorption.

“Absorptive muffler technology has been around since the 1950‘s,” explained Tauber. “The problem with this technology is that even though the muffler looks straight through, the turbulence caused by the sound and exhaust pulses trying to escape into the packing material, causing back pressure.”

“The quietest time in an absorptive muffler’s life is when you buy it,” says Flowmaster’s Nate Shelton. Shelton has over 40-years of experience with performance exhaust since starting at Hooker Headers in 1972.

As Benty explained above, the packing material gets burned or blown out of the muffler. Condensation can soak into the packing material adding to the degradation of the muffler’s ability to act as a silencer. Unless you plan on replacing your mufflers a lot more frequently, or wearing noise canceling headphones when you drive, straight-through mufflers may not offer the controlled sound level that you desire.


Sound waves move to the exterior though the packing material on it’s way out of the muffler. Many enthusiasts like the sound created by this style muffler.

Noward explained absorptive muffler’s perforated tubing as being a big difference between the reactive style and absorptive style muffler design. “We don’t use porous tubing as a primary means of sound deadening as this type of methodology is generally used with a packing muffler as the primary means of sound deadening. These methods can actually impede flow.”

[X53Jay4.8is]

Originally Posted by PropellerHead

I completely disagree.

The pressure of the system sealed up simply *must* allow the gasses to comingle and the evidence shows it does. If large water molecules will flow through, gassy air will as well. That air carries with it sound from the exhaust.

The unwelded center ovals through which the pipes are joined are there for support of the unwelded connections- not to seal any distinct chambers. We are then left with one unsealed chamber, pipes with holes in them, and a non-sealed pipe connecting them to the welds outside the open unit. The two cylinder banks are open to another. The gasses must mix and they do. They mix enough that the black soot coats the inside of the metal casing evenly across the two unsealed chambers. If the two chambers were distinct, the patterns would be unique. Welds would exist between them. There are none. Air flows. It joins the air from one bank to the other and rids us of the loppy sound we'd get otherwise.

It's a crossover. Whether we think it *looks* like enough of one or not doesn't matter. We don't know how much of an opening is needed, but we do know that one exists. It's really as simple as that, not only to my eye, but to my sense of logic.

Edit:

Provided research for support.

Besides, every V8 without a cross between the two banks will sound like lop sided ass. It's amplified in a dragster, but this is the extreme example of the resonance that joining the two banks is meant to allay.

Here's a solid link on how they work and why V8 exhausts are designed to be joined. And here's a pic also of a ~1" connection in an H pipe. Doesn't take a lot to balance the sound.

Here is a video of a straight pipe without any x over or H pipe. Note the loppies. This is what you hear bc the cylinder banks fire at times other than one another, send that sound straight out only their own side, and your ears are left looking for balance. You can almost visualize the cylinders moving up and down with the separate sounds:

https://www.youtube.com/watch?v=b6-zwK5th-4 Check at 1:37 for the same car with X Over pipes. It reveals a lot.

Also, they make clear that the smaller the openings between the two banks, the more low end performance will be gained. This is very good insight along with the small openings shown in the pics of the OE unit. We can infer that the smaller openings move less air and provide more back pressure which increases low end torque. This off-the-line grunt exactly what sells BMWs- especially a giant SAV, so the smaller openings make good 0-60 sense.



It also meshes well many folks experience of losing lower end grunt but seeing a happier rev up top. It never did make sense to me before, but now that I see it and pair the E53 experience with that of my E39 540, it's very clear.

I'm with you on this one prop.

[Fifty150hs]

Very interesting information Prop. I learned a lot. Thanks for posting it.

[PropellerHead]

Originally Posted by Fifty150hs

Very interesting information Prop. I learned a lot. Thanks for posting it.

This whole thread was a neat opportunity to learn. I had fun with the research.

[mr_robot]

Now I’m curious if the 3.0 resonator is the same inside as well.

[Fifty150hs]

Originally Posted by mr_robot

Now I’m curious if the 3.0 resonator is the same inside as well.

Me too!

[PropellerHead]

Originally Posted by mr_robot

Now I’m curious if the 3.0 resonator is the same inside as well.

Battery operated reciprocating saw and a junkyard, anyone?

[bcredliner]

Stock exhaust always has too much back pressure. Reducing back pressure is one of the best returns on investment.

The resonator is not intended to do more than decrease the exhaust decibels and/or eliminate drone. Since it disrupts the natural exhaust flow it should be eliminated for best performance.

The function of an X or H pipe is to balance the flow of exhaust from bank to bank and scavenging. In both cases they are installed between the resonator and the muffler.

An X pipe increases HP at high RPMs and the exhaust will have a higher pitch.

The H pipe increases low end torque and results in a lower exhaust note.

Maximizing exhaust flow is a science. The best route is to purchase a complete performance exhaust including headers. However, headers I have seen cost way too much for the benefits. Electric cutouts installed post cat and pre resonator are next best option as an add on to a performance exhaust system. If adding to a stock system is the route one prefers the X pipe is worth the investment and results in the greater performance improvement. A low restriction muffler is a good add on but it is best to go with something someone else has done, especially if you hear it and ride in the vehicle before you make the purchase. Videos are helpful but the accuracy of the sound depends on the quality of the recording and the speakers you have.

[Liamk]

Hi I’m getting a custom cat back system fitted on Monday at the exhaust shop, with the above things considered I think I will be going with an h pipe rather than straight or x pipes, the thing is I have been researching various 4.6is exhaust notes and have found what I like, thing is can anyone have an estimated guess on the exhaust setup in the link? Also I appreciate the above mentioned comment on speaker and recording quality! The question has already been asked previously to the video poster but there has been no reply?

Video link
https://m.youtube.com/watch?v=myq-VWv1BgY