308/328/Mondial performance exhaust development

excellent thread. all i can add is that my original thermo reactor on my car was a ticking bomb and i had it cut off. i now have a Magnaflow dual in, dual out. the exhaust on this black 77 GTB that had the TR is different from my old red GTB that had the factory Ansa on it. the Ansa system had longer mid pipes between the muffler and the manifold. my car has what look like headers straight off the head , so my connecting pipes to the muffler were very short. i paid $525 parts and labor to a local custom shop and i love both the sound, the weight loss and the performance gain from the Magnaflow. i am sure there are better "tuned" systems out there for the 308 though.
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Here is some good info.

http://www.ferrarichat.com/forum/showthread.php?t=103116

My car is in there somewhere (red/tan with the magnaflow dual set-up).

No real issues with heat so far in over a year.

No real "tunning" done per se, just some straight back pipes with magnaflows.

 

Which tips are these, as they're the best looking ones I've seen
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Went with Jet-Hot on the stock Euro headers, not sure what difference it would make to SS units. On the car here, the Jet-Hot coating allows for better cooling, are said to flow better due to the very smooth surface, and the coating will add life to the headers.

If it was me, i'd go with cherry bombs muffler, resonator tips, and adjustable Traps at the end. The Traps allow you to increase sound silencing when desired without causing much air flow reduction. During track days or when you want to hear the car more you can remove/reduce the Traps easily with a screwdriver.

Maybe, i can't say for sure as the PO did a true dual system on the Euro 308 here. More flow can be good, but remember that some back pressure may be good to keep torque in check. Am curious, have you dyno-tuned your car and if so, what were the #'s?

 

i did a magnaflow tru dual exhaust on my euro carb 308 4 years ago. surely woke up the car, i do get some popping on deceleration tho. its the onlyway to go as far as i am concerned. a noticeable improvement over the stock or tubi design....

 

Russ,

Muffler design is an art and science. I have years of experience designing and developing advanced free flow exhaust systems.

The idea is to get proper pulse timing and get the pulses in balance so that you yield a sweet sound throughout the range.

The well known high end systems do not do that regardless of what the makers say, and they are not quality free flow systems. Their goal is to yield an F1 sound in a specific frequency band. Who really cares about that based upon the multiple complaints folks have stated of their to be or not to be systems?

They achieve this by using smaller and restrictive tubing w/in the muffler. What kind of a free flow system is that? Since you can't see within the unit and since no one shows a cutaway, you don't know that.

However, if you dynoed the stock vs one of these, you would be surprised to discover that the replacement might be MORE restrictive than the OEM unit! All of that for sound? Big price to pay for little gain.

The design you show with the orange/red packing is a smart design, but if you can separate the mufflers per bank and then put two resonators in line rather than one large one, you can yield a very, very sweet sound. This arrangement would tend to better balance the exhaust pulses.

Keep the banks separate-no x-over pipes. OEM's do that because they only care about silencing the exhaust not augmenting it.

Of course, there is quite a bit of engineering that goes into this to get everything properly balanced.

As to packing, very high grade and high temp fiberglass packing makes the best silencer. Any internal metal has no ability to damp resonance. It is used primarily for support, but some use it to achieve the higher pitched sounds.

Keep playing with it, and you will result in a great product.

 

Russ,

Type "B" is what you want. You get balanced length in's and out's, and then you get a dual value resonance silencing. Type "C" does not give you that.

You also get a better weight distribution of the muffler itself which is easier on the hangers and vibrates less overall.

The whole idea with exhaust is to ensure that everything is as balanced as possible. Remember "equal length" headers from the 60's and 70's. They were then referred to on the Indy cars as "spaghetti".

V design engines are all about balance. You then want to keep the exhaust note in balance and keep the banks separate for exhaust. You mention what you have seen on the V-12 muffler designs. This is why.

Front engine cars are easier to work with, because you have tubing and room to layout the resonators. Tubing itself has some silencing capability but not much.

In the 60's we had flexible exhaust tubing that was great. It was itself almost a silencer. The problem was that it would collect the exhaust moisture and rust through quickly.

Another thing is to keep the ID of the piping the same all the way through.

I can't give away too much more as I am working backwards on exhaust designs for some of the 3X8 series.

 

Russ,

We are dealing with simple physics here. It's referred to noise cancellation technology. You try to either a) dampen the resonances that cause the multiple resultant harmonics or b) you create the equal and opposite frequency to net a 0 value. This then cancels the wave.

For example, if you take a speaker driver and hold it in free air while it's playing you get little output. Put that same driver on a baffle whose length exceeds the longest wavelength that speaker can create, you then get substantial output.

The reason for this is that what comes out the rear of the speaker is 180 degrees out of phase of what comes out the front. In free air you are, therefore, getting the nearly full cancellation. On the baffle, you are separating the frequencies, and you then hear substantial output.

In proper muffler design (and I emphasize that) we are trying to get similar resonances out of balance so they cancel. This then creates the exhaust harmony. Proper design achieves silencing the entire spectrum of exhaust frequencies. it is not tuning to a specific resonance to emulate an F1 racer.

You are then left with the resonance of 1) the exhaust gas explosions and 2) the air under pressure that is escaping.

So, by using the multiple resonators, you cause the above to occur by breaking up the waves rather than by passing them all through one resonator in one pass. This then yields the dual value concept I mentioned.

A one can design is an inexpensive way to make a muffler. Think of this when you are asked to pay $4K for it!

Rear engine cars are difficult to exhaust tune due to 1) limited tube length, 2) limited resonator space, and 3) proximate engine heat.

The 3X8's have mufflers below the engine. The 355 on have them at engine height. Which models sound better to you?

BTW, removing cats is not the answer. They are silencers themselves.

Hope this helps.

 

one thing to consider is that the flow of gases like liquid do not like 90* bends. each bend will cause a 'stacking' of pulses and a hot spot. the less bends the better. the same goes for reducing the flow of gases, the energy pulse is transfered to heat. if you painted the stock exhaust system where the paint flakes is the location of restrictions due to the heat build up.

i've got a great physics book 'the refigerator and the universe' that handles gas and thermodynamics in a very understandable way, well at least if you've had a course or two in it. anycase as Greg has pointed out there is science and art in the design of exhaust systems. not to detract from Greg but if you've got the coin $$$$ Jack Burns is the guy who can fab up the best system for you. AKA Burns stainless. but get in line behind the NASCAR and NHRA boys he's a BUSY man! oh and he's done the F1 Ferrari inconel periscope headers.

i've got a great article by him about the design and layout of basic systems and what to look for, i'll try and scan it this weekend when i have more free time.

 

Russ,

You do not want to add any bends as Scott has mentioned. So, stay away from the recent designs you just did. That would defeat the whole purpose of your design.

BTW, the "golf ball" test is a way to tell you that you ahve no restrictions w/in the muffler, but it has no actual effect upon design.

Keep looking for small resonators. There are manufacturers other than the ones you mentioned who may be able to help you, and check with the one Scott mentioned as well.

Try: http://www.ansaautomotive.com/index.html They may be able to sell a few to you.

I am presently working with a European firm who will be making mufflers for me, and I will have smaller blanks available. I just don't have a time frame, however, on their availability.

Take your time with this design, and the results will pay off.

Any other help you need let me know.

 

here is the layout on my mondi 8, euro headers and test pipes with tubi muffler if you call it that.
warning crude dwg!
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great thread!!! wow!

my question: does the Magnaflow muffler keep the exhausts seperate in side the housing , or do both banks "mix"? from what Greg has said, this is not desireable.

there was a huge in crease in felt performance with the new exhaust from the old , swollen thermoreactor my car had. but i am wondering if there is something better out there. i will state that the $500 or so dollars i spent parts and labor for the local guys to put this Magnaflow on was a deal. i would however, consider another system if its a better design for a carb 308. we need all the help we can get, our cars are SLOW!!!!

 

mine acctually has only 1 90* and thats the one coming down the front of the motor. the rest are 'U' turns and there are only 3 in total. the D & E scketch show 5 with out the header turn connected. hopefully all that was clear as mudd

my caution was to avoid as many turns as possible, i'd change mine too since i don't have cats and cut out those extra two leangths. more like the GT4 system you posted up in the pics.

i'll say mine is loud and 'barks' everyone that hears it loves it and says it sounds great. doesn't sound like any other 308 i've ever heard. highway drone isn't too bad, it's low and rumbly. oddly with the cats on it was painfull to drive at highway speeds, i really mean it hurt your ears it was so bad! removed the cats tuned the motor back to run right and she now sings. i can get a F1 scream when ripping thru the gears but at idle sounds like a small block chevy with a bark.

 

not if you join me on the dark side, MUWAHAHAHAHAHA!

ohhhh a black darth 308, mmmmm