Quote:
Originally posted by Vern!
"The extensively tuned system resulted in a low back-pressure, racing type exhaust design..."
and
"The overall design not only enhances exhaust efficiency contributing to the high output of the engine, but it also creates a pleasant, very sporty exhaust note."
Oh my oh MY this is lame. Brand new SVX had the exhaust note of a reedless clarinet. Racing type exhaust design, yet no manual transmission? Ah, sure. It appears that whoever was in charge of SOA PRODUCT PLANNING in March of 1990 was not at all up tp the task. The numbers on the diagram were obviously done by someone with little to no training in drafting, or the graphic arts.
Seeing this (http://www.subaru-svx.net/forum/atta...=&postid=47622) makes me wonder what delightful products the fools who failed at marketing the SVX have killed in the crib recently.
Please show us more! 
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Vern, I do agree with your thoughts on the exhaust note. As agressive as the passing of wind at a dinner party.!
But I do agree with the discription of the design and function. This is a very well thought out system. I don't think it could be improved and still fit under the car. The rear muffler is the only section that may be altered to change the sound, without degrading the engine's output.
This is how the exhaust system functions.
The SVX as you know is a flat six, of two banks of three cylinders. Each bank has it's own three branch header leading into a single pipe, this joins with the pipe from the other bank of cylinders to continue down to the muffler.
The engine has a 120 deg crank, this means that for every revolution (360degs) the engine fires three times, 120degs. apart, two revolutions(720degs) to fire all six cylinders. If we look at one bank only for simplicity, we have three cylinders that fire 240degs apart.
You would know that the exhaust is expelled during the exhaust stroke by the piston rising pushing the gas out of the cylinder. Unfortunate this is not quite the case, when the exhaust valve opens 55degs before bottom dead centre on the end of the power stroke, two things happen. First a positive sound wave is released (like popping the cork on a bottle of bubbly) travelling at about 1700ft/sec to the end opening of the pipe where it is replaced with a negative pressure wave which travels back up to the valve.
If the pipe length and the engine rpm match, this negative pressure will enter the combustion chamber in time for the inlet valve to open thus inducing the inlet flow.
The other thing to happen when the exhaust valve opens at the end of the power stroke, is a gas pressure of about 60 to 70 psi. is released this "gas pressure plug" travelling at about 300ft/sec exits the cylinder under it's own energy. This has to be out of the cylinder by .the time the piston starts to rise on the exhaust stroke otherwise we will use power to push it out.
Also if this pressure is even say 4 or 5 psi the rising piston will compress this gas in time for the inlet valve to open forcing it back up the inlet tract fouling and heating the inlet charge.
Well where does the resonator fit in, or expansion chamber to give it it's right name. If we look at our bank of three cylinders firing every 240 degs apart, this is about 20mil/sec, and the gas plug has time to travel down the pipe and dissipate, but when the rpm increases to 5or 6 thousand the time is only about 6.6mil/sec, to short for the gas plugs to push the long column of gas right down to the end of the exhaust pipe, for while this pressure exists in the pipe it will be acting on the piston robbing us of power.
So the answer is clear we need a shorter pipe for the higher rpm. Not easy to do on a car but we can put a chamber on the pipe up closer to the cylinder where this gas plug can expand into and have the gas plug and the sound wave act like they have reached the end of the pipe . This drops the pressure which bleeds down out the tail pipe, in time for the next gas plug 6mil/sec later.
I think you will now agree that the resonator does perform a vital function in allowing the engine to deliver good power right up to the red line.
At least that 's the way I see it.
Harvey.