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A rather interesting chain of events has lead me here, but the short of it is this:
My car is far too quiet. I don't enjoy the result of any available aftermarket exhaust for the 350, in fact the only attractive option I heard throughout my journey was a resonator/muffler delete.
I decided to do some research and actually start trying different things with the exhaust with some buddies. Keep in mind no matter what I do to my stock exhaust, my endgame is a full custom exhaust from headers to tips. I'd also like to take this opportunity to remind everyone that while opinions are more than valued in the forum community, to each their own.
To start, I spaced the muffler behind the resonator, effectively creating an exhaust leak which would allow me to get a firm idea of the effects of the muffler delete. The sound was thunderous to say the least. Drone levels were maximum on the highway at 3k rpm, and cabin volume/rattles were ever present especially considering the exhaust was now exiting under the passenger compartment. The spaced bolts were the spring variety, which when spaced would squeak incessantly. Again, all in the name of science.
Put that right back to stock.
I decided that I wanted the exhaust to look stock, which lead to the following. I considered this an opportunity to show you all what the inside of an IS 350 muffler looks like. While I was at it, I gutted the thing completely.
The following components appear to be the most restrictive of the bunch. A tensioned valve and an additional insulated/perforated mini muffler.
All cleaned out and ready to be closed up (for now).
At this point I'd just done the one. Stitched 'er back up like a pro, threw it on the car. To my absolute dismay, we'd stepped it up from 2 to 3 out of 11. Minor increase in low end growl, a bit more resonance on the higher end, but all in all still ridiculously conservative. Thursday I'll be gutting the second one, and if thats not enough I'll chop out the resonator for some 2.5". Let you know how it goes..
Wow! Thank you for doing that. I've wondered what's inside of those mufflers. What do you think the spring loaded valve/flap is for? Perhaps maybe for sound and extra flow?
By the way, have you ever looked into Spintech mufflers? They are usually associated more with V8's than 4 or 6 cyls.
I ran some on an old Chevy truck I had with a slightly modified 350 in it and loved them.
Granted they are not the prettiest thing around but they flow really well and can sound great.
So you would say the OEM muffler is restrictive? I've been contemplating on the Tanabe exhaust.
of course OEM mufflers are restricting. They are made to minimize noise hence "muffler". Car producers also have restrictions as to how much noise comes out and emissions.
Thats why changing exhaust are technically illegal for road use. That's also why every aftermarket part states "for off-road purpose only"
Wow! Thank you for doing that. I've wondered what's inside of those mufflers. What do you think the spring loaded valve/flap is for? Perhaps maybe for sound and extra flow?
I would presume the valve is there to control back pressure, opening up at higher rpms to allow better flow from the motor when the direct injection is doing it's thing. It is most likely responsible for a good portion of the restriction. I always noticed that the car got 'throatier' on the high end and that explains it!
I haven't heard of that exhaust company before, I'll take a look.
As far as how loud I'm shooting for, more than likely quieter than yours! I think I'll be happy with the additional rumble of the 2 gutted mufflers. Also, I'll have shaved off 50+ lbs of weight at the rear and removed a lot of the exhaust restrictions. Gains from the open flow, lighter, easier to break traction are all expected.
i have an invidia mid pipe + resonator
straight pipe hks hi-power axel (muffler deleted with new tips)
Basically a resonated 3" straight pipe. Sounds good but dangerous around cops. And I assume suuuper annoying for my neighbors
it is hella loud.
What part of Cali bro? I have the full HKS installed and it's hella quiet, a lil too quiet. Ever since I have had the IS I have NEVER been stopped by POPO. When I had my slammed civic I was constantly getting stopped because of the sound from the car. Now mind you it was str8 stock minus the muff delete. I had asked one POPO why he stopped me and he tried giving me a lecture about cars REALLY NOW! HUH. He said "let's open the hood and see what's in there." You dumb dumb don't you know I have 4 squirrels under there! No engine swap nothing! Str8 4! Anyways, I am also wanting a lil sound out of my exhaust and thinking about deleting as well.
Been wanting to do a cheap muffler internal delete mod, but no one local ever has an axle back F/S. Thanks for those pics; I figured it was more complicated than it seems.
One cut down the top center, and then again along the front and back, peel both sides back and voila. I should mention that the muffler housing is comprosed of 3 layers of sheet metal sandwiched together that you've gotta get through. MIG was sufficient for closing it back up.
@Gville glad I could help, I recommend giving it a shot.
I wonder if gutting it actually helps at all, or hurts performance. While reducing restriction, it also effectively creates a big stagnate volume, reducing exhaust gas velocity which aides in scavenging during overlap. Just a thought.
I wonder if gutting it actually helps at all, or hurts performance. While reducing restriction, it also effectively creates a big stagnate volume, reducing exhaust gas velocity which aides in scavenging during overlap. Just a thought.
The velocity/backpressure debate was had at length prior to the decision to give it a shot. I know its not necessarily wise to go throwing a 3" pipe down the length of the car for that very reason, but the front 90% of the exhaust remains factory so I wasn't too worried about it. It was decided that if there were any issues, we'd open them back up and continue the 2.5" through the inside of the now empty muffler housing. I haven't noticed too much, but I can tell you it feels more like a gain than a loss thus far. Honestly I'm happy to strip the weight, and this is all interim anyways. I should also note that the exhaust velocity on exit is at least 5 times that of the still restricted side.
What part of Cali bro? I have the full HKS installed and it's hella quiet, a lil too quiet. Ever since I have had the IS I have NEVER been stopped by POPO. When I had my slammed civic I was constantly getting stopped because of the sound from the car. Now mind you it was str8 stock minus the muff delete. I had asked one POPO why he stopped me and he tried giving me a lecture about cars REALLY NOW! HUH. He said "let's open the hood and see what's in there." You dumb dumb don't you know I have 4 squirrels under there! No engine swap nothing! Str8 4! Anyways, I am also wanting a lil sound out of my exhaust and thinking about deleting as well.
southern california. Heart of the police.
I have also never been pulled over. But there is a huge difference between a loud Lexus and a loud Honda. Hondas get a lot of hate from cops.
My nvidia mid pipe + HKS axel is the loudest aftermarket combo. The sound was still too quite for my ricer taste so I replaced my HKS mufflers and add some tips/pipes for the straight axel. I would have liked it somewhere between my current straight pipe and before with the muffler. I guess a louder muffler besides the HKS hi power would have been good.
As planned I got around to the second muffler and still just wasnt impressed at all. To be honest it gave me about a 5% volume increase at the rear and still sounded just as boring.
I took the leap and chopped the resonator right out. Had my boy drop the section and weld a 2.5" pipe in its place. I'm now super happy with the results! I haven't had the trans in automatic since it got done. Its about 50% louder, RHASPY at 2.5-3k, pops and crackles sufficiently on downshift and is at least 300% more fun to drive. It really does feel like its perhaps breathing a little easier.
All in all, I'm impressed. I'm having a custom intake manifold fabbed shortly, at which point I may 'inspect' the internals of my cats as well. It's not the life for everyone, but I now drive around with a ***** eating grin all day and thats good enough for me
06-28-17, 12:37 AM
IS350 Muffler Guts - Document & Delete
REALLY NOW! HUH. He said "let's open the hood and see what's in there." 
You dumb dumb don't you know I have 4 squirrels under there! No engine swap nothing! Str8 4! Anyways, I am also wanting a lil sound out of my exhaust and thinking about deleting as well.
