ke70dave Posted August 31, 2009 Report Share Posted August 31, 2009 well folks i have a tech Q for you tech heads. wasnt exactly sure where to put it so i chose general mechanical. anyway. the details: ke70 poorolla standard jap 4age jap ecu standard jap exhaust manifold and secondaries. 2.25" pipes all the way, over diff rest of exhaust system : high flow cat convertor 2 straight through mufflers, one just before the diff, and one after. i belive they are both the same "huricane". ok the problem: my original exhaust i had a "resonator" where one of the straight through mufflers is now. the problem was it was just to loud for my liking. it was ok when you wanted to have fun. but listening to music was a non event on the highway, as the drone was terribe. so i took it down to an exhaust shop and got them to take out the resonator, and put a muffler in instead (their recomendation). as my understanding is that a resonator is just a small muffler? thats what he told me anyway.. now with the new setup (dual mufflers) the noise is perfect. has a nice note when you put your foot down (and i can hear the intake roar more!) and when cruising its almost silent, just a slight brrrrr in the background. EXCEPT i have some epic resonance at certain frequencies, thus certain RPM. the frequencies being 1200rpm, 2000rpm, 3700rpm, 4500rpm, and around 5700 rpm. only aproximate values from my standard tacho. by resonance i mean that the exhaust gets REAAALLLYYY loud for a very very narrow band of RPM (ash tray shaking, tool box shakes in the boot, all plastic parts rattle, my bones shake etc). so anyone know any decent methods to move the natural frequencies of my exhaust system out of my rev range???? i thought about putting the old resonator in as well as the new muffler, but i dunno if it would even fit. and then i might lose all exhaust note. Quote Link to comment Share on other sites More sharing options...
LittleRedSpirit Posted August 31, 2009 Report Share Posted August 31, 2009 well folks i have a tech Q for you tech heads. wasnt exactly sure where to put it so i chose general mechanical. anyway. the details: ke70 poorolla standard jap 4age jap ecu standard jap exhaust manifold and secondaries. 2.25" pipes all the way, over diff rest of exhaust system : high flow cat convertor 2 straight through mufflers, one just before the diff, and one after. i belive they are both the same "huricane". ok the problem: my original exhaust i had a "resonator" where one of the straight through mufflers is now. the problem was it was just to loud for my liking. it was ok when you wanted to have fun. but listening to music was a non event on the highway, as the drone was terribe. so i took it down to an exhaust shop and got them to take out the resonator, and put a muffler in instead (their recomendation). as my understanding is that a resonator is just a small muffler? thats what he told me anyway.. now with the new setup (dual mufflers) the noise is perfect. has a nice note when you put your foot down (and i can hear the intake roar more!) and when cruising its almost silent, just a slight brrrrr in the background. EXCEPT i have some epic resonance at certain frequencies, thus certain RPM. the frequencies being 1200rpm, 2000rpm, 3700rpm, 4500rpm, and around 5700 rpm. only aproximate values from my standard tacho. by resonance i mean that the exhaust gets REAAALLLYYY loud for a very very narrow band of RPM (ash tray shaking, tool box shakes in the boot, all plastic parts rattle, my bones shake etc). so anyone know any decent methods to move the natural frequencies of my exhaust system out of my rev range???? i thought about putting the old resonator in as well as the new muffler, but i dunno if it would even fit. and then i might lose all exhaust note. Hey Dave. Firstly 4ages have a shocking raspy exhaust note as a rule. :lol: Secondly, the resonator belongs where the second muffler has been put. Its there for a reason as you discovered. Every exhaust place will put the resonator just before the diff bend. As far as I know the resonator is just a chamber of a larger volume than the pipe itself, and has no muffling qualitys, insulation or anything. You can lessen the vibtration with a flex pipe, but resonant noise will only be removed by a resonator. Trial and error for the win. I'd have just spent some money on a better quality of single muffler. Just get a really quiet normal muffler and get the resonator re-installed, or perhaps experiment with longer or shorter resonators before the first muffler. A lot of the noise that came from my exhaust as you know was from the shitty ultra thin and flappy heat shield above the muffler. This will give it a tinny rattle if you don't do something with it. Quote Link to comment Share on other sites More sharing options...
philbey Posted August 31, 2009 Report Share Posted August 31, 2009 The resonator is designed to remove those resonant frequencies as little red spirit said. It does it by using internally reflected soundwaves to cancel themselves out. in theory the size of the resonator will vary the frequency of the soundwave it's supposed to cancel. I'd get one put back in as well as a proper muffler. Quote Link to comment Share on other sites More sharing options...
Hiro Protagonist Posted August 31, 2009 Report Share Posted August 31, 2009 A resonator is not a muffler - as a general rule a muffler "muffles" the exhaut noise over the entire rev range, whilst a resonator cancels out specific resonant frequencies which are present at particular loads/revs. A muffler does little to combat resonance, and a resonator does little to muffle the exhaust. A good exhaust system should have both. Quote Link to comment Share on other sites More sharing options...
ke70dave Posted August 31, 2009 Author Report Share Posted August 31, 2009 hmm thanks for the replys guys looks like ive been given some wrong information from the exhaust shop. i thoguht it was a bit too easy if this other muffler was the solution. philby when you say "proper muffler" are you refering to a baffled muffler? or do you have any suggestions on a decent muffler? i thought huricane was supposed to be pretty good? apparently not for my wanting. i still have the resonator that they took out so getting that put back in isnt a problem. Quote Link to comment Share on other sites More sharing options...
LittleRedSpirit Posted August 31, 2009 Report Share Posted August 31, 2009 hmm thanks for the replys guys looks like ive been given some wrong information from the exhaust shop. i thoguht it was a bit too easy if this other muffler was the solution. philby when you say "proper muffler" are you refering to a baffled muffler? or do you have any suggestions on a decent muffler? i thought huricane was supposed to be pretty good? apparently not for my wanting. i still have the resonator that they took out so getting that put back in isnt a problem. Look for a muffler that isnt a straight through design, as these are generally quieter. Quote Link to comment Share on other sites More sharing options...
Hiro Protagonist Posted August 31, 2009 Report Share Posted August 31, 2009 philby when you say "proper muffler" are you refering to a baffled muffler? or do you have any suggestions on a decent muffler? i thought huricane was supposed to be pretty good? apparently not for my wanting. i still have the resonator that they took out so getting that put back in isnt a problem. There is nothing wrong with the mufflers you have or their quality, it's just that they probably aren't the right ones for your car and liking. 2 straight-through mufflers will be quite loud (and not very muffled :lol:), straight-throughs tend to get put on turbo cars because the turbo itself acts as a very good muffler so the rest of the system doesn't have to do as much muffling work. Quote Link to comment Share on other sites More sharing options...
orangeLJ Posted August 31, 2009 Report Share Posted August 31, 2009 Throw a small "hot-dog" (resonator) in there, you should be able to fit one of the smaller (from memory 8 inch long) resonators in with the two mufflers. It should help stop the probelms you have described. Also, straight through mufflers arent a turbo car thing, they are simply a performance thing. A straight through chamberless muffler is always going to flow better then a chambered muffler and its usually the easiest way to get a louder note from any car (90% of their use) Most aftermarket systems (as in off the shelf) will run straight through mufflers. But yeah throw a stubby hotdog in there wherever you have room and it should be fine. Quote Link to comment Share on other sites More sharing options...
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