Well if it's gonna sound bad any axle back exhausts that cut down that rasp? My boy was even considering making me a custom exhaust but we'll see.

 

Well from what i hear the precision muffler is excellent at getting rid of rasp, but looking at pics of it i can see that its nothing more than a 20" long 14" body length 6" body wide magnaflow resonator with a nice polished tip...

you could buy it from them...or just make your own for about 75% of the price...

 

I don't know too much about the TRD exhaust except that it sounds good with the stock header and just about everyone says it sounds terrible with an aftermarket header. If you have a mechanic that will help you out. Try your setup and take it to him to get a backpressure test done on the exhaust. There is a special tool that screws into your A/F sensor hole and measures backpressure, the tool costs about 175 bucks, but i'm not sure what a mechanic would charge. As long as the backpressure is at LEAST 2.5-3 pounds, then you should be fine. I think it's set at 6 pounds stock. If that is out of the question and not an option for you, then just do it and see how it feels. If it lags way down in low end and picks up real good up high, then you need to add backpressure. And it doesn't have to come in the form of a cat. It's just that a high flow cat seems to be the most efficient way to get backpressure...... cost-size-noise reduction-amount of backpressure= High flow cat for sure





I have heard the same thing from a couple people but it is in NO WAY from a lack of cats.... It's from a lack of back pressure. I heard it burns rings and even oil. It seems like it could be true but at the same time it seems pretty doubtful

 

I'm thinking of this current set-up: Megan Headers, Megan S-Pipe, Custom 2.5" Midpipe with a High Flow Cat and an Aero Resonator, into my Tsudo N1 Exhaust... What do you guys think?

 

OK, no such thing as necessary backpressure or too little backpressure. You will always have some backpresure because the exhaust gas will always cool to some degree and become more dense as it travels through the system.

What's important in exhaust is scavenging, which depends on a lot of factors. At high RPM's the biggie is flow - meaning low restriction- because the gases are moving so quickly they can't cool off much. But at low RPM's it's all about heat retention, keeping the exhaust gases hot because flow isn't very high. Because the parts that help keep the heat in - proper pipe size (usually smaller than you think), cats, OEM-style baffled/chambered mufflers - are also considered "restrictive", many people think you "need more backpressure for good low-end torque". But it's not - it's good scavenging that you need, and if designed properly an exhaust system can scavenge well across the band. And it's more complicated than can be explained in one paragraph.

Here's a link to a short article about exhaust theory. Don't like his simplified comment about OEM exhausts and low-end torque, and it's geared for turbo cars but good stuff about resonators, which is pertinent to rasp. By the way, the PM axleback uses a straight-through Magnaflow muffler, not a resonator, which is why there are posts about it quieting down enough to make rasp bearable but not really eliminating it.

http://www.nsxprime.com/FAQ/Miscella...austtheory.htm

 

could someone do me a HUGE favor and post a link as to where i can get one of these magnaflow reonators...i found some on hotexhaust.com, and thats the only place that ive found..but im shopping around and was wondering if yall could send me in the right direction

 

I didn't think Magnaflow made resonators anymore, they're not listed on their website nor at summit. Make sure they're not actually straight-through mufflers ...

Here's resonators at summitracing.com:

http://store.summitracing.com/egnsea...+115&x=38&y=12

Some have pictures and you can see that actual resonators don't have packing around them.

You can search for Aero resonators also, look for the website listed earlier in this thread.

 

hey man thanks...yeah i notcied that too...no resonators on the magnaflow website..and i saw thoes videos and the link to the aero resononators too..thanks for ur help!

 

Well most people call straight through mufflers, "resonators" they are just the absorbing type.

"magnapack" "resonator"= perforated tube with steel wool and fiberglass packing.
http://www.hottexhaust.com/detail.asp?PRODUCT_ID=10436

"straigh through" muffler= perforated tube with steel wool and fiberglass packing...
http://www.hottexhaust.com/detail.asp?PRODUCT_ID=12640

i don't see the difference...

If you are talking about TRUE resonators like the Helmholtz thats different...
BUT others are still the same principal, like the aero resonators, they just use ceramic packing instead of fiberglass or steel wool packing...

 

"Resonator" doesn't = "muffler", and this is an important point since we're talking about rasp. The solution for rasp, assuming the overall sound level of the exhaust is ok, is the proper resonator(s), like you said the Helmholtz, hollow type. If it's got packing then it's absorbing sound, and that's a muffler.

The first item you linked says "use as a resonator to reduce sound or for a more aggressive sound as a stand alone muffler" - that's misleading - they're trying to sell a product by making people think it will do both, but it can't. It's just another straight-through muffler. It will quiet ALL frequencies to some degree, including your rasp frequencies, but won't eliminate the rasp like the proper resonator will.

The kicker is if you replace your current muffler with this one, your exhaust characteristics will change, which means your rasp frequency(s) have changed. Possibly to a sound range where your current resonator doesn't work, giving you ... rasp.

The proper resonator will kill drone too, which I need - I'm beginning to drone on

 

thanks alot guys. This is why i love this site. I was asking people around this site about this same question. On my tc i have trd exhaust, trd cai, full megan piping "loved that set up, i called it a mini wrx" so last night i decided to add some dc headers. I can believe how freakin loud it was. Rasp like no other. today i decided to take out my megan mid and put in my stock for now. But since its off you guys helped me out by leading my into geting some aero resonator in the megan mid.

2 questions. didnt seem to find the answers in this forum. If i was to add an aero resonator would i have to remove the resonator thats already in the megan mid or is it supposed to stay? Second, is it recommended to add the high flow cat as talked about in this discussion?

 

I wish i would have read these post b4 invisting my cash in all my mods" trd exahust when using aftermarket headers". You guys could have saved me some cash. But what can i say other that i was excited.

 

eh you live and learn, I made a similar mistake( Alpha header + Greddy EVO2 = BAD!!) it seems all "tuned" exhausts sound like crap with a aftermarket header unless you heavily muffle them...

can't help you with the megan, i don't have so i don't know if the resonators are real or glasspacks or what(heard rumors they are just empty bulbs...) if they are true resonators leaving them on would be the bist, I guess.

anywho, high flow cats are alright, they will kill a tiny bit of your header's high end power, but i hear they help with rasp some too. and the little bit of back pressure they create is kinda nice on city street driving.

 

Wait a week before your next move, give the header time to build up a little carbon. Most people say an aftermarket header will quiet down after running it for a week or so.

The Megan midpipe has two resonators if I recall correctly. It probably has zero rasp when setup with their Megan axleback and stock exhaust manifold. But like Mugetsu mentioned, add a header or do something else to change the exhaust characteristics and the result is loud & raspy.

The one part of exhaust I haven't figured out is how to pick the proper size resonator for a modified exhaust. There must be some guidelines somewhere saying "if you have rasp at xxxx RPM you install a yy inch resonator". Hopefully one of us will figure it out before your week is up.

So right now you have DC header/stock midpipe/TRD exhaust. How does that sound so far?

 

i dont see why people make such a big deal of rasp and getting rid of it, its pretty easy, i did it without even trying kinda.. i didnt have two resonators, or large mufflers or anything like that..

My set up was: Fujita CAI > Megan Header > Megan S-pipe > Magnaflow 2.5" Hi Flow Metallic Core Cat > 30" Resonator > 2.5" Custom Mandrel Bent Midpipe > Custom 2.5" Mandrel Bent Axle Back w/ Magnaflow muffler

i had NO rasp and it was very QUIET

heres a vid for proof:

 

hey tc 909 do you have any pics of your exhaust set up? or at least of your axleback and magnaflow muffler?

 

here are some..

its basically a mock up of the magnaflow cat, but in my own way:






hope that helps

 

Does sound good in that clip. Like your setup - cat helps vs. rasp and looks like you're using same side inlet/outlet axleback muffler - much quieter than a straight-through fartcan.

I think you are actually using a large muffler. That "30" resonator" if it's a Magnaflow it's probably a straight-through muffler. Do you have the part number?

It's also hard to tell how high in RPM's you're getting up to on those short runs. Do you have a "driveway" video clip where you're revving in neutral from idle up to near redline?

 

did you do all the fabricating? You should build a couple and sell them. You'd make some good cash. Sounds good in the clips. Thinking of copying you set up.

 

Of course he has no rasp...Hes prob got a 6" round 30" long magnapack under there OR some 5" round 30" long glasspack of some kind and what looks like a "chambered" muffler in the back AND a CAT pffft... hes prob only seeing about 6 of the 11 to 12hp that megan manifold is giving...but i bet you his low ent TQ is great
thats pretty damn close to the "stock" systems set up that he "with out even trying kinda" decided to run...