6G Celicas Forums

So I made my own exhaust on my GT. After the stock resonator i upped the diameter of the pipe to 2.25 then it goes into a long glasspack muffler then a downpipe just before the rear axle. I seem to be getting better gas mileage, so i want to keep my flow through design, but its so LOUD. I ordered 2 vibrant resonators I heard one is good and two is better and they are flow through. The question is....Should I build the system resonator-resonator-glasspack,
resonator-glasspack-resonator, glasspack-resonator-resonator, or just leave the glasspack out?

Unless someone can correct me isnt it resonator-resonator-muffler?

The closer the muffler is to the tailpipe the quieter the car will sound

One resonator is sufficient in an exhaust system.

The trouble is that people don't know what a resonator is -- and it's not helped by the marketing of exhaust component companies.

A resonator is something that comes stock on pretty much every factory car. It is not a muffler, and it's primary role is not to reduce the volume -- at least not the measured volume. A resonator is an echo chamber, in which soundwaves are bounced into each other. When they collide, the soundwaves cancel out, transforming the sound energy into a bit of heat.

This naturally lowers the decibel level, but the primary reason for installing a resonator is to smooth the tone of the exhaust. By being less annoying, it is perceived as quieter. The awful buzzy sound of a badly done exhaust (see idiot in a Civic) is usually due to the lack of a resonator. If your exhaust is a wind instrument, a resonator is what keeps it in tune.

Unfortunately, because it sounds good and is easier to write, exhaust companies like to label their cylindrical under-body mufflers as resonators. They're lying, but nobody seems to call them on it, probably because actual resonators aren't expensive and therefore are not subject to the competition and marketing. These false resonators can be obsolete designs or modern straight-through designs, but if they involve insulation of any form they're not actually a resonator.

A glasspack is a 1950s-era design. Typically they're packed with fibreglass, which aside from not being the best sound insulator is prone to breaking down and blowing out. The interior pipe, around which the fibreglass is wrapped, is usually louvered. While all these little scoops do direct exhaust flow into the insulation, they also create turbulence, slowing the exhaust flow and reducing the efficiency of the engine as power that could have gone to the wheels is instead spent on pushing exhaust gases through the turbulence.

Modern straight-through mufflers utilize better and more durable sound absorbent materials such as ceramic matting and ultrafine stainless steel wool, wrapped around a smooth perforated inner pipe. This design keeps the exhaust flowing quickly and efficiently. As a result you can use longer or more numerous mufflers without significantly impairing engine performance.

The stock design is resonator--baffled muffler. To improve exhaust efficiency while keeping sound levels at a decent volume, you'd want resonator--straight-through muffler--straight-through muffler. Happily there's room for the underbody muffler where the secondary catalytic converter would go on a California-spec car.

ok i looked at my new "resonators" they are built similar to my stock resonators but they do have materiel inside. there is no echo if i knock on the outside of them. so according to galcobar's description they are actually mufflers. the real questions are: should i keep or lose the stock resonator and should i keep or lose the glass pack? ive also heard the glasspacks resonate as well but not necessarily in a good way. the stock resonator always made the car sound aggressive its just a lot worse without the baffled muffler. mabey it should go? is the glass pack making it worse?

I would love to try all the different combinations but i only have so much money and time.

A resonator can effectively lower exhaust dB. At least from personal experience, I've heard a straight-through mazdaspeed3, and then the exact same with the stock resonatorS back in place (it comes with 2 from the factory). It is very much quieter with the resonators on it.

I don't know how true that is, but it'd make sense, but I've heard that larger piping also increases exhaust loudness. Vibrant makes good stuff that is pretty quiet when used in conjunction with each other with the right bends in the exhaust as well.

If you have a header with larger primaries, that will also contribute to a much louder exhaust, even more if it's a 4-1 equal length design (AKA all eBay headers for the 5S)

i decided against getting a header for it. i heard it only helps at high revs and makes gas mileage worse. its stock until after the resonator except i deleted the second cat and my first cat might be slightly higher flow than the original. if i delete the stocker and put the vibrant there the size increase will be a little sooner (they dont even make a 2 inch one) i think ill take my stock resonator off, put the 2 vibrants on without the glass pack and see what happens. if its still too loud i can put the glass pack back on the end. i wonder if part of the problem is that the amount of pipe after the glasspack is like 6 inches. mabey they need more pipe behind them? i tried covering the exhaust halfway like a halfmoon at the end. not much difference in sound.

I'd always keep a resonator in the exhaust system. A smooth exhaust system will always seem quieter than an annoying one, even if the objective dB level is higher.

Straight flow mufflers will make your engine sound real loud

Ive got dual 2.5" Delta Flow straight thru mufflers and they are terribly loud.
I cant hear my radio on the highway and I set off car alarms at an idle.

The resonator is more about tone than anything else so leave it in. The engine isnt louder in a good way without it so I say keep it.


Oh and like I said the closer the muffler is to the tail pipe is to the muffler the better it will do its job.

This post has been edited by Special_Edy: Nov 29, 2012 - 11:11 PM

striaght flow is the loudest meaning headers, no cat, no resonator, and just a muffler.

Typical setup you need is just headers, cat or no cat, then resonator, then muffler. The resonator is usually used for sound silencing, if you get a good one, 1 should be enough. again that depends if you have a crappy muffler being welded on too. I would get a tanabe, apexi ws2, or cut off a greddy sp2 from another car and weld it on to your system. The vibrant oval type resonator (not the bottle) is the quietest especially depending on the length.

I have a M2 performance header (ebay header lol) and that's it. The rest of the exhaust is completely stock. It sounds pretty good (not like a fart can) and I get 27 to 30 mpg (5sfe). It's my understanding that the 5sfe doesn't make enough power to need the exhaust modified. If you reduce too much back pressure you could end up losing some torque.

Reduced backpressure leading to a loss of torque, well, not exactly a myth but certainly incorrect.

Backpressure is always bad. There are no circumstances in which allowing burnt fuel and oxygen-deprived air to remain in the combustion chamber improves performance. Fouling the air-fuel mix is bad for performance. So is making it harder for the engine to get the exhaust out of the combustion chamber, as energy spend forcing the exhaust gases out is energy not going to the wheels.

Reducing the barriers in an exhaust system will always improve performance. Generally, this means fewer bends in the piping, or switching from baffled mufflers which are designed to slow exhaust flow to straight-through mufflers which are designed to allow it to move unimpeded.

The other issue, which is where the mythology of backpressure arises, is the bigger-is-better belief when it comes to pipe diametre.

At a given flow speed, a bigger pipe will accommodate more exhaust flow. Naturally the bigger the engine, the more exhaust it will produce at a given RPM. A similar rule applies to engines with forced induction, since the compression allows a larger amount of fuel and air to be combusted at a time -- false displacement, if you will. This is why bigger engines, or engines with forced induction, benefit from larger exhaust piping.

Too small a pipe and the exhaust gases cannot exit the engine quickly enough; this is what is typically cited as backpressure. However, too big a pipe and the exhaust gases have room to spread out, cool off and slow down. Think of a river in winter. In the narrow sections the water flows quickly and stays liquid. Get into a wide section and the river slows down enough to freeze, which can cause flooding upstream. Cold exhaust gas acts just like ice in a river: it dams the flow and prevents the hot gases from quickly exiting the engine.

Too small a pipe and you get backpressure. Too big a pipe and you get ... backpressure. Same problem for different reasons.

The problem is that we don't use exhaust piping which can adjust to the amount of exhaust the engine is producing. If we did, then we could keep backpressure at a minimum value regardless of RPM while maintaining efficient/fast exhaust gas flow out of the engine.

Instead, we have to pick when (at what RPM) we want the engine to be most efficient, and match the exhaust pipe size to the amount of exhaust produced. Car manufacturers know that most drivers want good acceleration from a stop light, so they target low RPM efficiency and thus choose small piping to match. Enthusiasts who prize performance at high speeds will sacrifice engine efficiency at low RPMs for efficiency at high RPMs.

You don't lose torque from increasing your exhaust piping size. Rather, you move the peak efficiency point of your engine higher up the RPM scale. Or to put it another way, you're choosing where to have the least backpressure.

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TLDR: Straightening out your exhaust path and removing barriers to flow will improve engine performance at all engine speeds. Change the size of your exhaust piping only if you want to change the RPM at which your engine is most efficient.

I partially agree with you. I think this is an arguable subject from both sides. Everything I have read/researched and have been told by engine builders say that you need to have a proper size diameter of piping that matches your displacement or the amount of power your engine produces. All the engine builders I've talked too have told me to go only go a quarter of an inch up in size unless I'm producing over 300 hp (talking about the 5sfe). This is just my opinion and I'm not saying anyone is wrong.

This post has been edited by TRDweaponX: Dec 10, 2012 - 5:43 PM

Everything Glacobar I agree with, but Id like to add that-

Resonance plays a major part in exhaust design. Just like intake manifold runners, the exhaust system experiences pulses and these pulses can either resonate back into the cylinder or resonate out towards the tailpipe. This includes both sound and the pressure waves from the exhaust pulses.
This leads us to scavenging. Scavenging occurs when a high pressure exhaust pulse leaves the cylinder and travels down the exhaust pipe and header. The high pressure pulse leaves a low pressure void behind it, so if the wave frequency(relative to rpm) matches the pipe length and width the low pressure part of the pulses will actually suck the exhaust gasses out of the cylinder on the next pulse. If the pipe is too wide in diameter the velocity of the exhaust will be too slow for effective scavenging. If the pipe is longer it will have a harmonic better suited for low rpm so shorter pipe lengths will better benefit high rpms.

The optimal size and length of the exhaust fluctuates with rpm. Engines moving at low speed produce more torque from longer headers and smaller pipe diameter(until a certian point) but this exhaust will restrict the engine at high rpms. Shortening the header pipe and increasing its diameter(to a point) will increase the torque at higher rpms, though this exhaust will flow too much for low rpms. So you have to make a compromise between torque(drivability) at low speeds and torque(horsepower) at high rpms. This is part of why most engines seem to produce so little horsepower from the factory. The engineers had to decide between high rpm performance or low rpm performance on many different engine components.

This post has been edited by Special_Edy: Dec 10, 2012 - 6:37 PM

What exhaust setup then would you guys go with on a stock 5sfe?

This post has been edited by TRDweaponX: Dec 10, 2012 - 7:15 PM

The question is where in your RPM range do you want to see peak efficiency.

Ahhh I understand now. I dont know why I was being so dumb. For me I would like more in the upper rpm range so I would need a larger diameter pipe.