Just thought I would pass on a little tip I got as a surprise trying to solve another problem. I installed the TWM short shifter, which rocks BTW, but couldn't get the heat shield to stop hitting either the bottom of the shifter or the top of the resonator. So, after trying to tweak the problem for about 2 weeks, I pulled into a muffler shop and for $40 had them cut out my exhaust resonator and weld in a piece of straight pipe. Well, not only did this eliminate the heat shield problem, but gave my car a lot of pep. I didn't expect this to happen so when I drove the car home I was shocked at how much more fun the car was to drive. I still plan on getting an exhaust system, maybe Corksports catless one, but for $40......nuff said.


2003 Lazer Blue Mica ES
TWM short shifter
Resonator'less exhaust
Kart Boy shifter bushings and exhaust hangers

 

How did the exhaust not change? Louder? Any funny/noisy resonances somewhere in the rev range? Did you look at what the resonator had inside? Restrictions, baffles??

Sorry for all the questions...

 

Resonators are usually similar to a bullet style muffler. However, there are usually no visible restrictions (packing or baffles), just a perforated pipe within the casing. Although there are no visual indicators of restrictions, it does restrict exhaust flow. The perforations in the pipe allow portions of the exhaust pulses to reflect back. The portions that are reflected back collide with outgoing pulses - canceling out some sound and creating a restriction that you can't see when you look down the end of the resonator after removing it.

In general, removing the resonator will make an exhaust system louder and/or raspier. Usually it's not very noticeable from the inside of the vehicle, but very evident from the outside during heavy acceleration. It may be nocticeable at certain engine speeds as well, where resonance frequencies amplify the exhaust sound. Usually not noticeable when accelerating or decelerating, primarily a drone is noticed when the engine is held as specific RPMs. On the plus side, an increase in performance as MrPacSun has found.

 

I didn't notice, in the car, any increase in noise from the exhaust. I did notice an increase in a "sucking" sound from the engine under heavy accelleration. However, after I removed the screen from the MAF, the "sucking" sound wasn't as loud. I thought that when I did remove the resonator, I would experience an exhaust noise increase, just as GNO stated, however, even my wife who hates loud exhausts said she can't really tell the difference. The pep the car has now was well worth the $40 spent.

 

Sorry. The inside of the resonator is just as GNO stated, a tube with holes inside the solid tube.

 

I know that it sounded like a dumb question, but I haven't taken a good look under the car yet, and when you state that there is a noticable difference in performance...

Most good performance aftermarket exhaust system includes a resonator, so I was just wondering why this one was so restrictive. In general it is usually the diameter (undersized), the non-mandrel bent exhaust tubing, or the muffler that cause the most problems.

I have read the threads from others that have replaced the P5 muffler with the MP3 and Mazdaspeed exhausts, and that they like the tone, but have they noticed a good increase in performance as well? Can anyone answer that? I suppose I will have to look that one up... I absolutely want this car to NOT make a whole lot of noise when I zip (sorry, ZOOM-ZOOM) around town etc., but wouldn't mind a litle boost in performance. I will be looking into the exhaust and intake and anything else in the spring, when everything melts, and the earth is green, and when I am not worrying about the Christmas presents that need to be bought, or the winter holidays. (I definately need the money right now for the ski budget...)

 

The MP3 (MAzdaspeed) exhaust is good, and I'd pair it up with a simple drop-in K&N filter. That's what I have. It's not loud outside or inside, but it makes a nice sound that's a little more sporty than a stock system. It gives you a boost of performance that you can feel and won't cost you a bunch of money- so you can go skiing an extra day or 2.

 

Thanks for the great reply Jas00x, I think that I will be going with the Mazdaspeed exhaust. The intake might get a custom make over, some sort of cold air ram system that doesn't lose low end torque...

Isn't there a difference between the MP3 and Mazdaspeed mufflers? I know that a friend has owned the MP3, and now the Mazdaspeed, and the MP3 had an oval tip, while the MSP is round... either one better?

 

IchBinEinMP5,

The Mazdaspeed exhaust is an axle back muffler and consequently gives little, if any, gain in power. Most people who have it report that it is rather loud and can be annoying on long trips at Interstate speeds. The Racing Beat exhaust is a cat back system and most people who use it report that it provides a small but noticeable power increase. It is also one of the quietest aftermarket systems available. There are other cat back systems available that you might want to check out but I am not as familiar with them.

 

I have the MP3 Exhaust. I'm not sure if they are still available. It is the axle-back muffler that has "Racing Beat" printed on the side of the tip. They say the Mazdaspeed is the same- just a different tip, but I don't know for sure. I don't think mine is particularly loud- and no one that rides in the car has complained. The only "complaints" I get are from my friends at the autocross races who say my car is too quite!!

 

I removed my resonator a while ago just because I do it on all my cars, and i was disappointed and how little a difference it made. It sounded the same as stock and there was not really a noticable power difference to me.
Try unbolted your exhaust right before the resonator. It's loud as HECK but you will notice insane power differences I can chirp with 4 people in my car at 7000 ft above sea level with the exhaust off
With the exhaust dumping right under the shifter, the car drones at incredibly loud levels, but when my friend drives the car and i stand outside it's not that loud, so i was thinking of just getting rid of my muffler and have a straight pipe from before the resonator to the back of the car, so it wouldnt be dumping right under me.
I probably will never do it, but i've just been thinking about doing it for a while

 

Jas00x,

The MP3 axle back is totally different from Mazdaspeed Axle back muffler. Yes, the MP3 is made and design by Racing Beat for the MP3s and MSPs only and the Mazdaspeed Axle back mufflers are made by Bosal and is available at your local Mazda dealerships. The Mazdaspeed Axle back is definetly alot louder than the MP3 mufflers. The MP3 mufflers is just slightly louder than stock, just FYI.

 

I kind of have a problem that sounds like is related to this exhaust resonator you guys are talking about. I have a '99 ES 5-speed, and notice quite often lately that when I shift into 2nd or 3rd and accelerate, I hear a loud resonance from under the car that seems to correlate with a hesitation -- when the brief sound stops, the car gets peppier. Any ideas what this might be before I take it to the dealer and they try to screw me? :P

 

Sounds like a bad cat converter.

 

Does this Mazdaspeed axleback fit on any 3rd Gen Pro? (i.e. my 99 LX) If so, are they available at Mazda dealerships? How much do they go for? I'm going to a local exhuast shop this week and the guy is installing a performance muffler and a bigger pipe from the cat converter back. Do you think that this will provide me with the same performance as the axleback by Mazdaspeed/Bosal? Sorry for all the questions.