RoadsterSport HELMHOLTZ MX5 Miata Midpipe with Converter 2006-2015

NOTE: We have ended the polishing of the setup because costs have jumped so much and we didn't want to further increase the retail price. Polishing added no function, so we did away with it to keep the price more affordable.

A revolution in exhaust technology finally in a Miata application, this midpipe features an exclusive Helmholtz Resonator that massively reduces the standing wave 'boominess' inside the exhaust system BEFORE it gets to your muffler of choice! Cuts the 'booming' frequencies of 120-130hz by 48+db inside a top up Miata cabin which is a common source of complaints with aftermarket exhausts on the MX5. Bottom line: makes ANY exhaust system sound MUCH better!

Now with option for ultra flow FIVE inch converter. Standard 4 inch converter is great for 2.0 motors normally aspirated, the big 5 inch is for boosted cars and 2.5 conversions. Five inch fits manual transmission only.

We outfitted our Project 2012 PRHT Miata with a computer and sound spectrum analyzer and microphones and drove it under varying conditions and loads with mufflers and without any muffler to measure the frequencies coming out the midpipe. We then use that data and some special software to calculate the particulars of the Helmholtz chamber needed to precisely knock down the frequencies we do not want to hear while allowing the good throaty burble fun sounds to pass through. The result is all the fun, an almost exotic burble throaty result, without the drone! Note it is very dual personality because the effect of the Helmholtz is very frequency specific such that under decel it is mild and quiet, yet when you push hard toward redline it sounds exotic and racy. With the top down lots of fun throaty burble, but dramatically more tame when the top is up. In brief, FUN when you want it, and mild when just cruising.

Designed as a bolt-on replacement for the factory midpipe to carry higher flow all the way out any of our mufflers. Works with ANY of our muffler choices and customers report great results with everything from our RoadsterSport line to the original MazdaSpeed Mufflers. Simple Bolt on. Note you don't get much additional benefit running this Helmholtz with our Helmholtz Race muffler because both helmholtz chambers are tuned to attack same peak drone spike these cars tend to make.

INCLUDES TWO O2 SENSOR bungs which gives YOU the option to later add our RoadsterSport headers and avoid engine codes (by using our optional O2 plug and play extension cords to relocate the factory O2 sensors to before and after the converter in this midpipe).

All stainless steel construction for years of driving pleasure. This MX5 Miata midpipe is larger diameter than stock for superior flow, particularly when matched to our headers. Uses high quality SPUN catalytic converter with metal core (despite presence of converter this unit is not CARB approved...which makes it legal in California only for off-road/race track use). Note that there are states in addition to California that now follow the California model and require CARB compliance, please check the rules of your state before ordering, in some states this setup is legal only for race cars and may never be used on public highway.

This midpipe will raise the final sound level because of the higher flow larger diameter tubing and because the Helmholtz is frequency specific in operation.

SORRY, NOT CARB APPROVED, NOT LEGAL ON CALIFORNIA HIGHWAYS. Sorry, we will not ship these to residents of California.

Read full installation hints and notes in our forum Installation Instruction Section! (Click "Forum" at the top of our site, go to installation instruction section, and look for NC/ND Midpipe install thread).

STR LEGAL under Class Rules Update 2012. Pursuant to SCCA 14.10.E: our cat fits entirely in the space that the factory cat occupied pursuant to SCCA 14.10.E....and Magnaflow certifies the core for use in any application andlt;6.2L and 6000 pounds. Cat core has 2yr/25,000 mile manufacturing defect warranty (no core warranty for boosted or track cars), and the rest includes a lifetime warranty.

BRIAN'S APPLICATION NOTES: This is the ultimate Miata Midpipe and it's a serious revolution in Miata exhaust tech, the secret sauce to making a great sounding Miata exhaust system. I never seriously considered less than our RoadsterSport SuperQ as appropriate for the NC Generation Miata using any performance header upgrade but this midpipe makes ALL our choices MUCH more fun. The nature of this style of resonator is that the targeted frequencies are much LOWER volume and other frequencies not targeted are LOUDER than with our standard midpipe. This dual nature of the performance means when you are hard on the throttle it is LOUDER than with our standard midpipe, but on decel or running in the low rpm ranges where these cars tend to drone this setup is much quieter than our standard midpipe. You get all the racy fun, without the drone.

A little on the science, we targeted 120-130 hertz range which is where most folks report uncomfortable 'drone' or 'boominess' and got a total of 48 decibel max drop right at the 125 hertz level...which is a MASSIVE reduction. Nonetheless, looking at broader range we get an average 20 decibel drop from 115 to 138 hertz with reasonable 8 decibel drop in the ranges of 95 to 115 and 138 to 180 hertz. When used with our RoadsterSport Street header and SuperQ the result to my ears was so calm and collected that I think many would not realize the car was modified. When used with our RoadsterSport Max Power header and SuperQ the sound is certainly still louder than stock and almost exotic when on throttle, fun running through the gears and yet when you back off the throttle and just cruise down the freeway very controlled (no issues listening to music or your passenger, etc).

Video Sample:

Shot on our Project 2012 with our RoadsterSport Street Header, RoadsterSport Helmholtz Midpipe, RoadsterSport SuperQ Exhaust.

Video Sample: Shot from the bumper this clip massively exaggerates the volume but notice what you don't hear, no drone. Lots of racy sound when on throttle but with less throttle it quickly gets quiet instead of drone like many systems.

CUSTOMERS IN Australia CAN NOW GET THESE AT THIS LINK!

BRIAN'S Installation Notes: This item is NOT an easy install, though I often install our RoadsterSport items at home on ramps or with jack stands to be closer to the average user experience and snags, with this item I drive to our shop and use the lift every time because two sets of hands and a lift is just about required to get it done without a lot of frustration. Thus, we do NOT promise average Joes can install this without a professional mechanic, does not matter if you have installed 20 other midpipes before, this is MUCH BIGGER than the factory ever planned in the center tunnel and precise fitment on a lift is pretty much required. May not clear some aftermarket braces such as Beatrush or ILM. Clears our own braces and factory braces. Again, this is MUCH bigger than factory midpipe and install needs careful attention to detail, some fiddle time with the slip joint with two people to get it adjusted just right is normal to get it hanging just right when you are stuffing something three times bigger in the available space. We have installed it hundreds of times, all the units are the same because they come from the same JIG, two sets of hands makes it go much faster. That means doing this one at home is going to be too hard for many average Joes to get right with just jack stands or ramps, get the call all the time that it is 'impossible' and we tell them to get the car on a lift, and when they do they consistently report it got done easy once on a lift with two sets of hands. Adjust it too long at slip joint and it will hang too low and bang braces, make it too short at the slip joint in the middle and it will sit too high and tap the differential housing. For these reasons, a professional muffler shop install may be required. Spray a little soap and water on the slip joint between two halves of the midpipe so you can smoothly play with that length and alignment of both ends. You can spend 20 minutes on the first try and not have it right, or spend more time and get it right, we suggest more time up front to make sure you have no points of contact (grab finished install and yank in all directions to see if hit taps anything, adjust again if it does). Note the Helmholtz valve is temperature sensitive, if you live in cold climate just understand it will not do much for you on cold morning starts UNTIL the system is up to normal operating temperature. Please don't make your Mechanic fly blind on the install, instead PRINT THIS PAGE for your mechanic so they know what to look for in doing the install.

Note a few customers have reported strange metal noises from helmholtz chamber, loud enough to hear while driving and from behind the car. No moving parts in the Helmholtz setup but it will capture and broadcast noise from upstream and in our experience this includes stuck open EGR valve, loose O2 sensors, bent valve in the motor, tiny 3 inch O2 sensor heatshield, etc. Also had a customer with busted off spark plug tip that somehow got into the helmholtz chamber and set to buzzing madly. Typical sources of rattle reported turn out to be midpipe set too long at slip joint clamp in the middle and hits X brace below only when car is running, answer is open the clamp nut and push midpipe straight up to make assembly shorter before your tighten that nut again and it will sit high enough to not hit the X Brace.

NOTE that to offset massively higher converter costs we are dropping the full polishing, will update picture soon.

Warranty note on the converter: warranty covers defective converter only. But you can burn up a cat with abnormally high exhaust gas temperatures from track use, supercharger, aftermarket ECU tune, ignition system failure causing a rich mixture, and more. Warranty does NOT cover damage to the cat from these external variables. A failed cat must be sent to the factory for inspection before it can be determined if it is covered under warranty or not.