what exactly is inside of the thermal reactor that helps heat it to break down exhaust gas? anyone have a pic??? do they have a tendancy to go bad or crack? also, did earlier engines like the 10a or 10b or even earlier 13b's have the thermal reactor??

 

Thermal reactors are actually remarkably simple in design, as there is really nothing inside of it apart from the two inserts that help to direct exhaust gases against the outside wall and helps to direct the gases (somewhat) into the direction of the outlet leading to the 'downpipe'.

The thermal reactor's purpose is to get the exhaust gases to mix with fresh air that's being pumped in by the airpump, as well as remixing the exhaust gases from the reactor with the incoming exhaust gases to help to quiet the exhaust noise. The two inserts are simple 2" pipes that are cut off and the front insert has about a 45 degree cut in the end to help point the exhaust toward the rear of the car.

As the engine runs, the thermal reactor takes unburned fuel and combusts it within the reactor with the fresh air, thereby reducing emissions. It essentially gives the engine exhaust a bit more time to burn before it's released to the downpipe and there is an additional fresh air pipe that runs from the bottom of the thermal reactor to the expansion chamber just behind and below it. This secondary pipe is only open to fresh air under power (IIRC), and again, helps to burn any unburned hydrocarbons.

The thermal reactors were not very efficient at what they do, particularly when cold. My 80LS never had a problem passing inspection, however, as long as the engine was warmed up, the thermal reactor was hot, and the plugs were clean.

In 81, Mazda went with the more expensive, but much more effective platinum catalyst design commonly called a catalytic converter. All later designs had staged 'cats', both with and without fresh air being pumped into them to aid in the catalytic reaction. HTH,

 

longduck since you cannot recieve pm's, thank you for your help!!! regards, dave

 

As for your question about what earlier cars had the TR, according to Felix Miata's FAQ, all rotary engined cars from '70 onward were equipped with a TR, so that would include the 10A, 12A and 4-port 13B motors.

 

can the thermal reactor and exhaust be replaced with a performance exhaust with out negitive effects. this is not considering emissions.

 

yep

 

There are no negative effects to replacing the TR w/ performance exhaust. My car stopped backfiring, increased gas milage and performance, and ran more smoothly after replacing the TR w/ an RB header.

-Marques

 

My car responded beautifully to a RB header/presilencer system. As soon as I scrape together the cash for a new midpipe and muffler, I'll get some more gains. '79 motors have larger exhaust ports than the later models, so I would imagine that they may benefit slightly more from an exhaust system.

 

This is incorrect. There is an inner chamber where the actual combustion takes place. The air pump provides cooling air which flows between the chamber and the outer shell. This is why you don't want to nix the air pump if a TR is being used. The TR's inner chamber can overheat and break up, or in some cases heat can transfer back into the motor upon shutdown, possibly damaging an apex seal spring if an apex seal has "parked" itself in the exhaust port window.

 

thanks for the tech info. its always best to know how your things work. i am new to the pre 81 design and i want to make sure i know my ropes a little.

 

i think mine might be comming off

 

Wankelguy is correct.

 

do they go bad easialy and are they difficult to aquire?

 

yes and yes

 

what goes bad on them and is there any way to prevent them from going bad or prolong their life?

 

Well, the little exhaust sleeves get burnt up or loose, and the inner cores disintegrate when they get overheated. Make sure your air pump is working properly is about the only advice I can think of to make them last longer.

I gave away a couple of 12A thermal reactors some time back, I absolutely loathe the things. Once you finally get the damned things off, you just want to hurl them as far as you can.

 

awesome! because mine is coming out soon. Maybe a thermal reactor throwing contest?