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Catalytic converter necessary?
Hey everybody, I hope everyone is doing well.
After a four hour trip to my hometown, I drive around in my 88 GXL RX-7 for about 15 minutes and there is a clank sound, i slow down, my car steadies down to low RPM and dies. Turns out, my exhaust was so rusted, it broke off right after the headers. So I'm going to a custom exhaust place to get a whole new exhaust done. A quote from the 'wankel engine' article on wikipedia (http://en.wikipedia.org/wiki/Wankel_engine) says Just as the shape of the Wankel combustion chamber prevents preignition, it also leads to incomplete combustion of the air-fuel charge, with the remaining unburned hydrocarbons released into the exhaust. At first, while manufacturers of piston-engine cars were turning to expensive catalytic converters to completely oxidize the unburned hydrocarbons, Mazda was able to avoid this cost by enriching the air/fuel mixture enough to produce an exhaust stream which was rich enough in hydrocarbons to actually support complete combustion in a 'thermal reactor' (just an enlarged open chamber in the exhaust manifold) without the need for a catalytic converter, thereby producing a clean exhaust at the cost of some extra fuel consumption. |
what is meant by the "need" for a catalytic converter is the need to pass emissions testing
w/o a cat, your engine will produce more power because there will be less backpressure in the exhaust |
yeah, no need at all.
lol |
The stock main cat has a split air pipe on it that is used for measuring exhaust velocity, when exhaust velocity reaches a certain point it opens up your auxiliary intake ports. If you ditch the main cat and dont rig up another way of opening those up you will loose a lot of top end power.
On my '88 GXL i got a bonez replacement cat from rx7.com which has the opening for the split air pipe so the 6pi still works. |
You need it to pass emmissions only. The thermal reactor thingy they were reffering to were on the early first gens I think (maybe not even the US market ones, not sure).
* as previously mentioned it also is used for the 6-ports, racing beat offers exhaust systems without a cat that till open the 6-ports or you can just go with the many alternative opening methods avaliable on this forum, my favorite is the rpm activted switch method. |
I had to get my pathfinder to pass emitions....Which I knew wasn't going to happen...
I just had my friend throw on two cats..... We leaned it out ALOT It passed. |
It is important to note that it's a Federal offense to not have them (felony I believe). However, if it was enforced, 20% of the cars on the road would be felonious.
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I remember hearing a story like that from a old school rotary guy he said the thermal reactor was from early rotary's before the rx7 so what you where reading doesnt pertain to your car
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UPDATE: After calling around, comparing prices, and realizing that none of the local shops here (Casper, Wyoming) have ever heard of an RX-7 (exaggeration) and that any custom exhaust shop couldn't get me in until Wednesday (I called around today [Saturday morning]); I decided to order a pre-fit off the internet and install it myself with some friends, I'm not worried about the install, we have the knowledge and the tools. My choice...
http://www.mazdatrix.com/r-ex86nt.htm Part number: 16-16128 (top dual exhaust for the 86-88) Input on choice or process? Anything I should especially know about replacing this particular exhaust? Thanks again guys. |
if i had the money id do it, best advice is remember to use support the whole way down whether in rubber hangers or just welding to to body, and tons of patience and a gallon of wd40 :)
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