Catalytic converters vs small resonators?

[carnutjw]

If the fuel mixture or ignition is off it can send excessive unburned HCs into the cat where they can burn and melt the cat down. Rich or lean can do it.- Agreed.

catalytic converter horsepower test - Search Videos

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catalytic converter horsepower loss - Search Videos

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[olds307 and 403]

So diddly squat all, except at extreme power levels, which is what I have seen for the tests on modern cats. I think they will go on and I will price out an AEM wideband controller as well.

 

[carnutjw]

A computer controls the air fuel mixture in special carburetors via a solenoid operating the main rod jets, maintaining a 14.7 to 1 ratio except during power enrichment mode (WOT). These carburetors also feature a TPS. Also the smog pump pumps oxygen into the cat converter after warmup. Its very different from the truck version.

Just trying to understand- making some assumptions here- the CCC had to have feedback from somewhere- no O2 sensor or MAF meter, so I assume it used the Throttle Position Sensor and Engine Coolant Temp, maybe Air Charge Temp, Manifold Air Pressure(?) as references for a predetermined fuel enrichment/spark timing map? Hence the necessity of keeping everything factory-ish on the top end?

 

[Clone TIE Pilot]

Just trying to understand- making some assumptions here- the CCC had to have feedback from somewhere- no O2 sensor or MAF meter, so I assume it used the Throttle Position Sensor and Engine Coolant Temp, maybe Air Charge Temp, Manifold Air Pressure(?) as references for a predetermined fuel enrichment/spark timing map? Hence the necessity of keeping everything factory-ish on the top end?

CCC had O2 sensor, vacuum sensor, temp sensor, knock sensor, TPS, VSS, baro sensor, and used the dist pickup coil to read RPM speed. The original O2 sensors are 1 wire non heated types. It is common to upgrade CCC systems to 3 wire heated O2 sensors.

Outputs of the CCC are air fuel mixture control on the primary side of the carb, ignition advance with knock retard, EGR control, transmission lockup, smog pump diverter valves, and EVAP purge in later years.

 

[1 RARE T]

If you're going with cats trying to get emissions compliant in the event that new legislation might get you jammed up in a smog test, it's gonna be a tall order to pass unless everything else is tickety boo as my Grandpa used to say.

A pair of cats installed compared to what your signature says you have now is gonna choke the crap outta your engine.

That Supra or Mikey's Hellcat and their forced induction has huge power so the performance loss with cats is not a factor. Your horsepower level makes a difference in this discussion.

 

[olds307 and 403]

The current motor is mild, maybe 9 to 1 with a 204/214 cam. The one at the machine shop should be 500hp/500tq or close to it. I know modern cats aren't like the 70's cats which were restrictive as hell. That Supra basically lost nothing down low. I saw a magazine 4th gen Camaro test, factory cats cost like 2hp. I will do some more searching for dyno testing. Running shorty headers is already a compromise as is 2.5" exhaust. If I was worried about every ounce of power, American Racing headers and 3" or 3.5" exhaust would be on the car.

 

[motorheadmike]

Works here too:

1980 Pontiac LeMans Station Wagon - G-T-faux (stuck with it, and can't shake it... like a bad case of herpes)

That wagon will be fast enough to turn back the best before date on the groceries it's hauling.........:D

gbodyforum.com

Wonder if it would get faster with the cats punched out?

 

[olds307 and 403]

Glad I put this up, different views, some like Mike and myself see the loss as minimal. Others think these aftermarket cats will even choke my current mild motor. As far as modern cars, there are differences as well. My understanding on Challenger's, the R/T, SRT and Hellcats converters flow much better than the 3.6 converters, like on our GT. Supposedly, they are, along with a couple of kinked spots in the head pipes, the most restrictive part of the exhaust, the rest is straight through. Not sure if it is cost or pipe size that makes a difference. The front half is 2.5" and actually goes into 2.25" after the X pipe. I haven't researched the V8 head pipe size which may make the difference in flow over the V6 setup and have nothing to do with the cats themselves.

 

[Supercharged111]

I see the loss as minimal. Check out Kooks green cats. They run cleaner than the cheaper ones. Of course they cost more too.

 

[carnutjw]

Glad I put this up, different views, some like Mike and myself see the loss as minimal. Others think these aftermarket cats will even choke my current mild motor. As far as modern cars, there are differences as well. My understanding on Challenger's, the R/T, SRT and Hellcats converters flow much better than the 3.6 converters, like on our GT. Supposedly, they are, along with a couple of kinked spots in the head pipes, the most restrictive part of the exhaust, the rest is straight through. Not sure if it is cost or pipe size that makes a difference. The front half is 2.5" and actually goes into 2.25" after the X pipe. I haven't researched the V8 head pipe size which may make the difference in flow over the V6 setup and have nothing to do with the cats themselves.

Yeah me too. I'm not typically a tree hugger environmental justice warrior, but wow, CC talk seems to be a touchy subject. If it helps the exhaust to be a little cleaner and I'm not bothered by the minimal ding to my 150HP 305, why do you care? If you hate them, whack 'em off and throw them in the trash, doesn't trouble me a bit. I do think it would be good to have your A/F and ignition in good shape. As Clone TIE Pilot said, too rich or too lean can toast a CC if I'm understanding right.