circuitsmith
"a vacuum pulse when it hits the closed exhaust valve and then is re-reflected as a pressure pulse"
Actually, a wave reflected at a closed pipe is not inverted.
D’oh!! That’s what I get when I’m in a hurry to post. I stand corrected.
Most mufflers have an inlet pipe that has a whole bunch of little holes in it as it dumps exhaust into the plenum. I think this is an important feature, the perforated pipe does not have a well defined end to it and thus it reflects a weak and diffused vacuum pulse back to the engine.
I remember that Car Talk episode from many years ago . . . where the guy said his cat was plugged up, and he had no power. So he punched a hole in it and hollowed it out but good :naughty:
Years ago I owned a 1988 Olds Ciera. It was over 20 years old and on it’s last legs. I got a fresh NC inspection and soon after the CAT sprouted a hole in it. I wasn’t going to buy a new CAT for it so I cut it out and bolted in a pipe to take it’s place. No CEL because this car only had a forward O2 sensor. It drove fine for another year and then I donated it to the local consignment shop.
I had a split cat noted by a muffler bender guy when putting on a new exhaust. He welded it back together for $10. I don’t recall any advantage or disadvantage.
@kmccune
"Always was amazed at people punching the cats out and throwing the residue on the ground."
Not me, but then I probably grew up in a different era…
I grew up in a residential area, 3 houses from a dirt road that saw pretty heavy traffic. Regularly in summer a “dust control” tanker truck would drive up and down the dirt road applying huge quantities of black used oil.
Some oil would soak in, some would run off (much more so when it rained), and a lot of it would pool in pot holes. It made the road very slippery at times, especially when it would combine with dirt and make layers of ooze.
More than once, even being very careful, I fell of my bicycle into the stuff trying to cross the road when it was slippery. What a mess!
That’s only one of many examples of normal things from my era that would amaze many people today. We played with mercury in Elementary School… (Wow, I sound like a am a geezer)! CSA
Yeah we had what looked like a half pint bottle we passed around ,but for some reason everyone (pretty much so,as a rule ) was cognizant of the dangers of Mercury (perhaps good teachers )The little bottle sure had some heft to it,but we even got to experiment with some pretty dangerous chemicals ,cant see that happening now.
Believe it or not ,nature can handle a bit of oil as long as it isnt contaminated with a lot of heavy metals and other nasty chemicals .But back in the old days people were not to alarmed about various spills .One of my employers used have us dig a hole and dump used oil in it ,couldnt put it on the surface ,but it was alright by Him to bury it (I guess He never had an inkling how long the trail of culpability could be and how one could be traced (His brother reasoned ,since it came from the ground,it must be alright to return it to the ground ) I did my best to stop or discourage this practice ,but until ,the company acquired a waste oil heater ,there wasnt much improvement in the oil disposal dept .
Well…this is sortof a moral debate really… Someone Who Isn’t Me (SWIM Henceforth) would be better served Hollowing out the Cat and leaving it physically in place…
Your vehicle will not be emissions tested any longer due to age…so you now have the “freedom” to do whatever you want with it…
Unless the Cat is clogged…there is really no reason to do this… You wont see some magical performance gain…the car will be louder…and the engine able to breathe easier…but this is not a performance engine…so what do you gain… Now if your quest was more power…yes it COULD make more power WITH computer and fuel curve modifications…but with the standard fuel map…there would be no change happening.
There are more cons than pro’s here… But SWIM would do whatever they wanted since you are no longer bound by emissions laws or regulations. There may be Caveats aplenty here…such as the absence of the physical part from the car or what have you that would Hem you up come inspection time… Who knows…There is info aplenty on this and it varies State to State.
SWIM can probably do whatever he wants…but what is your goal ? SWIM probably should leave well enough alone…and just install what was designed. But SWIM who is not bound by regulations…will do whatever SWIM wants
As most of you know, I’m hardly the poster boy for fawning all over the latest eco regulation; in fact, I generally think they take things too far. But I’d never advise gutting a cat where it was functioning properly–the numbers just aren’t there.
To delete a cat, in a well-designed system, you’d probably pick up 5% HP, mostly at peak, and not at typical cruise settings. Probably little or no MPG gain overall. And your emissions would be around 10-20 TIMES worse! To me, “doing my part” to keep breathable air is well worth the modest peak HP hit…and keep in mind I’m a guy who’s pretty cynical re: doing my part for the Greater Common Good.