alright i hollowed out my cat for the hell of it cause it was all @!#$ up an throwing codes and now when i rev up to around 6grand it backfires like a @!#$ and shoots a flame. its cool and all but i know no backpressures not the greatest but i dont know many ppl with sunfires and hollowed cats that shoot flames maybe im running rich or something? and u think these backfires could @!#$ something up internally or no?

Quote:

i know no backpressures not the greatest

when will the myths END???

WTF?????

This i need to see

Walking to car ........

Cutting off Cat .............

Reaming car out at 6 grand.......................

Car go BOOM.................................

Coming to find you....................................



Edited 1 time(s). Last edited Saturday, February 02, 2008 7:28 PM

ok the lack of back pressure is not a myth cuz not enuf back pressure will screw up the reverb factor to help pull the exhaust gasses out of the cylinder. If you would have taken any engine building classes you would know that the proper runner lengths on both the intake and exhaust manifolds makes huge numbers when gotten perfect.

should of just cut the cat off took it to the scrap yard they might of handed you between $50 - $100 then went to your local parts store spent $65 - $80 for an aftermarket highflow cat and then you wouldn't be hear asking a stupid question!!!

The OBDII uses two EGO sensors in-line on the exhaust (One pre-cat, one after-cat). The second looks to see if the catalytic convertor is doing it's job effectively. If the management system senses no difference (or not enough of one) in the exhaust gases after the cat, it'll throw a code. Try using a EGO similator in place of the second EGO sensor to fool the system, which are commonly available for your app through various aftermarket performance parts suppliers. It's a simple plug-in, and wholy effective.

Go beyond the "bolt-on".

Corey Zarda wrote:ok the lack of back pressure is not a myth cuz not enuf back pressure will screw up the reverb factor to help pull the exhaust gasses out of the cylinder. If you would have taken any engine building classes you would know that the proper runner lengths on both the intake and exhaust manifolds makes huge numbers when gotten perfect.

I'm curious if you know why that is true?


-

"Youth in Asia"...I don't see anything wrong with that.

Corey Zarda wrote:ok the lack of back pressure is not a myth cuz not enuf back pressure will screw up the reverb factor to help pull the exhaust gasses out of the cylinder. If you would have taken any engine building classes you would know that the proper runner lengths on both the intake and exhaust manifolds makes huge numbers when gotten perfect.

<sigh>

keeping up exhaust gas velocity increases scavenging.
back pressure is NOT the same, and has nothing to do with scavenging.

I think you should either find a new school, or start paying attention.

Adam barberio wrote:alright i hollowed out my cat for the hell of it cause it was all @!#$ up an throwing codes and now when i rev up to around 6grand it backfires like a @!#$ and shoots a flame. its cool and all but i know no backpressures not the greatest but i dont know many ppl with sunfires and hollowed cats that shoot flames maybe im running rich or something? and u think these backfires could @!#$ something up internally or no?

Back-pressure...lol
Well, in hollowing your cat out you're probably messing up the second O2 sensor which in turn modifies your afr.


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Before this post goes any further I think it requires pictures....

I just want t clear up some misinformation here.

You probably are shooting flames because you are running rich. This would be why you are throwing codes, not because your cat it bad.

The second o2 sensor dtermines catalytic convertor efficency as Nickelin Dimer stated. It does not determine your afr as Rob Durret stated.





FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!

The only time my car would spit out a flame is if i stayed on my MSD two step limiter to long, which is like 3 grand for the first, and went straight to the second limiter, which is 6400. Does it bad when i launch at the track wrong.

Wade Jarvis wrote:I just want t clear up some misinformation here.

You probably are shooting flames because you are running rich. This would be why you are throwing codes, not because your cat it bad.

The second o2 sensor dtermines catalytic convertor efficency as Nickelin Dimer stated. It does not determine your afr as Rob Durrett stated.

Well, he's throwing codes now because of the gutted cat...
It would've been a good idea to hook it up to a computer before messing with your cat.


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i had it hooked up to a modis before i had gutted the cat, the second o2 sensor was faulty or something an showing a low voltage reading. so supposively the second o2 sensor was already messed up before hand.

between the spelling mistakes and misinformation, this thread = teh suxor

Adam barberio wrote:i had it hooked up to a modis before i had gutted the cat, the second o2 sensor was faulty or something an showing a low voltage reading. so supposively the second o2 sensor was already messed up before hand.

so you decide its a good idea to destroy your cat which is probably fine because you had a bad o2 sensor? yeah, great logic.



JBO Stickers! Get yours today!

Amen, Grayo. This is why all the service industry education & service manuals say: Test by replacing part in question with a known working part to determine if part in question is at fault. Man, you need to get some education before messing with complex things you don't understand the operation of (Old hillbilly woman: You get him away from that wheel-barrow! You know he don't know nuthin' but mechanical things!!).

Go beyond the "bolt-on".

Rich Grayo Jr. wrote:

Adam barberio wrote:i had it hooked up to a modis before i had gutted the cat, the second o2 sensor was faulty or something an showing a low voltage reading. so supposively the second o2 sensor was already messed up before hand.

so you decide its a good idea to destroy your cat which is probably fine because you had a bad o2 sensor? yeah, great logic.

Just proves my point. A bad/clogged cat is the number 1 most diagnosed problem by people who don't have a clue



FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!

like skwirl pointed out, exhaust back pressure and exhaust velocity are independent of each other but are more often than not confused. it is exhaust gas velocity that helps with exhaust gas scavenging, that and many other factors like manifold/header design, runner lengths, etc.

as for the flame, it could be do to that fact that the now non-existent cat is no longer there to bring the exhaust temps down. you are more than likely running rich as well and there may be unburnt fuel in your exhaust gas stream. this unburnt fuel, like any fuel, will burn with the right mixture of heat and oxygen. with the cat missing, the heat is probably there, and as soon as it gets towards the end of the tail pipe it gets enough oxygen. then... KaABOoOM!

the purpose of the cat is to clean and filter out potentially environmentally hazardous gases, however it usually brings down exhaust gas temps significantly. this is why when checking for a bad cat it is generally acceptable to take temperature readings of the exhaust pipe with an inferred thermometer both directly before and after the cat.

btw, wth you shooting flames, how long before the cops pull you over and check for a straight pipe?



1997 RedR - ZedR

well fortunately i dont have to worry about the cops around here. but even if they used a sniffer i still have the shell of the cat there, i could just say its messed up and need it replaced. the flame only happens if i push it haha i dont do that often so thats nothing to worry about.

Gotta agree with Wade, and add something:

When I first got my truck it had a horrendous rod knock. After replacing the oil pump & pickup, crank & bearings (and pressurizing the oil system) I ook itr for a short shake-down drive. About 1/2-block after I left the garage it felt very unresponsive to throttle input, like it was choking. Getting it back to the garage I checked everything related before drawing conclusion the catalytic convertor may be clogged (They're supposed to be replaced at 100,000mi, but no one ever seems to consider that, so...). I had to get it out of my uncle's garage, and didn't have money for a tow or a shop visit at that point, So, I began unbolting the tail section of it and grabbing the longest pipe section I could find immediately I went to work breakin' up & clearin' out the bricks within. A few times of wacking, a few start-ups & zaps between the wackings and it cleared out and ran fine (Obviously a good, educated guess on that call). Didn't worry about replacing it until emissions testing came along (It's an OBD I system), and it's been fine since the new one was installed. This is the only time gutting the cat is ever justified, and thurough testing of pre- & post-catalytic backpressure should done first before attempting it. Mind you I had only my hand by the tailpipe to gauge the flow (Also good for balancing indie carbs per cylinder on a multi-pipe bike), and a good ear for tuning & response gauging, but you get the point.

Go beyond the "bolt-on".

I hate to be your garden variety hippy, but don't hollow out your catalytic converter.
Its bad for the environment and it will cost you a chunk of money (at least where i live) if you get caught.
Seriously dude, its a street car. Be responsible.
Wait a sec, did you say you rev your (stock?) motor to 6000RPM with no load?
If you keep doing that it might throw more than codes...




ZZZZZZZ

spacemason wrote:I hate to be your garden variety hippy, but don't hollow out your catalytic converter.
Its bad for the environment and it will cost you a chunk of money (at least where i live) if you get caught.
Seriously dude, its a street car. Be responsible.
Wait a sec, did you say you rev your (stock?) motor to 6000RPM with no load?
If you keep doing that it might throw more than codes...

You mention hippie, ya know, I've always wanted to see a turbo diesel in a sport compact (making 250+hp).


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Quote:

as for the flame, it could be do to that fact that the now non-existent cat is no longer there to bring the exhaust temps down. you are more than likely running rich as well and there may be unburnt fuel in your exhaust gas stream. this unburnt fuel, like any fuel, will burn with the right mixture of heat and oxygen. with the cat missing, the heat is probably there, and as soon as it gets towards the end of the tail pipe it gets enough oxygen. then... KaABOoOM!

the purpose of the cat is to clean and filter out potentially environmentally hazardous gases, however it usually brings down exhaust gas temps significantly. this is why when checking for a bad cat it is generally acceptable to take temperature readings of the exhaust pipe with an inferred thermometer both directly before and after the cat.

The cat will not bring exhaust temps down. if anything, it will bring exhaust temps up- a cat operates at about 2000*F (no typo- two thousand degrees), more if he's running rich. so, while it is an acceptable test procedure to check exhaust temps pre- and post- cat, a lower reading after the cat would indicate a cat that is not functioning (though this could be because the cat isn't warmed up yet)
also, the cat doesn't filter out anything. the catalytic converter contains catalysts (as the name suggests) which convert CO, CO2, NOx, and HCs to CO2, H2O, and N2.

Well, if you can find one of the Isuzu diesel 4-cyl that saw use in GM's American models (1.8L N/A in '83-'85 Chevette, 2.2L N/A in '83-'85 S-10 pickup) and mate it to one of the Isuzu-built transaxles (Assuming they have the same bellhusing pattern) and work-up a air-air intercooled turbo system (Even though even Banks never seemed to bother touching them) then I'd say it's possible.

And yota: Yes, there are no filters in a catalytic convertor, but the treated ceramic monolithic bricks found in them are of a screen-like porous (called "cells") design . The higher the cell count the better they flow (800-1000 are considered best currently). But those cells get pretty small as the count goes up. And once those cells become clogged (By over-rich or under-lean conditions) the flow is reduced, choking the engine on it's own waste. And if it goes on for too long, the bricks break-down or melt and become slag, prompting the replacement of the convertor & a engine systems operation check. The same rules apply also to the older (Although I doubt most here have or will ever see one since their restrictive design was long abandoned years ago, even in the service replacement industry) pellet-bed catalytic convertors.

Go beyond the "bolt-on".