Gutting Catalytic Converters

[firedawg]

Hey WhalePirot, what benefit do the heated o2 sensors have?

 

[SQLDBA]

The later cars, with 'dual' O2 sensors use the first for ECM (engine) fine tuning and the second sensor for keeping track that the CAT's operation is acceptable. I cannot define acceptable.

I agree. The 1st O2 is for ECM tuning. The ECM would not be able to tune the fuel trims from the 2nd O2 because the CAT alters the exhaust fumes. I think acceptable is basically a set # of hydrocarbons and unburned fuel. If you lean the car out before the emmissions test everything should go fine.

Earlier cars, like mine (set up to look like an '87, but running a '90 speed density ECM) only have the 'first' O2 sensor. I also
changed to the heated type.

By heated type do you mean a wideband?

The popping sound, is unburned fuel exploding in your exhaust. I get a small amount of it, but you might wish to check your chip's adjustments to the fuel tables for a rich condition. My chip is very, very good, but might not be perfect in the decel area.

No flames; no pains.

I dont think that's unburned fuel. If it was you would get popping with the CAT too. Also if the 1st O2 is there and adjusting the fuel trims, before the CAT, then you're exhaust should still be clean for the most part. I think that the popping is due to the CAT being gutted and now it has essentially been turned into a resonating chamber. I had a brand new CAT on my 81 Z28 and I replaced the mufflers with glass packs and I had popping sounds from those. I dunno though, I could be wrong, I'm no mechanic by any means.

 

[SQLDBA]

Just my .02 cents if I may.I gutted the cat in my 1987 trans-am GTA with the 5.7 litre(350).It was just 2 years old.I did not find any "performance" enhancement even though it was faster than other 5.7 litre automatic trans-ams.Some people back then told me that it actually may have made my car slower. ...........I did however have a peculier smell of cooling fluid......Back then I had made just a few mods....air-foil,performance termostat and "powerchip".So I can't really say what it was that actually made my car a little quicker.......My guess is that the smell had something to do with the termostat.

I had a 93 LT1 T/A and noticed a huge performance gain from gutting the CAT. I had read an article about how a high flow CAT will actually out perform a gutted CAT. The article talked about how a gutted CAT will flow higher than a stock CAT but due to the chamber being hallow it causes air turbulence and flows less than a high flow CAT. Before I sold the car, to make it legal and to test the article I read, I put on a high flow CAT from www.racenet.net. After I got the CAT on I noticed that the exhaust was quiet enough to be tolerable; Althought, I did get a chance to hit Ennis (1/4mi) before I ended up selling the car and noticed a 2 1/2 mph loss in my traps. In my expirence the CAT does limit the performance considerably.

*legal quote* I only used my car off road while it had no CAT.

 

[ShaneL]

I've had no cats and no muffs for a while now and I am always getting comments about how the idle sounds so rough now... PURE EVIL SOUNDING

 

[Mad-Mic]

I've had no cats and no muffs for a while now and I am always getting comments about how the idle sounds so rough now... PURE EVIL SOUNDING

hehe like mine! sounds even more Evil with long tube headers

 

[WhalePirot]

A heated O2 has a heating element to get the sensor up to operating temperature faster than it will with only exhaust gasses warming it. If the car did not come so equipped, an ignition triggered, 12vdc source must be wired to the 'extra' wire on the heated sensor, for the heating element.

I believe that a wideband, which is a later sensor, used (so far) primarily on imports, is also heated, as a later device, but outputs a varying voltage to refine ECM adjustments. The 'old' sensors output three voltages for rich, lean and 14.7:1 stochiometric conditions.

My use entailed the hope that it woulod last longer, with less carbon fouling. Now that I know more about them, it may not be a real issue or solution.

 

[SSTibet]

Heated Oxygen Sensors

I would guess with unheated O2 sensors one would not get the SES light on short rides even if there was a problem with the sensor itself or somewhere else effecting the lean / rich condition...

The old fashion "thimble" type sensors work when the exhaust temperature reaches 650F degrees and therefore it takes some time for the O2 sensor to start doing its work. With a heated O2, the exhaust gas temperature is not waited for and the heating element inside the sensor provides the heat and makes the sensor to operate in a very short time after a cold start.

That's what I gather from an article I read in Bosch's web page. :cool

 

[SQLDBA]

I believe that a wideband, which is a later sensor, used (so far) primarily on imports, is also heated, as a later device, but outputs a varying voltage to refine ECM adjustments. The 'old' sensors output three voltages for rich, lean and 14.7:1 stochiometric conditions.

:J
I came from the import market. My 1st car was a 93 LT1 T/A. I had Borla, no cat, LG motorsports G2 intake, hyper tech 160 chip, 160 thermostat, transgo shift kit, power pulley, and home made ram air going into the G2 intake. I wanted to get a shaker hood for it but never did. I ended up almost trading that in for a white 95 vette but after driving the car for a week and having a problem with the ASR, I used the down payment on my wifes wedding ring. The dealer said all they need is an extra $500 down or a co-signer and they could get the deal done. I had already used my down payment up so I told them I dont have a co-signer and got my T/A back with a free $100 detail job :L . When I got married I got a 95 turbo Eclipse and upped the boost and was spanking stock LT1 F-Bodies. I then got a 93 AWD turbo Talon. Put tons of money into it and it never ran right. One thing I got on my Talon was the LM-1 Wideband. It shows you an exact AFR without oscilating like a narrowband O2 sensor does when not WOT. I dont really know where the widebands started other than the Lamda O2's at the dyno. I know that the LM-1 from innovate first became popular on the turbo mustang forums. I dont really think that a wideband is need for a N/A car but if you have a Grand National or any type of forced induction then a wideband is a huge help, because you can tune to an exact AFR. I guess if you've ever had your car dyno tuned then you probably have had a wideband on it. The LM-1 uses the Bosch sensor.

Anyway, I still say if you have a wideband and can lean out your car to 15.5 or so then you will pass emissions with no cat... well at least in Texas.

Sorry so long.

 

[wishIhadavette]

I'm surprised only one person mentioned turbulance with a gutted cat. insted of gutting the cat why not put a straight pipe through it so you won't get the turbulance. by the way I'm not going to even touch the legality or doing this.

 

[WhalePirot]

Ya know, a non-CAT car smells different from behind. I wonder when the SMOG cops will nail folks with the nasty EPA fine, based upon smell. Personally, I just feel much more comfy with a clean car, with great performance.

I'd like to know more about how a wideband O2 works with a '90 ECM, given that it was designed for the 'old' one. The fuel tables might not support that extra data very well or the ECM may not fully understand it.

 

[SQLDBA]

Ya know, a non-CAT car smells different from behind. I wonder when the SMOG cops will nail folks with the nasty EPA fine, based upon smell. Personally, I just feel much more comfy with a clean car, with great performance.

I'd like to know more about how a wideband O2 works with a '90 ECM, given that it was designed for the 'old' one. The fuel tables might not support that extra data very well or the ECM may not fully understand it.

All a wideband sensor does is just give you the readings. The wideband I have is just basically a fancy gauge that gives the exact voltage of your exhaust AFR. I used the Super AFC to tune my fuel trims. I would think that to tune the fuel trims on a vette you'll need to get a stand alone AEM or something like that.

The way the SAFC works is it takes the data from the MAF, before it goes to the ECU, and alters it to fool the ECU into thinking it has less or more air than what it acutally does.

I noticed on the corvette forum that this guy also has an LM-1
http://forums.corvetteforum.com/zerothread?id=815299

Here is the LM-1 website:
http://www.innovatemotorsports.com/lm1.php


There are lots of other widebands out there too like the FJO, MoTeC, Tech Edge, Dynojet, ... I just wouldnt know what to tune the corvette's fuel trims with.

 

[WhalePirot]

I understand the wideband term to refer to the newer design O2 sensors, which vary the voltage signal sent to the ECM over a wider band (range) than the earlier versions, which only send one of three voltages. This improved design allows a much finer trimming of the fuel/air ratio.

I suppose there are all sorts of readers which have wideband capability with much more ease than a DVOM affords. Perhaps the terms confused our chat.

Gee, we have strayed from the header topic......again!