Is the stock tubing really that bad from the cats back??

I am THINKING about just deleting the Cateletics and just welding bungs for the o2 sensors in the downtubes. Then just replacing the stock muffler and tail pipe...Waste of time or just go with Cat-Back from Gibson/Magnaflow/Flowmaster. I am not big into Noise. I would rather have a nice lil growl and ZERO drone in the cab.

Thanks in advance.


Brad

 

Hey Brad-

Just so I understand what you've said, you're thinking about getting rid of your cat converters and using straight tubing in their place, and hooking up to a Gibson cat-back system?

If I got it right, you may want to rethink this. Even aside from the Federal laws prohibiting the removal of originally installed anti-smog devices, in most states, you'll fail both the emissons test and the visual test, meaning they won't give you an inspection sticker...some states are tougher on this than others. I get what you're saying about adding back the O2 sensors, but the problem is they're designed to measure the amount of oxygen both before and after your cat converters to make sure they're doing their job. This allow the engine's computer to make adjustments to timing, air/fuel mixture, etc. So, your computer will be throwing codes at you left and right because you've eliminated an essential part of the engine control system.

I definitely see where you're coming from...my 1st car was a '77 Renegade; one of the first years with anti-smog stuff on it, which made it run like crap...so I removed it, and it ran like a champ. Unfortunately, the use of computers in vehicle engine management systems and much tougher emissions regulations make that idea pretty much impossible.

Sorry if I misunderstood what you meant.

Hope this helps,
Tim G.

 

The stock tubing has many restrictions at the bends as compared to the aftermarket systems that are mandrel bent. I would not delete any of the converters or O2 sensors as it would cause alot of computer codes and emission issues. I have a cat-back system from magnaflow that I am happy with.

 

Fellas....I live in the COUNTRY...haha...No worries with Emissions testing or even a simple visual. I know what its like though as I lived in CA for several years and its dead nice not having to deal with that since.

Anyways...I have done exactly what I described to my 90 & 94 Thunderbird Supercoupes. One is EEC-IV and the other is ODB-1...Both of them also have the EGR deleted along with the Cats. No codes and along with that no worries of a plugged or malfuntioning converter. My A/F tables are perfect as I have data-logged both cars as well.

I think I am going to DO IT...If I have any problems or ill effects I will post back. Also, I think I will just go with some JBA headers and full exhaust. Probably going to try using a resonator in the mid-section to keep the drone down.

Thanks for the replies fellas.


Brad

 

Hey Brad-

This is actually pretty interesting. So, I'm curious...how do you remove parts of the engine management system without messing it up...or messing up the other systems which get data/sensor readings from it? For example, from my reading on this board--it seems like the engine management system and transmission computers both exchange sensor readings and data from one another in order to both function properly, affecting A/F mixture, timing, shift points, etc. If I understand correctly, several of the computers in these trucks are pretty dependent on each other.

So, removing the EGR valve, and/or the O2 sensors sounds a lot like taking a person and shooting novocaine into both feet, blindfolding them, then asking them to run a marathon; more trouble than it's worth

Also, I'm hoping you never need/want to sell any of these cars...and since you're in WA State, better not let the tree-huggers find out....heh heh

Tim

 

Its pretty simple actually. The sensor "o2" is still there and will measure whatever is available. The computer will make changes accordingly. Its not looking for a specific value so it really does'nt matter what said value is.

TO cause a lean or rich condition with a modern computer controlled car these days you have to REALLY go out of your way to do so. None of what I have described SO FAR accomplishes any of that...haha...When you change your MAF, Injectors or add a aftermarket chip and of those can cause ill conditions.

Also...When I deleted my EGR I had to turn EGR OFF in my tune. I don't like EGR because its a pain in the **** to maintain and the returns are not worth the time or trouble...haha...Where I am from anyways.

Is it worth the trouble??? To me it is...To others it may not be. Regardless its not rocket science and nobody gets hurt...

I have had my Supercoupes a LONG time and don't ever see me getting rid of them. The 90 I have had since 92 & the 94 I have had since 99 and I have no intentions of sale because I have scads of MONEY in both of them...Really though it would only take a day to get them ready to pass ANY emissions inspection in WA...


Cheers,


Brad

 

The only thing the rear O2 sensors are for is measuring the efficiency of the cats. You can either get an O2 eliminator that you plug in, or you can have them disabled in the tune.

 

OR you can just leave them in place...Even with just downtubes sporting bungs with a fresh set of o2's I picked up alot of fuel milage. So apparently they can still be functional without a cat.

Brad