Engine 1st Gen 2nd Gen 3rd Gen A resistor to fool the O2 sensor?

Up until last week I had a high flow 200 cell catalytic converter attached to my 4-2-1 header via a doughnut connection. When I worked on my transmission recently I pulled the high-flow off and installed a used OEM cat that I bought from CL as I have my yearly inspection coming up that includes emissions.

The high-flow in conjunction with a O2 extender worked well for about 6 months but then the precious metals must have dissipated to the point that even with the extender codes started being thrown. I have done allot of research on cats and aware of the "magic" dimension for long life and how the matrix folding impacts life span as well. With the high-flow attached to the 4-2-1 and the JCW exhaust I had a great tone and the pops/burbles were quite nice, not overly loud.

Back to the O2, it does not really sense oxygen levels but rather the temperature of the exhaust as it exits the converter. If the engine mixture is rich then there will be more fuel, hydrocarbons, and the precious metals within the converter matrix will "burn off" this excess via a chemical reaction that creates heat. More unused fuel in the exhaust, the hotter the post converter exhaust stream. A lean fuel mixture will have less unused fuel so the the post converter stream will be cooler.

I am thinking that if you know what impedance range the ECU is looking for a resistor in conjunction with a capacitor may do the trick.

Something like the picture below.

Anybody had success with this?

 

I like the sound of the high-flow and my butt says its quicker so I will be putting it back on after my inspection. The CEL is a PIA as I don't like driving around with a the light on as you don't know if something else pops up. I don't know if this is different then "eliminating" the post stream O2 and then whether there are long term adverse affects.

I need to do more review.

 

From what I can find this should eliminate the codes. Below are the part numbers that you can get on Radio Shack or Amazon. Appears the biggest issue is keeping both dry and away from the muffler/cat. If I did it I would run some travelers up into either the ABS or the Brake Master Cylinder bays.

Also appears to work only on narrow band O2 sensors that the OEM system has.

A 1 Microfarad (1μF) Capacitor - RadioShack part number 272-1055
A 1 Mega ohm (1MΩ) Resistor - RadioShack part number 271-1134

 

OK, first let's talk about cats. The rule is thumb is the cheaper the price, the less precious metals to act as catalyst agents and that many will not hold up under the forced induction heat/pressures that forced induction produces. The space where the cat can be installed also is a factor. The factory cat is about 5.25 inches (diameter) on the Gen1. There are allot of high flow cats out there but longevity can be linked to the overall diameter and a minimum number that is discussed is 130 mm (5.1"). Many "green" highflows are 6" in diameter so unless they are very short they may hit part of the heat shield or body/frame.

The matrix within the cat comes in either metallic or ceramic. There is some discussion that the metallic matrix is better for forced induction but the OEM cat is ceramic.



Then the metallic matrix can be folded two different ways. The first, and least expensive method, is the "paper towel" type roll above. The "s-fold" like below is more expensive and many of the European exotic cars have this "s-fold" matrix that is said to stay together better.



Last is the number of cells that the matrix has. The higher the cell count, the OEM is 400, the more resistance and more "muffled" the sound. The last I knew Jan at RMW is using a Vibrant GESI high flow cat that is a 300 cell count. Kooks in North Carolina makes a 300 cell high flow that is rated for 900 HP forced induction. This unit is the "magic" 130 mm in diameter and when I spoke to them they said their unit would withstand numerous track days.

I went with an Eastern metallic matrix unit with a 200 cell count. I found that Yonaka, many Hondas use, has a 100 cell unit with a "s-fold." Remember the lower the cell count, the less resistance and the louder the sound. The Eastern 200 cell with my JCW exhaust was really sweet, similar to a 4 cylinder motorcycle sound. If Sully can get the video function up I will post some vids. The Eastern and the Yonaka are 100 mm/4" units and are usually less than $100. The green units such as what Jan uses or Kooks makes are over $300. This cost is the result of the amount of precious metal in the matrix.

I am thinking the cheaper cats through time consume the precious metals up and then are basically just a screen inside a metal tube. With no precious metals there is no "reaction" and therefore the O2 sensor is not sending proper voltage parameters back to the ECU. The precat narrowband O2 modulates between the 0.1 and 0.9 volts where the postcat sensor either sees around 0.05 volts in a rich state or 0.9 in a lean state. This makes me think that the O2 sensor is like a resistor where the richer mix that has a greater reaction/more heat allows less voltage to pass then when the mixture is lean/less heat that would pass more voltage.

Hopefully this thread will awaken a static member that has allot more mental functions then I have but has not been participating. About 1:45 in the below clip.

 

I am getting ready to fab up a wire harness on this. First, from what I can tell on the MINI O2 OEM harness, the two white leads are the heater circuit that are reflected as the black wires in the below. The MINI grey wire is the blue wire shown below and is the sensor ground. The MINI black wire is the white wire shown below and is the sensor wire.

I am thinking of getting a surface mounted modular phone jack box to use as my junction box that would be located up in the brake cylinder/ABS trough under the hood. Three 20 ga wires would be required. I would prefer to tap away from the heat shields so I need to wait until I get back under the car to figure more out.

The video below reflects the location of the Gen1 Post Cat O2 sensor.

 

That would work where there are no emissions testing but I am not that lucky.