F__king hummer cats

[iccon]

Anyone have a better fix for the typical Hummer cat problem other then replacing them with the factory ones?

[KenP]

There are aftermarket cats available. Check with your local muffler shop.

[8500lbs]

I am on my second set of Dyna Tech High flow Cats and its less than 2 years and less than 40,0000 miles. I am now trying to look into cheator Sensors and just punch the cats through. Has anyone Had expierence in Aftermarket or "Cheator Sensors". They are new O2 Sensors.

Thanks
B

[iccon]

I was told by one guy to install a larger cat farther back on the hummer then relocate the O2 sensors that are behind the cats.
He also said the reason why they **** the bed all the time is they are to close to the heads and all that heat so they will just keep failing.

[8500lbs]

This is something like I was talking about

http://www.yourhotcar.com/prod/Oxyge...Bypass/545967/

Thanks
B

[Metallic Red]

Their called MIL Eliminators, check at Summit.com

Also, are you running a Tuner or Programmer ??

[8500lbs]

I know I am as well al LT headers, Full exhaust, and Full intake.

I guess more air flow, more Power, more heat, = melted cat.

Thanks
b

[iccon]

What if I remove the cats and install threaded blind pockets on the pipes then install factory O2 sensors would this work

[LEcustoms]

Originally Posted by iccon

What if I remove the cats and install threaded blind pockets on the pipes then install factory O2 sensors would this work

I did not Write this it is a write up that i found thought it might help.

The 02 sensor can be considered a small batery that has an operating range of 0 to 1 volt when fully warmed up to 600F. Its voltage depends on the amount of oxygen in the exhaust stream.

All 02 sensors are vented to the atmosphere which contains Approximately 21% oxygen. The exhaust of the gasoline Powered engine typically contains up to 2% oxygen. The Sensor's output voltage depends on the oxygen content of the exhaust stream. That is, if the exhaust has 2% oxygen, it is lean. This produces a low voltage, below .3 volts (300millivolts). If the exhaust has near 0% oxygen, it is rich. This produces a high voltage, above .6 volts (600millivolts). These voltages are sent to the computer and it reacts by adjusting the air/fuel ratio. This is commonly known as the 02 feedback system and when this system is operating it is said to be in "closed loop". When it is not operating, meaning the computer is not reading and responding to the oxygen sensor, it is said to be in "open loop".

Keep in mind that the computer uses all the sensors to control timing, fuel mixture and emission systems. The 02 sensor as an input is used by the computer to keep the mixture as balanced as possible. When the air/fuel ratio is "balanced" it is at 14.7 parts of air to 1 part fuel by weight. That means that for every pound of gasoline the engine burns, it will need 14.7 pounds of air. Keep in mind that oxygen occupies only 21% of the total air volume needed by the engine. The term "stoichiometric" is the term refering to the point at which the catalyctic converter can be at its maximum efficiency when converting the three major pollutants (CO, HC, NOX) into harmless emissions (CO2, H2O, N, H).

The computer can only use the sensors output information under certain conditions. First, the sensor must be hot to produce a normal signal (600F). This is why most sensors today have built-in heaters to counteract the cooling effects of prolonged idling and to achieve closed loop mode sooner during warm-up. Heating the sensor also keeps it cleaner and extends its life considerably. The heater ussually gets voltage from a constant "key-on" source like the fuel pump relay fuse. This is what the four wires on the celicas 02 sensors are. The four wires are; 02 sensor output, 02 sensor ground, 12 volt heater feed, and heater ground. On 3 wire sensors, the 02 sensor grounds through its case and doesn't require a seperate ground wire.

Secondly, the computer is programed not to go into closed loop operation until the coolant temperature sensor tells the computer the engine is warmed up. If the system tries to go into closed loop too early in the warm up period, the leaning effect on the system would cause drivability problems and pollutants.

Thirdly, the computer is also programmed to ignore the 02 sensor at near wide open throttle conditions. Maximum power requires maximum enrichment.

Also, some manufacturers have built-in time delay. For example, on some GM models, closed loop is delayed for 1 to 2 minutes every time the car starts. This allows engine stabilization to take palce before the engine goes into closed loop.

In order to read the 02 sensor, most computers send out a certain voltage to the output terminal of the sensor. This is typically around 450 millivolts. Since we know that the sensor sends low voltage (under 300mv) when a lean condition is present and high voltage (over 600mv) when rich condition is present, the computer can count the number of times the sensor crosses the 450mv mark. Cross-counts are the number of times the 02 sensor crosses 450mv. A scanner can "look" at this for you. Even though you can't see the numbers of cross counts without a scanner, you can use a digital voltmeter to watch the open/closed loop system operate.