O2 sensor?
Thread Starter
4th Gear Member
Joined: Feb 2006
Posts: 1,018
From: SE Minnesota & SW WI & Bloomington, IL
RE: O2 sensor?
urban your first link didn't work. And these aren't the good ol' days anymore
If the technology is available to tune my vehicle better than before, than why wouldn't I??
If the technology is available to tune my vehicle better than before, than why wouldn't I??
Thread Starter
4th Gear Member
Joined: Feb 2006
Posts: 1,018
From: SE Minnesota & SW WI & Bloomington, IL
RE: O2 sensor?
Here is the email my brother sent me. I thought I'd share the knowledge, hopefully it will benefit others.
"I think I have the PLX M300 http://www.plxdevices.com/M-Series_productinfo.htm
An A/F meter is the same thing as a O2 sensor, most O2 sensors give a 0-1 volt output which equates to an air/fuel ratio of 14.7 parts air to 1 part fuel which is perfectly stoichometric, in other words all the fuel that is put into the cylinder burns with all the air in the cylinder.The voltage oscillates between 0 and 1 volt and the computer adds orsubtracts fuel by opening the injectors longer or shorter to keep a constant .5 volt signal.
If too much fuel is input into the cylinder and not all of it burns with all the airyou are running rich and the air/fuel ratio is less than 14.7/1, typically best power is made at an air/fuel ratio of ~12.5/1 If too little fuel is input into the cylinder and you have excess air you are running lean and have an air/fuel ratio of greater than 14.7/1. This is usually a bad thing, but some companies will run around 15/1, as you decelerate or let off the throttle quickly you also will run quite lean all the way up to ~17/1
When you go to 100% throttle, the computer ignores theO2 sensor and uses a look up table pre-determined at the factory whichinjects morefuel sotheair/fuel ratio is at ~12.5/1 in order to makemore power. Now imagine adding an intake or headers to an EFI car which adds a lot of air flow into the cylinder.This meansthat lookup table is no longer correct, so the computer does not know how much fuel to inject at 100% throttle and youare at risk of running lean and hurting your engine. Hencesome people increase fuel pressure, so for the same amount of time the injector is open, more fuel will be input into the cylinder. The best option is to get a custom tuner and create a new lookup tablesoyou get the correct amount of fuel injected into the cylinder to maintain the 12.5/1 air/fuel ratio during 100% throttle events.
In order to create this new lookup table or for your case, select the proper jets, we need an A/F meter (O2 sensor) capable of outputting a voltage that varies with the air/fuel ratio all the way from ~10/1 up to 20/1. This is what they call a Wideband O2 sensor and they vary voltage from 0-5 volts. Hence 0v = 10/1 air/fuel and 5v = 20/1 air/fuel ratio. Instead of just switching back and forth from 0 to 1 volt, it is a continuous signal.
The little black box that outputs a number from 10 to 20 is just an electronic chip made to convert the 0-5 volt signal into a number. Actually is does a little more than this, the voltage coming out of the O2 sensor is actually really small ~0 to 5 mill volts. So the black box amplifies this signal by 1000 times to get the 0-5 volt output.
You need to make sure I have this exact kit as the O2 sensor that you buy will vary from kit to kit. I think we can use my black box and just unplug it from my car. We'll have to do some checking. You will want to do some checking into where to weld the bung, I think it is something like 20 inches after all the pipes are converted into 1 tube. I think mine is in the h pipe right after the header."
"I think I have the PLX M300 http://www.plxdevices.com/M-Series_productinfo.htm
An A/F meter is the same thing as a O2 sensor, most O2 sensors give a 0-1 volt output which equates to an air/fuel ratio of 14.7 parts air to 1 part fuel which is perfectly stoichometric, in other words all the fuel that is put into the cylinder burns with all the air in the cylinder.The voltage oscillates between 0 and 1 volt and the computer adds orsubtracts fuel by opening the injectors longer or shorter to keep a constant .5 volt signal.
If too much fuel is input into the cylinder and not all of it burns with all the airyou are running rich and the air/fuel ratio is less than 14.7/1, typically best power is made at an air/fuel ratio of ~12.5/1 If too little fuel is input into the cylinder and you have excess air you are running lean and have an air/fuel ratio of greater than 14.7/1. This is usually a bad thing, but some companies will run around 15/1, as you decelerate or let off the throttle quickly you also will run quite lean all the way up to ~17/1
When you go to 100% throttle, the computer ignores theO2 sensor and uses a look up table pre-determined at the factory whichinjects morefuel sotheair/fuel ratio is at ~12.5/1 in order to makemore power. Now imagine adding an intake or headers to an EFI car which adds a lot of air flow into the cylinder.This meansthat lookup table is no longer correct, so the computer does not know how much fuel to inject at 100% throttle and youare at risk of running lean and hurting your engine. Hencesome people increase fuel pressure, so for the same amount of time the injector is open, more fuel will be input into the cylinder. The best option is to get a custom tuner and create a new lookup tablesoyou get the correct amount of fuel injected into the cylinder to maintain the 12.5/1 air/fuel ratio during 100% throttle events.
In order to create this new lookup table or for your case, select the proper jets, we need an A/F meter (O2 sensor) capable of outputting a voltage that varies with the air/fuel ratio all the way from ~10/1 up to 20/1. This is what they call a Wideband O2 sensor and they vary voltage from 0-5 volts. Hence 0v = 10/1 air/fuel and 5v = 20/1 air/fuel ratio. Instead of just switching back and forth from 0 to 1 volt, it is a continuous signal.
The little black box that outputs a number from 10 to 20 is just an electronic chip made to convert the 0-5 volt signal into a number. Actually is does a little more than this, the voltage coming out of the O2 sensor is actually really small ~0 to 5 mill volts. So the black box amplifies this signal by 1000 times to get the 0-5 volt output.
You need to make sure I have this exact kit as the O2 sensor that you buy will vary from kit to kit. I think we can use my black box and just unplug it from my car. We'll have to do some checking. You will want to do some checking into where to weld the bung, I think it is something like 20 inches after all the pipes are converted into 1 tube. I think mine is in the h pipe right after the header."
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