Oxygen sensor

[Jim_Ferrell]

Re: Chevy 454, 9.5:1, Holley 750, Air Gap intake, MSD ignition, 2inch headers

I am going to put an oxygen sensor port in each header; any recommendation for which cylinders to choose, one left bank, one right. I do not want to use the side pipes.

My thought is that 3,5,2,4 have better flow than 1,7,2,8; therefore the fuel stays suspended better and more complete combustion occurs; this would use the oxygen better and give slightly lower Ox readings.

Any thoughts?

Jim

[jeffko]

Where is Jerry??

[Jerry Clayton]

You called Jeff?

[Jerry Clayton]

Jim

Why don't you want to use the side pipes?

[RedSnake351]

Jim, Jerry Clayton must still be sleeping, otherwise he would have already responded!
Crash

[Jerry Clayton]

I've been studying Jim's posts--they are all at around 5 AM--doesn't he know there isn't any oxygen at that time---oxygen occurrs as an catilitic event after 2 or 3 cups of coffee

Jerry

[RedSnake351]

OOOOPS! I see while I was doing my SLOW typing, Jerry won the speed typing contest.

[Jerry Clayton]

You were just admiring the new girls in your photo gallery

[RedSnake351]

Originally Posted by Jerry Clayton

You were just admiring the new girls in your photo gallery

Boy, you are sharp Jerry, nothing escapes you, especially having to do with GIRLS!
Crash

[vettestr]

For my 2 cents I ran into a lot of grief with 02 sensor placement on my toy. I did not want it to be visable so the options were limited. You want it as close to the engine as possible to for more accurate readings. As you get farther away from head you loose heat quickly and this will skew reading I found out the hard way. You also want to install sensor so moisture runs away from it rather than into the sensor from condensate. After getting readings I did not believe I moved mine to the rear most tubes on each side (ran 2 sensors) thinking the rear cyl. would be the hottest so would be most effected by lean settings first.
Wound up with sensor about 18 inches down from the header head flange . This placement changed my readings by (.20) OR leaner than when in sidepipe without and setting change. So just placing closer to the head changed my display from .84 to .64 and that was about where I expected I was at. There was just no way I was running as rich as what it was trlling me when in the sidepipe just after the last 90 degree turn.

[Jim_Ferrell]

Why don't you want to use the side pipes?I do not like the look of the sensor sticking out the side of the pipe and I do not have the ground clearance to put it on the bottom.

I've been studying Jim's posts--they are all at around 5 AM--doesn't he know there isn't any oxygen at that time---oxygen occurrs as an catilitic event after 2 or 3 cups of coffeeFor some reason, age or jet lag, not sure which, I am often up before 5; also at this time of the day I hear less complaints about the time I am spending on this hobby.

Jim

[vettestr]

Jim,
I too am a early AM person but 5 oclock is not good and 7 oclock for the other side is not good either. The only way to clock the sensors so they are the least visable and still protected is to place in the bottom inside of the sidepipe. This does protect from getting hit and from being seen for the most part but exposes to contaminates every time it goes through a cold start up and too some degree all other times as gravity does its thing. Placing in the lower 5 or 7 oclock position means the sensor is in the lowest part of pipe and becomes a water trap. WATER ??? what the hell is this guy talking about, water ? At cold start up condensation occurs from the cold to hot transition. Yep it is hot enough to dry out in a reasonable time but it is not only the few CC's of water but the crap it washes to the new water trap in the system that will lessen then kill the sensor after time.
Go too any of the aftermarket kit installation instructions and read the warnings about placement. The common area of multiple cyl. EX. gas is best as it gives you an average and not just the 1 cyl. it sees if in a single tube = BUT.
After several installs and seeing first hand results I found the rear tubes on either side it fits best gave me the most accurate results. I have installed dual sensors on a car in the rear tubes from concern about single cyl. readings but in the end found they were always so close to each other just not worth trouble and expense. A single FAST sensor works for me in #8 as a rule. Good luck and have fun.

[wtm442]

I always thought the O2 sensor should be located in the header extension, not in an individual runner. But what do I know ... its all second hand

[TurboVenom]

Place your sensor bung as close to the collector as you can. You should face it inward so as to keep it out of sight, don't place it under the pipe. It should be parallel to the ground, or upward from that position if possible. Putting it on one port won't work as it will give you incorrect readings.

Sensors must be 900 deg F to be properly active. Less than that temperature will skew the voltage readings and make your car run excessively rich. Cooler temperatures lower the mv readings.
I would recommend a heated sensor - four wire - for that application as the free-flowing sidepipes reduce the exhaust temperatures. And, depending on what fuel control system you plan to use, you will need either one or two...put ports on each side just in case.

My personal recommendation is the use of a wideband sensor and a fuel control system such as the XFI or FAST system.
John

[Jerry Clayton]

Jim,

Check out the second photo in my gallery--Yeh, I know its a 32 5 window ford but, I built the headers and side pipes as if it was a 32 Cobra---see the hole in the frame hole by the collector? That is where the O2 sensor comes thru for the FAST system--Can't see it--proves that it is hardly noticeable!!!!

Anyway, if you are going to run a carb you will only need the sensor while you are tuning it--you can weld in a bung and then put a plug it in

Jerry

[Jim_Ferrell]

Yes, I am only using the oxy sensor to tune the carb. A few laps at 1.0+ Gs around the carousel at Road America might motivate me to change to fuel injection.

I am using the wide band 4 wire version sensor.

Thanks for the ideas.

Jim

[TurboVenom]

Wideband sensors have 5 wires, and with the calibration resistor, 7 wires total. You probably have a narrow band heated sensor if it has four wires.

John