O2 sensor bungs

[NICK C]

I have FFR7622 with a 429 BB. I am installing a Mass Flo EFI. The instructions woul have me weld the O2 bungs 9 to 18 inches from the heads. That would put me at one of the primaries. I would think I would get a better sample for the sensors just after the collectors on the narrow part of the side pipes. Any thoughts on this topic would be appreciated. Thanks Nick

[tazmandevil735]

That's where I put mine in the narrow part of the collector and it works just fine there.
I angled them down just slightly so they face under the car and you can't even see them.
One thing I had to do was buy two o2 sensor extension harnesses to extend my wireing

[NICK C]

Thanks Taz. That's what I have been leaning towards. It makes sense to me to be after the collector.

[skullandbones]

The O2 sensors are narrow band anyway. So there is limited input to the computer. However, I'm with you. It just doesn't make sense to get input from one cylinder. I'd rather get the data from each complete bank even if it is a little further downstream. Haven't seen any evidence to disprove the idea (several people have done this successfully). It was difficult to get the angle for the bung correct to keep the sensor from hitting the body or hanging too low. Got it to be above the 4 inch tube level and about a finger width from the body. So far so good. Looking for a shorter O2 sensor but no luck yet. I soldered each extension wire and staggered them and shrink wrapped each one. My ECU seems perfectly happy with the modification. Good luck, WEK.

[Bob Cowan]

Some sensors need to be closer to the head port, because the exhaust gasses are hotter there. Yes, it would be a better sampling if the sensor is in the collector. But if it doesn't get hot enough, the computer will be fed an erroneous signal.

I would follow the directions that came with the Mass-Flo kit. Chris usually knows what he's doing.

[NICK C]

Thanks for the info. I may give Chris a call and see his thoughts. If I do need the extensions, where's a good source to purchase? Nick C

[skullandbones]

Bob brings up a good point about the heat of the O2 sensor/exhaust gases. I have ceramic headers that are coated both inside and out. There is significant heat containment delivered by these headers. So I think it lends itself to the above mentioned modification. I haven't measured it yet but just got a direct read thermometer to do that. After the engine is turned off, it's only a few minutes before you can touch the header without a burn. However, the side pipe is still capable of giving you a "cobra bite" and a second degree burn. WEK.

[CHOTIS BILL]

I seem to recall instruction for installing O2 sensors that said it is better to have the sensors pointing down so that condensation won’t collect in the sensor and shorten it life, but I may be wrong.

Bill Lomenick

[Bob Cowan]

That is also true. The sensor should NOT be installed between 5 o'clock and 7 o'clock.

[tazmandevil735]

Been running for two years now with no problems.
Little bit of bug juice on one photo
Included a picture of the stainless side pipe support I made with a rubber bump pad on it to protect my fiberglass body should the engine torque too much. (never hit yet)

[tazmandevil735]

I don't like sampling one exhaust tube either because if that cylinder is running richer than the rest the computer will lean out and possibly damage the others.
Sampling at the collector at least gives you an average of all 4 cylinders.

[skullandbones]

Don't want to be argumentative so please don't take it that way. I like to filter info and do what is best for my application. I think the reason for the no install at 5 to 7 o'clock may have to do with moisture leaking down into the sensor housing that could cause sensor failure. In my case, in AZ with 15% humidity, this works fine. I have removed them just to check and they look like they did when I installed them. We don't have to contend with rain, condensation, rust (for the most part), dew on my telescope, or fleas on my cats and dogs. So there are advantages to living in an arid environment. Please use info judiciously for your application. Good idea taz. I will have to add the protection, too. Thank you, WEK.