O2 Sensors

[Alpine 1789]

I know absolutely nothing about 02 sensors, but have seen their benefits touted here enough to trust that they are the best way to go for getting jetting right. I have a number of questions about them, but would like to start with some basics. In response to a recent question on DCOEs, RootsRacer said:

...If you can get your car down to west arvada and can weld an O2 bung on your exhaust system, I'd be happy to help you jet either setup.

I am going to have to remove the header from my car to have it re-coated (went with a local guy who came well recommended, but his ceramic coating barely lasted a year) and was thinking that this might be a good time to weld on a bung, just in case I ever buy a sensor or get the chance to hook the car up to one. For that matter, I may add one to my S3 and SIV V6 exhaust systems when the time comes, just in case. First though, I have a couple of questions: what the hell is a "bung" and where do you put it?

 

[Barry]

http://www.jegs.com/webapp/wcs/stor...=0&Ne=1+2+3+1147708&searchTerm=o2+sensor+bung

An oxygen sensor "bung" is nothing more than a piece of metal threaded 18x1.5 that is welded into the exhaust system. In general, it should be located immediately AFTER the primary exhaust tubes come together.

 

[RootesRacer]

The purpose designed O2 bungs are nice, but I usually just go to the autoparts store and buy a spark plug extender (anti-fowler) for an M18 thread spark plug.

Now you also will need an O2 sensor (wideband) and a controller.

AEM has a reasonable controller/meter that runs under $200 for everything.
Its not the best setup but for the money its pretty good.

Oh, and when you weld the bung into the exhaust, weld it so the sensor is at least 30 degrees pointing upwards.
Condensation kills these sensors and the angle keeps the sensor free of liquid condensate.

 

[Alpine 1789]

Thanks Jarrid and Barry. That helps a lot. Especially the comment about AEM. I spent a little time on their website and am now much better educated that I was just a few hours ago...at least on this subject. That does lead me to a few new questions.

Given that I won't need to be doing constant jetting and may even want to be able to move the system from one car to another, it looks to me like I should get the system without a gauge and hook up my laptop to see the data. Would you agree, or spend the extra $25 or so and have the gauge? http://www.aemelectronics.com/inline-wideband-uego-controller-1159

The ARM indicates that four cylinder cars should use the single channel controller and 6 and 8 cylinder engines need a "dual-channel controller module or two single-channel Gauge-Type controllers if you want to monitor both cylinder banks." Is this necessary, or can the 2.8 V6/4-barrel Holley combination be adequately jetted by just looking at one side at a time. For that matter, for all of the talk here about using an O2 sensor to get downdraft and sidedraft Webers jetted on a Rootes engine, I don't recall reading much about using them with Jose's kit. Is the Holley so fool proof that this isn't needed?

 

[MikeH]

What purpose will the O2 sensor server on a non catalytic converter/non-ECU equipped vehicle? Wouldn't an exhaust analyzer serve the pupose better for checking fuel/air mixture?

 

[Bill Blue]

Jim, it seems to me that unless you are willing to individually jet each side of the Holley, there is no need for a sensor in each bank. And no, the Holley 390 is not that fool proof. While the Holley can be jetted and adjusted to fuel a wide range of engines, it is not a tolerant carb like the Carter 410, which out of the box, would do a decent job on most any engine.

Bill

 

[Alpine 1789]

Thanks. I am probably going to wait to until late fall to pull the header and weld in the bung; I don't want to be without the car during the driving season. There is probably some risk in doing this, but I don't think the header will rust too badly between now and then, especially as I am careful to never start the car unless it is going to be driven enough to warm everything up. Maybe I'll ask for that sensor for my birthday in September.

 

[RootesRacer]

I dont recommend much of anything from AEM, they, much like MSD have turned into warranty nightmares fir most product they sell.

The single channel wideband gauge with sensor is the ONLY product I can recommend from them since its proven reliable and it hits a fair pricepoint IMO.

The multi-channel and bench units, I dont recommend since they are not well proven in the field and as I eluded AEM makes cheap[ junk and doesn't support their products, that is they send you to a forum like this.

A wideband sensor in a single header should be OK on a multi-bank engine.
Its a nice feature on a "V" engine but realistcially if you saw a 1/4 point AFR difference between banks, what would you do anyway? Would you trust both meters? A great metrology engineer once taught me a great saying, "man with two watches never knows what time it is".

I install O2 sensor bungs all the time in-situ, no reason to remove the headers to do it.

If you are interested in a good benchtop unit, perhaps we could talk.

 

[RootesRacer]

What purpose will the O2 sensor server on a non catalytic converter/non-ECU equipped vehicle? Wouldn't an exhaust analyzer serve the pupose better for checking fuel/air mixture?

The Wideband O2 sensor tells you when you have jetted the carb correctly for max power (12.8 to 13.5 AFR on N/A engines).
The catalytic converter doesnt even enter into the argument.
A 5 gas analyzer would certainly be better, but you dont get to drive your car while its being continually sniffed, and more importantly do you own one?

A carbon monoxide measurement really is all you need from the 5 gas, but those are not readily available like a $50 wideband O2 sensor.

 

[MikeH]

The catalytic converter doesnt even enter into the argument.

I understand that now. The use of the "downstream" sensor is only to determine that the cat is working properly (required by emission regs in the US).

Interesting writeup.

http://en.wikipedia.org/wiki/Oxygen_sensor

 

[Bill Blue]

No, but he has a good estimate of the correct time. The man with one watch (and one data point) who thinks he knows what time it is, is a fool.

Wasn't someone recently telling me about the importance of data?

Bill

 

[RootesRacer]

No, but he has a good estimate of the correct time. The man with one watch (and one data point) who thinks he knows what time it is, is a fool.

Wasn't someone recently telling me about the importance of data?

Bill

Estimate not good enough in metrology.

I think you get the point though.

 

[Bill Blue]

Yes, I do. But all measurements are estimates of a true value.

Bill

 

[RootesRacer]

Yes, I do. But all measurements are estimates of a true value.

Bill

Even when one of the readings is wrong?

 

[Bill Blue]

Even when one of the readings is wrong?

What makes you think one (any one) would be right? One watch may be more correct (not as wrong) as the other one, but that is the value of a third watch. If a man that has two watches never knows the correct time, a man with one watch only THINKS he knows the correct time.

Bill

 

[RootesRacer]

What makes you think one (any one) would be right? One watch may be more correct (not as wrong) as the other one, but that is the value of a third watch. If a man that has two watches never knows the correct time, a man with one watch only THINKS he knows the correct time.

Bill

OK you will Bill, I see there is no end to this...

 

[Bill Blue]

OK you will Bill, I see there is no end to this...

A very wise man. It was fun while it lasted.

Bill

 

[Alpine 1789]

I am bring this back up to the top because I am now the owner of a sensor kit and gauge. I am going to have lots of questions once I get it hooked up, but my first challenge is going to be hooking it up. Being basically cheap, I would love to weld the bung in myself, but I'd have to get a different shielding gas tank to be able to weld stainless steel which would cost me more than having it done (there isn't a gas that is good for both stainless and non-stainless, is there?). However, here is what I am thinking, not just because it would be cheap but because it would be easily removable:

I buy a short steel exhaust pipe connector and weld the bung into that. Then, I cut a section off of the stainless steel exhaust pipe where it enters the Bill Atalla header and replace it with the new connector. Rotate the connector so the sensor is at the right angle, add a couple of exhaust clamps, and I am ready to go. If it rusted, who cares? I could just replace it with a new one for a couple of dollars.

Does anyone see a flaw in this plan?

 

[Ken Ellis]

Is there a local muffler shop you trust? Perhaps if you locate and drill the hole, they could correctly weld in the bung for $not-too-much. Plug the hole with a strap-type clamp for the ride over.

A quick run up the lift, zap, drive home in time for tea and crumpets. Doesn't address the removable aspect, but I'm thinking it might be fun to keep an eye on that number.

Ken

 

[Bill Blue]

I'm with Ken on this. For openers, why would you want it to be removable? If the sensor is no longer needed, you can leave the sensor in, replace it with a spark plug (tell others it is part of an afterburner) or buy a plug to fill the hole.

The weld job will probably cost less than the stuff you need to do it yourself.

Bill