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Discussion Starter #1
I've read that the 02 sensors need to be within 15" of the port to get sufficient heat to operate. Also that they should be in a place where they can sample exhaust from all the cylinders on a side.

Can't do both with long tubes! What to do? Do the heated sensors cancel the problem of putting them in long tubes collectors and being too far away from the heads and so not hot enuf?
 

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If you have ceramic coated headers, which retain heat in the exhaust, I would think you would be fine to put the 02 in the collector....

talking out of my ass though

I have MAC 1 5/8 shorties...which leak...and I want BBK LT's but don't have the money...
 

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My BBK long tubes had the O2 sensor bungs right before the collector, came like that from BBK.
 

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I keep hearing this and I know it's true they must reach a certain temp. 600 dg I do believe? Anyhow I have MAC LTs and the sensors come in after the collector (needed extension wires). I am also using a 195 dg thermostat right now so the engine hits normal operating temp.
I have never taken an actual reading but I know this. I average 22-24 MPG on the highway so I know they are working.
 

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As most long tubes my O2s are at the collector. It just takes them a touch longer to operating properly. When the car is cold it just stumbles a 'touch' more than usual. Nothing major, sounds like the cam is bigger than it is for the first 5 minutes or so
 

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1-5/8" LT's, ceramic coated, O2's in the collector.
No stumble/surge/hunting on start-up... or ever...
 

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st515O said:
Our O2 senesors have built in heaters. Don't listen to the hype. Install long tubes and enjoy them like the rest of us.
Not so fast...I'm almost positive that the heaters in the O2 sensors only work on startup, not on closed-loop, so after a couple minutes they might as well not be heated and with some combos they don't STAY hot enough to work properly. I've heard this from people who know a ****load more about this stuff than I do so I believe it, and then couple that with knowing about the countless people who've had O2-related driveability issues after installing longtubes and there's got to be something there. The confusing thing is it only strikes some people and I haven't seen the pattern as to why but if *I* were installing longtubes with the sensor in the collector I would ceramic-coat them.

Now the thing about having to sample the gases from all cylinders is not all that important IMHO. I don't think the cylinder-to-cylinder variations are going to be large at all, as long as the injectors all work properly, certainly not as bad as the variations in a carbureted car with its runners all different lengths. So I would not worry at all about having the sensor in a primary unless I was doing a ragged-edge engine and if that were the case I'd probably want to sample each primary individually anyway.
 

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good point MFE

the heaters are there just so the 02's start operating more quickely. I think it is quite possible that the heaters shut off after a few minutes....
 

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MFE-- I can't count the number of local Mustangs, both 5.O and 4.6's around here that have long tubes and no O2 sensor heating problems. I wrote it off as another internet folk lore that doesn't exist here in California ;)


Are you sure the heaters are only durring warm up??? I could have sworn the heater wire is connected to the positive switched iginition wire.
 

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In regards to the heaters, that's only on SN95s and up, correct? The older fox body O2s don't have heaters, I don't think. Do they?
 

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st515O said:
Are you sure the heaters are only durring warm up???
No, I'm not sure, but I believe it to be true and would welcome proof either way.
 

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91fiveoh said:
In regards to the heaters, that's only on SN95s and up, correct? The older fox body O2s don't have heaters, I don't think. Do they?
Not sure about that either. They're often referred to as HEGO's (Heated Exhaust Gas Oxygen) sensors but I thought that only the 4-wire sensors were heated and I think the Fox-bodies are 3-wire. But I'm reaaaallly foggy on that. I can't recall what the wires are. IIRC one is power, one is signal return, and the third is either ground or heater. If it's ground, then the 4th wire on a 4-wire is heater.
 

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I bought new O2 sensors from Auto Zone with the longest leads. Drove the car to Lidio www.alternativeauto.com for a custom chip for the 42# and S-trim... and he programmed it not to use them. DOH! (so I sold them thru the classifieds as near new, with 40 miles)
 

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The O2 sensors are powered from the ignition switch and I am not aware of any timing device to turn the power off. The heaters however are not sufficient to run the sensors without proper heat levels from the exhaust stream - they are there to get the sensors up to temp quicker.

The stockers are in the 15-16" range from the head, so that is a good length to shoot for. Ceramic coating will most certainly help keep temps up. The EEC has a O2 sample timing table in it to time the O2 samples to coincide with the exhaust pulse arrival.

Some guys do not have problems with LTs and others do. One guy I know who did bought the TwEECer RT and went into the timing table and extended the sample timing to match his LT needs. It seems to be a hit or miss deal.
 

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Discussion Starter #18
Certified Ford expert answer

Thanks for all the input!

I took a chance and emailed Ron at www.ronmorrisperformance.com (trained, certified Ford efi and eec tech) who specializes in Ford efi into older vehicles. He was good enuf to answer. He says the sensors are heated, so put them in the collectors. He has a very informative website and a number of specialized parts for efi related issues.
 

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I proved that they are heated on my car (91 gt) by leaving them hanging from the harness and starting the car. They got very warm quite quickely. But I really doubt that the heaters alone can heat the 02's to 600+ degrees, where they need to be to operate correctly.

It takes a lot of current to make the same heat as an open flame.
 
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