locating an O2 sensor in a side pipe

[eschaider]

Very likely true, Mike. The downward angling is both a road debris issue and also a water issue. It turns out the water is less a flow of liquid in but rather a collection without escape provisions of vapor condensate in the sensor prior to coming up to temperature, ie startup.

With the sensor angled downward the condensate collects in the inside of the sensor instead of runing out to the exhaust. It is that collection of condensate as it is being warmed up that ultimately kills the sensor. While they work at 4 o'clock or 8 o'clock they have a longer service life and drift less with the sensor probe end angled slightly downward to allow condensate to be pulled out by gravity.


Ed

[ERA 626]

Originally Posted by eschaider

Very likely true, Mike. The downward angling is both a road debris issue and also a water issue. It turns out the water is less a flow of liquid in but rather a collection without escape provisions of vapor condensate in the sensor prior to coming up to temperature, ie startup.

With the sensor angled downward the condensate collects in the inside of the sensor instead of runing out to the exhaust. It is that collection of condensate as it is being warmed up that ultimately kills the sensor. While they work at 4 o'clock or 8 o'clock they have a longer service life and drift less with the sensor probe end angled slightly downward to allow condensate to be pulled out by gravity.


Ed

When mounting the sensor on the side pipe it will look horrible facing down at 1:00 or 11:00 if not impossible.

[eschaider]

Originally Posted by ERA 626

When mounting the sensor on the side pipe it will look horrible facing down at 1:00 or 11:00 if not impossible.

You want the end of the sensor internal to the side pipe facing down to drain condensate. That puts the sensor and all it's wiring higher up and potentially a little safer from road debris impact.

My personal preference is not to mount the sensor in the side pipe collector at all. It is too far from the exhaust port for a timely reporting of the exhaust oxygen content necessary to correctly calculate injector pulse widths.

This is why I like the inch or so thick internally open square stainless block sandwiched between the side pipes and the headers. The sensor is safe, the location is in the 12 to 18 inch sensor sweet spot, in terms of distance from the exhaust port, and there are no funky looking electronics connections dangling in the air outside the car around the side pipes.


Ed

[eschaider]

Originally Posted by olddog

I would have guessed Laughing gas and blown as my second guess.

Back in 89 to 93 years, Ford commanded about a 10:1 AFR at WOT. Chip makers were commanding 12:1 AFR and getting about 30 Hp gain. They stated must use premium fuel with the chip installed. Those who didn't read and head often ended up with pistons like you pictured.

In the ovoid detonation world of tuning, pulling timing or going rich is the only tools. Timing kills more Hp than going richer. Obviously fuel and combustion chamber matter but the tuner has no control over those. My guess is that the tuner tuned the engine with a good premium fuel and the owner bought low octane fuel. He didn't hear a ping and thought he got away with it, and he did for a while. Now he thinks it was the tunner's fault. The tuners should make you sign a paper acknowledging that you were warned that you must run a premium fuel.

You're pretty close to the mark, Rick. If I remember correctly the tune commanded a 12:1 AFR on 93 octane E10. A supercharged car will normally want an 11.8:1 AFR on pure 93 octane with moderate timing. The timing was not that wild on this engine, I want to say it was 18 degrees IIRC. For those unfamiliar with these small bore Modulars, 21 to 23 degrees is a lot of advance.

When you go to E10 the equivalent AFR for the change in stoich point becomes 11.08:1 which puts the 12:1 AFR out in a patch in the back 40 that is getting progressively leaner. This particular whoops occurred well over ten years ago so a lot of the 'tuners' at that time were just getting their sea legs and some of their customers were paying for those legs.

Your point about fuel choices is absolutely spot on, Rick. If you take your car to be tuned on whatever fuel. Be prepared to run that fuel all the time or you are putting your 'stuff' at unnecessary risk.


Ed

[maui]

Originally Posted by eschaider

You want the end of the sensor internal to the side pipe facing down to drain condensate. That puts the sensor and all it's wiring higher up and potentially a little safer from road debris impact.

My personal preference is not to mount the sensor in the side pipe collector at all. It is too far from the exhaust port for a timely reporting of the exhaust oxygen content necessary to correctly calculate injector pulse widths.

This is why I like the inch or so thick internally open square stainless block sandwiched between the side pipes and the headers. The sensor is safe, the location is in the 12 to 18 inch sensor sweet spot, in terms of distance from the exhaust port, and there are no funky looking electronics connections dangling in the air outside the car around the side pipes.


Ed

does your stainless steel sensor concept have all four primaries going into it then returning to four primaries again pre-collector or are you thinking one primary tube reading?

[eschaider]

It is just a square stainless block with the same bolt pattern and external dims as the SPF flange and fits between the header and the sidepipes. The entire center of the block is cut out to provide one large cavity. You need to move the header flange back on the header a distance equal to the thickness of the block you decide to use. Place your O2 bung in the block at 3,9,or 12 o'clock, wherever it works best for you.

Once the exhaust leaves the header pipe it enters the square cavity in your stainless block, between the header and the sidepipe flange, where I am sure there is a lot of mixing going on. The sensor detects and reports whatever O2 content it finds to your ECU for injector pulse width calculations to meet your target AFR. The exhaust gas exits through which ever side pipe tube it is nearest to. No fancy science here just a simple way to plumb an O2 sensor, keep it 12 to 18 inches from the exhaust port, protect it from road debris and positioned so as to minimize the condensation of water in the sensor after initial startup.


Ed

[Dominik]

Originally Posted by olddog

There is more, but I doubt you want to know, and I'm too lazy to type it all.

:-)

On a side note, Rochester had Oxygen Sensors for leaded fuel in the 90s. Mainly for the South American market. They lasted 40.000 mls.

They may be beneficial for all sorts of fuel run in our cars.

[maui]

Originally Posted by eschaider

It is just a square stainless block with the same bolt pattern and external dims as the SPF flange and fits between the header and the sidepipes. The entire center of the block is cut out to provide one large cavity. You need to move the header flange back on the header a distance equal to the thickness of the block you decide to use. Place your O2 bung in the block at 3,9,or 12 o'clock, wherever it works best for you.

Once the exhaust leaves the header pipe it enters the square cavity in your stainless block, between the header and the sidepipe flange, where I am sure there is a lot of mixing going on. The sensor detects and reports whatever O2 content it finds to your ECU for injector pulse width calculations to meet your target AFR. The exhaust gas exits through which ever side pipe tube it is nearest to. No fancy science here just a simple way to plumb an O2 sensor, keep it 12 to 18 inches from the exhaust port, protect it from road debris and positioned so as to minimize the condensation of water in the sensor after initial startup.


Ed

Ed, thanks for the clarification. I appreciate your time in responding.

Jeff

[Gaz64]

Originally Posted by Dominik

:-)

On a side note, Rochester had Oxygen Sensors for leaded fuel in the 90s. Mainly for the South American market. They lasted 40.000 mls.

They may be beneficial for all sorts of fuel run in our cars.

Except they are 1 wire narrow band.

Inaccurate either side of stoic.

Why run a 1 wire, when we can have accuracy within 0.1 with a wide band sensor.

[Luce]

I made a pocket about 1" x 2" that the sensor screws into, at about 3 oclock, parallel to the side pipe. It' held on for 17000 miles.

[Shizznizz]

Never saw this thread until now.. but here it goes
I got a backdraft with EFI, got Innovate LC2 widebands in both banks (left and right exhaust, on the outside of the bodywork just past the 90deg bend).

My first sensors failed quickly, but I realised I made a wiring mistake that a lot of people make/have by their supplier.
The 4-oclock position isn't ideal, because condensation of exhaust gasses (that contain loads of H2O) will collect there.
The trick is, to NEVER heat up the wideband sensor before the motor is running. So if you power-on your sensor and controllor with key-on (as I had before) it will get hot with the water droplets hitting it, thermal shock breaking the ceramic element.

Now I have it wired in with my fuel pump relay. Only when the motor is running, will the element start warming up. Because of the exhaust gas temperatures racing through the pipe, the moisture is evaporated in paralel to the sensor warming up, and i've been enjoying my sensors with no issues ever since.

[Andheeezonit]

Does anyone have experience with putting the O2 sensors in the end of the side pipes on a temporary basis just to tune the car? My Weber setup is pretty good but I know it could be better. I would like to try this to see exactly where my AFR is, and the products are available. Thanks.

[eschaider]

You will get ambient air backwash which will affect the accuracy of the O2 measurement the sensor is trying to perform.


Ed

[Gaz64]

Originally Posted by Andheeezonit

Does anyone have experience with putting the O2 sensors in the end of the side pipes on a temporary basis just to tune the car? My Weber setup is pretty good but I know it could be better. I would like to try this to see exactly where my AFR is, and the products are available. Thanks.

You will get lean readings since the O2 sensors would see ambient air.
They need to be near the engine, closer than halfway along the system, preferably at the exhaust collector.

[Andheeezonit]

Thanks for the knowledge. Tech at FAST confirms your advice, says may read leaner than actual by up to one full point. I’ve been told the Webers like to be a little rich so this could work out. I just don’t want to tear back down and drill, weld, and re coat the exhaust.

[CoyoteCobra]

I placed my sensors on the collectors on each side. I also have bungs welded into 1, 4, 5, and 8 in case I needed to move them but for the first try I went on the collectors to get a reading from the whole bank vs. just off of a single cyl on each side.

The response times at idle were a minor issue during the datalog with the sensors in the collectors. I did not notice any stumbling, rich smelling exhaust, etc. but the the tuner said in the datalog he could see an issue. He had to make some adjustments for when the engine is at idle to slow the responses and keep it from spiking back and forth. The last log came out clean.

Another thing to consider, outside of just the HEGO placement is the length of your intake track. If the MAF is too close you can get pulsation in the sensors readings, but if the MAF is too far away you get too sluggish of a response. There's a balance to strike so your FTs and response don't get screwed up.