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O2 Sensors on 496HO??

Old 12-04-2005, 11:42 PM
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Default Re: O2 Sensors on 496HO??

Dustin,

hey, you now your stuff. I was waiting for a good reply

"If you can get an accurate wide range a/f meter, you would be wasting your time measuring exhaust temp. First, you would be looking at the average of 4 cylinders unless you go to one cylinder or all, next if your not data logging and have accurate sensors, then the numbers are not accurate enough to do much with unless you have a prior baseline."

I agree with ya. I wrote and posted it and then thought twice. That really isnt a good idea to run "8" thermos to try to gather info on your A/F in a boat. But on a test stand It is good secondary info if your running a data aq. I also agree if you dont have a baseline prior, you preaty much have no where to go.

"Next, temp will vary with spark advance as well, so depending on the load based table of the 496, it may very, then you have cylinder to cylinder timing which will retard/advance in certain cylinders during knock and occassional AE, again changing your numbers.

As for EGT's going up while afr goes down, that would only happen if your getting raw fuel burnt in the pipe or you have a very inefficient cylinder such as low compression with low air flow. Otherwise, your going to get you hottest readings at 14.7:1, after that, it will actually cool down as you get leaner. If your richer, it will cool down as well.."

THis is some good info. I have only dealt with steady state testing small engines. As far as 14.7:1, is that when you running stochiometric. If so, then plotiing on a T-S diagram does agree with excactly with what you are saying. Then it does make sense when running fat, your not at stoich. and yuor exhaust temps are low and CO is high. when you start leaning to stoich. exhaust temps go up and CO goes down

"Stock NA motors, cast iron heads, with 91 octane fuel should run around 12.5:1 for peak HP and reliability. With aluminum heads, I like 12.8:1. If a motor gets close to detonation, then you have to richen the motor and or modify timing. There's usually a balance where you can get more power with timing and slightly richer air fuels than leaner air fuels and lower timing. The leaner you are, the more dependent you are on temperature variation, whether it's engine temp, outside air temp, etc.

Dustin"

As far as running A/F meter I tthought the sensors hated moisture?

Thanks for the schooling
Jack Jr.
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Old 12-05-2005, 09:16 AM
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Default Re: O2 Sensors on 496HO??

All (wide band or duel state) Oxygen sensors will be come thermo-shocked if you hit them with water(you can tell this has happened to a duel state when it starts to give a negative voltage signal). An Oxygen sensor measures the amount of oxygen in the exhaust stream. If you have water that has turned to steam you now have some extra oxygen molecules in there that will skew your readings.
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Old 12-05-2005, 10:36 AM
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Default Re: O2 Sensors on 496HO??

Originally Posted by Mike&Paula
All (wide band or duel state) Oxygen sensors will be come thermo-shocked if you hit them with water(you can tell this has happened to a duel state when it starts to give a negative voltage signal). An Oxygen sensor measures the amount of oxygen in the exhaust stream. If you have water that has turned to steam you now have some extra oxygen molecules in there that will skew your readings.

Then the only way to run on in a marine application is when you run dry stackw aterjacketed all the way out to the stern?
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Old 12-05-2005, 11:23 AM
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Default Re: O2 Sensors on 496HO??

Here is some of the info about O2 from my Basic Engine Management power point that I have put together. Remember an O2 is nothing more than a galvanic battery. What it is trying to due is balance out the Oxygen from the reference air to the exhaust. That (oxygen) ion movement across the ceramic (the magic part) is what crates the voltage.

Duel state
Operates under Nernst Effect Concept :
• Requires Exhaust gas temp to be 325-350C
• At high temperatures, the ceramic (electrolyte) displays electrical conductivity
• Voltage is produced at the sensor’s electrical connections

Sensor produces a high voltage (600mV - 1000mV) when λ < 1 (rich)
• Low oxygen content on exhaust gas electrode
• High oxygen content on reference air electrode

Sensor produces a low voltage (0mV - 300mV) when λ > 1 (lean)
• High oxygen content on exhaust gas electrode
• High oxygen content on reference air electrode

Wide band
• Sensor is used across a very extensive range to determine the oxygen concentration in the exhaust gas
• Broad-band Lambda sensors are capable of precise measurements of the air fuel mixture in the range from 0.7 < l
• These sensors generate an unmistakable, continuous electrical signal
• Heater is pulse-width modulated
• Sensor is operational within 20 seconds
• Operating temperature is 700° - 800° C (1292° - 1472° F)
• Current is applied to oxygen-pump cell to keep Nernst cell at a constant 450mV output
• λ > 1, positive current is needed to pump oxygen out of diffusion gap (Lean)
• λ < 1, negative current is needed to pump oxygen into diffusion gap (Rich)
In other words we control a wide band at .450mV and monitor the amount of current need to add (rich) or take away (lean)to mantain 450mV.

Last edited by Mike&Paula; 12-06-2005 at 10:36 AM.
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Old 12-05-2005, 02:27 PM
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Default Re: O2 Sensors on 496HO??

Originally Posted by J-Bonz
Dustin,

hey, you now your stuff. I was waiting for a good reply

"If you can get an accurate wide range a/f meter, you would be wasting your time measuring exhaust temp. First, you would be looking at the average of 4 cylinders unless you go to one cylinder or all, next if your not data logging and have accurate sensors, then the numbers are not accurate enough to do much with unless you have a prior baseline."

I agree with ya. I wrote and posted it and then thought twice. That really isnt a good idea to run "8" thermos to try to gather info on your A/F in a boat. But on a test stand It is good secondary info if your running a data aq. I also agree if you dont have a baseline prior, you preaty much have no where to go.

"Next, temp will vary with spark advance as well, so depending on the load based table of the 496, it may very, then you have cylinder to cylinder timing which will retard/advance in certain cylinders during knock and occassional AE, again changing your numbers.

As for EGT's going up while afr goes down, that would only happen if your getting raw fuel burnt in the pipe or you have a very inefficient cylinder such as low compression with low air flow. Otherwise, your going to get you hottest readings at 14.7:1, after that, it will actually cool down as you get leaner. If your richer, it will cool down as well.."

THis is some good info. I have only dealt with steady state testing small engines. As far as 14.7:1, is that when you running stochiometric. If so, then plotiing on a T-S diagram does agree with excactly with what you are saying. Then it does make sense when running fat, your not at stoich. and yuor exhaust temps are low and CO is high. when you start leaning to stoich. exhaust temps go up and CO goes down

"Stock NA motors, cast iron heads, with 91 octane fuel should run around 12.5:1 for peak HP and reliability. With aluminum heads, I like 12.8:1. If a motor gets close to detonation, then you have to richen the motor and or modify timing. There's usually a balance where you can get more power with timing and slightly richer air fuels than leaner air fuels and lower timing. The leaner you are, the more dependent you are on temperature variation, whether it's engine temp, outside air temp, etc.

Dustin"

As far as running A/F meter I tthought the sensors hated moisture?

Thanks for the schooling
Jack Jr.




Sorry, the diagram i was reffering to is plotting adiabatic flame temp vs. A/F
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Old 12-05-2005, 10:29 PM
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Default Re: O2 Sensors on 496HO??

Originally Posted by Whipple Charged
If you can get an accurate wide range a/f meter, you would be wasting your time measuring exhaust temp. First, you would be looking at the average of 4 cylinders unless you go to one cylinder or all, next if your not data logging and have accurate sensors, then the numbers are not accurate enough to do much with unless you have a prior baseline. Next, temp will vary with spark advance as well, so depending on the load based table of the 496, it may very, then you have cylinder to cylinder timing which will retard/advance in certain cylinders during knock and occassional AE, again changing your numbers.

As for EGT's going up while afr goes down, that would only happen if your getting raw fuel burnt in the pipe or you have a very inefficient cylinder such as low compression with low air flow. Otherwise, your going to get you hottest readings at 14.7:1, after that, it will actually cool down as you get leaner. If your richer, it will cool down as well.

Stock NA motors, cast iron heads, with 91 octane fuel should run around 12.5:1 for peak HP and reliability. With aluminum heads, I like 12.8:1. If a motor gets close to detonation, then you have to richen the motor and or modify timing. There's usually a balance where you can get more power with timing and slightly richer air fuels than leaner air fuels and lower timing. The leaner you are, the more dependent you are on temperature variation, whether it's engine temp, outside air temp, etc.

Dustin
Dustin,

Thanks for the excellent clarification.

If instead of 91 octain fuel what would be your F/A ratio recomendation for a stock NA motor for peak HP and reliability with 87 octain, iron heads and stock Merc 496HO timing of 28 degrees maximum?

Thanks!
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Old 12-07-2005, 02:25 PM
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Default Re: O2 Sensors on 496HO??

Originally Posted by bobl
Buy the LM-1 from Innovate. I've been using it for several years. I won't tune an engine without it anymore.

www.innovatemotorsports.com
bobl,

Is it feasible to properly tune a motor using the LM-1 with the motor in the boat running on the water or do you have to always take it out and to a dyno test lab?

Thanks!
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Old 12-07-2005, 03:23 PM
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Default Re: O2 Sensors on 496HO??

Rage, yes it is better to tune on the water. The Dyno cannot simulate the various load & conditions you encounter in the boat. I just hook up the LM1 and document the A/F ratio throughout the operating range. Ironically I was testing a boat yesterday and got some water on my 02 sensor and killed it. He had lightning headers with an 02 bung very near the end of the collector, so water reverted back and hit it. That's the first time I've destroyed a sensor.
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Old 12-07-2005, 05:02 PM
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Default Re: O2 Sensors on 496HO??

Originally Posted by bobl
Rage, yes it is better to tune on the water. The Dyno cannot simulate the various load & conditions you encounter in the boat. I just hook up the LM1 and document the A/F ratio throughout the operating range. Ironically I was testing a boat yesterday and got some water on my 02 sensor and killed it. He had lightning headers with an 02 bung very near the end of the collector, so water reverted back and hit it. That's the first time I've destroyed a sensor.
bobl,

It's good to hear that I can do this on the water.

You say 'through the operating range'. Can you share the step by step process you use to tune a motor with a new setup (heads, cam, exhaust, etc.) on the water? i.e run and hold while recording at 1000 rpms, then 1500 rpms then 2000 rpms, etc. or other? Some times at 3000 rpms lets say you are cruising light load and other times pulling a wake boarder with a boat full of people, do you need to try to recreate all expected conditions or does one cookie cutter test formate cover it all?

I assume you have the unit that records the engine rpm as well. Do you need additional data input to reference as well for tuning?

When you see in the data a need to change the A/F what typically do you do then? Injector pulse width? Fuel pressure change?

Thanks for the help as always!
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