O2 Sensors on 496HO??
 

Has anyone successfully installed O2 sensors on the 496HO stock exhaust manofolds?

Thanks!

Re: O2 Sensors on 496HO??
 

Rage,
Why????

Re: O2 Sensors on 496HO??
 

To dial in proper air/fuel ratio when changing to high flow heads, intake manifold and cam so as to prevent detonation.

Re: O2 Sensors on 496HO??
 

O2 sensors arent very common at all in marine applications, they are commonly used on the dyno to tune the motor but thast done with dry exhuast.

Re: O2 Sensors on 496HO??
 

So...you can RE-Tune your ECU with a laptop while you are driving the boat with sofware from who?

Re: O2 Sensors on 496HO??
 

There is no real way to install an O2 sensor on stock 496 manifolds. The problem you will run into is trying to keep it from getting wet. As soon as that wide band gets wet she is usually done working. However, I do it all day long on CMI exhaust. I would think if you are installing new heads you might want to consider getting rid of the old manifolds anyway. That is very smart of you to be worrying about the O2 sensor when replacing heads. What efi system are you using? Thanks Cam-shaft.

Re: O2 Sensors on 496HO??
 

axapowell,


Actually there is no plans to touch the ECU which I prefer to retain as stock. If the A/F ratio is too lean I would increase the fuel pressure and rerun until it comes iton the desired range.

Re: O2 Sensors on 496HO??
 

Cam-shaft,

Thanks for the response. From what I have been reading the wet exhaust did appear to be the main problem for using an O2 sensor with the stock exhaust manifolds.

The ECU is the stock Merc for the 496HO. I am taking the DIY low tech/low cost approach and want to retain the stock exhaust manifolds and all the fail safes built into the Merc ECU unit as well. No dyno time in my future.

Any other way to confirm appropriate A/F ratio other than trying to 'read' the plugs?

Re: O2 Sensors on 496HO??
 

I have yet to see a fuel/air ratio meter that works well, and then to add the whole water thing. Was just wondering if you had a way to reprogram the ECU and who designed the software,

Good luck with the o2 sensors. Like to hear how you make out.

Dave

Re: O2 Sensors on 496HO??
 

Doesn't the stock computer on the 496 have it's own sensor in the exhaust manifolds to make it's own adjustments with air/fuel mixture?

Re: O2 Sensors on 496HO??
 

No those are temp sensors in the manifolds, not 02.

Re: O2 Sensors on 496HO??
 

What are there purpose then? Do they sense a higher temp when running lean and add more fuel? Or do do they do something completely different?

Re: O2 Sensors on 496HO??
 

I dont beleive they have anything to with running parmeters they onl effect the guardian system, becuase it is closed cooling you would't know if you lost a se pump for a couple minutes and this way you know pretty quick.

Re: O2 Sensors on 496HO??
 

ok, just wondering.

Re: O2 Sensors on 496HO??
 

axapowell,

Thanks, but it looks like the O2 sensors on my set up is a non starter. Probablty just as well given the reliability issue you describe.

Re: O2 Sensors on 496HO??
 

You may also be able to change to larger fuel injectors at the same fuel pressure to accomodate the increase in airflow. The computer wouldn't know what size the injector actually only sending pulsewidth instructions based upon the program of the computer.

Re: O2 Sensors on 496HO??
 

Looks like round two on the O2 idea.

I think the O2 stops at the end of the boat ramp....It's in my truck :D :D :D

Re: O2 Sensors on 496HO??
 

It's easy, remove a riser, drill a hole approx. 1" above flange on the outer side of riser. Use a stainless bung, which you can get from Imco, CMI, etc. with a step in it. Weld the outside, then weld the inside. You will need to repowdercoat or paint the riser. I've done it quite a few times, very easy to do. Always replace gaskets when removing so you ensure no leaks.

Thanks,
Dustin

Re: O2 Sensors on 496HO??
 

Dustin,

Thanks for the guidance!

So on the stock Mercruiser risers you install a SS bung for the O2 sensor that will pass through the water jacket and is welded on the inside tube and the outside tube located one inch above the flange? Very good!

Any suggestions on what O2 sensor monitouring equipment to purchase/use for this kind of onboard testing that will work but not break the bank?

Re: O2 Sensors on 496HO??
 

Dustin,

Which gauge do you use? The ones I've seen just look like a disco light moving up and down.

How do you weld inside the riser(pipe) to assure a good seal. Seems like tight quarters to get it right.

Dave

Re: O2 Sensors on 496HO??
 

Dustin,

I looked up the SS O2 sensor bungs. They are not very tall. If this thickness of bung is used to bridge the distance between the inner and out walls of the riser it would seem that the bung would end up essentially flush with the inner and outer walls of the riser when welded so as to seal the water jacket. Is that the case or is there a taller/longer SS bung that must be used?

Re: O2 Sensors on 496HO??
 

Like what Dustin said or you could drill the hole in the top layer (don't go all the way thru) a little bigger than the one on the inside layer then set your bung in and weld the inside layer first then fill in the the outside layer. I have some ss o2 bungs that are about 1/2 inch tall If you need some.

Re: O2 Sensors on 496HO??
 

muffman,

Yes I need two ssO2 bungs (and two ss plugs for the bungs as well). Let me know how to proceed.

Thanks,

[email protected]

Re: O2 Sensors on 496HO??
 

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

Re: O2 Sensors on 496HO??
 

You could forget about the o2 sensor and dial in with your exhaust temp
You will still need to weld bungs in so you can insert your thermocouple.
you can use a hand held fluke that has to be a hellavu better than comparable guages that are out there.
Jr.

Re: O2 Sensors on 496HO??
 

J-Bonz,

Have you done this?

What is the step by step procedure to dial in using exhaust manifold temperature?

Thanks!

Re: O2 Sensors on 496HO??
 

Exhaust temp and CO coincide. As your temp goes up, your afr goes down.
It would have been best to gather your before data from you original setup, but its to late for that. What you need to figure out is your exhaust temps when u run to lean and to rich. These i dont know right off hand but, I beleive any repitable full time engine/dyno man could tell ya right of the top of there head. You should take some caution though since your dealing with efi, I am not up to date on how the 496 operates, especially choke mode. Ask AKA hillbilly for this knowledge, the dude knows his Sh*t.
I hope this helps,
Jr

Re: O2 Sensors on 496HO??
 

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

Re: O2 Sensors on 496HO??
 

I has also used this set up, nice piece
http://www.innovatemotorsports.com/x...cat=252&page=1

Re: O2 Sensors on 496HO??
 

A/F sensor (wide band) is the only way to go. they are good from λ=.7 to λ=2.2 a Duel stage O2 is only accurate from λ=.9 to λ=1.05

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.

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.

Re: O2 Sensors on 496HO??
 

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?

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.

Re: O2 Sensors on 496HO??
 

Sorry, the diagram i was reffering to is plotting adiabatic flame temp vs. A/F

Re: O2 Sensors on 496HO??
 

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!

Re: O2 Sensors on 496HO??
 

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!

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.

Re: O2 Sensors on 496HO??
 

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!