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Author Topic: wideband O2 sensor q's  (Read 25207 times)
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fordboy628
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« Reply #30 on: September 15, 2015, 06:20:36 AM »

At the risk of parroting Sister "Godzilla", parochial principal from my youth:

"Do your homework."

Accurate measuring and/or testing devices are the "backbone" of "good science".    Accuracy requires calibration, sometimes constantly, sometimes occasionally.

Just do it.

 cheers
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« Reply #31 on: September 15, 2015, 11:13:51 AM »

.... Big deal, calibrating 2 sensors is far easier than pulling 8 plugs 3 times a weekend. ....

I agree, calibration is simple and only takes a couple minutes.  Remove the sensor from the pipe, disconnect the plug going to it, turn on the power to the sensor for less than a minute, turn it off, reconnect it using the plug and turn it back on and in a minute or so it is re-calibrated correctly to the free air at the time compensating for altitude and it is also now re-calibrated for any wear the sensor has experienced.



For about $150 you have the sensor, the gauge and the wideband O2 controller all in one unit.  You can also easily customize the LED's that ring the gauge face to turn from green to yellow to red at any air/fuel mixtures you so desire and it is compatible with all fuels and it will interface with most data-loggers,

Sumner


« Last Edit: September 15, 2015, 11:18:41 AM by Sumner » Logged

Steve Cole
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« Reply #32 on: September 15, 2015, 11:35:55 AM »

Guys, your still skipping over the exhaust pressure issue and the other corrections. Yes, the Innovate still does not correct for these issues, even when you remove the Bosch sensor from the pipe and calibrate it for free air and altitude. I'm only letting you know and you can find it all by reading the Bosch specifications sheets. It's all up to you what you do with the information but please do not go at it blindly and ignore it as it's all there in black and white.

There are plenty of others that allow for free air calibration as well so it's not something that Innovate came up with, nor does it solve the correction issues for them either. The only one that I know of today is the unit in the link I gave you all before.
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« Reply #33 on: September 15, 2015, 12:36:06 PM »

....your still skipping over the exhaust pressure issue and the other corrections....

So exactly how much do those effect the reading?  I'm having a hard time understanding the graph you posted.  To me it looks like at say 5000 feet they might effect the reading by less than 1/2 of a tenth of a point and if the Innovate can compensate to the free air at 5000 feet then it might be less than that.

If that is the case for our situation and considering we can afford the Innovate it is well worth using it as it easily works with all the other items we are data-logging at the same time,

Sumner

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« Reply #34 on: September 15, 2015, 01:52:48 PM »

Exactly!  If you look at the chart; the difference in AFR from Los Angles (sea level) to Bonneville (4,200 ft) is 0.06 AFR! Using 1 bar (sea level) the AFR is 13.24. Go to 4,200ft and the AFR becomes 13.18.

The most serious delta P to consider is a blown application where the pressure can be 2 or 3 bar. A situation where one is hardly relying on just a single sensor to aid in tuning. EGT and plugs are still the important tools in the quiver.
« Last Edit: September 15, 2015, 01:55:08 PM by Saltfever » Logged
NathanStewart
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« Reply #35 on: September 15, 2015, 02:20:18 PM »

Exhaust back pressure?  What exhaust back pressure?  Aren't these race vehicles with unrestricted, open exhausts?  Unless the sensors are pre-turbo, you don't really need to worry about exhaust back pressure unless you've got some kind of restriction which I'm guessing most race vehicles won't have.  Now, if going pre-turbo, you'd probably want something like THIS.
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« Reply #36 on: September 15, 2015, 04:36:38 PM »

Exhaust back pressure?  What exhaust back pressure?  Aren't these race vehicles with unrestricted, open exhausts?  Unless the sensors are pre-turbo, you don't really need to worry about exhaust back pressure unless you've got some kind of restriction which I'm guessing most race vehicles won't have.  Now, if going pre-turbo, you'd probably want something like THIS.

This is a very incorrect assumption. We are dealing in Absolute pressure, not gauge pressure here. For those of you that may not know or understand the difference, Absolute pressure is Baro + measure pressure, so that means as you change in altitude you move from one line to another as well as side to side on the chart I provided. So if you connect a gauge to the exhaust and watch the exhaust pulse come down a pipe you are going to see a pressure increase each time the pulse travels down the pipe and thats what you need to know, the absolute pressure when the sensor is read.

Each line on the chart I made for you all, is a different altitude and you follow the curve of the line based on absolute exhaust pressure. You would have to measure your system to see what you have at the location of your sensor but it is not uncommon to see +/- 0.5 bar pressure changes on a open exhaust and that will rise as engine speed and volume increase. So based on the total power output you will and do get different readings. So what you read at say 2000 RPM versus what you read at 8000 RPM can and will have completely different correction facts needed to get an accurate readings.

Also remember what I told you all before, and that is the curve I did was for 13.23 AFR ONLY! As the mixture goes richer the curves change and the amount of mixture change gets greater and greater. As the mixture goes leaner the curves get smaller too, so as you get back to a 14.68 mixture there is next to no curve at all and the correction there really doesn't much matter. Now as you go leaner than 14.68 it all starts back the other direction again but I did not think any of you would much care about the Lean burn side of things. The range of error at a fixed altitude is going to be about 0.63 AFR if you use the whole chart at a mixture ratio of 13.23. That gets greater as you run richer mixtures and smaller as you run leaner mixture up to 14.68.

For the record I am not saying do not use one, what I am saying is understand the tool and what it can and cannot do! I've seen to many people burned by a meter that they believed to be correct and did not understand why they burned a piston when the data told them the mixture was fine.
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« Reply #37 on: September 15, 2015, 04:43:19 PM »

Pre-turbine is an extremely poor installation because of  extreme heat and pressure. You would never design such a system unless there was an unusual and compelling reason. The Bosch sensor body temp can never exceed 950 deg F. Pre-turbine temps range 1200-1400 F and pressures are 1-2 bar. That is a fatal environment for any Nertz cell. The WB is installed downstream of all that mess so it can live and give reasonably good AFR.
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« Reply #38 on: September 15, 2015, 11:51:54 PM »

Pre-turbine is an extremely poor installation because of  extreme heat and pressure. You would never design such a system unless there was an unusual and compelling reason. The Bosch sensor body temp can never exceed 950 deg F. Pre-turbine temps range 1200-1400 F and pressures are 1-2 bar. That is a fatal environment for any Nertz cell. The WB is installed downstream of all that mess so it can live and give reasonably good AFR.

I run 6 Bosch O2 sensors pre-turbine on our roadster because that way I can see the individual cylinder AFR's and trim accordingly. The max continuous exhaust gas temp allowed is 930C (1700F) and I am below that. The measured back pressure is almost 370kPa and it is compensated for by my controller. I compare those 6 sensors with a 7th one in the downpipe for a sanity check. That one runs in normal pressure and quite a bit cooler than the individual cylinder units. Those individual cylinder sensors are now all going on their 3rd season. The 7th one is new this season because I dropped it ( tongue) and didn't want to risk running it again. The new one reads the same as the old one did.

Our motors don't burn oil and we haven't lifted a head so the sensors are still fine. If we lose an engine I expect to change them all. It's pretty simple really.
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NathanStewart
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« Reply #39 on: September 16, 2015, 10:04:37 AM »

Exhaust back pressure?  What exhaust back pressure?  Aren't these race vehicles with unrestricted, open exhausts?  Unless the sensors are pre-turbo, you don't really need to worry about exhaust back pressure unless you've got some kind of restriction which I'm guessing most race vehicles won't have.  Now, if going pre-turbo, you'd probably want something like THIS.
This is a very incorrect assumption. We are dealing in Absolute pressure, not gauge pressure here. For those of you that may not know or understand the difference, Absolute pressure is Baro + measure pressure, so that means as you change in altitude you move from one line to another as well as side to side on the chart I provided. So if you connect a gauge to the exhaust and watch the exhaust pulse come down a pipe you are going to see a pressure increase each time the pulse travels down the pipe and thats what you need to know, the absolute pressure when the sensor is read.

Each line on the chart I made for you all, is a different altitude and you follow the curve of the line based on absolute exhaust pressure. You would have to measure your system to see what you have at the location of your sensor but it is not uncommon to see +/- 0.5 bar pressure changes on a open exhaust and that will rise as engine speed and volume increase. So based on the total power output you will and do get different readings. So what you read at say 2000 RPM versus what you read at 8000 RPM can and will have completely different correction facts needed to get an accurate readings.

Changes in elevation and changes in exhaust pressure aren't the same thing as your chart shows.  Unless you're racing up Pikes Peak, one can generally assume elevation changes are fairly minimal thus the impact on measure AFR variance is pretty small.  Also, a change in exhaust pressure from 2000 rpm to 8000 rpm isn't really all that significant when you're racing at WOT for extended periods of time.  The point being that exhaust pressure is largely the same (and I've personally never seen an EBP of 7psi on an open exhaust) when you care to look at it which is at high rpm, high power, high exhaust flow and not at idle.  So your measured AFR changed by a tenth of a point at most between idle and WOT.  Does that really matter?  These aren't OEM cars trying to pass stringent emissions regulations - these are race vehicles running at comparatively rich AFRs.  A tenth variance in AFR shouldn't be hurting anyone tuning/running a performance engine that's running rich anyways and I think the aftermarket UEGO controller manufacturers realize this and have thus decided that minor changes in pressure/elevation are... minor.  
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« Reply #40 on: September 16, 2015, 03:35:23 PM »

Edit . . . I run 6 Bosch O2 sensors pre-turbine on our roadster because that way I can see the individual cylinder AFR's and trim accordingly. The max continuous exhaust gas temp allowed is 930C (1700F) and I am below that. The measured back pressure is almost 370kPa and it is compensated for by my controller.

Because of cost I never installed individual AFR on each header. Although I agree I would love to have perfect AFR for each cylinder. I am converting to a lower cost alternative of running EGT at each cylinder and a single AFR on each side of the motor. It is not as good as your set-up but the EGT will point to any problematic cylinder and the AFR (even though it is averaging all 4 cylinders will tell me if the EGT-cylinder-of-interest is rich or lean). I also dont have EFI with the ability to trim individual cylinders. Sounds like you have a wonderful Motec system!

I am surprised at the life and accuracy you are getting from your installation pre-turbine. I know there are tricks you can do to heat-sink the sensor body temps but your numbers are way beyond what my brand recommends. I am following these Innovate installation instructions for fear of destroying my sensor.

The Bosch LSU4.2 wide-band O2 sensor (shipped as part of the LM-1 kit) is rated to operate at an exhaust gas temperature of < 1300 degrees (F), and a sensor housing temperature of < 900 degrees (measured at the bung) for maximum accuracy and control. When either of these operating temperature ranges is exceeded, the sensor can no longer be accurately controlled. Further, operating at or over these temperatures for any length of time can significantly reduce the lifetime of the sensor.

http://www.innovatemotorsports.com/support/faq.php

What system are you running?

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« Reply #41 on: September 16, 2015, 03:52:54 PM »

I'm running 2 of the AEM 4 channel UEGO systems Nathan linked to earlier. They have the option of pressure compensation which I am using since I am pre-turbine.

The numbers I quoted are the ones in the most recent Bosch LSU 4.2 spec I have on hand.

Code:
2.2 Operating temperatures
Exhaust gas at sensor element: ≤ 930C (1,706F)
Hexagon of the sensor housing: ≤ 570C (1,058F)

2.3 Maximum temperatures (max. 250 h accumulated over lifetime)
Exhaust gas at sensor element: ≤ 1030C (1,886F)
Hexagon of the sensor housing: ≤ 630C (1,166F)

Notes:
If the exhaust gas temperature of 930C is exceeded, the heater power must be switched off. In this case the accuracy of the sensor signal is limited.
If the max. gas temperature exceeds 930C or hexagon temperature exceeds 570C, the use of a longer thread boss is recommended.
If the operating temperature is exceeded (within the max. temperature limits) for more then 10 minutes without break, the sensor function might be affected during this time.

The AEM multi-channel systems come with special extended and finned bungs specifically designed for primary runner installation.
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Steve Cole
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« Reply #42 on: September 16, 2015, 06:17:56 PM »

Exhaust back pressure?  What exhaust back pressure?  Aren't these race vehicles with unrestricted, open exhausts?  Unless the sensors are pre-turbo, you don't really need to worry about exhaust back pressure unless you've got some kind of restriction which I'm guessing most race vehicles won't have.  Now, if going pre-turbo, you'd probably want something like THIS.
This is a very incorrect assumption. We are dealing in Absolute pressure, not gauge pressure here. For those of you that may not know or understand the difference, Absolute pressure is Baro + measure pressure, so that means as you change in altitude you move from one line to another as well as side to side on the chart I provided. So if you connect a gauge to the exhaust and watch the exhaust pulse come down a pipe you are going to see a pressure increase each time the pulse travels down the pipe and thats what you need to know, the absolute pressure when the sensor is read.

Each line on the chart I made for you all, is a different altitude and you follow the curve of the line based on absolute exhaust pressure. You would have to measure your system to see what you have at the location of your sensor but it is not uncommon to see +/- 0.5 bar pressure changes on a open exhaust and that will rise as engine speed and volume increase. So based on the total power output you will and do get different readings. So what you read at say 2000 RPM versus what you read at 8000 RPM can and will have completely different correction facts needed to get an accurate readings.

Changes in elevation and changes in exhaust pressure aren't the same thing as your chart shows.  Unless you're racing up Pikes Peak, one can generally assume elevation changes are fairly minimal thus the impact on measure AFR variance is pretty small.  Also, a change in exhaust pressure from 2000 rpm to 8000 rpm isn't really all that significant when you're racing at WOT for extended periods of time.  The point being that exhaust pressure is largely the same (and I've personally never seen an EBP of 7psi on an open exhaust) when you care to look at it which is at high rpm, high power, high exhaust flow and not at idle.  So your measured AFR changed by a tenth of a point at most between idle and WOT.  Does that really matter?  These aren't OEM cars trying to pass stringent emissions regulations - these are race vehicles running at comparatively rich AFRs.  A tenth variance in AFR shouldn't be hurting anyone tuning/running a performance engine that's running rich anyways and I think the aftermarket UEGO controller manufacturers realize this and have thus decided that minor changes in pressure/elevation are... minor.  

You may want to invest in a fast reading absolute pressure gauge, and I think you will see things differently. You will need something down in the less than 100 Ms response time range, better is < 50 Ms. If your gauge isn't showing pulsing of the pressure in an open type exhaust then you gauge is most likely reading to slowly. A standard pressure gauge will not do the trick here. Also remember to think in terms of absolute pressure as that is what were working with, not gauge pressure. As for you thinking it is only 0.1 AFR your looking at, I have to disagree with you as I have personally seen much more than that. You also have to deal with guys not running on gasoline, that will not be running around the 13.23 AFR level chart I posted, the alcohol engines are running typically down around 6:1 AFR and the errors get much larger there.

Look everyone can do what they can and I've only posted this so that you all know. What you do with it is up to you, but some of us had to learn it the hard way.
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« Reply #43 on: November 20, 2015, 09:54:20 PM »

One interesting tidbit I'll add:  I have 3 LM1 tuners from innovate, and if I take the same cables and the same O2 sensor and calibrate it on each LM1 unit, all 3 will have different readings, in a range of about .7 AFR from lowest to highest.  I bought all 3 new, and all 3 have the same internal settings.    2 of them have been sent in for repairs, sent back with the exact same (different from each other) calibrations.  be wary of your gauge readings, even if the sensors are new.  What it comes down to is that they are great for comparison, but not great for perfect data.  Use other sensors such as EGT, plus spark plug color, dyno results, and common sense to make the most of your tune.  Data you gain from any one sensor will never be the inherent truth.  If you heldd that state of mind, records will prove very, very difficult at best.   cheers
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« Reply #44 on: November 20, 2015, 11:01:48 PM »

What sensors work best with leaded gas having a small dose of top end lube?
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