two sensors one AF gauge
 

ive been considering this for a while and recently started researching it again to have an AEM AF sensor in each header bank with a single gauge. what im looking for input on would be running two separate AEM harnesses and 4.9 bosch sensors which I already have to the back of the gauge mounted in the clock hole in the dash. I would label the passenger/driver side and plug in which ever bank I wanted to monitor.

as most are aware an 02 sensor needs current to stay in clean working order and this is where my idea comes in. the image below is the bosch 4.9 sensor plug layout and as you can see the white and gray wires provide the heating current.

http://forums.pelicanparts.com/uploa...1573667581.png

my plan is to jumper the heater circuits at some point in the AEM harnesses to provide current to both sensors continuously no matter which side is being monitored and plugged into the back of the gauge.

a few of concerns-

will this work? should I expect there to be a shortage of current to maintain both sensors when the source would generally only be keeping a single sensor in good standing?

where to jumper it? I would like to implement the jumper wires as ive noted in the 11' AEM wire harnesses somewhere within the cabin to keep the splices out of the elements in the motor compartment. I currently have a single AEM wire running through the tunnel day lighting at the front opening where ive routed the wire up under the dash to the afore mentioned clock hole. I will be pulling a second through if I move forward with this depending on input here. I was thinking where it left the tunnel headed up to the dash would likely be the best place to splice them together. it could be hidden under the carpet as the single line is now. thoughts?


I also would like the splices to be easy, but not hacked in and easily concealed. I am aware of the crimp fittings you might use on trailer wiring to join wires together from a single continues wire but those I think would be entirely to big for both the harness wire (20 gauge?) and too bulky to hide. can someone suggest a splicing piece that might fit the criteria im looking for?


ive looked to the innovative dual unit and as ive read the company has recently been bough by a larger group and the customer service stinks. this concerns me as many reviews of the units are not favorable. I can't say whether it was installer error or something else not related to the quality of the product, but im not interested in the innovative unit so save that suggestion for somebody with $400 buring a whole in their pocket...;) plus, I already have the second 4.9 bosch sensor and the 2nd 11' harness in hand.

thanks in advance, and any input would be appreciated.

t

Why not get a dual AFR instrument like the Daytona- Sensors in the link below. Unlike Innovate this is a great uint with terrific customer support.

Pelican used to carry this one, but here is a good reliable source.

Great unit. Logs data for 2 hours or more. I have had one in my 1073 MFI 2.7 for over 10 years......LOVE IT!!!

WEGO IV DUAL AFR INSTRUMENT by Daytona-Sensors - IG3TECH

im retired on a fixed income with more time than money and have all of the pieces in hand to accomplish what ive considered. looking for any insight on the questions ive raised.

appreciate the lead on a $600 part.

I pieced together a budget dual display using components from wide-band.com. About $80 for the two controllers and simple dual numeric display. Plus the 4.2 Bosch O2 sensors at about $45 each. It has proven quite valuable tuning carbs across different ranges and weather conditions. Simple display that I 3D printed...

Karl

You're on the right track to provide constant heat to both sensors. Looks like the grey, + heater wires on both sensors could be connected to a common ignition activated voltage source. The – heater wires also need permanent grounding.

Signal wires:
To switch the signals to display L vs R WB sensor data, you'll need a double-throw switchwith enough poles for the remaining WB signal wires (3 sets of 3 wires, thus 3-pole); one set of source wires from each WB sensor, the third set to the common WB gauge.

https://www.hogslat.com/toggle-switch-tpdt-10-amp-250v-3-4-hp

Not sure of the best location to connect, but maybe assume the closest proximity of the two sensor harness connectors. ID each signal wire, then route each through a their own dedicated and protected harness sleeve through the tunnel to a convenient switch location (e.g. next to emergency brake). If running through the tunnel, perhaps simple bullet connectors, ID'd, crimped and shrink wrapped directly under the back seat tunnel cover. Most weather-resistant harness connectors are bulky, but can be easily hidden under the seat area. If near moving car parts, restrain them accordingly. Also suggest wrapping with foam to minimize noise from a rattling plastic housing, group of spliced wires. Minimizing vibrations minimizes potential wire splice failures.

Not a recipe; just some thoughts based on my install of a single WB sensor and some non-expert wiring experience.

Sherwood

thanks for the lead Karl. if I was starting from scratch I would consider what you've accomplished, but as ive said I have the two 02 sensors and two 11' AEM wire sets already in hand.

the switched AF signal is likely beyond what im capable of and pulling the gauge out of the dash to switch harness plugs will only take a second I suspect and don't mind doing. it's a big improvement as to what im doing now which is swapping 02 sensors and wire harness at the rear end of the tunnel. that's a half hour and requires putting the car in the air.

with that said I was operating off the assumption (bad to assume, I know;)) that the gauge provided the current for the heater through the gray wire and the neg side of the circuit through the white wire. if a ground for the circuit was required would the sensor not ground to the header?

thanks for the thoughtful insight and an improved upon approach Sherwood as id expect from ya. im hoping to hear further thoughts on my approach.

quick connect T tap connector seems just what i need. never knew such a thing existed


https://www.youtube.com/watch?v=ikZZBmvFEho

Years ago we had a similar need. We had a car that had a digital afr display run off of two sensors. We wired in a toggle switch to move between the 2 sensors. It was years ago, be dammed if I can remember where we sourced the parts....

Looks like you are on a path toward success. If I can be of any help, please feel free to ping me

As you may remember, I have done a lot of wiring projects and I had a stint developing wiring harnesses for new types of digital x-ray systems back in the day. EE by training, though that has not been my profession.

I think you have my e-mail address.

Best Holiday wishes!

thanks mike.

waiting on the T tapping pieces that should arrive today from McMaster. I got the second AEM wiring harness pulled yesterday and when I get the jumpers spliced I will check for voltage at both of them at the declared power ports in each. ive decided I will do the jumper splices in the trunk area after the harnesses daylight heading toward the back of the dash area.

with the gauge providing the current for the heater(s) my concern is that the voltage meant to serve a single sensor may be too slight for two. we shall see.

Your car is 12v, so there will be volts aplenty. The two O2 sensors will pull whatever current they need. The two O2 sensors may draw more amps than your current system is designed for. Therein lies the risk.
As long as your power supply for the gauge/sensor is fused, the worst that should happen is a popped fuse.

I'm curious to see how this all plays out.

chris, thanks for the further insight. I did some additional research on amperage required for 02 sensor heating circuitry and found they can pull as much as 5.5 amps at start up and generally require 3.5 amps for continued operation. this was not the specifics for the 4.9 bosch units I have in place though.

the gauge power itself is pulled from the main fuse box on the car from an empty bank, the sunroof in this case. I have a few of empty fuse block positions on the fused side of the panel due to crank windows and no sunroof. there is currently a red, 16amp fuse in place for the gauge power. I believe it will be fused adequately, but will the gauge itself handle the additional draw is what ive wondered all along. thoughts on going from say 5.5 amps to 11 plus at start up?

further on the point chris makes above here is some data from the AEM controller tech specs maybe somebody with greater electrical knowledge can help me with.

Additional features:

* Bosch 4.9LSU wideband UEGO sensor
* Factory-calibrated resistor does not require free-air calibration—but technology allows for free-air calibration as sensor ages, if user desires
* Compatible with vehicle/system voltages up to 16 V
* 0-5 V and RS232 output for data-logging and feedback control
* AEMnet (CANbus) for data-logging and daisy-chaining multiple controllers up to 16 cylinders
* Can display AFR values in hundredths of a percent
* 52mm gauge diameter and slim 0.825 in. gauge depth
* Gauge cup depth only .200 in. deep
* Locking connectors


couple things that stood out to me was the 16v capacity of the unit and the fact it states you can daisy chain multiple controllers up to 16 cylinders. i don't know if any of this is relevant to my efforts but it seems like the 16v capacity indicated it can handle a great deal of current.

well, it seems to have worked. I have not driven the car yet as I need to tuck and secure harness wires away but in running it with the heat lines jumped I am getting AF reading from both sides back to the gauge.

in an effort to measure amps going to the 02 sensors I did not want to cut wires to test load so tried going from the sensor to the header with a meter per some suggesting the sensor would likely need to be grounded. no current measured. what I did find was a tad more efficient in that the 02 sensor got hot in my hand indicating it was being heated.

during the effort noted above where the passenger side sensor became hot in hand the driver's side harness was plugged into the gauge indicating the jumper was working with the ignition in the run position. I at the same time rolled over to the driver side and that sensor was warm as well. not nearly as warm as it was on the passenger side but I attribute that to the fact that with it in the header much of the heat was being absorbed by the header. the 02 bung was warmer than anywhere else on the otherwise cold header tubes.

I will button the wires up tomorrow securing them from the new passenger side sensor to the tunnel and dress the T splice locations up some and go drive it. really only the test of time and some miles will tell the tale moving the monitoring from side to side to see if the sensors remain sound and are being heated accordingly to be maintained.

what I would like to know is what are the symptoms I should be looking for with a carbon fouled 02 sensor? will it quit reading all together or with there be funky skewed numbers experienced on the gauge? any insight here would be appreciated.

thanks to those that contributed here thus far and may continue too.

t

You didn’t describe separating the signals from each sensor. Are you content with combining and displaying the data from both banks into the single gauge? Unknown as to the accuracy or any potential long term damage to the gauge with your current setup.

Sherwood

only one of the sensors will be monitored at a time at the gauge with the other on "standby" not being plugged in. I have not considered the toggle switch to move from side to side display at this point.

I did a bunch of research on wideband sensors last night and found that the heating of the sensor is not really for keeping them clean, but to have them operate sooner in the start up process. the fly in my ointment may be power draw as the AF changes in real time. the draw of power will increase the leaner the mixture is according to this https://www.aa1car.com/library/wraf.htm the car gets lean off throttle so that may be when the power draw increases possibly beyond the current 16amp fuse and harness wire gauge capacity.

after reading further on the current supplied to the sensor and it's purpose im wondering if maintaining power to them when not in use is required. by nature the carbs run rich so the excessive carbon may foul the sensor in my application.

plenty of unknowns remain, agreed. there may be damage incurred with the components yet to be determined. ive come this far so im going to see where it goes good or bad and ill share the results here. if this 1st effort works I may try your suggestion of a toggle to switch the data side of the system in the future.

appreciate your continued participation here Sherwood.

I have spent a lot of time looking at these things, and I have tapped my network.

I used the AEM product for years as did many of my friends.

Our application was racing, and we used leaded fuel. And open loop. ANd only one bank, although one of us had an untoward experience where that proved to be disadvantageous (the only situation I have heard about with a pretty big sigma).

For years the sensors did pretty well in terms of life.

A few years ago we started seeing the sensor life go down. Possibly supply chain issues.

Now our "herd" has moved to Ballenger Motorsports products. We were lead there by the experts at Reno Rennsport.

The folks there have high levels of both experience and expertise. And their customer support has been a 10 out of 10 for me.

A bunch of us are using the NGK sensors because it seems that experts have determined their design and materials are more robust over time in terms of lead contamination.

Everyone should be extremely careful to avoid pitfalls caused by supply chain issues with oxygen sensors. Happy to elaborate further if it can be helpful here.

Maybe you’re referring to NTK sensors.

An installled sensor w/o a working heater circuit can become unresponsive or provide inaccurate AF data due to deposits of unburned fuel (soot), oil, and/or phosphorous from the fortified oils we use (VR-1, Brad Penn, etc.).

Tech articles describe heater circuits controlled by a relay and current levels up to 8A in some cases.

More info here and in other links w/specific info on AFR (wide band) sensors:
https://www.aa1car.com/library/wraf.htm

Sherwood

that is the same exact article I linked above and found very informative reading it recently.

as I stated I found that this jumper system is in fact heating both sensors no matter which is being monitored. im confident this will keep the heaters in working order, but what remains to be seen is if the data collection sensor in the unit will become fouled by carbon. in addition to the oils noted the carbs run rich by nature so as I said previously only time will tell.

regarding the relay and power source Sherwood states above I have a 16amp fuse serving the gauge and even during lean spikes off throttle yesterday (the linked article explains higher need for current at lean and less at rich conditions) the circuit was supplied with out blowing the fuse. when I say lean spike when off throttle it will jump between 15 & mid 16 AF for a second. I had found a chart that shows the current draw with a wideband sensor assigning a specific amperage for every 1/10 of AF reading that I can no longer find that was very useful.

I did go for about a 50 mile drive yesterday moving the monitored bank from side to side a couple times and got consistent AF reading that I would expect to see from the car.

im confident enough now that I will button up the routing and securing of the harnesses in a more workman way and get underway with the "long term" testing of my work.

just to update this effort 500 miles in both sensors are still functioning and sending signals to the guage with no fouling due to exhaust carbon build up.

as noted the gauge is in the clock hole in the dash and after adding a small little handle I can pull the gauge and swap the harness connection right to left in like 30 seconds, found by tilting the gauge to driver or passenger side I can recall which side im monitoring if it's been a while since ive been in the car.

i will keep updating good or bad on this system as time and miles continue to accumulate. so far so good.