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hey guys! has anyone managed to accomplish, a pretty straightforward DIY controller for wideband lambda sensors?? thanks!

i've bought one innovative device from 17point7 - seems to be a canadian guy who developed his own chip. didn't have a chance to try it tho…

I've wanted to play with the waltech thing, but haven't gotten around to it. http://rusefi.com/forum/viewtopic.php?f=4&t=387

17point is laterally too far for me but yes, i thing i will do a version of the waltech think...

maybe i could try, to start with a 4wire heated O2 sensor... they only tell rich or lean, right??
do i need anything special, to heat them? or is 14v from car battery okey??

The battery voltage is varied. You need to keep the cell at a consistent temperature. You can increase or decrease the temperature by changing the average current through the heater, you can also measure the resistance of the heater element to determine the temperature. I think that's noted in Waltech's write ups of WO2.

so, use PWM?? in waltech it says how to monitor, on a 5 wire. but i dont think the same method could be applied to the 4wire.
battery voltage is not constant, but it dosent change so much tbh... it does some spikes up and down, but are they enough to change the temperature of the sensor?? i dont think so... my only concern, is if it where to overheat, with constant 14.5v ??...

I seem to recall the walltech and many systems will PWM then in the dead time of the PWM, it measures the temperature or something like that. However other systems will vary the voltage, then other systems will dither the signals to decrease the response time. There are lots of options in how you might get the reading. I don't think it can be done with less than 6 wires. If you have less than 6 wires it's very likely that it's a NO2, not WO2. Here's a picture of a the LSU series of sensors.

yiap. 4 wires is narrowband. when i asked if their heating requaired anything special, i was talking about narrowband sensor

NO2 is less concerned with the exact temperature of the element, as long as it's hot enough that all that really matters. The issue is that if you run it 100% heat, it burns up and shortens the life of the sensor. The heater elements aren't well defined like with WO2, so you can't really measure the heaters temperature with those by measuring the variation in resistance cause by heat either. Some NO2's are designed such that the exhaust keeps them warm, and the heaters are only to get them up to temperature quicker, others keep the heaters on 100%. NO2 is kind of a crap shoot. I would suggest sniffing one in an OEM setup to see what they did and try to mimic what ever the OEM did with it. It might be on for the first 5 minutes of engine operation, then off. Or PWM based on coolant temperature, or it might be on 100%.

As for a 5 wire O2, that's generally a 4 wire with an additional GND to help ensure a good signal to the ECU. When you GND through the engine block and rusty exhaust, you can get some funky issues.

The Walltech uses a WO2 sensor, then mimics a NO2 signal.

cool. i think i will begin with trying to mesure the resistance, with a thermistor or something (if able) , and use PWM to heat it ! sooner or latter i will anyway have to go for a WO2 thanks!

I can't speak for all sensors but the Nippon Denso NBO2s on my '91 Toyota pickup are 4 wire, where 2 are signal and 2 are heater. The heater wires are 12v and ground all the time; there is no current limiting going on. The same is generally true for 3 wire sensors used as well, where 2 wires are signal and one is 12v and the heater grounds through the sensor body.

On my truck, when not wide open throttle, the ECU samples the sensor and adjusts fuel mixture around stoichiometric roughly 8 times per second, basically oscillating between slightly rich and slightly lean that often. If it has to deviate significantly from basic fuel durations, the ECU applies compensations, both short and long term, that get incorporated into the fuel calculations.

The CJ125 solution is the most straightforward although I seem to recall that there is a more modern version of that chip.

I will do. The CJ125 was used on OEM ECUs at the last place that I worked, I wasn't the designer for that although I recall that there were some issues with a lack of decent documentation. With a working unit and a protocol analyser it should be a breeze.

I have a KICAD schematic and footprints and such for a CJ125 some where. I can find it if we desire. Is it worth while to spin our own board for a CJ125?

kb1gtt wrote:I have a KICAD schematic and footprints and such for a CJ125 some where.

https://svn.code.sf.net/p/rusefi/code/trunk/hardware/CJ125_board/

apsx d1 extracted http://rusefi.com/forum/viewtopic.php?f=4&t=983

I think we can all agree, at the end of the day AFR information is mandatory.

I understand that AEM's wideband solution is the golden standard, But does it have to be that way?

What other solutions are available?

I see there are plenty of Sensors of various prices.

http://www.oxygensensor.net/widebandsensors.php

And almost every relatively new car comes with an wideband from factory.

There are a few "open source" projects but, reliability and data quality is a concern.

http://www.wide-band.com/product-p/apsx_d1diy.htm

http://www.14point7.com/products/slc-free

If your getting false AFR readings from one of these devices that is worst than having no information at all. And just going off smell.


So what is your opinion on the matter? Is it worth the risk of going diy when it comes to AFR meters?

Or should someone just stick to something like AEM or innovative?

It depends on the goals. Your engine gets damaged with things like knock. lean operation, or detonation. AFR is really either for emissions, or for a dirty way of tuning power with out a DYNO. I understand that real race cars do not have WO2's, as it's an air flow restriction. They instead rely on strict maintenance regiments and that you do not have un-expected air leaks and such. They tune on the DYNO then relay on the equipment being the same during the race.

So I would say that DIY WO2 is accurate enough for most people. If you are looking for more speed at the track, a better WO2 would help you tune it better which would result in a bit faster run. However the DIY will get you the majority of that speed for much less $.

kb1gtt wrote:It depends on the goals. Your engine gets damaged with things like knock. lean operation, or detonation. AFR is really either for emissions, or for a dirty way of tuning power with out a DYNO. I understand that real race cars do not have WO2's, as it's an air flow restriction. They instead rely on strict maintenance regiments and that you do not have un-expected air leaks and such. They tune on the DYNO then relay on the equipment being the same during the race.

So I would say that DIY WO2 is accurate enough for most people. If you are looking for more speed at the track, a better WO2 would help you tune it better which would result in a bit faster run. However the DIY will get you the majority of that speed for much less $.

Yeah thats the only reason i bring it up. Lean operation deterrent. Especially when boosting around on the road, you dont wanna push an engine thats already running lean for what ever reason. could leave you stranded.

But do you think those mentioned DIY versions are safe or should I say reliable? From an electrical and automotive standpoint?

And if so, whats up with this?
https://oshpark.com/shared_projects/WIfD0IyG

The chipset looks bulletproof, straight from BOSCH.
What were the limitations with this board, and why didn't it "take off"?

RustyGargoyle wrote:What were the limitations with this board, and why didn't it "take off"?

Time to popuate and time to write the code

The priority has dropped since an external WBO works better than rusEfi WBO would be for a while. If you have time to populate I would commit some time to make progress on the firmware.

russian wrote:

RustyGargoyle wrote:What were the limitations with this board, and why didn't it "take off"?

Time to popuate and time to write the code

The priority has dropped since an external WBO works better than rusEfi WBO would be for a while. If you have time to populate I would commit some time to make progress on the firmware.

Maybe next paycheck
gotta get my hands on some rus hardware already

You can buy CJ125 equipment, from here http://www.ecotrons.com/products/wideband_controller_alm-board/ so it's been a bit lower priority. I would generally suggest a CJ125 chip if you are looking for good quality and reliable operation. These other circuits often include some dithering of the pump currents which allows for a slightly faster response time. However it's kind of an unknown if that alters the long term accuracy. This dithering frequency thing might fatigue the sensor and shorten it's life span. Already O2 sensors are only good for something like 50k miles. Bosh is who made the LSU series of sensors, and they have a chip to drive them, and a multi-billion liability if they get it wrong. So I would think using their chip with their sensor is the most reliable way to go about it. However the other chips and other circuits probably work good enough for track day tuning.

On on a side note, the catalytic converter needs to run rich, then lean to burn out a particular build up. It would probably be good if there was an option to turn on and off this catalytic converter oscillation. If you have a cat and you do not do this, you'll likely plug your cat given time.