Idle hunt

[Bitsyncmaster]

I had two users of my idle ECU not able to stop idle hunt with high lift long duration cams. But they could stop it using the stock idle ECU. So my car has an idle hunt at 3 minuets after a cold start (lambda starts working closed loop) and it pretty much stops at 8 minuets. So I put a stock idle ECU in my car (I shorted the idle switch signal since I removed my idle switch) and it got about the same idle hunt at 4 minuets and pretty much stopped at 9 minuets.

When I was running a wideband (heated O2) it never hunted. The wideband went closed loop 15 seconds after cold start.

I also tried setting my wideband to slower response and that resulted in very bad idle hunting all the time.

So one problem causing idle hunt is the lambda swinging the mixture a lot when the O2 sensor is not fully warmed up. Also if the O2 sensor is resulting in slow response.

I think I will investigate the lambda ECU as to what starts closed loop. I assume after the O2 produces a set voltage it starts closed loop. I will see if I can adjust that voltage a little higher. But I think the real fix for this problem is to use a heated O2 sensor. I have about 5 lambda ECUs and will see if some set that starting voltage higher then others. There is not a lot to work with since the O2 sensor only produces about 0.50 volts around the AFR of 14.7 volts.

I'm guessing the hot cams affect the O2 running temps but don't know why the stock ECU cured that.

Of course a sticky idle motor can be another cause of hunting.

[Bitsyncmaster]

This data is for people that understand how a lambda system works. Basically the narrow band O2 sensor is high impedance (floating) when cold. When the O2 warms up it's impedance drops and provides a voltage above 0.54 volts if the mixture is rich and below 0.54 volts if the mixture is lean. It takes about 300 ms for the sensor to swing from full rich (0.9 volts) to full lean (0.1 volts).

My testing is driving the lambda ECU and a resistor load for the frequency valve output at 13.50 volts.

Unit #1
With the O2 sensor input floating the voltage on that signal line is 0.54 volts measured with my 10 M_ohm impedance DVM. So the lambda ECU is holding a dwell of 45.6 deg. until the O2 sensor has warmed up and it's impedance drops enough to change that floating voltage.

1) Adjusting my input voltage from 0.54 to 0.57 volts still holds the 45.6 deg. At 0.58 volts the dwell swings to 11.2 deg.
2) Adjusting from 0.58 to 0.57 volts still holds 11.2 deg but dropping to 0.56 volts the dwell swings to 45.6 deg.
3) Adjusting from 0.56 to 0.51 volts still holds 45.6 deg but dropping to 0.50 volts the dwell swings to 86.7 deg.
4) Adjusting from 0.50 to 0.52 volts still holds 86.7 deg but raising to 0.52 volts the dwell swings to 45.6.

Conclusion:
This first ECU has hysteresis. Not sure why they used hysteresis because that would make the dwell swing a lot (mixture swing a lot) which is what we see when setting the dwell value. I would think setting above 0.54 volts swing dwell low and below 0.54 volts swing dwell high would result in more stable mixture and maybe cause less hunting. When I was running my wideband I did set it's output to swing from 1.0 volts to 0.3 volts which may be why I got no hunting with that unit.

I will test some more ECUs to see if they all act the same way.

[Bitsyncmaster]

Well I tested all 6 of my spare ECUs and they all have about the same hysteresis.

Three stock ECUs pn 0280 800 023 and one black 0280 800 050 have floating voltage of 0.54 volts.

Two black 0280 800 052 have floating voltage of 0.48 volts.

I have another stock unit in my car not bench tested yet. I may try one of those with the lower float voltage to see what changes with hunting.

[Bitsyncmaster]

I looked at the circuit of the lambda ECU and I now see why they had to add the hysteresis. The circuit is all analog and they had to spread the range (add hysteresis) to compensate for the variables of the analog circuit. I know I could design a better circuit with a micro which would eliminate hunt caused by the lambda swinging but you can fix this using a wideband driving the stock lambda ECU.

The wideband would also let you adjust mixture to most any AFR you like. When I was running wideband I has a switch to set either 14.7 AFR or 12.0 AFR.

[Michael]

Dave, I have a stage II (with aggressive cams) and my problems are the same. With your unit, idle hunt is prevalent but with the stock control unit, it's smooth as silk hot or cold so I just kept what works.

[Bitsyncmaster]

As always I can't stop thinking about this. I may do some R&D with the lambda ECU. Like I said it would be very easy to do the ECU with a micro, one op-amp and a MOSFET. I did see the OEM unit is driving the ground of the FV though a resistor so it must be the FV should not take the full 12 volts.

I wonder if the mixture is swinging excessively with hot cams and the stock lambda ECU.

[Bitsyncmaster]

I thought of a simple way to test if removing the hysteresis will cure hunting. I can wire up one of my fuel gauge PCBs which has the micro and op-amp. I will add an analog switch so I can drive the stock ECU O2 input with a float, 3.3 volts or 0 volts from micro I/O pins. I will just mount that added PCB inside the stock lambda ECU.

This way I keep the stock rate of change of the duty cycle so all it does is remove the hysteresis. The micro can produce software controlled duty cycle with software but that would be a later effort. Using the micro to produce the duty cycle can fine tune the lambda if the first test does not cure hunting.

So I ordered some analog switch ICs and have to write some simple software to finish this first test.

[Bitsyncmaster]

While waiting on my chip to arrive, I did some more testing of the stock lambda ECU. When the O2 voltage goes above the threshold the dwell slowly (about one second) creeps to max dwell but when the O2 drops to the threshold it almost instantly goes to 45 deg. Same going below the threshold takes about one second to creep to min dwell.

So I feed a square wave signal generator into the lambda and it went to max and stayed there with a 0.1 Hz frequency. If I played with the frequency a little I could find a spot where it would swing slowly from max to min duty. So I'm not sure my simple test will work driving 0 or 3.3 volts into the input. But that sweet spot of frequency is what I want it to do.

I think that fast jump to 45 deg is what is causing idle hunting.

Edit:
On second thought it should work driving a low or high voltage because that is what the wideband unit did. I think I set the wideband to drive 1 volt above set AFR and 0.2 volts below set AFR.

[Elvis]

Well I tested all 6 of my spare ECUs and they all have about the same hysteresis.

Three stock ECUs pn 0280 800 023 and one black 0280 800 050 have floating voltage of 0.54 volts.

Two black 0280 800 052 have floating voltage of 0.48 volts.

I have another stock unit in my car not bench tested yet. I may try one of those with the lower float voltage to see what changes with hunting.


Hi Dave,

it can't just have a hysteresis of 0,0x V. Lambda wire has no GND cable, you have voltage drops on the engine
and other wires and connectors depending of other loads that would always disturb it.

Elvis & 6548

[Bitsyncmaster]

Hi Dave,

it can't just have a hysteresis of 0,0x V. Lambda wire has no GND cable, you have voltage drops on the engine
and other wires and connectors depending of other loads that would always disturb it.

Elvis & 6548

They did the hysteresis so they could tell when the O2 sensor was not warmed up. They used a resistor network to bias the input at 0.54 volts. So around that voltage they force the dwell to 45 deg. since the sensor is high impedance when cold. So the hysteresis is needed to keep that fixed dwell until it warms up.

What I'm going to do is pull the input up to 3.3 volts with a 200 Kohm. Then my software reads the voltage and if above 2.5 volts I float the signal to the stock lambda ECU. If voltage is between 0.50 volts and 2.5 volts I will drive 3.3 volts to the stock lambda ECU. If voltage is below 0.50 volts I will drive 0 volts to the stock lambda ECU.

Now it would be very easy for my micro to drive the FV with software controlled duty cycle. It could even adjust it via the amount of O2 voltage offset. But going to do the simple testing first.

[Bitsyncmaster]

Got my chip and hooked it to the car. Well 200 Kohm pull up is way to low resistance. I increased it to 3.6 Mohm and it could get down to the 0.5 volt threshold. But I need to run a test of what the sensor puts out without the lambda duty changing. I was getting hunting (more so then stock) and the O2 sensor was jumping all over.

So needs much more work. I think I can modify the warmup software by waiting for the O2 to drop to a lower voltage and maybe adding a short time delay after that before going closed loop.

[Bitsyncmaster]

I changed my O2 input to load it to ground with a 3.6 Mohm. I monitored the O2 voltage and it takes about 2 minuets warming up to hit 0.2 volts and at 3 minuets it is up to 0.50 volts. So for now I wrote my software to wait till it goes above 0.50 volts and then go closed loop. Results are the same as the stock setup. About the same amount of hunt with my setup or stock.

I'm going to play with filtering in software the O2 reading and see if that helps hunting. If that does not work then I will resort to my micro producing the dwell output. That way I can find out if faster or slower dwell changes help or hurt hunting.

[Bitsyncmaster]

Check out this info when using high duration camshafts. Only seems to affect idle as far as the lambda system.

https://www.enginelabs.com/engine-tech/wideband-realities-the-truth-about-oxygen-sensors-limitations/

[Bitsyncmaster]

I think I know the problem with the stock lambda ECU. It very slow responding to changes with the O2 voltage which I think is why I get hunting.

Only thing left to do is use my micro to eliminate the stock lambda ECU.

[Bitsyncmaster]

I'm writing the software to produce the duty cycle with my micro. Here is what I see happens to cause the mixture (duty cycle) to get into an over adjustment result.

1). The frequency of the frequency valve is 67 Hz. So a change can only take place 67 times a second.
2). If your reading the O2 input faster then a change of the FV then your reading the still unchanged mixture again.
3). It takes time (delayed) for the mixture to change from a change in the FV
4). It takes time (delayed) for the O2 sensor to respond to the mixture change at the exhaust.

So I'm making my software wait till the dwell completes one cycle and then read the O2 to output a duty cycle change to the FV. But even that does not account for 3 and 4 causes. I would have to wait (delay) making another change to the FV.

I can set the frequency of the FV higher to get faster response but not sure how fast the FV can work at. How fast does the mixture change? It would not be a problem with fixed RPM but when you punch the pedal you will go lean but the lambda system can't respond that fast.

[Bitsyncmaster]

First test in the car works like a champ. No hunting.

I set a one second wait delay before the next PWM change which makes the new reading of the O2 sensor accurate. Now I will reduce that wait time but even with one second it looks like the dwell does not need to change much when I go to 2500 RPM.

My ECU circuit could be put on a one square inch circuit board but the stock circuit board is 5.4" x 4.6". I may just get a few prototype full size boards to get a few working units for testing. With the full size I would just replace the original one with my board and everything would be plug and play.

[WHO1DMC]

I was wondering when you would be working on something like this. I'm curious if circuitry could be added that could indicate failures in the system. Say for example that the FV, sensor switch and probe wasn't functioning as far as a current failure?



I'm definitely interested when you bring them to market.
Dave B.

[Bitsyncmaster]

I was wondering when you would be working on something like this. I'm curious if circuitry could be added that could indicate failures in the system. Say for example that the FV, sensor switch and probe wasn't functioning as far as a current failure?



I'm definitely interested when you bring them to market.
Dave B.

I can try to add extra test functions. Only problem is how to show the user. An LED would not be seen in the closed up unit. There are a few spare pins on the connector but no mating pins in the harness.

[WHO1DMC]

I can try to add extra test functions. Only problem is how to show the user. An LED would not be seen in the closed up unit. There are a few spare pins on the connector but no mating pins in the harness.


Myself personally I would have no problem making a window in the side of the case. Not trying to be difficult it was just a thought. I have the utmost respect for you and your products. If it wasn't for you I don't think anyone else would be willing to undertake such reverse engineering for obsolete electronics. I certainly don't have the skills!



Dave B.

[Bitsyncmaster]

Myself personally I would have no problem making a window in the side of the case. Not trying to be difficult it was just a thought. I have the utmost respect for you and your products. If it wasn't for you I don't think anyone else would be willing to undertake such reverse engineering for obsolete electronics. I certainly don't have the skills!



Dave B.

I can put an LED on the board to use for signaling the user. I have all the space to put down extras.

[mhanch]

Love this work you do. Thanks!

[Bitsyncmaster]

Wait till you see the non-swinging dwell setting.

[Bitsyncmaster]

I've been working on the PCB a lot. Got almost done just have to check the new components I had to layout.

I tested with a half second delay and still no hunting. Not sure if I will try shorter since I read the narrow band sensor take 300 ms to respond.

[Bitsyncmaster]

I ordered 3 circuit boards. Advanced Circuits has a special to order 3 or more boards with a 3 day turn for $33 each board. But shipping is $42 for ground UPS.

Anyway I have a lot to do on the firmware. I need to add the WOT to set that fixed dwell when on. Also need to add checking when the O2 input goes dead (disconnected) and set the fixed 45 deg. dwell. I have to do some testing of the warmup which is working great for a normal engine but I have to make sure it works when the mixture setting is way off normal.

I added an LED which is on the top side of the board on a spacer so you could drill a hole in the case and see it working.

I have one user jumper but have not decided if that will be used yet.

I should have looked into the redesign of the lambda ECU a long time ago. But I never had much hunting and it never bothered me. I think this will cure 90% or more hunting issues but a nice thing is when your adjusting your dwell it will not be swinging like the stock ECUs do.

[Timeless]

Is this similar to the idle hunt in question? This is my DMC stage 2.

https://drive.google.com/file/d/1h4pcPNSmGbRFyisfnJ7NlUBWg0SEggQd/view?usp=sharing

[Bitsyncmaster]

Is this similar to the idle hunt in question? This is my DMC stage 2.

https://drive.google.com/file/d/1h4pcPNSmGbRFyisfnJ7NlUBWg0SEggQd/view?usp=sharing

You must have set it privet. Can not access.

[Bitsyncmaster]

Thought of using my LED to light green when the dwell is between 35 deg and 45 deg (book value for normal setting). So running near an edge it will be flashing. To bad you can not see it from the rear of the car. That would let users adjust mixture without a dwell meter.

By the way my dwell setting is very accurate since it's based of the micro clock. The clock is +/- 1% spec but typical is 0.1%.

[Timeless]

You must have set it privet. Can not access.
I have it set to public access. - weird.

[Bitsyncmaster]

Thought of using my LED to light green when the dwell is between 35 deg and 45 deg (book value for normal setting). So running near an edge it will be flashing. To bad you can not see it from the rear of the car. That would let users adjust mixture without a dwell meter.

By the way my dwell setting is very accurate since it's based of the micro clock. The clock is +/- 1% spec but typical is 0.1%.

Well after thinking about this my dwell frequency is only affected by clock. The duty cycle is always exact since it works with counters. I'm only using 8 bits of resolution so I can set it with 0.3 % steps. The PWM does have 10 bits but I don't need that kind of resolution.

I also think on production boards I will use a red/green LED. The green will indicate running closed loop between 35 and 45 dwell and red would indicate dwell is max at 10 deg or 85 deg. I can set my PWM to any limits but for now I will just copy the stock limits.

[Bitsyncmaster]

I have it set to public access. - weird.

I saw it with your PM. You really have excessive swing in closed loop. I would change the O2 sensor and see if that fixes it.

[Timeless]

I saw it with your PM. You really have excessive swing in closed loop. I would change the O2 sensor and see if that fixes it.
PM relied. Thanks Dave! :wave2:

[bytes311]

Once in production, will we need to send our ECU cores to you for the board swap, or could we swap them out ourselves? I ask because as a CA resident whose subject to bi-annual smog tests, the service tech may want to get a reading off the dwell, and if it ain't swinging, he may chalk it up as a bad o2 sensor, or something. It'd be nice to keep both units, but if that's not a possibility that's fine. Appreciate your work!

[WHO1DMC]

Once in production, will we need to send our ECU cores to you for the board swap, or could we swap them out ourselves? I ask because as a CA resident whose subject to bi-annual smog tests, the service tech may want to get a reading off the dwell, and if it ain't swinging, he may chalk it up as a bad o2 sensor, or something. It'd be nice to keep both units, but if that's not a possibility that's fine. Appreciate your work!

Get yourself a core for the transplant because there's no going back unless you like doing a lot of soldering. That's what I did when I got his idle ECU.
Dave will do the work when you send him the core.


Dave B.

[Bitsyncmaster]

Once in production, will we need to send our ECU cores to you for the board swap, or could we swap them out ourselves? I ask because as a CA resident whose subject to bi-annual smog tests, the service tech may want to get a reading off the dwell, and if it ain't swinging, he may chalk it up as a bad o2 sensor, or something. It'd be nice to keep both units, but if that's not a possibility that's fine. Appreciate your work!

I am using the stock 10 ohm resistor mounted on the outside of the case. I decided to use that to keep the heat away from the inside. So that is soldering those two wires. I could put a high power 10 ohm on the board to avoid that. Otherwise you would need to un-solder the connector and solder it to my board. The OEM board is riveted into the case where the connector mounts on each end. So you would need to drill those rivets to remove the old board.

I would think any smog test would just read the tailpipe emissions. I would not think any service guys even know about reading dwell and they would need a plug to connect to the engine diagnostic plug.

[bytes311]

I am using the stock 10 ohm resistor mounted on the outside of the case. I decided to use that to keep the heat away from the inside. So that is soldering those two wires. I could put a high power 10 ohm on the board to avoid that. Otherwise you would need to un-solder the connector and solder it to my board. The OEM board is riveted into the case where the connector mounts on each end. So you would need to drill those rivets to remove the old board.

I would think any smog test would just read the tailpipe emissions. I would not think any service guys even know about reading dwell and they would need a plug to connect to the engine diagnostic plug.

I'll keep a spare unit on hand as WHO1DMC suggested. Not sure why I didn't even think of that.

My car has a tendency to fail the first go-around, so it's not uncommon at my shop for the tech to "tweak" the mixture a little to get it to pass.

[Bitsyncmaster]

I'll keep a spare unit on hand as WHO1DMC suggested. Not sure why I didn't even think of that.

My car has a tendency to fail the first go-around, so it's not uncommon at my shop for the tech to "tweak" the mixture a little to get it to pass.

I bet mine will do better then a stock unit since the dwell holds without swinging. I would guess that swing rich and lean would average out when measuring the smog.

[WHO1DMC]

Get your cores early people before the cheap ones disappear! This will get popular I think!
0280 800 023, 0280 800 033. Also eliminate spaces for different results.
I just got one for 26 bucks.


Dave B.

[bytes311]

I bet mine will do better then a stock unit since the dwell holds without swinging. I would guess that swing rich and lean would average out when measuring the smog.

Perfect! Looking forward to another solid-state upgrade. :)

[WHO1DMC]

Get your cores early people before the cheap ones disappear! This will get popular I think!
0280 800 023, 0280 800 033. Also eliminate spaces for different results.
I just got one for 26 bucks.


Dave B.


Here's another core that will work 0280 800 021,0280 800 050,0280 800 053.



Dave B.

[bytes311]

Here's another core that will work 0280 800 021,0280 800 050,0280 800 053.



Dave B.

Scooped one up myself for $20. :)

[Bitsyncmaster]

Working on the software I did some more testing of the stock ECU.

1). Stock ECU takes 8 to 9 seconds to step the duty cycle from one extreme to the other. My ECU with the half second wait takes about 60 seconds. I tested mine with a 1/4 second wait and it got some hunting at idle. So it looks like that 300 ms O2 sensor response time I read about is about right.

2) Doing the book testing which has you float, ground and 1.5 volt battery testing does keep that stock step rate. Ground and 1.5 volt is just so the input is below or above 0.5 volts. It still runs closed loop. So doing that testing with my ECU will take 6 times as long to see the min and max duty cycle. You can do that testing without the engine running if you jumper the RPM relay brown wire pin to the double yellow/red wire pin.

3) Wide open throttle also takes that same rate of change with the stock ECU. I think I will make my ECU change to that 55% dwell instantly on and normal closed loop timing for off.

When I get my first circuit boards I have to add an IC for a change needed to sense when the O2 input is floated (disconnected).

[DMC5180]

Dave, I just stumbled on this thread. For clarity, which ECU are experimenting with. Lambda or Idle ECU?


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[Bitsyncmaster]

Dave, I just stumbled on this thread. For clarity, which ECU are experimenting with. Lambda or Idle ECU?


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Lambda ECU. It's better to fix the cause of idle hunt rather than try to find a fix via other means.

[DMC5180]

In that case, I?m open for any testing. Just went for nice drive today and the pesky hunting is still there no matter how I?ve configured your Idle ECU.


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[Bitsyncmaster]

In that case, I?m open for any testing. Just went for nice drive today and the pesky hunting is still there no matter how I?ve configured your Idle ECU.


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I've got 3 circuit boards that should be here Wednesday. One is going to a local owner with "hot" camshafts for testing. Turns out high duration camshafts fake out the O2 sensor at idle speeds feeding more air into the exhaust. I will need to keep one for my R&D work doing software and getting a larger order ready.

So far the only reason for my ECU is to cure idle hunt. The stock ECU only draws about 50 ma and mine will be much less but heat does not seem to be an issue in the drivers side cubby.

[DMC5180]

Great, I?ve got Stage II setup with there Cams. Not as Aggressive as some I?ve heard though. How invasive is what you are doing?


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[Bitsyncmaster]

Great, I?ve got Stage II setup with there Cams. Not as Aggressive as some I?ve heard though. How invasive is what you are doing?


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Plug and play. So far no reason to have any user adjustments inside the units. Of course I will need a core. You can test my unit without removing your ECU because the connector can be unplugged and then plugging my unit in with it sitting somewhere with the open cubby. At least my car's harness can do that.

[DMC-Ron]

Or, if you want to test on a totally original set up, I'm happy to volunteer.

Ron

[DMC5180]

I grabbed a couple 033?s for cores. $28 ea including shipping. The 023?s from the same seller were $85 [emoji2369]. Not sure the difference other than 033 listed for volvo 240 and 023 listed volvo 260.


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[Bitsyncmaster]

I grabbed a couple 033?s for cores. $28 ea including shipping. The 023?s from the same seller were $85 [emoji2369]. Not sure the difference other than 033 listed for volvo 240 and 023 listed volvo 260.


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I think the black Volvo units will work with the same PCB. I have some black ones already.

[Bitsyncmaster]

I thought of a change that can speed up my rate of change but I'm still not sure why you would need faster rate of change to mixture control. What makes me think about it is why did the Bosch designers make their rate so fast. Of course I have more options since I can do these things in software and they had to do it in hardware. If you can think of a reason for faster rate of change, let me know what it is.

Anyway I tried incrementing and decrementing the PWM by two counts instead of one. That still lets me wait a half second for the O2 reading to respond but doubles my rate of change. I may do more testing increasing that count change. With a narrow band sensor you can't really read when mixture is further off which I could use to make the count variable. Wide band I could do that.

I also will play with my idle ECU after I finish the lambda ECU to see how rock steady I can make the idle RPM. Without fighting hunting, I may be able to tailor the idle ECU different.

[Bitsyncmaster]

Still waiting on my first boards to arrive. UPS says today but tracking has not shown it even arrived in Maryland. Anyway was trying to find a way to plot my RPM very accurately with fast updates. Can't do it via ignition pulses since at 800 RPM those just have a count of 40 each second. Was thinking about using the RPM pulses from the stock diagnostic plug but I've removed my sensor and plug. Not sure I want to put that back in but that would give me much more resolution. Measuring the time between each ignition pulse may work but would have to account for the uneven fire.

[Bitsyncmaster]

Finally got my first three boards today. Here is the first one which ended up fitting very well. I am going to modify the board so it can detect an open sensor better than what I was using.

[Bitsyncmaster]

Design testing:

This may just interest a few people that have knowledge of the narrow band sensor and the lambda system.

The narrow band O2 sensor will output 0.1 volts with a lean running engine and 0.9 volts with a rich running engine. The range of those values is very sharp centering around 14.7 AFR which is when no oxygen is in the exhaust.

Our cars recommend the dwell setting of 40 deg when the engine is warmed up and everything running as designed. When the O2 sensor is warming up, the lambda ECU drives a fixed 45 deg. dwell which would result in a little richer mixture than 14.7 AFR. So I set my ECU to hold 45 deg. and measured the O2 voltage as it warmed up. My ECU has a test point which is the O2 voltage buffered with an op-amp so your meter will not affect the sensor values.

This is the result on my cold engine start.

0:30 .0016 volts
1:00 .0047 volts
1:30 .039 volts
2:00 .17 volts
2:30 .38 volts
3:00 .55 volts
3:30 .68 volts
4:00 .74 volts
4:30 .79 volts
5:00 .81 volts
5:30 .83 volts
6:00 .84 volts

This result was interesting with how good things work with design. I have not adjusted my mixture so it looks like it is still set correctly at 40 deg. dwell.

Now I'm going to set my ECU to hold 35 deg. dwell and do the same test reading the O2 voltage.

[Bitsyncmaster]

Ran with 35 deg fixed dwell. O2 voltage still climbed to .53 volts at 2 minuets time and then started dropping to .31 volts at 5 minuets. So I'm impressed that the lambda systems works so good as designed (except for the idle hunt problem with stock lambda ECU). So the WUR is still keeping mixture rich till about two minuets of running.

Idle is notably not as good sounding as the normal 14.7 AFR or the richer mixture. So as expected a rich mixture gives a better idle.

I have more testing to do. I keep thinking of ways to perfect my ECU design. I found out the O2 sensor is not good at sinking voltage (pulling the signal up to 3.3 volts) but seems pretty good at sourcing voltage (driving a load resistor).

[Bitsyncmaster]

FYI: If you do a lot idling without revving the engine it will mess up the narrow band O2 sensor. Some high RPMs for a few minuets seems to clear it up.

I am doing a lot of idling testing my software changes and suddenly had unexpected results from my lambda ECU. This drove me nuts for a while till I measured the O2 voltage and it was not responding.

Turns out also the O2 sensor cools off fast even though the engine is warm. A quick punch of the throttle bring it back up quick.

Also the sensor voltage does jump around during normal idle. One sample every half second still works (what I started with) but I'm thinking of doing a bunch of samples and averaging to see if it helps working at a faster rate.

[cis6409]

Great work, Very interesting results, Thanks for posting them.
Very enlightening

Shane

[David T]

More modern cars have a heater in the O2 sensor to (a) warm it up faster to get into closed loop quicker, and (b) to avoid the sensor from cooling because of prolonged idle. Maybe changing over to a heated sensor is the way to go.

[Bitsyncmaster]

Well my O2 sensor died. Not sure if it was all the idling or when I was doing early testing with a pull resistor on the sensor. I will need to replace it to continue testing. Think I have an old one somewhere, if not will order one.

[Bitsyncmaster]

Got a new O2 sensor and installed it and still showed same problem. Turns out I was turning closed loop on to soon so swung the duty cycle to much and caused the sensor voltage to max.

Anyway the new sensor looks like it produces a cleaner voltage with less noise.

[Bitsyncmaster]

It bothered me that my ECU showed that problem starting closed loop early and bench testing showed no problems.

Well I did a couple scope shots. One with the scope ground on the signal ground pin and one on the power ground pin. The stock wiring has two signal ground pins (one connected to the shielded sensor input wire). The power ground is where the FV driver conducts current. Well I connected my buffer op-amp to the signal ground and my micro to the power ground. That is a problem as you can see in the attached scope shots. My micro has the A/D ground reference to the power ground.

[Bitsyncmaster]

Here is a scope shot of the stock ECU O2 voltage. I slowed the time base on my O-scope so getting the same slow swinging O2 voltage as my ECU. Don't know why that voltage swings like that. It is not caused by the dwell changing because my ECU shows the same and I slowed the dwell change real slow. As it warms up the voltage is very flat and says flat even when closed loop starts but about one minute later voltage starts swinging like that. That is what is causing the idle hunt because the dwell on the stock ECU is following that voltage change. My ECU I can slow the dwell change so as not to swing dwell that much.

[Helirich]

So read the first post and some of the others. (I haven?t read it all) Is your goal to make an after market part that will not hunt? That would be great. My car hunts sometimes and some times it works perfect. There seems to be no rhyme or reason. It hasn?t been a big problem, so I haven?t really investigated it.

Most of your posts are over my head, but please keep at it. If anyone can do it, you are the one. I await the announcement of your new product. Please take my money. Lol.

[Bitsyncmaster]

So read the first post and some of the others. (I haven?t read it all) Is your goal to make an after market part that will not hunt? That would be great. My car hunts sometimes and some times it works perfect. There seems to be no rhyme or reason. It hasn?t been a big problem, so I haven?t really investigated it.

Most of your posts are over my head, but please keep at it. If anyone can do it, you are the one. I await the announcement of your new product. Please take my money. Lol.

Yes, cure idle hunt caused by the lambda ECU. A lot of owners unplug the O2 sensor to cure their idle hunt but I just had two owners with high duration cams get idle hunt with my idle ECU and not get it with the stock ECU. So I decided to cure the cause. It turns out high duration cams make the O2 sensor show lean at idle RPM (does not affect normal RPM).

I bet that O2 voltage swing increases with those cams. I'm going to look into what causes that O2 swing but it may just be normal for narrow band sensors. My ECU can eliminate the hunt by slow dwell changes so as not to follow that O2 swing but still maintain the 14.7 AFR.

[Bitsyncmaster]

I put a user switch onto my ECU so I could stop the update (holds current dwell). So I found out holding the dwell does stop that O2 voltage from swinging. So the stock lambda ECU is swinging the mixture in that 4.5 second sequence. My ECU will currently do an occasional swing with the present timing. I think running slower would stop that but it does not hunt as is.

I guess there is not really a reason to run fast since the many owners that pull the O2 wire don't get any mixture adjustments. Have not heard of any complaints with the fixed duty cycle at 45 deg which is what you get pulling the O2.

[Bitsyncmaster]

The more I test the more I hate a narrow banc O2 sensor. If you let the car idle from cold the sensor gets into that swinging voltage change (My ECU is slow enough not to hunt with that). If you do a normal RPM after that the sensor seems to clear out after a while. If you punch the throttle voltage jumps and then falls to zero volts. I guess the punch cools the sensor off so it goes high impedance.

Now I'm going to add a circuit to my ECU to detect when the sensor is high impedance. Need that to set when to go closed loop. It also lets the ECU set the fixed 45 deg. dwell when a user pulls the O2 wire. This will also let me know if the user is testing with a short circuit on the O2 input to get minimum dwell.

[dmcman73]

The more I test the more I hate a narrow banc O2 sensor. If you let the car idle from cold the sensor gets into that swinging voltage change (My ECU is slow enough not to hunt with that). If you do a normal RPM after that the sensor seems to clear out after a while. If you punch the throttle voltage jumps and then falls to zero volts. I guess the punch cools the sensor off so it goes high impedance.

Now I'm going to add a circuit to my ECU to detect when the sensor is high impedance. Need that to set when to go closed loop. It also lets the ECU set the fixed 45 deg. dwell when a user pulls the O2 wire. This will also let me know if the user is testing with a short circuit on the O2 input to get minimum dwell.

Why not use a wideband O2? If it works with that, the end user will just need to switch over to a wideband O2, you can even make it where the power comes off your new unit (if you're creating one.

[Bitsyncmaster]

Why not use a wideband O2? If it works with that, the end user will just need to switch over to a wideband O2, you can even make it where the power comes off your new unit (if you're creating one.

The wideband devices take very complex hardware and software which has already been designed. They output an analog output which can drive the stock lambda ECU input. I did have one installed in my car before but I removed it when I was trouble shooting a skip in my engine. Wish I left it in because it never hunted but then I would not have started this R&D. After I finish this design I may get a heated narrow band sensor just to measure if it corrects some of the problems I've seen without the heated sensor.

Now you give me an idea to have a user switch to run my unit without a delay if the owner has installed a wideband.

[Bitsyncmaster]

Well with more testing, it's not as bad as I thought. I keep thinking the O2 voltage is an analog device showing AFR but it is really almost a switch showing above or below 14.7 AFR. So even if the AFR is holding solid at 14.7 +/- .1 AFR your going to get swinging O2 voltage.

That and controlling the AFR with the frequency valve is also not that precise.

So I'm getting close to finishing up the software to do road testing and have a few other owners do testing.

[Timeless]

So I'm getting close to finishing up the software to do road testing and have a few other owners do testing.
I'm happy to test on my DMC stage 2 car if you need.

[David T]

There is a "built in" hysteresis delay that your software can't overcome. By the time the O2 sensor senses a change in the AFR, that cylinder has already fired and the motor has gone on to the next cylinder. By the time the Freq valve is modulated you are firing on another cylinder so you will ALWAYS be behind. The only way you can reduce the idle hunt is to make sure ALL of the cylinders are as balanced to each other as possible. That includes;
Compression
Spark plug gap
Valve clearances
Fuel injectors (opening pressure, amount and pattern)
Even with everything as balanced as you can make it you have built-in differences because of the varying distances of the cylinders and the differences in flow. You also have the idle motor system trying to maintain a fixed RPM and it is having the same problems, it is always reacting to the drop (or increase) and it will always be behind. Some idle hunt is considered normal.

[Bitsyncmaster]

Well software work fine for idle but when you punch the throttle hard I need faster FV changes. A punch drive the mixture very lean and then very rich. So I have some ideas to speed things up in that condition.

[Bitsyncmaster]

I think I got the fix working for the need for faster response after a punch of the throttle.

Found out not to go closed loop to early because the engine does not idle as smooth at 14.7 AFR when it is still warming up. During warm up your engine is running very rich and if I lean it via closed loop it kind of "lumps" sounding till it warms up a little more. It still idles at a stable RPM just sounds different.

I should be road testing soon.

[lazabby]

Back in 2017 NickT addressed the hunting idle and found a solution that he said works with D's with various configurations:
https://dmctalk.org/showthread.php?15633-Attempting-to-destroy-my-idle-lumpiness/page2&highlight=catalysed

See post 19 for his method. Would this work for the cars in question here?

[Bitsyncmaster]

Back in 2017 NickT addressed the hunting idle and found a solution that he said works with D's with various configurations:
https://dmctalk.org/showthread.php?15633-Attempting-to-destroy-my-idle-lumpiness/page2&highlight=catalysed

See post 19 for his method. Would this work for the cars in question here?

There is more than one thing that can cause idle hunt. My lambda ECU is to stop idle hunt due to mixture changing in a rhythm timing. If that rhythm timing matches the rhythm timing of the idle ECU response the idle can hunt.

Making an adjustment that affects that timing (frequency) can bring the system out of that idle hunt condition.

[Bitsyncmaster]

Interesting find. I accidentally moved some of my software so the FV did not turn on at power up. Well the noise I thought was my fuel pump is actually noise from the FV. I think it is the return fuel resonating in the return line.

If I ever lift the body, I will put some rubber grommets on the holders for that return line. So this is something you guys may want to do. You can test this if your fuel pump primes by pulling the lambda relay and listen to the prime noise.

[Bitsyncmaster]

Did my first road test today with the new lambda ECU and I can't tell any difference from the stock ECU except for more constant idle RPM. I may think of more things to test but I don't think any hardware (electronic circuits) will change. I did make a hardware change in my first unit but it is now what the new units will have for hardware.

[SShaw]

Hi Dave, I’m one of the two owners mentioned in the original post. I reverted to a stock idle ECU which mostly eliminated my hunt. Except for an occasion cold start hunt which didn’t happen with your ECU. Anyway, I still have your idle ECU and have a lambda ECU core in my parts box. I?m happy to do some testing if it would help. I’m only about an hour North of you so shipping would be fast and cheap. Let me know.

[Bitsyncmaster]

Hi Dave, I?m one of the two owners mentioned in the original post. I reverted to a stock idle ECU which mostly eliminated my hunt. Except for an occasion cold start hunt which didn?t happen with your ECU. Anyway, I still have your idle ECU and have a lambda ECU core in my parts box. I?m happy to do some testing if it would help. I?m only about an hour North of you so shipping would be fast and cheap. Let me know.

I only got three circuit boards for testing and have two users lined up to use those two extras. I want to keep one in case they find a problem so I can simulate the problem with mine. But if testing goes fast I will order a full set of boards to sell updated units. I will need your core unit to update so it's a plug and play unit.

[SShaw]

I only got three circuit boards for testing and have two users lined up to use those two extras. I want to keep one in case they find a problem so I can simulate the problem with mine. But if testing goes fast I will order a full set of boards to sell updated units. I will need your core unit to update so it's a plug and play unit.

Great. If you have a waiting list, official or otherwise, I’d like to be on it. I could even send my core in advance. I’d love to switch back to your idle ECU if possible.

[Bitsyncmaster]

First owner with the stage 2 found my lambda ECU did stop idle hunting. He still has a problem with my idle ECU with his auto transmission getting hunting when slow driving parking lot speeds. My idle ECU would get into a throttle increase. Not sure how to find that problem since I have a manual transmission.

Second owner should get my lambda ECU on Friday.

Have been thinking. Wish I could find the female pins for the lambda ECU connector. Our ECU connector has a few extra unused pin but the mating harness connector has no pins installed into those positions. I would like to drive an LED output signal from one extra pin. I could make that LED turn green with dwell between 35 and 45 deg. Make it turn red when dwell is at min or max. I am doing that with an LED on my circuit board but to see it you will need to drill a hole in the ECU case.

Also with an extra pin I could input the ignition advance solenoid signal and know when the engine is at idle. I could use that to have my ECU run slow (that prevents idle hunt) or run the same speed at the stock ECU when not at idle.

[Bitsyncmaster]

Here is a photo of the hybrid unit in all the stock lambda ECUs (cover removed).

Just interesting for the electronic gurus. The O2 sensor feeds directly into this unit. Not sure what it does and wonder if that micro circuit is analog or digital. I would not think it's a micro since early 80's they did not have micros with clocks or memory.

[Michael]

Once you get this figured out, is that something you could do to existing ecu's? I've had mine on a shelf for a few years because I had the exact idle surge issues in my stage II.

[Bitsyncmaster]

Once you get this figured out, is that something you could do to existing ecu's? I've had mine on a shelf for a few years because I had the exact idle surge issues in my stage II.

Yes. My circuit board replaces the stock board. So far plug and play.

[Timeless]

I have an extra ECU as well and would be interested. Stage 2 automatic car.

[Dhennick99]

I'm running a stock auto and have had issues with idle hunt as well. I'd be curious in updating when Dave is ready.

[Bitsyncmaster]

I've had three users with auto stage two users still get problems when using my idle ECU along with my prototype lambda ECU. It looks like I need to do work on the idle ECU to correct that. But any warmup hunting issues seem to go away with my lambda ECU.

I have done more work on the software for the lambda ECU. I now have fine adjustment of dwell (1024 steps) and a duel speed of that adjustment. I was able to do that by averaging 256 readings of the O2 sensor voltage over a 1/4 second time. Not sure if that will help anything but it doubles my speed of change when needed.

I think I'm ready to order the production circuit boards.

[Bitsyncmaster]

I was working on my idle ECU software. Trying to fix a problem people have with an auto with stage 2 installed. Hard to find that problem since my car does not have either. Anyway I found a nice improvement for even my car. I was getting the RPM value timing between two ignition pulses. Well I changed that RPM value to time between 6 pulses so it always starts the timing on the same distributor "lobe". That removes any inaccuracy of the lobe spacing and pickup variance because it always starts timing on the same lobe. Now my RPM gauge is "nailed" solid except for an occasional miss fire. I have to track down that miss fire cause.

I would not think that fix affects the problem I was looking for.

[Bitsyncmaster]

I should get 40 production lambda circuit boards tomorrow.

I've been playing with the idle ECU and thought of a way to measure how good the idle holds. I just put in the idle ECU software a check on every other ignition pulse to output a trigger signal when it goes below 50 RPM or above 50 RPM from the set idle RPM. I will keep tightening up on those values until I can put a counter on that trigger to give a a value I can use to measure any improvements.

[Michael]

I should get 40 production lambda circuit boards tomorrow.

I've been playing with the idle ECU and thought of a way to measure how good the idle holds. I just put in the idle ECU software a check on every other ignition pulse to output a trigger signal when it goes below 50 RPM or above 50 RPM from the set idle RPM. I will keep tightening up on those values until I can put a counter on that trigger to give a a value I can use to measure any improvements.

If you need a stage II test mule, I'm game. My ecu has been on a shelf for like 6 or 7 years.

[TheStoot]

I'd be interested in sending you my stock unit to swap out as my cars garaged for the winter currently

[Bitsyncmaster]

I'd be interested in sending you my stock unit to swap out as my cars garaged for the winter currently

I'm getting close to finishing the software. Not much control software has changed but I put a red/green LED on the production board. I plan to have have the LED off during initial open loop (unit is waiting for O2 sensor to warm up so it holds 45 deg. dwell). In closed loop the LED is green when dwell is between 35 and 45 deg. dwell. Running outside that range LED is flashing green. When unit hits the min or max dwell, Led is red.

Now it's a shame I can not get that LED outside the unit because you could use that to set your mixture adjustment (looking for solid green). I guess you could do the adjustment in the dark (see it inside the car). I do provide a user jumper to turn the LED off but it should not show with your cover on the rear compartment.

I did build up 10 production boards so I can start updating customer units. I'm charging $164 to do the update and return the unit to US addresses. Shipping requires priority mail to US address but I still can do first class to addresses over the boarder but because the weight is over 8 oz. that shipping cost goes up 3 to 4 times.

I do require a core to update.

Remember this unit is designed to stop idle hunting caused by the stock lambda ECU. If you have a sticky idle motor or marginal O2 sensor you may still get idle hunt. My unit does all the same functions of the stock unit but delays the loop timing.

[DMC-Ron]

Dave,
Would it be possible to add a plug for a remote LED? Then we could have an indicator on an extension cord that we could see when working in the engine compartment.
Ron

[Michael]

Dave,
Would it be possible to add a plug for a remote LED? Then we could have an indicator on an extension cord that we could see when working in the engine compartment.
Ron

The LED is probably board mounted but what I have done on other applications is drill a small hole in the outer case over the led and use a larger piece of fiber optic cable, (around 1mm) to glue to the case with it lining up over the led.

[Bitsyncmaster]

The LED is probably board mounted but what I have done on other applications is drill a small hole in the outer case over the led and use a larger piece of fiber optic cable, (around 1mm) to glue to the case with it lining up over the led.

Great idea. I do plan to make a jig to drill a hole in the case.

I just finished the LED software. I made one change in that when the unit has a floating O2 either during warm up or a disconnected O2 the LED is off

[Bitsyncmaster]

Dave,
Would it be possible to add a plug for a remote LED? Then we could have an indicator on an extension cord that we could see when working in the engine compartment.
Ron

It would be complicated to add a connector. The unit slides into the box case so it could not extent past that height. I could not find the pins to install into the lambda connector to add LED wires to. The circuit board connector does have some extra pins but there are no mating pins in the connector for those.

[Bitsyncmaster]

The LED is probably board mounted but what I have done on other applications is drill a small hole in the outer case over the led and use a larger piece of fiber optic cable, (around 1mm) to glue to the case with it lining up over the led.

As always an idea gets me thinking. You (I can't add another product) could 3D print a holder for the fiber optic cable that holds it and screws onto the case.

[Bitsyncmaster]

Finished my software. Tested in the car and found out you really need to let the engine warm to full heat to get a solid green LED. So if your adjusting the mixture I suggest you take a drive first. That will clean up your O2 sensor and get the engine to full temp.

I need to do more car testing. This lambda software is faster then my REV A boards but I put a user jumper in to slow it down if needed. This software also has a fine dwell adjustment if the O2 sensor is reading between 0.35 to 0.65 volts.

[poidog]

Hey Dave,
Any update on the lambda boards?

[Bitsyncmaster]

Hey Dave,
Any update on the lambda boards?

I have been using it during all my idle ECU testing. It is nice seeing by the LED when lambda goes active. That is when the idle seems to run a little different. Also interesting I would see the LED go red (max dwell) which indicated my engine was still to rich. That red would only last for maybe 30 seconds. I don't know if that red will go away now that I've fixed some things with my K-jet.

I have 5 units ready to ship. I built those before I got tied up with my idle ECU update.

[poidog]

I have been using it during all my idle ECU testing. It is nice seeing by the LED when lambda goes active. That is when the idle seems to run a little different. Also interesting I would see the LED go red (max dwell) which indicated my engine was still to rich. That red would only last for maybe 30 seconds. I don't know if that red will go away now that I've fixed some things with my K-jet.

I have 5 units ready to ship. I built those before I got tied up with my idle ECU update.

Very cool. I?d like to try one out :) what updates to the idle ECU are you working on? I have your Rev B board.

[Bitsyncmaster]

Very cool. I?d like to try one out :) what updates to the idle ECU are you working on? I have your Rev B board.

Just trying to solve issues with auto owners with stage 2 engines. Have not found anything that would cause those issues but I'm changing the software so it requires the use of the idle switch. That helps me to use more options writing the software.

[Bitsyncmaster]

I have done more software work on my lambda ECU. First I think I had a bug causing my whole engine issues. But I continued work on the software and now I'm running it 4 times faster then my first units and I still don't get idle hunt. I will have to try an OEM lambda ECU to make sure I still get idle hunt with that.

So OEM changes the dwell from max to min in 8 to 10 seconds (speed of dwell changes).
My lambda now does that in 16 seconds or has a user jumper to change it to 32 seconds.

[DMC5180]

I have done more software work on my lambda ECU. First I think I had a bug causing my whole engine issues. But I continued work on the software and now I'm running it 4 times faster then my first units and I still don't get idle hunt. I will have to try an OEM lambda ECU to make sure I still get idle hunt with that.

So OEM changes the dwell from max to min in 8 to 10 seconds (speed of dwell changes).
My lambda now does that in 16 seconds or has a user jumper to change it to 32 seconds.

Dave, I was just wondering how things were progressing on this front. Let know when you?re ready to ship some. I have a core ECU case ready for you.


Sent from my iPhone using Tapatalk

[Bitsyncmaster]

Dave, I was just wondering how things were progressing on this front. Let know when you?re ready to ship some. I have a core ECU case ready for you.


Sent from my iPhone using Tapatalk

Now that I can drive my D for errands I probably start selling them pretty soon. Just want to make sure no problems.

I started writing up some info.

LAMBDA ECU

This ECU was developed to eliminate idle hunt caused by the stock lambda ECU.

I also added a status LED but so far you only can see that LED looking at the front of the ECU case. With the LED off it indicates the O2 input is high impedance which is normal the O2 sensor is cold or disconnected. In that state the frequency valve is running at 50% duty cycle (45 deg. Dwell). With the LED green it shows your FV dwell is between 35 to 45 deg. Dwell. With the LED flashing green, it shows the dwell is running outside that range. With the LED solid red, it shows your dwell is holding at the minimum or maximum dwell. A fast-flashing red indicates wide open throttle is on holding 55 deg. Dwell.

One owner had a suggestion. Put it in a smaller box so there is more room in the cubby for a speaker/amp. This could be done but would require a new PCB and I want to wait till a few owners are using it.

[Bitsyncmaster]

Well here is good new. I just plugged in a stock lambda ECU and when it goes closed loop I still get the idle hunt. That is good news for me because my ECU does not do that.

[Ron]

:thumbup:

[jimgravina]

Dave,

Do you think this would help the stage 2 guys?

[Bitsyncmaster]

Dave,

Do you think this would help the stage 2 guys?

Really only advantage is to stop idle hunt. My unit still holds the same 14.7 AFR which is all you can do using a narrow band sensor. Only thing that may feel a difference is my wide open throttle instantly goes to 55 deg. dwell where as the stock unit steps to 55 deg. from where it was.

My unit also performs the same testing function as the stock unit. Open sensor, shorted sensor and 1.5 volt battery tests.

If your looking for more performance (AFR 12 or 13) you can install a wideband sensor and feed that output as an analog into the stock lambda ECU or my ECU would also do the same.