Idle hunt

[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?1...ight=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?1...ight=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.