Tuners Rejoice! Free Tuning For M4.4!

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Today I had a major breaktrough with my Lambda Commander.

The high speed of the simulated narrowband signal is no problem for the ECU.

What is essential is to give a reference voltage on the lambda minus input of the ECU and make sure the low signal is close to 0.1V and the high signal is close to 0.9V above reference.

0V and 1V will not do!

Holiday is coming soon. Detailed log results will follow in a week or three.

Very curious to see some screenshots of the setup & logging results. Sounds like a worthwhile option, I just don't fully understand from your description alone.

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But i've been struggeling with my lambda light (not CEL), the OBD code is P0164 Heated Oxygen Sensor (HO2S) Circuit High Voltage (Bank 2 - Sensor 3). The front o2 sensor is a brand new bosch and i've dissabled al the rear o2 sensor checks in the bin but the code keeps comming back after about 20 seconds after i start the engine.

do you have any idea whats causing this?

thanks in advance!


PO164 is a rear O2 code. Something must be missing.

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Does anybody know the interrupt priority of the ECU?

It becomes interesting, or it already was. ;)

I'm not quite sure how to understand it, but there is a table at page 62 in this document.


It appears that the priority levels are somewhat programmable, so the settings used in the ECU has to be found.

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Thank you rkam.

I will take a good look at it, as well as the information Maarten sent on the Dutch volvo850forum.nl.

More information about the interrupt priority helps me to prevent possible CPU stress with the new semi wideband regulation.

Although, it seems while reading Maartens post and some own investigation that the initial setup of M 4.4 allows for a much faster lambda regulation.

Time and investigation will tell.

I appreciate your very essential contribution a lot.

Edited by razorx
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Good evening!

I decided to make a short explanation about the functioning of the Lambda Commander. Pictures say more than words.
Below is the normal behavior of a car with a conventional narrow band lambda probe:

At part load the ECU ensures that the exact AFR value is 14.7. This is exactly the value at which the probe switches from rich to poor or vice versa. Something else it cannot.
Under higher load than at part load you do not want that. You would then strive towards an AFR of 12 or so. For that reason, the ECU will not take the lambda signal in the calculation of the injector times.

Instead, there are fixed tables to "predict” injection times . It's a lot of work to get all the cells right. In addition, those tables will eventually no longer be correct due to aging of your MAF sensor, injectors, pressure regulator, and a lot of other things.

That is why I have made the following after a suggestion from Piet. But first the picture:

For each load value, the system behaves as if there is another narrow band oxygen sensor is placed.
At partial load is an AFR value of 14.7 nice but not optimal for consumption. A value of 16 is better for your budget and not bad for the car. For the test, I just used 15.5. When doing this, keep in mind that NOx in the exhaust gasses wil increase slightly.

As soon as the load is higher the behaviour of the simulated oxygen sensor changes and the AFR switchpoint will go down. It is like you have an 02 sensor set to an AFR of 12 or whatever..

And this is the result on the meter:

Today I changed the system so that when switching to LPG other AFR or better said lambda values ​​are chosen.
If you suffer from detonation under full load on petrol you may consider injecting more gasoline within reasonable limits. That has a cooling effect.
If you are going to inject into LPG more than the correct amount of the exhaust gases will become hotter instead and you will just get detonation.

Edited by razorx
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Hey razorx

i think is agreat thing, a wide Band Lambda Regulation

but i dont understand 100% how this can be done with wich Hardware

can i use a innovate lc-2 i can programm one of the outputs of the Controller as narrowband Signal! and then go into the m4.4 ecu

regards Zeno

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@Zeno: it is possible with any good wideband with a controller. Although I am not an Innovate fan ;) . You only need a conversion board behind it to dynamically adjust you lambda switchpoint depending on load and RPM.

Just a did a logging ride with the wideband regulation . Not everything is perfect.
Up to a load of 5 to 8 everything is fine. The system remains beautiful in its wideband control and enriches where necessary. But:

Sometimes over a load of 5ms and sometimes above 8 it does not regulate. The short term fuel trim then goes to 0.
I suspect, because I send lambda data with unlimited speed and that is just a little too fast for the ECU.
It probably drowns in the interrupts. I know that the ECU is very busy under load. MAF and RPM values ​​to be converted to load and continuously rapidly calculating the TCV control, ingnition etc.

I will slow down my system a bit. See if that helps.

Edited by razorx
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It's gone quiet on here. Im stuck, at a dead end, still not moving any closer to anything, Fed up :(

I have been struggling to eliminate some knock I've had for a long time now. Its quite bad on 3 and 5. Ive swapped the injectors over, tried 3 sets of spark plugs, 2 sets of ignition coils, added fuel, reduced timing, tried various cam timing setings but it just won't go away.
Today I had another play, I used the stock V70 Target load as the XPCP_TV was negative nearly all the way through the log and I used the I used the stock V70R ignition table. Still have the same knock even though I've advanced the timing by quite a bit and the XPCP_TV is still negative.

MIL (knock) only comes on at mid RPM under light load just as I press the throttle, about 20% but under little load, boost is about 5 PSI but at WOT, 5500RPM, 18 PSI, AFR 12.1 nothing, sweet as a nut.

AAARRRRGGGGGHHHHHHH!!!!!!!!!!! I've run out of ideas

Here is my latest log to see if anyone can see any issues https://www.dropbox.com/s/kicrz81ch7mo1hk/17-8-14-1.csv

Edited by Avinitlarge
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Maybe something with your knocksensors or knocksensorwiring?

Are they torqued exactly at the prescribed torque?

Normally an engine will have very little (if not none) tendency for knock at light loads.

Edited by Piet
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Im pulling the inlet off to fit a temp sensor this week so will check then. Also got a pair of replacement sensors so may fit them. The only thing that put me off of knock sensors is, the one on the right is mounted between 3 & 4, knock on 4 is virtually zero, I would have thought, if it was the sensor, 4 would show knock too.

You having a nice holiday, Sunning it up in Italy ;)

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Been having some crazy knock issues too...

But mostly at high loads (22 psi +) where the ECU will actually pull me down to 0-1.5 btdc when only trying to run 6.75 deg btdc.

I'm curious to see if you find any resolutions.

I might invest in some new sensors but I'm not sure if that would really make a difference.

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I had a look though various AFR tables last night, most of what I found showed AFR around 5 load is about 12.8, Mine was about 14.3, when I added more fuel in that area, I didn't go as rich as that. I know its varies from car to car but it could be a point in the right direction.

Simply, Could it be EGT or IAT that is high?

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