Mazda CX-5 2.2 SkyActiv-D - DPF filling fast

[spektr]

Is this like an external module?

[lowend]

If the values from the EXHTEMP2 sensor are cheated for too long, it throws off the whole algorithm.
By using this simple circuit https://www.aliexpress.com/item/32842154532.html i can set necessary time only (few minutes) to reduce PM_GEN.

[spektr]

And where did you connect this circuit?

[lowend]

And where did you connect this circuit?

I disconnected the sensor, cut the connector and made extension (about 30 cm) with extra jumpers pulled into the cabin.
EXHTEMP2 sensor (SH0118845A - located in middle of the DPF container) is still connected, I only occasionally activate the magic button that switches the relay.

[spektr]

Interesting

[maciekelga]

My plug is already on the way to make extension
I think I will make extension connected between original connector and try with timer relay or will implement into my DPF indicator.

[spektr]

I didn't get what does exttemp2 sensor has to do with pm_gen? So this sensor measures temperature in dpf filter? So what is the idea around this?

[Valiv1985]

And where did you connect this circuit?

I disconnected the sensor, cut the connector and made extension (about 30 cm) with extra jumpers pulled into the cabin.
EXHTEMP2 sensor (SH0118845A - located in middle of the DPF container) is still connected, I only occasionally activate the magic button that switches the relay.

This PM_GEN mod seems great and I think it reguires a separate thread for itself. If its not asking for too much, would you be able/willing to write a step by step guide of how to do it and what are the pro and cons?

[Mareng]

I didn't get what does exttemp2 sensor has to do with pm_gen? So this sensor measures temperature in dpf filter? So what is the idea around this?

I aggree with you there Spektr, a DPF has to regen when its 'full', so don't see the point in fiddling with Mazda's design.
If they are having regens every 150-200 mile or the Km equivalent then everything is fine and should let the ECU do its job. If the mileage is dropping into the 0-50 mile range then they need to find the cause.
If as it seems they are fitting this relay box because they will be stopping halfway through a regen, its not the end of the world and next time all the parameters are met it will regen normally.

The downside to this mod may prevent the regens when required and cause a blocked DPF, then you are in trouble.

[lowend]

The PM_GEN values does not take into account the current state of the filter. As a result, individuals with good combustion and high-quality fuel may surpass the PM_GEN threshold, despite having only half-full filters.

Each Sky-D owner's situation is unique, and it is not advisable to push the system to its limits, as this can cause filter clogging. One way to gauge the safety of the system is to look at the value of DP_DPF at idle. It is difficult to determine a safe value, but I have successfully regenerated it with 2.1 kPa down to 0.4 kPa, which I consider to be the maximum.

It is a common belief that those who disable their EGR tend to regenerate later, which is thought to be due to slower clogging of the filter. However, this might not be the case. The control unit operates in a slightly different mode and calculates values for PM_ACC differently, so the filter may clog in a similar way as before, but the regenerations are considerably delayed. The table I recently sent showed values of around 1.6 kPa with EGR disabled, compared to 1.1 kPa previously, supporting this idea.

Interestingly, the control unit initiated the regeneration even though I had not reached the required values for regeneration, which are known to be around 5.5 g/l.

I cannot determine all the factors that affect the growth of PM_ACC_DSD or PM_GEN, and my observations are merely speculative. However, I have discovered that the values decrease when the measured temperature at EXHTEMP2 exceeds 450 °C for at least 2 minutes. 450 °C is the initial point where the values decrease slowly, so to speed up the process, it is necessary to set it to 550 °C.

Another issue is that PM_ACC_DSD also decreases in this mode, which is an undesirable state. To combat this, I used a timer circuit to reduce the PM_GEN values to the required level for a necessary time (for example, 8 minutes), and after this time, everything returns to normal.

If you want to try this mode, there are a few things to consider:

1. It's at your own risk.
2. If you regenerate too often and only based on PM_ACC, I would not recommend this modification. Also, if you do not have the necessary tools, you may get stuck halfway through.
3. Access to the EXHTEMP2 sensor connector is difficult unless the engine is removed. The cable is additionally held by a piece of bracket on an M10 nut. I reached the nut from the bottom of the engine, and the right front wheel had to go down together with the plastic that protects part of the timing belt.
4. When the sensor is disconnected, you need to figure out how to reconnect it, or you can cut it off and connect another cable with extra jumpers leading to the cabin, as I did.
5. Whether you will control it with a circuit or a simple switch is up to your imagination. As an example, I recently sent a bridging diagram. Someone will surely be able to do it more intelligently.

Finally, here are some approximate values of the NTC sensor:
90 kΩ - 51 °C, 20 kΩ - 125 °C, 4 kΩ - 255 °C, 600 Ω - 525 °C, 80 Ω - 1134 °C
80 kΩ - 54 °C, 10 kΩ - 171 °C, 3 kΩ - 282 °C, 500 Ω - 562 °C, 70 Ω - 1176 °C
70 kΩ - 58 °C, 9 kΩ - 180 °C , 2 kΩ - 328 °C, 400 Ω - 613 °C, 60 Ω - 1224 °C
60 kΩ - 63 °C, 8 kΩ - 190 °C , 1 kΩ - 431 °C, 300 Ω - 686 °C, 50 Ω - 1271 °C
50 kΩ - 69 °C, 7 kΩ - 200 °C, 900 Ω - 448 °C, 200 Ω - 815 °C, 40 Ω - 1289 °C
40 kΩ - 79 °C, 6 kΩ - 215 °C, 800 Ω - 470 °C, 100 Ω - 1060 °C, 30 Ω - 1289 °C
30 kΩ - 95 °C, 5 kΩ - 232 °C, 700 Ω - 495 °C, 90 Ω - 1096 °C, short - 1289°C

Perhaps it would be helpful to start a new thread for this topic. Currently, the mode is relatively untested, and the results in the future are uncertain