### [Differential pressure-air flow volume] ratio analysis

Posted:

**Tue Aug 20, 2019 4:20 pm**Today I logged some values from my TDI and placed in a graph

I included also the

As reported in technical documents, in fact, the ECU uses that ratio to calculate the soot mass deposit.

All values are related to the left vertical axis but the ratio value (and its trend line) that's related to the right axis.

As you can see, the ratio value (in brown) oscillates but its trend line (in red) is constant. This was a short trip so the soot mass value (in purple) didn't increase enough remaining more or less constant too.

The next step will be to log a long trip to verify if the ratio trend line will increase proportionally with the soot mass calculated value.

In a tech document I've found a graph that let me calculate the limit values for the ratio between a filter full of soot mass and a filter empty, but I'm not sure these values can be used for all kind of DPFs. So I'm going to verify them in my DETA engine.

What I've found:

I included also the

**DPF gas volume**that isn't present in released app, just to understand the relationship between the ratio [differential pressure/air volume] and the [soot mass calculate].As reported in technical documents, in fact, the ECU uses that ratio to calculate the soot mass deposit.

All values are related to the left vertical axis but the ratio value (and its trend line) that's related to the right axis.

As you can see, the ratio value (in brown) oscillates but its trend line (in red) is constant. This was a short trip so the soot mass value (in purple) didn't increase enough remaining more or less constant too.

The next step will be to log a long trip to verify if the ratio trend line will increase proportionally with the soot mass calculated value.

In a tech document I've found a graph that let me calculate the limit values for the ratio between a filter full of soot mass and a filter empty, but I'm not sure these values can be used for all kind of DPFs. So I'm going to verify them in my DETA engine.

What I've found:

**ratio (differential pressure [mbar]) / (dpf air mass [m3/h])**

- 0,48 = filter full (I think full for a field regeneration)

- 0,075 = filter empty

- < 0,04 = filter defective