PDM Installation & Configuration: PDM Logging
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PDM Logging
03.37
| 00:00 | - A feature that the majority of PMUs on the market include is the ability to log data. |
| 00:05 | And in particular the current flowing through each of its output channels at any time. |
| 00:09 | This data can be useful in a couple of different ways, when we're first installing a component on the car we've of course determined its current draw, sized the wires and configured the PMU output channel properly so it'll test fine with the vehicle stationary but this is only part of the story. |
| 00:27 | Testing the initial condition like this is helpful but it only tells a small part of the picture as the vehicle operation sitting stationary in the garage or pits is very different to when it's out on the road or track. |
| 00:38 | Being able to log the current the components on the car are drawing while the vehicle is being driven under different conditions can help us pick up problems early and correct them before they cause further damage. |
| 00:50 | An example of this is an in tank fuel pump. |
| 00:53 | In tank fuel pumps rely on the fuel running through and around them to keep them cool. |
| 00:58 | As this fuel is pumped up to the fuel rail and some of it is returned to the tank from the regulator it does gain some heat. |
| 01:05 | The more we drive, the more fuel is used and the less physical mass there is to absorb this heat. |
| 01:12 | If the fuel tank is subject to radiant heat from an exhaust, the problem is compounded and the fuel can really start to heat up. |
| 01:19 | All this heat in the fuel compromises its ability to cool the fuel pump motor and this will result in the fuel pump becoming less efficient. |
| 01:27 | Fuel pumps are typically sized with a good level of head room. |
| 01:30 | So it's likely the pump will still be able to supply the required fuel at the set regulator pressure but as it's doing so less efficiently, will draw more current. |
| 01:40 | Something that we will be able to see in our logging. |
| 01:42 | Now as with any logged data, it can be interpreted in many different ways but if we saw an increase in the current drawn by the fuel pump over a stint of relatively consistent driving, it points to there being a problem that we need to investigate. |
| 01:57 | Fuel heating might be our hypothesis but we'd need to do further experiments and measurements to prove or disprove this. |
| 02:04 | But at least our data has told us that there's something we need to look at. |
| 02:08 | This fuel pump example looks at data gathered over a relatively short time period but it's also common to look at logged PMU data over much longer periods and use this as a guide to spot failing components. |
| 02:20 | If we think about something like a differential oil cooling pump, this is usually a fairly set and forget component. |
| 02:26 | If there's some temperature monitoring of the differential oil the pump might be set to turn on and off at set temperatures but it's unlikely anything going wrong would be spotted until there was a complete failure of the pump which could quickly retire a car from a race. |
| 02:41 | If the average current draw of the diff pump is looked at over several race sessions and is seen to either increase or decrease significantly, this could point to the pump being in the process of failing. |
| 02:52 | Once again, there are many ways that this data could be interpreted but it can now be investigated before there's a race ending event. |
| 03:00 | In professional race teams, race engineers will have scripts that they process data like this through that compares all that latest data to historical data and will flag any troublesome long term trends. |
| 03:12 | In this module we've talked about PMU logging and how being able to keep track of how the current through each channel helps us spot potential problems. |
| 03:20 | While the logged data won't usually provide a smoking gun that directly points to a problem, it at least tells us that there's something that needs investigating and lets us fix a problem before a component fails completely, possibly causing further damage. |
