Technical Explanations

How hot does an exhaust get during a DPF burn?

Diesel Particulate Filters (DPFs) are here to stay, and here to burn.

THE MODERN DIESEL is no longer the simple motor of old. There’s computer-controlled common rail injection, exhaust gas circulation, AdBlue (fully explained here) and DPFs, or Diesel Particulate Filters. We have a full explanation of how a DPF works here, but you may be interested to know how hot the exhaust gets during a regular burn.

Toyota has done a better job with its DPFs that most manufacturers, actually allowing the driver some level of manual control and an idea of what’s going on, as opposed to the usual method of “don’t worry driver, the car will do it all”. In the case of the LC79 you have a display that shows how full the DPF is, on a scale of 0 to 10.

When the vehicle gets to 4 it’ll initiate a burn, provided it is warmed up and moving fast enough. You can see this happen as the count goes backwards from 4 to 0 in the space of a few minutes. So I let it get to 3 and went for a freeway drive. When the LC79 started a burn I hopped out and was ready with the temperature gun:

Yep, pretty hot. For comparison, this is what it’s like when the vehicle is warmed up but not doing a DPF burn:

So the moral of the story is – don’t do a DPF burn anywhere near anything remotely flammable, particularly dry grass. At least with the LC79 you have some measure of knowledge and control, most other 4X4s are completely automated.

How the LC79’s manual DPF burn works
By default, the LC79 will burn its DPF as and when it needs to, which appears to be as soon as possible after it reaches 40% full. If you drive in conditions where it won’t start an automatic burn such as low range work, then the DPF will fill up and eventually illimuniate a warning sign on the dash. You can then initiate a manual burn when stopped. However, you can ask your Toyota dealer to enable a manual burn whenever you like so you don’t need to wait for the DPF to fill up and warning light to come on.

How quick does a DPF fill up? It depends a lot on your use, load and driving style. It is not unknown for cars to fill a DPF in a day’s worth of low-range or low-speed work. Low speed and cold starts are what fills DPFs, not high-speed, hot running.

DPFs are here to stay, and as such we need to know how to handle them. Good on Toyota for providing the dash display and a manual burn option. Pity the other manufacturers are not quite as bush-aware. That said, the LC200 Sahara has a similar system, but Hilux and Fortuner do not.

Further reading


Robert Pepper

Robert Pepper

Robert Pepper is the editor of PM4x4, an offroad driver trainer and photographer interested in anything with wings, sails or wheels. He is the author of four books on offroading, and owns a modified Ford Ranger PX which he uses for offroad touring. His other car is a Toyota 86 which exists purely to drive in circles on racetracks. Visit his website: www.l2sfbc.com