Ok, not many people reporting active GPF/OPF regeneration with their performance Golfs, but pretty much everyone reporting experiencing their first one with their Polo GTI is doing so at around 4k miles. Maybe there's a "just in case" cycle programmed in for the Polo's EA888 3b variant engine that isn't present on the Golf's EA888 3 variant? Perhaps as a result of the audi valve-lift tech on the inlet and use of Budack-cycle for greater economy under low load?
From what I have read, petrol cars generally run with a stoichiometrically correct fuel:air mix (just the right ratio, no sizeable excess of air), so injecting fuel into the exhaust system is a waste of time because there is almost no oxygen in the exhaust gas to ignite it. The petrol exhaust is up to temp (in excess of 550C) in a matter of a few miles due to petrol engines chucking so much of the engine's output away in the exhaust (diesels are more economical because more energy released in ignition is converted into kinetic energy that the drivetrain can make use of).
So after 2 miles from cold, the petrol engine has the fuel source (the soot), the heat, but not necessarily the oxygen (ever heard of the combustion triangle in Chemistry lessons?). By comparison, diesels have the oxygen, the fuel (soot), but not necessarily the heat on shorter journeys, necessitating ignition of fuel in the exhaust system to raise the temp during an active or forced regen.
Excess oxygen in the exhaust of a petrol engine comes from engine braking ("motoring the engine"), as the engine under no load requires no fuel and just compresses air to get rid through the exhaust while doing so.
It seems to me then, a lack of ideal conditions to passively combust soot collected in a GPF/OPF is down to the driver never easing off the accelerator to allow oxygen rich air into the exhaust. So you could blame it on driving style if someone is either on the accelerator or brake, never letting the car slow down under no load.
I could quite easily believe this of my wife's driving style- she brakes a lot more than me, and her car always runs a bit better after I've had it.
Some of the blame could also be attributed to everyone having a DSG box now. Running in auto mode, engine braking is negligible, the engine always seems to be getting some fuel even when you've come off the accelerator because the rate of deceleration in any particular gear with no throttle input seems much less with DSG than with a manual box.
There's definitely something happening with GPF/OPF equipped cars to forcibly clear the load as it builds up. My guess is it combusts under low fuel concentration and an oxygen excess so that some oxygen is available to the exhaust. I found the mpg drop unbelievable 1/3 drop in fuel economy for 2 x 8 mile journeys.
I prefer my Polo GTI+ without GPF to the wife's with GPF.
