DPF on Diesel Cars

[webjaved]

Hello,

DPF is it good or bad? From what I've read if you don't drive the car like on a motorway it can cause you problems. Are they good for local use only with minimum use on motorways. 

What's people thoughts & experience on DPF? Good or bad? 

Thanks

J

[FROSTYBALLS]

The long held belief is that DPF equipped vehicles, regardless of manufacturer, are not at their best when just doing short journeys, and this type of use can exacerbate issues.

[Cyker]

Bad - They sap 2-5% of the car's power, lower mpg, increase all emissions apart from particulates, and make what was a more reliable engine than petrol to a less reliable one.

Because of this, despite being a diesel fan, I'd never recommend a modern one to anybody.

The problem is they need to get really hot to burn off the soot, otherwise it just builds and builds and then the car will try to burn if off by squirting diesel into it, but if that doesn't get hot it just turns into a sludgy mess and eventually drains into the oil sump.

If the car is doing long journeys, e.g. regular motorway runs, or is just on literally all day like with a taxi/cab driver, then it can work, but otherwise petrols and hybrids and even EVs just work better.

That and the demonization of diesel means you won't be able to take one near a major city without attracting what's effectively a daily fine.

It sucks because diesel efficiency is incredible - It was better than even hybrids for a long long time, and even now the running costs match the best hybrids and even EVs that only use public DC charging. Diesel is also kinder to its engine than petrol, and is much easier to synthesize than petrol or hydrogen, which would make it more sustainable. Things like air-blast injection or ducted injection had the potential to make it as clean-burning as petrol, paving the way for 3-way cats to tackle the NOx issue that is the achilles heel of all lean-burning engines, including petrol ones. It really bites that we'll likely never see how good it could have been!

[webjaved]

Thank you both for your replies, I wasn't aware of DPF. When I heard about it I was surprised and it put me off. My brother in law made me aware of it. He's into his cars more than I am. 

[NGRhodes]

10 hours ago, Cyker said:

Bad - They sap 2-5% of the car's power, lower mpg, increase all emissions apart from particulates, and make what was a more reliable engine than petrol to a less reliable one.

Because of this, despite being a diesel fan, I'd never recommend a modern one to anybody.

The problem is they need to get really hot to burn off the soot, otherwise it just builds and builds and then the car will try to burn if off by squirting diesel into it, but if that doesn't get hot it just turns into a sludgy mess and eventually drains into the oil sump.

If the car is doing long journeys, e.g. regular motorway runs, or is just on literally all day like with a taxi/cab driver, then it can work, but otherwise petrols and hybrids and even EVs just work better.

That and the demonization of diesel means you won't be able to take one near a major city without attracting what's effectively a daily fine.

It sucks because diesel efficiency is incredible - It was better than even hybrids for a long long time, and even now the running costs match the best hybrids and even EVs that only use public DC charging. Diesel is also kinder to its engine than petrol, and is much easier to synthesize than petrol or hydrogen, which would make it more sustainable. Things like air-blast injection or ducted injection had the potential to make it as clean-burning as petrol, paving the way for 3-way cats to tackle the NOx issue that is the achilles heel of all lean-burning engines, including petrol ones. It really bites that we'll likely never see how good it could have been!

In theory a sufficiently sized DPF or catalytic convertor will make no measurable impedance to exhaust gas flow, in practice mass produced cars will use the minimum size possible that meets emissions and power targets to cut down on costs, cars are highly compromised designs.
The soot from a DPF cant go near the sump, it will just continue to collect until the DPF blocks.
Toyota's D-Cat was far more advanced than any competition at point of launch, but like with any emissions treatment system on a derv, an extra layer of complexity to go wrong, that do go wrong, as you say.
 

[Cyker]

Sorry I meant the injected diesel ends up in the sump (Although any soot that got dissolved into it from the exhaust would also end up there I guess!) - We had quite a few people here who had that problem, where the car was trying to inject diesel to regenerate but it couldn't burn for one reason or another and drained back into the sump, causing the oil level to rise over the maximum!

DPFs are just an awful kludge - I still think air-blast injection or ducted injection would be far better alternatives if they can sort the R&D out, but alas too late for that now...