Particulate Filters - petrol and diesel

[GuidoBrunetti]

I understand that new petrol engined cars now have an exhaust particulate filter. Why is this necessary since I didn't think they produced carbon particles to anywhere near the same extent. Are the filters therefore similar to the ones which have been fitted to diesel cars for some time and subject to the same problems with re-generation and clogging?

[Goodshot]

Honest John in the Telegraph yesterday said the petrol filters were self cleaning and no problem compared to DPF's which need a good high rev run to burn them clean. Having said that my last 4 cars have had DPF's without problem, although I've kept none of them for more than 3 years.

[Clan]

Originally Posted by Goodshot

Honest John in the Telegraph yesterday said the petrol filters were self cleaning and no problem compared to DPF's which need a good high rev run to burn them clean. Having said that my last 4 cars have had DPF's without problem, although I've kept none of them for more than 3 years.

That is simply not the case , all it needs is driving at 50 mph for 20 mins or so , the car recognises this and when conditions are right will do the regeneration in the background without you noticing anything ..

[Quacker]

Direct injection petrol engines do indeed produce enough soot to come into the same regulations as Diesel engines.
Personally I run four diesel cars concurrently and have never had a DPF issue. PPF [petrol particulate filters] should be basically the same as DPF and should have even less of an issue. This is because petrol engine exhaust generally have far hotter exhaust to instigate a successful burn of the residual captured soot.

[Quacker]

Originally Posted by Clan

That is simply not the case , all it needs is driving at 50 mph for 20 mins or so , the car recognises this and when conditions are right will do the regeneration in the background without you noticing anything ..

High revs are actually counterproductive. What’s needed is a constant load at moderate revs of round 2000 to 2750. Driving up hill at 50mph in fourth or fifth is ideal.

Car will not regenerate unless it needs to though, even if driving conditions are ideal

[Ringthane]

Like Quacker, my D5 has never had a DPF issue in the 7 odd years I’ve had it. I’ve never even noticed it regenerating, even though I do a lot of short journeys.

[Goodshot]

Originally Posted by Clan

That is simply not the case , all it needs is driving at 50 mph for 20 mins or so , the car recognises this and when conditions are right will do the regeneration in the background without you noticing anything ..

Yes that's what I meant - sorry for the imprecision. Never had any problem with them because my driving pattern fits that. Only really bothers cars who drive local short distances without the 20 minute 50mph spin.

[Goodshot]

Originally Posted by Quacker

Direct injection petrol engines do indeed produce enough soot to come into the same regulations as Diesel engines.
Personally I run four diesel cars concurrently and have never had a DPF issue. PPF [petrol particulate filters] should be basically the same as DPF and should have even less of an issue. This is because petrol engine exhaust generally have far hotter exhaust to instigate a successful burn of the residual captured soot.

2500 rpm are high revs to me!

[Quacker]

Originally Posted by Goodshot

2500 rpm are high revs to me!

That's high for a farm tractor or truck but not high for a light duty high speed diesel car engine.

Almost all four cylinder engines have a lower limit operating range under load set at about 1500rpm. Petrol of diesel, it doesn't matter. Any lower than that under near full load and they become unstable in operation and operating stresses on the crankshaft increase exponentially. Which is why many operating manuals suggest not driving under load at less than 1500. Why any manual gear change indicator will advise to down change at those revs and why automatics invariable do down change at those revs when there is any load on the engine.
So limiting yourself to only 1000 rpm operating range is very restrictive unless you like gear changing in a manual and drive like a 90 year old with cataracts, a blue rinse or flat cap.

1500 to 2500 is, however, usually the optimum rev range for maximum fuel efficiency and with diesels, coincides with the area where maximum torque is generated. That is also increasingly the case with modern turbocharged direct injection petrol engines.

[Goodshot]

Originally Posted by Quacker

That's high for a farm tractor or truck but not high for a light duty high speed diesel car engine.

Almost all four cylinder engines have a lower limit operating range under load set at about 1500rpm. Petrol of diesel, it doesn't matter. Any lower than that under near full load and they become unstable in operation and operating stresses on the crankshaft increase exponentially. Which is why many operating manuals suggest not driving under load at less than 1500. Why any manual gear change indicator will advise to down change at those revs and why automatics invariable do down change at those revs when there is any load on the engine.
So limiting yourself to only 1000 rpm operating range is very restrictive unless you like gear changing in a manual and drive like a 90 year old with cataracts, a blue rinse or flat cap.

1500 to 2500 is, however, usually the optimum rev range for maximum fuel efficiency and with diesels, coincides with the area where maximum torque is generated. That is also increasingly the case with modern turbocharged direct injection petrol engines.

I was joking about the 2500 rpm!