Particulate Filters for … Everyone!

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VW – desperate to appear chastened over its “cheating” sins – has just announced it is going to fit particulate filters to its 2017 model year cars in anticipation of the next round of Uncle’s emissions fatwas.particulate filter

No surprise, right?

Diesel-powered cars have had particulate filters for years. They’re used to catch… particulates, which are small particles of soot that – while not a factor in smog or even an alleged contributor to (equally alleged) “climate change” – are a potential health issue for some people with asthma.

Soot/particulate emissions are – were – a problem specific to diesel engines.

But these aren’t diesel-powered cars we’re talking about. They are gas-engined cars.


VW (see here) will be fitting particulate filters to all its cars henceforth – whether diesel or gas powered.

Because it turns out that gas engines fitted with direct injection (DI) have a Soot Problem, too.

It’s a new problem. An unanticipated one.DI vs. PFI image

Port fuel injection (PFI) engines and TBI engines do not have this problem. But DI – in which the fuel is sprayed (under extremely high pressure; several thousand psi) directly into the cylinder as opposed to being mixed with air before it enters the cylinder results in … Too Much Soot.

In order to avoid the wrath of Uncle, particulate filters will be be necessary henceforth.

Probably not just for VWs, either.

DI (marketed as GDI, TSI and so on) is already in widespread use by pretty much every major automaker – chiefly because it offers a slight MPG gain over PFI (which replaced Throttle Body Injection for the same Uncle-nudged reasons). And with Uncle decreeing every-higher gas mileage mandatory minimums (35.5 MPG today, more than 50 MPG less than ten years from now) even slight gains matter. Maybe not to the car buyer, but to the car maker. Who either complies with the fuel economy fatwas – or gets fined. These “gas guzzler” fines are folded into the price of its new cars, making them less competitive on the market – or they are eaten by the automaker, reducing the automaker’s profit margins and leaving less cash on hand for designing/engineering next year’s new cars.

So, we get DI.

But – as with most things – there are downsides.

With DI, the known downsides are increased complexity (the systems have two fuel pumps, to “step up” the pressure to 3,000-plus PSI vs. the 35-40 or so psi typical of PFI systems) and so, cost. The car itself – and the cost to maintain the car, down the road.

This includes dealing with carbon build-up on the intake valves.

In a PFI system, the incoming fuel is sprayed just behind the intake valves, the fuel cleaning (and cooling) the valves’ backsides as you drive. It’s one of the reasons why they put detergent additives into gasoline. But in a DI system, the intake valves are not cooled or cleaned by the incoming fuel because the fuel is sprayed directly into the cylinder. As a result DI engine intake valves are susceptible to the formation of combustion deposits on their surfaces. When enough crud builds up, it can affect the valve’s ability to seat (close) properly, which means the cylinder doesn’t seal properly – which isn’t good news for anybody except your mechanic.carbon on valves

To remove the deposits he will (best case) use solvent and a flushing machine. Worst case, he will have to partially disassemble the engine to get at the valves in order to manually clean them.

Not cheap.

And your new car salesman – you know, the guy who touted all the benefits of the DI-equipped car you just bought – probably didn’t tell you about it, either.

But now there’s a third downside – unacceptably high (to Uncle) particulate emissions. It’s probably (again) a fractional amount we’re talking about – because emissions of everything an IC engines produces (except carbon dioxide and water) are and have been barely whole numbers since the 1990s. Whole digit reductions are no longer economically and probably, mechanically possible without turning the engine off.

Of course, they’re doing that, too. Many new cars now have cylinder deactivation or “Auto stop/start” systems for just this reason.

Regardless, Uncle is on his hobbyhorse about particulates now. It gives him something to do.

Hence the need for particulate filters. VW first – the others to follow.

Guess who’s gonna be paying for these?Uncle pic

Hint: It won’t be Uncle.

These filters (see here) add another layer of cost complexity to the car – to its exhaust system.

In diesel engines, particulate filters work like a catalytic converter does in a gas-burning car, chemically converting the exhaust’s composition. They also literally filter – trap – the offending particles.

Cars with gas engines will still have catalytic converters (most new cars have at least two) because burning gas rather than diesel creates its own emissions issues.

But now they’ll also have particulate filters.

These will likely have to be cleaned or even replaced periodically (just like an oil or air filter) because a filter eventually fills up with whatever’s being filtered out and once that happens, it’s no longer any good as a filter.

A clogged filter would also increase backpressure – like a cork put in the tailpipe – not good for anyone (except your mechanic).

In diesel engines, a “regeneration” process using extremely high heat (and sometimes, a spritz of fuel shot into the exhaust stream) cleans the filter automatically. Maybe such a system will be used in gas-engine applications, too – though that creates another set of potential issues, including reduced fuel efficiency and (of course) the cost of all the plumbing.

So, to recap: We got saddled DI over PFI (which worked just fine) to eke out fractional increases in MPG, to make Uncle temporarily happy. But this has apparently caused a fractional increase in particulates – which will require particulate filters to keep Uncle happy.

For the moment.

I wonder what not-yet-known problems will be caused by these particulate filters?

Unintended consequences, anyone?

It’s Uncle’s specialty. depends on you to keep the wheels turning! The control freaks (Clovers) hate us. Goo-guhl blackballed us.

Will you help us? 

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  1. You’re waxing quite philosophic, 8, though I have to agree w/much of what you say.
    ” June 1st the early morning came with a freeze and two days later it was 100 degrees.” Now that’s what I call ‘climate change.’

    • Texas=Climate change. As long as I can recall people used to tell non-Texans “If you don’t like the weather, stay around for a little while, it’ll change.”

      When I made fun of Car and Driver for touting the time it took to raise or lower the convertible top, as if that was the mainstay of a car, I wasn’t kidding when I said 17 seconds is an eternity in Texas. The wind will go from zero to 80 or 90mph and back in less than 17 seconds. A good Texas dirtdevil would take down most structures in the southeast. Breathless reporter “Today, Suckass, Georgia was hit with winds up to 55 mph” and show building torn to shit. Quit using cardboard and moats for building matgerials MF’s and that shit’ll stay up.

      • “If you don’t like the weather, stay around for a little while, it’ll change.”
        I’ve lived in several places, and visited many more, and the ‘natives’ have said that everywhere, as if it were unique to their location. But hey, that’s weather.
        And then there’s a blue norther.

  2. I firmly believe that one day I will be telling my future grandchildren about the wild days when people could buy whatever car they wanted and drive wherever and whenever they wanted….maybe even take them to my secret hidden garage where I hide my hemi Challenger Demolition Man style. That’s how I’ll go out, in a cloud of tire smoke driving my archaic and illegal gas burning Challenger just before the Department of Human Safety drone takes me out.

    Dystopian? Maybe. Possible? Increasingly so.

    • Hi Shemp,

      I see it developing this way, too.

      I’ve been a car journalist since the early ’90s and for most of that time, the changes were “creeping” (incremental). Lately, over the past 2-3 years, I have witnessed dramatic changes in the way cars are being built, an escalation to the hysterical/ridiculous level of the various “safety” and “emissions” mandates and a now-open-about-it (and worse, no longer fringe) animosity toward the car as such.

      It’s another example of the battle lines being drawn. It really will come down to Us – or Them.

      • eric, it’s coming. I only wish I could affect the outcome to a greater extent.

        I see it more as those like us caught between the warring tides of neocons and new age commies. Maybe if we go to ground we can watch them do each other in.

        What’s so hilarious about it all is there’s almost no difference between the two groups. They both want to be controllers of everyone else.

        The college crowd seems to have drunk so much blue cool-aid it’s literally addled their ability to think.

        The neocons are simply your greedy, run of the mill psychopaths……and there ends up being almost no difference.

        Keep the oil in the ground. They send me eletters(I keep up with both sides, know your enemy) hoping I’ll donate money to stop drilling for oil, anywhere, everywhere, leave it in the ground is their mantra. I’m assuming they have enough sense(probably my mistake)to know that computer is mostly a petroleum product as is nearly everything they wear unless they wear only clothes and shoes (hemp, they have too much money)harvested by monks, toted on the backs of burros(lost PITA members there)to someplace they use hydraulic water power and it’s then carted to them by poor immigrants they then share their daddies money with. They wouldn’t be caught eating anything that required fuel to find it or grow it or transport it……right?

        At least the oil producers don’t beg me to beg for them. I consider oil to be a fair price and not something I should get for free since I’m knowledgeable of every step in getting it and refining it. When you consider the price of labor, fuel needed, astronomical prices of everything used($200K for that big rig that picks it up and the one that delivers the fuel), millions for a drilling rig and many more millions to punch a hole, more to complete it and more to store it or pipe it somewhere(they hate pipelines too).

        This entire country has gone off the deep end as far as the radicals on those two ends are concerned.

        Ok, let those people from NY go through a winter with no heat, no shelter and no food. That takes care of one side. Let the neocons go without the big bucks they need to survive, there goes the other side. Hey, maybe leaving oil in the ground isn’t such a bad idea. After everybody gets a little fire going we won’t be worrying about such as CO2 when there’s no vegetation to produce oxygen from CO2 and we can all choke to death on the billions of fires worldwide……

        They must no longer teach humans survive by their wits and not because they can adapt to any environment. I’ll give that one group money after they’ve survived for a year with no clothes.

        Two years ago I was working in Seagraves Tx. June 1st the early morning came with a freeze and two days later it was 100 degrees. How’s that working out for naked people who wished to be at one with the earth? Pretty well I suspect since the earth and themselves will be as one……soon. Dust to dust so to speak.

        • Quite a number of these people truly believe we need a plague to thin out the population. They also believe they will somehow survive because of their superior genes (eugenics just won’t go away). If the cost of energy skyrockets and people start to die, that’s good news to them. If you can’t afford to heat or cool your house, well, maybe your genes aren’t as productive as the elite genes. More room for their future generations.


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