Wild Weasel

Does anyone have a firm grasp on the reasons everyone needs to go to turbos to reduce emissions?

I understand how a turbo can improve fuel efficiency on tests, even if they're faking it. You're effectively using a much smaller NA engine for efficiency while running tests while providing the turbo to give extra power in the real world. It's my impression that real world fuel economy isn't all that different for engines producing the same power.

What I don't understand is how this effects things like particulate counts and whatever else they use to measure pollutants. I keep hearing about things like particulate filters and other regulations and how they are the death knell to the naturally aspirated engines. I just don't understand how this all plays out.

Does boost actually reduce pollutants? Does fuel burn cleaner at compression ratios higher than a NA engine can produce? If this is the case, do they run just as dirty when not in boost and run cleaner when you're pushing them?

Do naturally aspirated engines actually pollute more or are they simply unable to game the testing methodology?

Why can't we have nice things?

GrantG

I think the biggest benefit is that the displacement of a turbo motor is typically smaller than NA and they test the cars without running much/any boost in the simulated city/hwy driving (never full throttle)...

Brosef

my understanding is that it all comes down to fuel economy (i.e. turbos don't burn any cleaner, they just burn less when off throttle). that's obviously all under "ordinary" driving, and under hard driving, they probably burn about the same as a similar hp NA engine.

I could be wrong, but that's my experience and understanding.

evilfij

Wild Weasel

Is efficiency directly related to measurable pollution? Couldn't an engine burn more fuel but do it cleaner if it's designed to do so?

Is it that dramatic a difference? I don't really know how the tests are run. I know that boosted engines are generally never in boost during testing, but I don't know too much beyond that.

STG

It's all smoke and mirrors. They're just better under test conditions and not everyday use. That's all that matters, meeting the "test criteria".

STG

https://jalopnik.com/the-tech-that-w...ion-1788662897

Wild Weasel

Whoopsy

Turbo engines are only more fuel efficient than NA engine when under no load, which is what the scenarios are for testing purposes.

The moment one put the foot down the fuel usage goes way up. On boost they do make more power, and power takes fuel. On top of that, extra fuel is also pumped in to cool the charge, so even more wasteful.

If only governments around noted world use a more realistic testing scenario, like using perhaps more than 50% throttle, the trend will reverse and turbos will fall out of favour.

soulsea

Read this a few years ago ... similar type of nonsense from automakers.

The Catalytic Converter Conspiracy

If you drive an American automobile of a later year than 1975, which should be about everyone in America, it has a catalytic converter. Unless it's older than 1984 in which case you can cut the sucker off, and pitch it. The catalytic converter or "cat" for short was first thought of in the early 1950s by a french engineer living in L.A. named Eugene Houdry. He was tired of all the smog, and worked in catalytic oil refining. The first production cats weren't introduced until 1973 when lead was taken out of gasoline as an anti-knock agent, and some other guys fussed around with the design, and improved it. Lead gunked up the converter. By 1975 all vehicles had to have a cat from the factory, and by 1985 it was a crime to take it off your vehicle if it was built in that year, or later.

The idea behind the cat is to burn unburned hydrocarbons(fuel molecules) left over from the combustion cycle. It wasn't really too bad of an idea for the time because cars were carbureted then, and the fuel mix ratio was just set to the best compromise for most conditions. If it got cold, or you had a big drop in altitude it would be a little lean, if it got hot, or you went up into the mountains it would be a little rich. Most of them were set on the rich side because a spark ignition engine runs better a little rich than it does too lean. So this meant unburned fuel coming out the tail pipe. The cat was supposed to burn this extra gas and clean up the emissions. Good idea right?

Maybe sort of at first. The biggest problem with early converters is that they took a long time to get hot, and they had a problem staying hot enough to burn the fuel all the time because the carburetor wasn't always that far off, and sometimes was too lean to keep the cat hot, but rich enough to still waste some gas. Enter the smog pump. It blew air into the cat like a blast on a furnace to keep it hot, and the carburetors were intentionally set even richer to make sure they wasted enough fuel to keep the cat hot. Plus the smog pump pulled about 5 horsepower. So now we are wasting fuel to support a device to catch wasted fuel, brilliant. Now I'm sure all the oil companies were just heart broken that every single car on the road was going to have to consume about 30% more fuel to catch any incidental unburned fuel that might escape due to the carburetion system.

Then in the mid 80s we started getting good at fuel injection, and now we can control how much fuel the engine gets at any time. Coincidentally about the same time the feds mandate the catalytic converter to be on all engines about 25HP all the time, for all time, and with no exceptions, EVER. A little convenient? Seeing as there should be very little waste fuel now that we can accurately meter the fuel to the engine's needs. Your modern vehicle's computer is now so sophisticated that it can vary the pulse of every injector by 1/100th of a gram every single rotation of the engine. There is absolutely NO reason whatsoever for a modern vehicle to have a catalytic converter. Accept that it takes about 15%-20% more of your fuel(read money) to keep it hot, and running. Better than the 30% or more from days of yore, but still very wasteful. Not to mention the less than beneficial side effects produced by the cat. Like acid rain from hydrogen sulfide.

Anyone with a moderate understanding of combustion theory, and an understanding of engine control systems knows that a properly electronically tuned engine burns many times cleaner than the federally mandated system. Some european contries won't even allow california smog equipped vehicles in their country because they are so dirty. At our current level of technology it is abundantly apparent that it has nothing to do with clean air, and everything to do with $$$.

disden

It does seem like smoke and mirrors. My 2011 Panamera with V8 got identical gas mileage to my newer 2014 with the improved turbo V6; only difference of course was that it sounded awful. Torque boost made driving around town much more zippy feeling though.

LnC993

Europe's Emissions Crisis Is Causing a Return to Bigger Engines

"Tiny engines do great in lab testing, but pollute more in real-world driving. The solution, it seems, is more displacement."

http://www.roadandtrack.com/new-cars...igger-engines/

pitt911

Fuel consumption is related to power used . Unfortunately the RL crowd are different than the majority of people in driving style and usually we don't get any benefit " fuel consumption wise" from turbo engines
but the majority of drivers use less fuel with Turbo engines and see less fuel consumption because they drive like " grandma"
I think most new cars now get the higher fuel rating related to transmissions with higher " cruising " gears as compared to turbo engines

GT3

NA or Turbo, I will still average 8 mpg...

BillS

It's thermodynamics. If you google the Otto cycle it will show you why a turbo motor is more efficient than a NA motor. The higher the compression the more energy you can extract from a given amount of fuel. Turbo motors have the advantage of running at effective compression ratios much greater than what you can do with a NA motor.