71–80 of 152 posts
Any way to know how they accomplish the variable compression?
- Will the ignition need to be cut off before the ratio change happens ?
- Will this apply the change to all the cylinders at the same time ?
Earlier quoted context omitted.
That article is kind of shitty too. Higher compression ratio = better combustion = more power with less fuel, regardless of turbo. Higher compression will always mean better fuel efficiency. My moms Mazda CX-5 runs a 13.5 compression ratio and gets 27mpg. The power/efficiency trade off appears when you're talking about turbocharged engines. Turbos compress air into the combustion chamber, so when you compress compres…
So this only reduces inefficiency while the the engine revs too low for the turbo to kick in? Then it is competing with electrically assisted turbocharging (spin the turbo electrically when there is not enough exhaust pressure, basically a super/turbo hybrid using electric transmission), as both are addressing the same inefficiency. I know where I would put my bets in terms of price, reliability and ease of developme…
Earlier quoted context omitted.
Diesel's fatal flaw is particulate emissions. Attempts to mitigate those, without cheating (e.g., VW), have proven difficult.
Volkswagen cheated to try to get a less expensive system in place. DPFs and urea injection are pretty well proven technologies and work pretty well.
The real problem is 5-10 years later when these systems need repair or replacement. For many the economic temptation to have them "nulled" is too great (fuel efficiency is improved by removing the DPF) - and that once-clean diesel is now a toxic, polluting nightmare.
This is a huge problem in the UK - and why we need to phase out diesel in private/light motor vehicles.
Earlier quoted context omitted.
Volkswagen cheated to try to get a less expensive system in place. DPFs and urea injection are pretty well proven technologies and work pretty well.
They work well enough on new vehicles coming out of the factory. The real problem is 5-10 years later when these systems need repair or replacement. For many the economic temptation to have them "nulled" is too great (fuel efficiency is improved by removing the DPF) - and that once-clean diesel is now a toxic, polluting nightmare. This is a huge problem in the UK - and why we need to phase out diesel in private/light…
Earlier quoted context omitted.
They work well enough on new vehicles coming out of the factory. The real problem is 5-10 years later when these systems need repair or replacement. For many the economic temptation to have them "nulled" is too great (fuel efficiency is improved by removing the DPF) - and that once-clean diesel is now a toxic, polluting nightmare. This is a huge problem in the UK - and why we need to phase out diesel in private/light…
How do they pass the emissions test?
A visual inspection for the presence of the DPF is required, but this is easily defeated by installing a look-alike "null" filter.
The people doing the MOT testing can be pretty shady anyway. Since any mechanic can operate as a testing facility, it's often the same people who remove DPFs that will then pass them in the MOT inspection.
How are they preventing engine knock ? At 14:1 compression you'd have to be running premium gas, which would pretty much cancel the efficiency saving, in a $$ perspective.
I think there isn't much improvements to be had for engines at full power. But lots of room for improvement at partial power. Interesting bit, hybrid cars have really low emissions. Which says to me they're avoiding running their engines at power/rpm ranges that create high emissions.
That's the thesis?
Here is a simple explanation gathered from this image http://o.aolcdn.com/hss/storage/midas/de3e84cf46030cd7b3ea39... : The difference from a conventional engine is that the engine stroke is increased or decreased automatically. The stroke is the distance the piston travels up and down in order to turn the crankshaft. A shorter distance that is closer to the combustion chamber increases the compression ratio because…
> Make sure to wait two years Haha, this reminded me of a friend who did a summer engineering internship with a U.S. automaker. He came back and related one of the most important things he learned: "never, ever buy a first-run car." I remember hearing him tell about tolerances still being adjusted after all these cars had shipped, cringing to think of all the problems that could cause.
(They had to write their own linter, because they need to ship slightly broken code written by code generators, and last I heard Windows XP is still part of the compilation chain…)
Thanks, but no thanks: I'll just stick to my simple (by comparison) direct injected turbo diesel cars.
When there is a gasoline engine which can ignite the fuel without spark plugs and ignition timing, that'll be the right solution. mazda experimented with this (see "VCCI"), but it never made it into production, because it's not a trivial problem to solve. This Nissan patent is a mechanical engineer's equivalent of a duct tape hack.
Or we could just ditch this entire nonsense with pistons and optimize the Chrysler's super simple turbine car engine until it matches today's exhaust emission regulations. This was a tough problem to solve in 1978, but should be doable now with a particulate filter. And that engine isn't picky: since it's a turbine, it'll run on anything that's combustible, from filtered cooking oil to cologne.
Here is a simple explanation gathered from this image http://o.aolcdn.com/hss/storage/midas/de3e84cf46030cd7b3ea39... : The difference from a conventional engine is that the engine stroke is increased or decreased automatically. The stroke is the distance the piston travels up and down in order to turn the crankshaft. A shorter distance that is closer to the combustion chamber increases the compression ratio because…
> Make sure to wait two years Haha, this reminded me of a friend who did a summer engineering internship with a U.S. automaker. He came back and related one of the most important things he learned: "never, ever buy a first-run car." I remember hearing him tell about tolerances still being adjusted after all these cars had shipped, cringing to think of all the problems that could cause.