Slashdot Mirror
Camless Internal Combustion and the Digital Age (hackaday.com)
szczys writes: The internal combustion engine is amazing, and it continues to evolve. Carburetors gave way to fuel injection, and a computer now monitors all kinds of sensors to ensure these engines operate at peak efficiency. But there is one thing that has remained largely unchanged: the cam shaft. This is a device responsible for mechanically timing the operation of the cylinders. It's possible to build an engine that uses digitally controlled actuators instead of a camshaft to decide when each cylinder should fire. These exist as prototypes — we have the technology, so why aren't we building with it? The answer is that change is hard, and as with the carburetor it could take an outside force (in that case mandatory efficiency benchmarks) to get automobile manufacturers to wager a bet on new technology.
It's possible to build an engine that uses digitally controlled actuators instead of a camshaft to decide when each cylinder should fire.
Camshafts don't control when cylinders should fire, that's an already replaced component called the distributor. Camshafts control the timing of inlet and outlet valves, and there are already formula one and other engines using electronically actuated pneumatic valve lifters.
The problem is that cam shafts are very reliable, and a single fault in valve timing, in an interference engine especially, results in catastrophic engine damage, so the software and hardware has a very high bar to meet for it to replace mechanical cams.
Also firstpost.
-puddingpimp
But the failure of a mistimed valve is way more catastrophic than that of a misfiring injector or spark plug. Even if an electrically actuated valve system was to be used in production I'd expect it either to be supported by a backup mechanical system or to be designed never to interfere with the volume occupied by a piston. In the first case the electronic valve would be an additional cost only justified on high performance engines, in the second case it would affect the performance negatively. Perhaps this could work with sleeve valve engines?
Yeah, the idea of something smashing into something else due to a failure is what concerns me. I've already experienced what happens when a camshaft position sensor fails gradually enough that it doesn't trigger a fault in a computer...nasty ignition timing with backfires at high RPM...a Ford Taurus belching fire on the highway...and the idea of parts flying around without protection is why I don't own an interference engine. https://en.wikipedia.org/wiki/...
The sparkplug of a gas engine requires... electricity.
A modern car engine uses an ECU which regulates spark timing and the transmission (usually called a PCU or Powertrain Control Unit nowadays) - it adjusts the spark timing and spark power based on the load of the engine. Lose battery power and the ECU goes dead. Depending on the vehicle, if you drop the battery, it may or may not continue running - the alternator will produce more than sufficient power to keep the engine running, but the battery provides voltage regulation of the entire system.
And there are still completely mechanically driven engines - small aircraft use them, and they're a PITA to manage because you have to manually adjust the mixture (fuel-air ratio) for optimum power as you change altitudes. Experimental avgas aircraft, and production diesels (running on Jet-A) use a FADEC (Full Authority Digital Engine Control) which runs off the ship battery and a backup battery that fully controls the engine. The pilot only has a lever that tells the FADECs (there are two of them for redundancy) how much power to develop - the FADEC figures out the optimum settings to achieve that. You get an increase in efficiency, a decrease in pilot workload and all around increases in efficiency.
Heck, Electronic Fuel Injection isn't on aircraft engines yet - yes, they've had fuel injection for around 25 years or so but it's generally of the continuous spray type.
As for this, it does have some advantages like extreme variable valve timing. Hybrid cars, for example, often use a modified Atkinson cycle engine (modified because it's really an Otto cycle engine, with the intake valve kept open well into the compression stroke to reduce the fuel charge). Atkinson engines are extremely efficient - they have a small intake and compression stroke but a large power stroke (the goal is at the end of the power stroke to have 0 differential between cylinder pressure and air pressure, thus ensuring you have extracted all the energy).. But at the same time, Atkinson engines don't develop as much power. Being able to switch operating modes on the fly can be useful in pure gas-only cars - switch to Atkinson during low power for maximum efficiency (idling, highway), while being able to switch to Otto when you need power (accelerating, for example)
I just, I just can't see any benefit to this? ... What efficiency gains are here?
Follow the links and do some research? 30% fuel economy increase at low end, 30% increase in power at the high end, 50% reduction in emissions for standard driving, 4cyl engine in the same space as a 3cyl engine in the engine bay, a 20cm reduction in vertical height of the engine, reduction in engine weight (benefit increases with engine size).
Oooh and then you get into the really interesting things:
Ability to shutdown cylinders completely on demand by holding the valve open when not needed.
Eliminate engine breaking completely further increasing fuel efficiency by allowing an engine to freewheel without compression eating up efficiency.
And then you can do other things like using the back stroke of an engine to compress cylinder during engine breaking and sore it in a compressed vessel which can then be reused to boost power when needed either at take-off or at peak power.
Yep, no benefit at all.
Also this is not new. Not at all. Industrial compressors have had electronically diven continuous unloaders for the best part of 25 years now, and I guarantee that most of the compressors I've worked with have more rotations through their cylinders than any slashdot driver.