by "Demon-Xanth knows how to operate a street." (demon-xanth)
Published 03/16/2017 at 15:03
by "Demon-Xanth knows how to operate a street." (demon-xanth)
Published 03/16/2017 at 15:03
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With electromagnetic valve actuation, direct injection, coil on plug, and turbo charging. Could engine be made that could operate as a 4 stroke diesel at idle, 4 stroke gas at moderate load, and 2 stroke gas at high load via the turbocharger’s boost.
"Roadster Man" (roadsterman)
03/16/2017 at 15:07, STARS: 0
I know you didn’t put a question mark in there, but the answer is NO.
2-stroke would require oil injection, diesel needs glow plugs and not spark plugs, and turbocharging would just make everything hotter and more prone to detonation, thus exploding this imaginary engine.
"For Sweden" (rallybeetle)
03/16/2017 at 15:08, STARS: 1
You could combine 4 stroke gas and diesel, if you’re willing to have two fuel systems and two ignition systems (spark and glow plugs)
"jimz" (jimz)
03/16/2017 at 15:13, STARS: 1
externally scavenged two-strokes don’t need oil injection (also called total-loss oiling) like an internally/crankcase scavenged engine. since they use a blower or compressor to provide airflow, the crankcase can be closed off and a normal pressurized lubrication system used. The 2-stroke Detroit Diesel engines (as well as many locomotive and marine diesels) worked that way.
"Steve is equipped with Electronic Fool Injection" (itsalwayssteve)
03/16/2017 at 15:14, STARS: 1
A lot of car companies have been developing HCCI engines - including a GM Ecotec modified to do compression ignition at low speeds/rpms and spark ignition at higher load
"Demon-Xanth knows how to operate a street." (demon-xanth)
03/16/2017 at 15:14, STARS: 1
The two stroke needs oil when the crankcase is used to push the air in. A valved two stroke doesn’t. See the series 71 Detroit Diesels as an example of this. I’m picturing the two stroke mode simply having a valve overlap where the boost pushes the air through the cylinder for a brief moment. Two stroke diesels and miller cycle engines need a supercharger to do this at low RPM since a turbo won’t do it, but if it can operate in four stroke mode at low boost levels, it bypasses the need.
Diesels also only need glow plugs to start. Being able to use the gas mode when cold eliminates this need.
"Cé hé sin" (michael-m-mouse)
03/16/2017 at 15:15, STARS: 1
Oil injection or oil/fuel mix isn’t essential (two stroke diesels don’t use it) so in principle it might be possible. Of no practical use of course.
There have been designs suggested for two/four stroke engines but I don’t know if anyone actually proceeded with them.
"lone_liberal" (token-liberal)
03/16/2017 at 15:15, STARS: 1
But do diesel engines need glow plugs for anything other than cold starts? If the theoretical engine started in gas mode wouldn’t it be warm enough for diesel ignition?
"jimz" (jimz)
03/16/2017 at 15:21, STARS: 1
the only way it could operate as both a “gas” and a “diesel” engine is to finally get HCCI working well.
as for the alternate two/four stroke operation- sure, it’s possible, but near as I can tell having both the inlet and exhaust valves at the top of the cylinder would result in poor exhaust scavenging and fresh air charging. There’s a reason most if not all two-stroke diesel engines use inlet ports in the cylinder wall.
"jimz" (jimz)
03/16/2017 at 15:22, STARS: 1
nope. glow plugs are strictly cold-start aids. if the engine is fully warmed up they won’t be needed.
"Roadster Man" (roadsterman)
03/16/2017 at 15:29, STARS: 0
I am learning a lot today! Thanks for the info everyone and not for flaming me.
"jimz" (jimz)
03/16/2017 at 15:33, STARS: 0
yeah, they’re different from the glow plugs used in radio control airplane engines. R/C glow plugs are a platinum wire which acts as a catalyst with the methanol fuel under heat and compression to initiate combustion. they also automatically “advance” the ignition timing since the glow wire gets hotter the faster the engine runs.
diesel glow plugs are just a hot wire which helps the fuel evaporate and burn in a cold engine.
"bhtooefr" (bhtooefr)
03/16/2017 at 15:51, STARS: 0
Koenigsegg’s Freevalve technology has explicitly been suggested for a 2/4-stroke switchable configuration.
As far as switching between diesel and gasoline operation... really the only use case I can see for it is when distillates are dirt cheap, and you’re trying to convert an existing gasoline design without raising compression. There were tractor engines that used a carburetor to run on gasoline for warm-up, and then once they were nice and toasty, you switched to kerosene injection, in the 1940s-1950s.
The idling efficiency of a diesel comes from the fact that diesels always run lean... but you can get the same effect on a gasoline engine. The caveat is that you get high NOx emissions, but that’s also true of the diesel.
"Grindintosecond" (Grindintosecond)
03/16/2017 at 16:03, STARS: 0
Correct on that. somewhere on youtube, there’s video of a diesel Kubota starting without a glow plug cause it quit working. So by capping the intake, the engine cycled the same charge of air until the compression added enough heat that the diesel fuel would ignite with the compression. Glow plugs and heated screens in the intake do the same things for starting but are useless afterward.
"RamblinRover Luxury-Yacht" (ramblininexile)
03/16/2017 at 16:08, STARS: 0
Or just never start on diesel, I suppose.
"RamblinRover Luxury-Yacht" (ramblininexile)
03/16/2017 at 16:11, STARS: 0
Only if the turbo is used to have a *massive* level of control over effective displacement and diesel-mode compression is comparatively low, which negates some of the benefits. Control of effective compression via valvetrain might also be possible - instinct suggests that both that and extreme turbo variance would tend toward wasteful, but I don’t know it for a fact.
"RamblinRover Luxury-Yacht" (ramblininexile)
03/16/2017 at 16:18, STARS: 0
Second look at sleeve valves?
I think as a diesel engine he means as a diesel-diesel, which is to say not gas CI. I also suspect that being able to run diesel fuel through variable compression might preclude CI gas to a point, at least in terms of capacity switch on the fly. It would have to transition between gas CI compression levels and diesel oil compression levels, so either there would be a couple dead cycles on diesel or a couple dry cycles - how few would depend on if the whole difference in compression was valve-managed, because that would allow a much faster switch, but would tend to be wasteful in normal operation. I think.
"That Bastard Kurtis - An Attempt to Standardize My Username Across Platforms" (thatbastardkurtis5)
03/16/2017 at 17:09, STARS: 0
That’s correct, glow plugs are only for starting. Once the pistons are moving, just inject diesel and you get combustion simply from the heat caused by compression.
"pip bip - choose Corrour" (hhgttg69)
03/17/2017 at 07:20, STARS: 0
design it and see.
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