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DFI has to work on a closed loop FI system. Meaning it must have an O2 or wide band sensor. All those leaded fuels are a no no. And im not 100% but guessing that premix wouldnt be doing any favors either.
And if the DFI system was operated as an open loop FI system the compression of the motor would have to be consistant inorder for it not to go insanely rich as the motor looses comp over time...meaning much more frequent rebuilds.
I believe FI is coming for 2t, but definitely not DFI.
If it works in sleds, there isn't really a mechanical reason it wouldn't also work in dirtbikes and would only be a cost issue.
DFI will come to motorcycles. Like it or not. We live in a world of change.
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Outboard Etec engines have been DI for a long time....same with my fathers Mercury.
Pretty sure everything you just listed is a hell of a lot more durable than a 250sx being rung out.
I cant view those links on this 386, I will have to look when my daughter gets home with a laptop.
Yes, hillbilly, outboards have an oil tank, that lubes the bottom end.
FI to me for a two stroke is just plain stupid.
DI makes some sense, but its not like it is gonna turn your bike into a rocket.
Does anyone know what happens to a DI engine when on the pipe???? Really motorcycles are the only motors I know of that optimize the pipe to "supercharge" the engine. (I know nothing about snomobiles or jet skis) I am just confused about how this would work, or if it would work, as the DI charge would be after the exhaust port is closed and theoretically there would be no unburnt fuel in the expansion chamber.
However there's the rub - if the DI 2 stroke is not appreciably better than current four strokes, what is the compelling business case to invest R&D and manufacturing infrastructure to develop and produce them?
I think this was the main thing that Orbital achieved.
I believe most (maybe all?) current DI strokes (outboards, sleds etc) utilise Orbital technology under license.
Two strokes booted four strokes because they were light, made more power etc...
Four strokes booted two strokes because they closed the weight gap and with their CC advantage, power and rideability was way up on two strokes.
If two stroke development gets rideability and keeps the lighter weight... maybe it helps. The CC issue is still there though for MX.
I want one for offroad tho!
Marine outboards and snowmobiles were a success for DI 2 strokes because they faced mandatory and strict emissions targets. Until something similar happens for dirtbikes I can't see much happening, especially not for closed course competition machines.
I first saw Ralph Sarich on The Inventors in the Seventies, with his Orbital Engine. That pretty much went nowhere, but his stratified injectors / injection system that was a key part of it, well , I wish I was a teenager with money to invest in his companies at that time. I would have retired a decade or two earlier than I have, and been filthy rich, instead of being merely "comfortable".
Doug Lampkin used one to win the Scottish Six Day Trial this year.
Pit Row
But, even better - no wasted fuel charge, as the burnt charge could be pushed out by just the air charge, with far less reintroduction of contaminating exhaust. You could tune the engine to still make use of a far cleaner return of purging air, with then the stoicometric ratio taken care of through the injector.
Plenty of people think that DFI will negate the need for expansion chambers. Well, it may reduce the need / use of them, but not for when you want the best performance possible, for a variety of applications. To throw away one of the key advancements in 2t design, brought to the world by the great, Walter Kaaden, seems a bit bloody stupid.
What you are saying is that the burnt charge be pushed out by air charge, I am confused.
IN order for that to happen the charge would fire prior to the piston clearing the exhaust port.
Just trying to understand how you could do this and still have a supercharging effect and "a pipe".
I can see it with fuel injection(inject the fuel below the cylinder), but not direct injection.
I am no engineer, just trying to wrap my head around it.
CC-for-CC performance - no, that is not an issue for marine outboards.
As far as rideability goes, I'm of the opinion that no amount of playing around with capacity is going to make a current two stroke as good as a four stroke. I just don't believe there is a magical capacity that hits the spot. Unless the technology changes then nothing else will change.
Maybe DI two strokes will change that, but then you start paying penalties in weight, complexity and cost - the key things that still make a two stroke somewhat competitive.
Every design has it's advantages and limitations. It's bit like a turbine engine - the best power-to-weight ratio of any internal combustion engine (hence their use on aircraft) but horribly inefficient, and with very high shaft speeds, so they are useless as a vehicle engine.
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