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  #1  
Old 22-07-2011, 11:40 PM
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Whyzed Whyzed is offline
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Default Direct Injection 2 Stroke

Hey All,

I was just reading Australian Dirt Bike and came across an interesting article I thought I'd share .. don't know if anyone has read it yet or not.

Apparently KTM are putting some serious R&D into a direct injection two stroke engine =D! Initially i thought .. HELL YEH. My love of my old yz250 runs deep, there is no more fun in the world than reeling through a two stroke gear from idle to limiter.

But then I thought again... direct injection would effectively flatten out most of the two stroke powerband we all know and love wouldn't it? We would no longer need the expansion chamber for the back pressure to keep the fuel in the cylinder at higher rpm's as the injectors would only activate once the piston was past the exhaust.

Effectively it would mean that a direct injection two stroke would look, act and perform just like a four stroke? but with the sounds and smells of yesteryear (and much cheaper rebuilds/parts). Still not sure if this is good or bad or just progress.. food for thought eh?
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Old 23-07-2011, 06:58 AM
Turbo Turbo is offline
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I am unsure bro, but I couldn't see the mechanics change a great deal... it is still a 2 stroke engine... and would create it's power from the band and and rev range. They would only do it to make it better / smoother but I doubt they could flatten it out to a 4 stroke level? Sounds cool though.
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Old 23-07-2011, 07:11 AM
Jeram Jeram is offline
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nope there is no need to ditch the expansion chamber on a direct injected two stroke,

The expansion chamber is not to "keep the fuel in" it is to presurise the cylinder with a fresh charge (with or without fuel). the only reason they would ditch it is if the changed the port layout so that the inlet ports were higher than the exh port or something crazy like that so that a pipe wouldnt work.

the only things that will change is the smoothness of power (no more "ning ning ning" splutering, it will purr as it will properly fire on every revolution, It will still sound like a 2T, just smoother.

However orbital has been experimenting with removing the expansion chamber to give a direct comparison between a 2T and a 4T.
they got a 450cc Direct injected 2T without an expanion chamber to make the same power as a 450 four stroke. the 2T had much better fuel efficiency, less emissions, more reliability, less moving parts, lighter wieghts, and lower overall cost to manufacture.

KTM has been 'investing' in this for years and they keep spinning rumors each year that "its comming this year on a husaberg" but its complete BS.
Iv stopped holding my breath.
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Old 23-07-2011, 07:25 AM
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they are always working on things hey.. which is good... maybe they will bring out a diesel 4 stroke! Save the trees! Diesel locomotives are all 2 stroke, sounds strange hey.
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Old 23-07-2011, 08:44 AM
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bimota brought out one years ago
v twin 500cc direct injection

those trains are a combo with
intake valves and ex ports
same as the detriot v engines ?
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Old 23-07-2011, 08:56 AM
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If they do manage to pull it off while keeping the inherent two stroke characteristics, I'm sold 100%.

If they lose the "twostrokeness" I think i'll still probably be sold, and I think there would be a good chance we'd see the entire bike scene (MX especially seeing as its been very 4T happy over recent years) switch back.
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Old 23-07-2011, 10:14 AM
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Quote:
Originally Posted by dafunk View Post
bimota brought out one years ago
v twin 500cc direct injection

those trains are a combo with
intake valves and ex ports
same as the detriot v engines ?
the vdue was just normally fuel injected. it was a translation error.
when they said directly enjected, they meant 'directly injected after the reedcage'
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Old 23-07-2011, 11:08 AM
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Quote:
Originally Posted by Turbo View Post
they are always working on things hey.. which is good... maybe they will bring out a diesel 4 stroke! Save the trees! Diesel locomotives are all 2 stroke, sounds strange hey.
We had a truck mounted Barco log loader years ago and the interesting thing about it was the fact that it was a 2 stroke diesel.It had a supercharged Detriot engine that redlined at about 23,000RPM's and made around 300HP.
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Old 25-07-2011, 11:35 AM
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There is a lot of misconceptions about DI 2T's.
Think of it as a 4t bottom end and a 2t top. The smell will be gone and the power bands will be smooth. It will just be a more efficient internal combustion engine that is it.
Orbital put a few of their motors in a car many years ago and it was impressive, but that was a while ago and I believe there is many difference's now.
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Old 25-07-2011, 02:20 PM
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There are two main things still holding this back. First is the R&D involved, DI in a car does not have to worry about being super compact and light weight like it would in a bike. Also cylinder head and piston design to incorporate the fuel injector need to be developed for performance and efficiency. Secondly, the world is full of stupid people, the idea of a two stroke scares most wanna be greenies and the like. Getting funding to develop a two stroke would be very difficult given the likely returns.
Look at engine production, 2T V 4T. Most people only think about the emissions coming out of the exhaust pipe as the pollution cars make. They never think about the manufacturing process. 2T engines have very few parts compared to a 4T. No need for heat treating cams, springs etc. ADB also covered this topic a while ago.
Also consider the current trend to electric vehicles. Where does our power come from currently. BURNING FOSSEL FUELS! 8 hours of charge for and electric vehicle is 12 months of driving for a small petrol powered car.

I read the article and found it interesting. Does anyone know where I could read more about it.
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