Why no EFI 2 strokes?

colintrax
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colintrax 9/15/2015 7:34pm
9/15/2015 7:34pm
colintrax wrote:
How do you know?
BobPA wrote:
Because I understand how two strokes operate?
Then please explain why a 2 stroke can't use an oil bath system.
colintrax
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colintrax 9/15/2015 7:37pm
9/15/2015 7:37pm
On a side note, they could also inject oil into the intake.
scrubbin627 9/15/2015 8:04pm
9/15/2015 8:04pm Edited Date/Time 9/15/2015 8:11pm
BobPA wrote:
And I have a 12" dick named Frank....
That's cool. Mine is probably around half that on a good day Laughing

GM went to DI to squeeze a few more hp from their current line-up with less emissions. It makes such an efficient burn they can run more compression, cam and timing with no detonation while using less fuel. Its rumored to be the last gas powered v8 due to the ever changing emission laws.
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BobPA 9/15/2015 8:20pm
9/15/2015 8:20pm
colintrax wrote:
On a side note, they could also inject oil into the intake.
The current DI (well now non existent) two stroke jet skis did exactly this.....so did the carb models that used an injection system.

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colintrax
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colintrax 9/15/2015 8:30pm
9/15/2015 8:30pm
colintrax wrote:
On a side note, they could also inject oil into the intake.
BobPA wrote:
The current DI (well now non existent) two stroke jet skis did exactly this.....so did the carb models that used an injection system.

I'm aware, but please explain why 2 strokes can't have oil sitting in the crankcase?
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BobPA 9/15/2015 9:05pm
9/15/2015 9:05pm
colintrax wrote:
I'm aware, but please explain why 2 strokes can't have oil sitting in the crankcase?
Two strokes pull their intake charge through the crankcase, thus a full oil bath would be pulling a ton of excess oil into the combustion chamber.

We test jet ski oil pumps at 3k rpm and they pump ALOT less than a modern four stroke mx bike. The oilers on my KTM 350 crank toss a shit ton more oil than any jet ski I have seen....and that is at with just the electric starter turning the engine over.
The Rock
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The Rock 9/15/2015 11:21pm
9/15/2015 11:21pm
colintrax wrote:
I'm aware, but please explain why 2 strokes can't have oil sitting in the crankcase?
Here is a 2 stroke primer that should provide some good background.

Are you a newbie or a recycle?
Bearuno
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Bearuno 9/16/2015 6:03am
9/16/2015 6:03am Edited Date/Time 9/16/2015 6:07am
resetjet wrote:
Well, my point is, that the two stroke pipe is a sound chamber that is tuned to reflect the sound (and therefore create a pressure wave)...
Well, my point is, that the two stroke pipe is a sound chamber that is tuned to reflect the sound (and therefore create a pressure wave) back into the cylinder shoving the "contaminated" charge back into the cylinder creating a supercharging effect. This is when the bike is "one the pipe". If the DI charge is inserted in the top of cylinder and fires after the exhaust port is closed, how is this possible?????

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.
That returning , no fuel laden charge, that went out the exhaust port, helping remove the burnt charge / exhaust, is the same as the charge that exists in conventional 2t that is returned back into the cylinder / combustion chamber. Just no fuel within the charge.

It's the same basic pressure / flow patterns as you can see in any 2t pictures/video/ GIF. Have a sqizz at the primer The Rock put up.

Fuel would be injected into that / all the aircharge, by whatever injector(s) you have to deliver that fuel. Be it directly in the head, facing down, as is the 'norm' that people seem to regard as the 'only' type of DFI (that requires the much feared high pressures, and all of the hardware / complications that so many don't want), or, far simpler, much lower pressure injector(s) mounted very high up on the barrel, or lower in the head.

How would the amount of fuel to be injected be determined? Just as it is with any modern tech, with extensive testing / development by those that design and set up the entire system. ECUs and sensors are getting ever more clever.

None of this is "rocket science" by any of today's standards. It's just basically been ignored / not developed by the majority of manufacturers. Yes, it's all more complicated than a carb, but hell, we've been dealing with 4ts that are far past the old XR engine type for years now. The current 2ts we have, really are stuck back at a comparable engine tech levels of XRs / KTMs 1st LC4s.

Hell, my very favourite bike I have to ride, is a Axe simple 2t without even a PV. But I have no fears of finally being able to have a modern, new tech, 2t. That's the sort of ICE powered bike that will get me to "vote with my wallet". Until then, no manufacturer gets my current vote, I've got a good selection of Bikes that I've placed my vote with, already.
resetjet
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resetjet 9/16/2015 6:38am
9/16/2015 6:38am
Where I am confused when you jet a 2 stroke you have the "wet line", so clearly there is alot of fuel in that charge. However, I guess that doesn't matter, its the stuffing of the air that is important, that gives it more compression. You could simply add whatever fuel mixture you wanted via the injector.


Still, I'll take a carb.
motomike137
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motomike137 9/16/2015 6:51am
9/16/2015 6:51am
scrubbin627 wrote:
That's cool. Mine is probably around half that on a good day :laugh: GM went to DI to squeeze a few more hp from their current...
That's cool. Mine is probably around half that on a good day Laughing

GM went to DI to squeeze a few more hp from their current line-up with less emissions. It makes such an efficient burn they can run more compression, cam and timing with no detonation while using less fuel. Its rumored to be the last gas powered v8 due to the ever changing emission laws.
Gas powered or naturally aspirated?
clem
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clem 9/16/2015 9:24am
9/16/2015 9:24am
I don't know if it has been mentioned but the Suzuki GT550's used separate oil injection points for the crank and the top end. Seems like you could use that as a starting point for oiling a DI 2T.
scrubbin627 9/16/2015 10:24am
9/16/2015 10:24am
motomike137 wrote:
Gas powered or naturally aspirated?
Both....gasoline powered v8's are being fazed out by the EPA because they burn to much fuel. I heard sometime around 2020 they will be totally out of production and replaced with high output DI 4 & 6 cylinder engines. The work trucks will retain turbo diesels but will be a smaller displacement and cleaner burning.
colintrax
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colintrax 9/18/2015 2:35pm
9/18/2015 2:35pm
colintrax wrote:
I'm aware, but please explain why 2 strokes can't have oil sitting in the crankcase?
The Rock wrote:
Here is a 2 stroke primer that should provide some good background.

Are you a newbie or a recycle?
Not sure why y'all think I'm retarded. I'm well aware how a 2 stroke runs.

I think theres some extra hours to be had from 2 strokes if they are oiled like a 4 stroke. Obviously case reed injection has to go, but weed eaters and some other 2 strokes shoot straight into the ports. I doubt you can get the same power output without the positive pressure from the crank case. In which case you could use a "pcv" type system and reeds to get the pressure boost. Oil sitting in the crank case. Direct Injection 2 stroke power.

Seems like a win to me. But please, tell me how I'm wrong. I haven't graduated yet, nor had an engineering job. So maybe I am wrong.
motomike137
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motomike137 9/18/2015 5:19pm
9/18/2015 5:19pm Edited Date/Time 9/18/2015 5:19pm
scrubbin627 wrote:
Both....gasoline powered v8's are being fazed out by the EPA because they burn to much fuel. I heard sometime around 2020 they will be totally out...
Both....gasoline powered v8's are being fazed out by the EPA because they burn to much fuel. I heard sometime around 2020 they will be totally out of production and replaced with high output DI 4 & 6 cylinder engines. The work trucks will retain turbo diesels but will be a smaller displacement and cleaner burning.
Lol, I didn't get that you meant gas powered V8's and thought that you meant all gas powered engines Smile I don't think V8's will be completely gone but they will become a definite rarity.

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