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  • Black_Moons
    replied
    I think id be more interested in a rotary exhaust valve. Reed valves can handle the intake. Also reed valves should allow a supercharger/turbocharger, they would even let the intake cycle continue into the (crankcase) compression cycle at higher RPM where airflow would be restricted.

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  • A.K. Boomer
    replied
    You and I think allot alike that way,,, I had an old suzuki 90, my first motorcycle, and it had a rotary valve system,

    many times I have wondered about VVT with a system like that,,,

    actually Reed valves are already a kind of VVT --- but there is a restrictive price to pay in operation,

    not so with the rotary valve and if you could get one dialed throughout the range you would rule the roost as compared to reed, but - it would not be a simple task as both RPM's and load/demand would all have to be linked into the control/monitoring and then translated to the VVT mechanisms...



    oops things are starting to get a little complicated... but far more advanced systems have been tried even in production vehicles...

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  • ironmonger
    replied
    Originally posted by A.K. Boomer View Post
    Would definitely increase the charge effect --- but it's allot of extra hoopla to go through, and drag,,,
    <<snip>>
    If there is some way you could incorporate some kind of massive fast acting intake valve (or two or three or four smaller ones) at the top of the chamber then you could scavenge most all spent exhaust from the chamber almost as good as a four stroke, the charge would come in from the top and would pump the exhaust out the bottom, the exhaust would welcome this as it would be leaving with such a fury anyways it would do nothing but help suck in the intake,,,

    your power production would be off the charts... No "normal" two stroke or four stroke could touch it... there's also really no reason as to why this engine could not be very efficient, and although the immense power production would certainly effect longevity it's life would not be any shorter simply because of the fact that it's a two stroke...
    Just to add to Boomer"s comments on intake valving alternatives consider the rotary valved intakes of the Bridgestone and Kawasaki motorcycles, and the B-bomb gokart engines. These were still conventional aspirated intakes but the crank mounted disk type valve allowed for an asymmetrical intake porting. While it was never done, to my knowledge, the intake port on the carb side could also have been bee advanced or retarded. They would also lend them selves to supercharging.

    Here are some pics of the intake parts:

    http://motorcyclepartschief.com/kw/engine-motor-rotary

    paul

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  • A.K. Boomer
    replied
    Originally posted by Black_Moons View Post

    There have been 2 strokes that use a second (larger but lighter construction) piston to supercharge the crankcase, You could just skip the crankcase and make a V twin 2 stroke. Of course, that is sort of just a 4 stroke divided up.

    .

    Would definitely increase the charge effect --- but it's allot of extra hoopla to go through, and drag,,,

    Two strokes as is are all supercharged to some degree - just in design, many people think that just because the piston is the same size it's a direct exchange of tit for tat,,, not so, the bottom crankcase side of the two strokes piston is higher dynamic volume due to it leading and most all of it's travel being dedicated to both intake and compression, while the top sides effective stroke is more like 2/3rds due to having to deal with the intake porting,

    Now at first glance this appears to still be a 1:1 exchange rate, and for the most part it is - statically --------- if the engine was rotated extremely slow, then as the piston started to come up from BDC and the top part was dealing with the charge porting the bottom would be starting to loose it's maximum pressure at the same exact time,,, but it's not rotated real slow, and due to the crankcase side leading the charge rate it has one huge advantage --- if the timing is correct it gets to use the mass of the air to it's advantage - another words, dynamically it gets to dictate to the combustion chamber a pressure wave that is just as effective as if the engine had a mild supercharger on it, things are happening way too fast for the airflow to do an "about face" even though the bottom of the piston is already heading back up - so the top part is not only getting the full pressure charge - it's having to deal with the momentum of the air.

    This is why when all engineering is correct and your on a two stroke and you hit that sweet spot within a certain RPM range way up high all hell breaks loose, they get very "comfortable" with this flow rate between the two chambers,,, and if the air is directed correctly there is a little bit of "stacking" going on... even though there's still an exhaust port open to some degree, that's all it takes when your making a power stroke every revolution,,, best to be hanging on to the handlebars...

    But what an incredible juggling act,,, stack too much and you throw some of the mix out with the exhaust, stack too little and you misfire or create a very weak powerstroke due to not having enough to either light off properly or make effective...

    This is one of the reasons direct injection gas would help two strokes so much, just put an air flow meter on the engine and an oxygen sensor on the other end, ------ no more wasted fuel, and overstackings not an issue, after all it's just air your throwing away,,,

    you could keep the engine conventional --- or you could supercharge the hell out of it, if you did the latter your porting would be way at the bottom and you could have much longer effective power stroke closer to what a 4 stroke achieves --- torque would be radically increased due to getting into the optimum crank/rod angle (max piston speed)
    and like Andy stated you could run a sealed crankcase like a 4 stroke, no oil injection what-so-ever... and no burning of it with the fuel...

    If there is some way you could incorporate some kind of massive fast acting intake valve (or two or three or four smaller ones) at the top of the chamber then you could scavenge most all spent exhaust from the chamber almost as good as a four stroke, the charge would come in from the top and would pump the exhaust out the bottom, the exhaust would welcome this as it would be leaving with such a fury anyways it would do nothing but help suck in the intake,,,

    your power production would be off the charts... No "normal" two stroke or four stroke could touch it... there's also really no reason as to why this engine could not be very efficient, and although the immense power production would certainly effect longevity it's life would not be any shorter simply because of the fact that it's a two stroke...

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  • Black_Moons
    replied
    A.K. Boomer: You should always engage the clutch while going down long hills in a 2 stroke, especially with premix bikes. (Except on bikes where the clutch disengages the oil pump...). Some bikes even have a one way clutch in the drive train to prevent the motor being driven down hills and oil starved. its actually surprisingly nice having a bike go back down to idle every time you release the throttle. Very quiet going down hills and coasting.

    There have been 2 strokes that use a second (larger but lighter construction) piston to supercharge the crankcase, You could just skip the crankcase and make a V twin 2 stroke. Of course, that is sort of just a 4 stroke divided up.

    Just finished replacing the throttle and clutch cables (Boy that clutch is fussy to get just right.. Had to get the cheap ultra thin Chinese washers out I use as shims to adjust the clutch drive pin that I had to replace with a 2" long machine screw))

    Wow, is it ever a totally different beast with the right spark plug, a well working clutch and throttle. Also just adjusted the head set torque as it was too stiff. Does not bog down anymore or try and do pop-a-wheelies due to poor throttle control. The throttle would not even spring back at all on its own before, you basically had to force it back with the throttle grip. Someone thought a sharply bent too short cable could replace a noodle.

    Also found a piece of 1" cast iron pipe being used as a standoff for the axle... around 1/2" axle.. the threaded end of a cast iron pipe no less. tons of room for it to shift around and not very strong.. Replaced it with a chunk of steel turned to just over 1" and drilled for the 1/2" axle, nice snug fit and stronger then most of the bike. Forgot to paint it but I'll do that when I replace the couple of broken spokes. Also it was not even long enough to put a cotter pin in the castle nut to secure the back tire.

    If you look really hard at the cast iron pipe, You can make out the inscription: "Bubba wuz here"

    Surprisingly, engine cylinders look good (Very low carbon deposits, no scoring), just kinda low compression. Runs and shifts good and that is the important part.
    Last edited by Black_Moons; 08-06-2014, 07:14 AM.

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  • vpt
    replied
    Originally posted by A.K. Boomer View Post
    I don't like the inefficiency, the lack of longevity - I also don't like the oil burning,,, four strokes have also come a long way as far as power production, they may only make half the mount of power strokes per revolutions but there power stroke is almost twice as potent and way over twice as potent if you toss on a supercharger or turbo,,,

    not something you can do easily on a two stroke, (unless it's a detroit diesel ((direct injection))

    but the entire rule book is changing right now,,, direct injection gas is changing the way both these engines run and the two stroke is going to make a huge comeback due to it benefiting it on so many levels... they will be far cleaner, they will last much longer, and they will have much better efficiency,,, but there is still one inherent problem left --- they cannot achieve as optimum of a crank/rod angle for torque production as much of their piston travel at the lower half of the bore is dedicated to both intake and exhaust porting,,,

    but, toss in a valve at the top of the chamber - an intake --- now you can run just an exhaust port way at the bottom of the stroke and either turbo or super the intake, now you got something,,, immense power with increased efficiency...

    they are going to be tough to beat... mark my words they are about to make a crazy comeback and we will even be seeing them in cars (again).


    I had the idea of forced induction 2 stroke where it wouldn't rely on the crank case for "pushing" the air/gas mixture into the cylinder. That way a recirculating oil system could be used and sealed crank case. So now you don't need the oil in the gas and could run strait gas threw a 2 cycle, the air charge just supplied by turbo/supercharger/etc.

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  • Willy
    replied
    In my opinion at least I believe the fallacy of unreliability of the oil injection systems stems from several sources. New owners that have no previous experience with the system letting them run dry has got to be at the top. After all they are are conditioned to top off the gas tanks just like on their previous 4 strokes and simply fail to top off the oil tank because this important task is not burned into their thought process...yet! Blame the injection system.

    When they do fill it up, usually after having one of the oil lines off, they fail to bleed the system of air. These system require a specified protocol of ensuring that ALL air be purged before operation. They simply will not work properly with air in the system. This is again the fault of whoever worked on it or filled it without ensuring there is no air in the system. But once again it's easier to blame the the injection system.

    Also at the top of giving the oil injection systems a bad name is owners using anything that resembles oil in these systems. This includes straight grade automotive 4 stroke oil, pre-mix 2 stroke oil and just about anything other than the proper specified 2 stroke injector oil.

    Oil has also drastically been reformulated over the last 30-40 years. A good name brand synthetic 2 stroke injector oil is light years ahead of what was available when these systems were first introduced...and they worked well back then.

    No I think the only unreliable component in the oil injection system, and giving it a bad name, was the operator.

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  • Mike279
    replied
    The pumps I had on the 70's enduros were variable output. Driven by shaft it turned slow or fast with engine speed. Then the cable was tied into the throttle and that turned a cam which varied the length of the pump stroke. I think that pretty much covers all the bases. Engine speed is oiled at one rate and load is added by the pump stroke. Most tanks I had would hold enough oil for several tanks of fuel. They also had a nice viewing window to verify oil in the tank at a glance. Not foolproof, but nicer than carrying oil cans and finding a can to mix with at gas stations away from home. Mike

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  • ironmonger
    replied
    Originally posted by Mister ED View Post
    Also, some oil pumps also supplied the oil directly thorough the bearings to provide adequate oiling of said bearing. The old Kawasaki sled engines (with oil pumps) used to be like this. People unhook the very dependable oil system and end up eventually with toasted center bearings.
    Along those same lines of thought, my 1976ish Suzuki 500cc twin injected the oil into the crank bearings and through the cylinder walls directly to the piston skirt. It's been a long time, but I don't think that it injected any oil into the fuel stream,

    paul

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  • A.K. Boomer
    replied
    I don't like the inefficiency, the lack of longevity - I also don't like the oil burning,,, four strokes have also come a long way as far as power production, they may only make half the mount of power strokes per revolutions but there power stroke is almost twice as potent and way over twice as potent if you toss on a supercharger or turbo,,,

    not something you can do easily on a two stroke, (unless it's a detroit diesel ((direct injection))

    but the entire rule book is changing right now,,, direct injection gas is changing the way both these engines run and the two stroke is going to make a huge comeback due to it benefiting it on so many levels... they will be far cleaner, they will last much longer, and they will have much better efficiency,,, but there is still one inherent problem left --- they cannot achieve as optimum of a crank/rod angle for torque production as much of their piston travel at the lower half of the bore is dedicated to both intake and exhaust porting,,,

    but, toss in a valve at the top of the chamber - an intake --- now you can run just an exhaust port way at the bottom of the stroke and either turbo or super the intake, now you got something,,, immense power with increased efficiency...

    they are going to be tough to beat... mark my words they are about to make a crazy comeback and we will even be seeing them in cars (again).

    Leave a comment:


  • vpt
    replied
    I like 2 strokes allot more than 4 strokes. It just makes more sense to me to power every stroke of the piston instead of every other stroke. No oil changes, motor can run upside down, sideways, what have you. 2 strokes are smaller lighter and put out more power and they smell great!

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  • A.K. Boomer
    replied
    Originally posted by Black_Moons View Post
    AK boomer: I believe the pumps output would also vary with RPM.
    Velocette: Of course there are millions of 2 strokes with working oil pumps. The ones with non working oil pumps are usually scrap by time the owner finds out his oil pump is not working.

    That's a good point and it will vary things, still should be a huge difference between the pump locked on full as compared to Idle, no matter the RPM's - Now it makes me wonder, does "lugging" one of these engines load it up with extra oil?

    what about coasting in gear down a huge grade? throttle all the way backed off (and pump) yet RPM's up high...

    I don't think with just a few things controlling the oil injection that it's an exact science, but I would not go with the "smokeless" oil if using a pump and trying to dial it in - would be using the smoke as a gauge...

    In all my years as a motorcycle mechanic iv never had one of those pumps apart,,, im curious now what they use for a pump and how they meter it...



    I also would think that with all the emphasis on emissions and such and many engines already running off of computer controlling that it would be an area to further refine and clean up the two stroke as far as the oil part,
    would actually surprise me if they don't already have computer controlled oil injection that not only uses TPS and RPM's for the pump but also has it hooked to load sensors or even just run it in parallel with the fuel injection rates...

    There has to be some crazy plans on the drawing board right now for two strokes and direct injection gas, this could help clean up the other part of these engines and drastically increase their efficiency in the process,,, no more raw fuel going directly out the exhaust port,,, they could concentrate little amounts of oil in hard working area's without it getting diluted, and just inject pure fuel, doing anything else would be a total waste of oil and create extra emissions.

    In fact two strokes stand to benefit from direct injection gas more so than typical four strokes... it would cure many inherent problemo's

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  • Hopefuldave
    replied
    The pump output varies with rpm, yes, but so.does the need for oil - look at it the.other way, the.pump delivers the same amount of oil per revolution of the engine at a constant throttle, and.the link to the.throttle cable increases it under load, just what you want. With premix you need enough oil for all conditions at all times, so it over-oils and.fouls plugs at light loads!
    I like pumped oil, my old Suzuki triple.had it and I never managed to seize it, not.even once, my premix-lubed Bultaco was.always seizing....

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  • Yow Ling
    replied
    I am a big fan of premix, for the reasons Black Moons stated. Its not so good for commuter bikes as the high ratio of oil is likely to cause fouling at low engine speeds, because my bike runs in the 7500 to 10,500 range this is not a problem. If I mix up 20 litters of fuel (5 US Gallons) I use 640ml (1 pint) of oil, a pump would half that. When you convert to a premix you need to jet a bit richer as 3% of the fuel mixture isn't fuel , or the engine will run lean

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  • Black_Moons
    replied
    This one injects the oil into the intake. I put a vacuum cap over it. I have had good luck with premix, especially at 30:1. No fouling if you use a good oil and have your carb set right.

    I don't even know if the oil pump is broken, it just came disconnected. Personally Id rather just stick to premix.

    We do have lots of hills around here, but none of them go downhill for very long and they are way too steep to use engine brake.

    AK boomer: I believe the pumps output would also vary with RPM.
    Velocette: Of course there are millions of 2 strokes with working oil pumps. The ones with non working oil pumps are usually scrap by time the owner finds out his oil pump is not working.

    Incidentally I took a look in the combustion chamber, very clean, almost no deposits. Although maybe that is because it has not run much since the owner last did maintenance and put in the wrong spark plug.

    Hmm, I may of just realized the biggest reason for removing the oil pump and using premix.

    Its fool proof. Well ok you can put non mixed gas in and ruin the engine, but as long as you grab the right gas can (I use 1gallon cans only for premix, 2.5 gallon cans for pure gas), if you ever run out the engine just stops till you add more gas. If you run outta oil with an oil pump, the engine just stops... And never turns over again.

    One less tank to check.
    Last edited by Black_Moons; 08-05-2014, 12:42 AM.

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