Oil injection fuel pump

Discussion in '2-Stroke Aircaft Engines' started by mmatt, Nov 14, 2016.

  1. Nov 14, 2016 #1

    mmatt

    mmatt

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    Is this such a thing? If not, why not? How hard would it be to design a fuel pump (either vacuum or electric) to pump a ratio of oil and fuel? We mix fuel and oil by volume, right? Wouldn't a fuel pump that had a two draws, one for fuel (normal sized) and one for oil (50 times smaller) draw a ratio of 50:1 therefore negating the need for a more complicated carb injection system? Obviously the carb injection system is the way to go if your engine has that option, but since mine doesn't, I'm trying to come up with a solution.

    One of the unknowns is; will the ratio stay the same at different power settings (more likely a problem for the vacuum driven pump since the electric would probably just put out a constant 3 psi or whatever)

    Anyway, just a thought that hit me last night. Please discuss. :)
     
  2. Nov 14, 2016 #2

    TFF

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    Rotax uses them on some engines. The question comes on reliability. Some don't like the possibility of the pump malfunctioning so they rather mix. Tons of mopeds have used it to.
     
  3. Nov 14, 2016 #3

    mmatt

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    I don't mean an oil injection kit, but a fuel pump that also pumps oil at the same time, but at a reduced ratio via a smaller port.... or is this really a thing? If so... links?!? I'd love to put one on my plane since the engine on it is not set up for an oil injection kit. (old Bosch ignition 503)
     
  4. Nov 15, 2016 #4

    Armilite

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    Fuel Pumps also fail. Oil Injection Pumps Fail. People Fail to PreMix right ratio needed, or Fail to even Add the Oil. Easy to solve, use dual Fuel Pumps. Figure out Why the Oil Punmps Fail and make the Upgrade. If you PreMix, have a Check List and pay Attention to what your doing! The Oil Pump failure is the Plastic Gear used, Center Hub.
     
  5. Nov 15, 2016 #5

    THRC12

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    I'll happily stick with my pre-mix! That way, I'm the only thing to fail.
     
  6. Nov 15, 2016 #6

    Turd Ferguson

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    If you are trying to avoid mixing fuel and oil in a container then pouring it in the fuel tank, perhaps you can come up with a system than injects oil into the fuel tank anytime you refuel?
    Say a manually operated PD pump that draws oil from a reservoir and dispenses ~5oz of oil per actuation of crank or handle?
     
  7. Nov 15, 2016 #7

    mmatt

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    Yes, I get all that. I'm not trying to make a better product, I'm trying to come up with a solution for people who don't have the option for an oil injection system on their engine.

    I understand that a proper oil injection system will regulate the the ratio differently at different RPMs. The solution I'm thinking of won't do this. It will simply mix the gas/oil at 50:1 right at the fuel pump before it hits the carbs. No, this is not an ideal set-up, just one that will allow people who don't have the option of proper oil injection for their engine.

    The benefits of this system will be less than the benefits of a proper oil injection system but there will be benefits nonetheless:
    - pre-mixed gas lasts only 10 or so days before it must be burned (unmixed is easily good for a month)
    - easier to re-fuel away from your home airport
    - any 2-stroke engine will be able to use it

    So, back to the original question; what do you think would be the best way to design a fuel pump that also pumps oil at a pre-set ratio for 2-stroke engines that don't have the option of a proper oil injection kit?
     
  8. Nov 15, 2016 #8

    mmatt

    mmatt

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    That would also make things a bit easier. But if I'm going that far, why not just attach it to the aircraft have it do that for me while I fly? The benefits of the system I have in mind that I'm most concerned with is the fact that the unmixed gas lasts longer (the weather where I live is very volatile and I have wasted many a tank of gas when I simply couldn't get out in time to fly) and the ease of re-fueling away from home where I might not have my mixing apparatus.
     
  9. Nov 15, 2016 #9

    Turd Ferguson

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    I see you plan to "T" the fuel and oil line together prior to entering the carb(s) and I think that will be a problem. They won't mix together at that point as you desire. Would ruin your day if a slug of oil blocked or restricted fuel flow. It's just too easy to foul the carbs by mixing at that point that I wouldn't attempt it.

    I think you are underestimating the shelf life of gas and gas/oil mixture. Not a bad thing but if you're going to dispose of pre-mixed fuel because it's >10 days old, just need a system of containers for fresh fuel and old fuel and some transfer pumps.

    Back in another lifetime when I rode pre-mix two-stroke road bikes, they were always refueled at a gas station. Simply carried a container of measured oil in the storage compartment. Pull into a gas station, dump the oil in the gas tank, add the desired amount of gasoline and it was good to go.
     
  10. Nov 15, 2016 #10

    Armilite

    Armilite

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    Many Multi Millions of 2 Strokes use Oil Injection today successfully, but only a Small Amount are subjected to the Endurance factor of being used on an Airplane. Make that White Plastic Gear, and the White Shaft on the Oil Injection out of a better material and you solve 99.9% of the Oil Injection Failures. Around me when I canvased Airports in 50 mile Radius Circles, only 1 out of 21 even carried Mo Gas. So burn 100LL which has a 5 year shelve life and you don't have to worry about Detonation. Oil Injection Failure on Skidoo/Rotax Sleds is almost unheard of, Why, they Speed up, Slow down, Stop, Speed up, Slow Down, Stop, etc. They are not run at Continious Rpms for hours like on Planes. It's the Center Hub failing on the Gear, shaped like a D.
     

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  11. Nov 15, 2016 #11

    Armilite

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    A Plastic that can handle more Heat also.

    =================================================================

    Almost all 2 Strokes made today use Oil Injection, and older ones can have it upgraded. Only Weed Wackers have held out. To do what your talking about would take a Computer Controled Electronic Oil Injection. Remember the KISS principle, "Keep it Simple Stupid" lees thing to fail. A Mechanical Oil Injection is the most reliable way. Make the Center part of the gear thicker, or add a Metal Stamped D Hub, or use better Material, or combination of all three. Like the Blue one would be my choice.
     

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  12. Nov 15, 2016 #12

    StarJar

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    You could put the T or Y near the tank and oil container to give it a couple feet to mix.
    The biggest problem is that it might decide sometime to draw just fuel. The slightest impedance to oil flow would just stop it possibly.
     
  13. Nov 15, 2016 #13

    Armilite

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    =============================================================================
    Pump Gas has a 6 month shelf life. But it can loose 2 points in Octane in as little as 2 Weeks. So if you fueled up with 91, and you come back say a week or two later, your not burning 91 Octane now, but 90, maybe 89, and that's Why People have Detonation problems with their Rotax 2 Strokes used in planes. The few engines using lower Compression like 9.6cr, may not suffer from it as soon as the guy using 10.8 to 11.8cr. People who use lower rpm's will have less problems also. That's Why, some Pistons seem to get slowly eaten away, little pits in the Top, and others suffer Piston/Ring Failure all at once!

    Put your favorite Pump gas in a Gas Jar with a lid and set it aside for 6-12 months and watch it slowly change.
     
  14. Nov 15, 2016 #14

    Turd Ferguson

    Turd Ferguson

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    My Polaris watercraft have a PD gear pump that varies oil delivery with engine speed and throttle position, anywhere between 20:1 to 80:1. None of the parts are plastic and I've never heard of the system failing. Have some pumps that were run ~500 hrs, reinstalled when the engines were rebuilt so are well past that mark now.
     
  15. Nov 15, 2016 #15

    Turd Ferguson

    Turd Ferguson

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    Ya, there's a reason why 2 stroke powerplant companies never did it that way.
     
  16. Nov 15, 2016 #16

    mmatt

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    OK what about an oil pump driven by the flowing fuel? The faster the fuel moves, the faster the oil pump would turn which should keep the ratio the same no matter how much fuel you're drawing.

    I get that most modern engines have factory designed oil injection kits, but I want to develop something that can be used on an engine without that option. MZ202, Rotax 447, Simonini, etc.
     
  17. Nov 16, 2016 #17

    Turd Ferguson

    Turd Ferguson

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    So what are you thinking? You'll need a flow transducer in the fuel line. Not sure if you can build one that has enough mechanical power to drive a pump directly so you'll have to use the flow transducer to generate a proportional electrical signal. The oil injection pump will have to be electrically powered?
     
  18. Nov 16, 2016 #18

    Armilite

    Armilite

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    ===================================================================
    Almost all Rotax's can have Oil Injection added to them. On the Rotax 447 look at the end of the Crank, if there is a Square Hole, it can be added. Since Rotax held over 80% of the World 2 stroke market, targeting them with an Upgrade to the OilInjection would be smart.

    If you want something to design, maked a Fuel Injection setup for Rotax's. Make a Single designed off SKidoo/Seadoo/Rotax readly available off the shelf parts like the 54hp Simonini.
     
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  19. Nov 16, 2016 #19

    mmatt

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    Ya, but mine doesn't. And I feel that there are likely thousands of other engines out there who don't have the ability either.


    Sure...? I have no idea. I'd rather have it purely mechanical but if that's not possible, I guess electric is ok. I've never heard the word 'transducer' before so that at least gets me going in the right direction. I'll do some research on that today and see what's out there and how they work. Thanks! :)
     
  20. Nov 16, 2016 #20

    Armilite

    Armilite

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    Last edited: Nov 17, 2016

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