Digital Fuel Injection for Chinese 2-stroke motorised bicycle engines

Discussion in 'General Questions' started by Fabian, Sep 27, 2009.

  1. Fabian

    Fabian Well-Known Member

    G'day all

    In between doing other things, i was thinking of the advantages of engineering a much better solution to the carburation issues we seem to be having with our Chinese motorised bicycle engines.

    I've been looking into Formula 1 fuel injection systems as those engines were spinning at up to 21,000 rpm before they had an 18,000 rpm limit applied to the rule book.
    Also, modern fuel injected sports bikes like the Honda Fireblade, Kawasaski ZX-10, Suzuki GSX-R 1000, and Yamaha R1, reliably rev to 12,000 rpm

    Since a two stroke makes twice as many power strokes as a 4 stroke and since Chinese motorised bicycle engines rev to a maximum of 6000 rpm, they need a fuel injection system capable of 12,000 pulses per minute.
    This is exactly the number we need to make digital fuel injection a real possibility on these small engines.

    With closed loop engine management and a wide band oxygen sensor connected to the electronics it would be a set and forget system, regardless of what parameters you experimented with, (different tuned exhaust systems, different intake systems, different grades of fuel ect).

    Anybody have ideas that's knowledgeable in this field of engine technology, because i just want fuel injection fitted to my bike.

    Last edited: Sep 27, 2009

  2. arceeguy

    arceeguy Active Member

    At 6000 RPM, you would need 6000 injector pulse events, not 12,000. The injector would fire every revolution, not twice per revolution. A four stroke would fire once every other revolution.

    In any case, I think fitting computerized engine management on a two stroke engine is totally counter to what two strokes are meant for. And that is a simple, inexpensive, and lightweight source of power.
  3. Foximus

    Foximus Member

    Building a mechanical injection system would be a cinche. And probably work far better than an electronic one ever would. o2 sensors dont like 2cycle fuel.
  4. GearNut

    GearNut Active Member

    Foximus is right. The leftover oil in the exhaust will quickly coat the oxygen sensor and cause it to malfunction.
    A mechanical injection system would be the only way I could think of to do it.
    In the 70's Halborn (or is it Halbourn?) was a popular company that produced such a system.
  5. Foximus

    Foximus Member

    Take a look at jetski setups. You can get them fairly cheap and would be a Breeze to adapt this onto the billet aluminum intake manifold that guy sells.

    Made by a company called MRD. they are on ebay or jetski forums quite often. They make HUGE power all over the RPM range but as soon as you unhook the pump from the water they bog down the motor like crazy. No good for the freestyle stuff I'm into, only big boat racing.
  6. kerf

    kerf Guest

    It would be much cheaper and more practical to replace your troublesome float style carb with a Walbro pulse carb. On my CY R460, I never have any carb issues, no valves to shut off even with a sealed fuel system that will build pressure. Just a couple of pulls and I'm riding.
  7. motorpsycho

    motorpsycho Active Member

    are you serious?
    why bother...the rpm's on these motors are kind of limited because of the gear ratio anyway. (unless you have a shift kit.).
    i would think that a fuel injection set up from a 650 c.c. jet-ski / watercraft would supply way too much fuel even with a closed loop set up.
    you are only going to get so much horsepower out of these engines because the precision of a high performance engine is not built into these things.
    you want power? add an expansion chamber and a nitrous set up. it would be far cheaper than trying to make a fuel injection set up work on one of these things.
    contrary to what alot of people think, nitrous oxide will not make an engine blow up. nitrous oxide is not flamable, and as long as you have a rich mixture, the motor will be fine. i have ran several drag cars with nitrous and i NEVER had an engine failure, broken parts, or anything because of nitrous. it's all in the set up, fuel mixture and the tune that will make nitrous work and not destroy an engine.
    just my opinion.
  8. Fabian

    Fabian Well-Known Member

    Hi arceeguy

    I stand corrected - It's comforting to know there are people in here who are a good deal smarter than i am.

    What i should have said: 12,000 rpm for a 4 stroke = 6,000 injector pulses, so a high performance motorcycle fuel injection system would be able to meter fuel at 6,000 rpm for a 2 cycle engine.

    Thanks for correcting my erroneous statement

    Timbone likes this.
  9. Foximus

    Foximus Member

    Actually they are completely tuneable using mikuni fuel jets. Normally youd have a 100 size jet or so... but you could just as easily install a size 30 jet. You can even adjust the fuel popoff pressure in the kit. They really are well thought out, and you power it off the crank, which would be really easy to mod over. Eitherway he asked about injection, and thats an option. :grin5:
  10. JemmaUK

    JemmaUK Guest

    Wonderful idea - until the china motor does its usual trick and you get an external combustion engine with an electric fuel pump ...

    CH kit $200
    EFI kit $150

    6 months in the specialist burns unit .... priceless

    .... for everything else theres Mastercard....

    Why do I have the feeling that burning petroil directed at ones groin is a bad thing... or maybe its just me

    Promising idea but just tooooo dangerous with the build quality of these motors.

  11. Foximus

    Foximus Member

    Mechanical fuel pump... electric fuel pump would be a pain to use as you have to have variable fuel pressures.... 3 at idle at 6-10psi at WOT.
  12. Fabian

    Fabian Well-Known Member

    It's already been done - a company called Rock Solid Engines is selling nitrous kits for Chinese motorised bicycle engines and from memory it uses an electric fuel pump to spray in extra fuel metered to the nitrous delivery system.

    I was looking at digital fuel injection as adding simplicity, not complexity as it could and would be a set and forget system in closed loop mode, i.e.

    add a tuned pipe - wammo - the fuel injection system just compensates - no fuss

    add a cylinder with different porting - the fuel injection system just compensates - no fuss

    Add nitrous - the fuel injection system just compensates - no fuss

    Change fuel type or density - the fuel injection system just compensates - no fuss

    I've done some research and an Italian company (Bimota) made a 2-stroke 500cc v-twin sports bike.
    It used fuel injection but wasn't very reliable as a first generation direct injection 2-stroke, but they made it work, when it was working.

  13. Foximus

    Foximus Member

    EFI doesnt exactly work like this though. You have to have a really intelligent ECU to do this... they cost in the upward thousands. Otherwise you have to actually sit down and program your fuel curves everytime you change something, as a 2 stroke motor works more like a supercharged motor than a N/A motor. Fuel injection is not as dummy proof as you'd think.
  14. kerf

    kerf Guest

    Numbness in the groin area can leave a man completely oblivious to risk. Only reason I can give.
  15. Fabian

    Fabian Well-Known Member

    Hi Foximus

    It's probably becoming rapidly obvious that i know very little about the deeper technicial aspects of fuel injection.

    I just made a bad assumption, that in this day and age of home computing power doubling every 18 months, that we would (by now) have ECU units capable of doing everything in "automatic mode" for a couple hundred dollars.

    And i made a bad assumption, you just install the thing like a Chinese CDI unit - connect blue wire to blue wire and black wire to black wire and hit the button labeled "auto mode".

    It's not as simple as i would have hoped it could have been.

    Last edited: Sep 28, 2009
  16. arceeguy

    arceeguy Active Member

    The microcontroller isn't the expensive part of an EFI system. There was a similar thread a few weeks back about EFI for small engines. The chips were about a buck a piece in production quantities. The expensive part is the electric fuel pump, all the sensors and the injector itself.

    If an enterprising person could invent a simple EFI setup that would run off of a magneto, be self contained, and cost less than $25 - they'd be an instant billionaire. As emission standards for small engines get tighter, first you'll see the two strokes go extinct (surpised to see them around now!), then the little four strokes will go away.

    It'll be wimpy electric lawn mowers, string trimmers and electric "assisted" bicycles. Blech.
  17. kerf

    kerf Guest

    All the more reason to strike hard in 2010!
  18. motorpsycho

    motorpsycho Active Member

    well if it was set up to run in closed loop, the computer would make NO adjustments to the fuel injection. closed loop is a fixed setting. when it is in open loop, that's when it (and you) will make adjustments to the fuel curve. for example, when you first start your car on a cold morning the computer runs in open loop so that it can get the air temp, exhaust temp and all that, to adjust the fuel curve to make the engine run right.
    once the engine is warmed up, it switches to closed loop. this is how and why fuel injection does not require a choke like a carb does.
    also, if you add nitrous to a f.i. motor, the computer WILL NOT automatically add more fuel. if you add nitrous to a f.i. motor, you have to increase the size of the injectors, and add a secondary fuel line to add more fuel when the nitrous is activated. this second fuel line would be tapped into the return fuel line and would be hooked to a solenoid. when you push the nitrous button a nitrous solenoid and the seconadry fuel solenoid are activated, spraying both the nitrous and the fuel from the return line into the intake under pressure. the more nitrous you use, the more fuel you need to add. i think that the kits for these 2 stroke engines add a small enough amount of nitrous that you could get away with just running the carb a little rich to compensate for the extra fuel needed. i don't see you having to run a secondary fuel source into the carb. for the nitrous. now when you are talking a 200 horsepower nitrous set up, then it is crucial to add more fuel. the other thing about nitrous is that you actually need to retard the ignition timing 2-4 degrees and run a colder plug to make it most effective.
    this is how it works on a 4 stroke v-8 anyway.

    one thing taht got me wondering....aren't there some weedeater out right now that are 2 strokes with f.i. ?
    if there is, one of those set ups would be the way to go.
    if there are f.i. weedeaters, i can imagine that they are probably mechanical f.i. and don't need a computer. but the injector size may be too small, and they may not give enough fuel to an 80 c.c. motor. most weedeaters are 30-35 c.c.'s and running too small of an injector would make the motor run too lean.
    just a thought.
  19. GearNut

    GearNut Active Member

    I already have experience with electric lawn mowers, weed eaters, and leaf blowers. In my opinion they are not worth the price of the cardboard box they were packaged in.
    The electric motors burn out way too easily.
    The batteries loose capacity with each re-charge.
    The better ones are heavier than their gas counterparts.
    The cost of replacement batteries makes them a disposable commodity.
    With the price, you are better off buying a new one rather than buying new batteries.
    The "plug in the wall" corded ones are a pain to use.
    While I have never accidentally mowed over the extension cord, I have had a few close calls.
    Alot of folks are not as lucky, and many an extension cord has been chopped up.
    I have never had a gas leaf blower catch fire while in use. I did have an electric one that did though.

    And all of this is just my experience with the "new wave of outdoor technology".

    Does anyone here have better experiences?
  20. arceeguy

    arceeguy Active Member

    You've got it right, but reversed. In closed loop operation, the ECM takes input from all the sensors to fine tune the A/F ratio. Open loop operation is when your engine runs at pre-set parameters until the O2 sensors come up to temp, and the engine is warmed up.

    But even in closed loop operation, an EFI setup is designed and optimized for a particular engine and can only "self adjust" within a certain range. So yes, you can make changes to the intake and exhaust on a car and the ECM will adjust. But if you make radical changes, you'll just set off the MIL (check engine light) when the ECM cannot compensate enough for the changes you've made. This is where the custom ECM's can let you tune outside the OEM parameters.

    Amen brother!

    Electric lawn equipment sucks. Overpriced, underpowered, short lived.

    How many 10+ year old cordless electric mowers do you see out there.................