Lightweight 70 CC DIESEL!

Discussion in 'Performance Mods' started by andyinchville1, Aug 7, 2007.

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  1. OK, May be off the wall but we could get us better performance and fuel economy by Dieselizing our engines ! (after about 100 MPGs or so do we really need more?....OK.... YES!)

    Years ago I remember a company called David Diesel was converting small glow engines (like RC plane engines) to diesel use and getting better fuel economy & power to boot (yes they are still around and you can read more about them on their website)....So what about us?....It'd be kinda cool to smoke out a tailgater on our bikes huh ( I know I love to do that in my Dodge Diesel!)....

    Any experimenters out there?


  2. skyl4rk

    skyl4rk Guest

  3. rcjunkie

    rcjunkie Guest

    It does not make sense to convert a gas engine to diesel for a variety of reasons but the main one being reliability and performance. Diesel engines are BEEFY and the term lightweight is NOT associated with them. Engine components must be able to withstand the 20:1 compression ratio required to ignite the fuel mixture. Our engines have a 6.6:1 compression ratio by the way. General Motors (GM) literally destroyed the automotive (not truck) diesel engine market by converting a gas V8 into a diesel engine. The low power and poor reliability of this engine is the reason why we have few diesel cars in the US while in Europe 55% of all vehicles sold today are diesel powered.

    This is an expensive proposition because small diesel engines seen in the model airplane hobby are not "pure diesels". They are run on a mixture of 35 % diethyl ether, 42 % Kerosene, 20% Castor with 2-3 % ignition promoter such as 2-ethyl-hexyl Nitrate. The ether would most likely evaporate from our fuel tanks quickly.
  4. skyl4rk

    skyl4rk Guest

    It would be nice to find a small diesel four stroke motor in about 50cc's that would run on hot vegetable oil after starting on diesel. I wonder if there is some difficulty in injecting such a small amount of fuel. Most or all of the rc diesels are two stroke diesels, which is OK but four stroke would be better. It may not be cost effective to make such a small diesel.
    Last edited by a moderator: Aug 8, 2007
  5. HI,

    Is that link good?...I tries two times to look at it but no go.

  6. turbo/chaos

    turbo/chaos Guest


    well ther is a far out question (and belive me more to come in the future)
    can you mix diesel fuel with synth oil to run the motor but the burn spark seems to weak for it?
    now another the magneto is a 6volt and VW's electric system is that so mabey
    with a honda battery helping you can make a real light system plus turn signals with a breaker fuse to make it flash

    but for another how stealthy can a motorized bike be maide ?
  7. LOL just seen a 3HP diesel engine, water cooled, a hefty 73 lbs, rated speed 2400.

    It's local to me, I may have to stop and see it in person someday.
  8. Herrmanator8

    Herrmanator8 Guest

    the hatz-diesel's are interesting, and could be fabbed onto a bike, yet the price isnt within my budget, as if anyone would pay that money for 4.6hp

    i think that converting a 2 stroke engine is a complete waste of time to diesel because its a whole nother concept and would never work... but just my opinion. interesting idea though, wouldnt have thought about converting a 2 stroke.

  9. StreetPlanes

    StreetPlanes Guest

    The big issues with diesel are weight, heat and the possibility that the compression would turn the engine into a little bomb just waiting it's chance to explode between your legs. 2 Cycle engines would be easier to convert to diesel (Millions of two stroke truck engines were once built by Detroit Diesel, Deutz and other truck companies. Truckers called the 318 Detroit the Double Breasted Yamaha.) but cooling would be a nightmare as they often exceed 1700 Degrees F., whereas gasoline engines rarely go over 750 Degrees.

    That said: If I had the cash I'd love to toy with the idea. Steam too!
  10. rcjunkie

    rcjunkie Guest

    If I recall correctly, 2 stroke diesels had valves so conversion for us would not be easy.

    Hey, I'm all for diesel power. 2 out of 3 vehicles in our family are diesel powered, an 06 VW TDI which nets me 48mpg on the highway at 75mph and an 06 Jeep Liberty CRD that gets 30mph on highway and 24mpg in city.

    Would love a diesel motorbike, would also love a diesel snowmobile, ATV (polaris has one I think now), and a diesel lawnmower.
  11. Atriot

    Atriot Guest

    Diesels would also require glow plugs instead of spark plugs unless under very high compression. If using glow plugs you would need a powerful battery source to heat them up. Correct me if im wrong...
  12. StreetPlanes

    StreetPlanes Guest

    The valves on the 2 stroke diesels were for air intake, fuel was via injectors. Converting a 2 stroke would still be easier because of timing issues. Of course the 20-1 compression ratio is still going to make the thing blow up between your legs so it's all a mute point.

    And yes, glow plugs and a huge electrical system would be required unless...

    My grandpa owned and operated a saw mill that was powered by an engine that cranked on gasoline and switched to diesel when it was fully warmed up. Once it was warmed-up you pulled a lever that switched from the gas tank to the diesel tank and retarded the timing. This was because it didn't have glow plugs and the compression ratio was too low to crank on diesel. And if you pulled that lever before the temp guage said 180 it would stall out every time. It was an inline 6 about 400 cubic inches, had a carb on one side of the motor and mechanicly timed fuel injectors down the other side. After a grandpa died my uncle took over the sawmill until he retired. The mill engine ran over 60 years with nothing more than tune-ups and oil changes. But it did foul a lot of spark plugs.

    I've seen gas car engines that would run on diesel but they have to be carborated, the gas filters have to be removed (Diesel is too thick) and they have to be cranked on gasoline or alcohol.

    On a two stroke bike engine the fuel is your lubricant. Diesel is also a lubricant. It's great in theory but alas I think weight, safety and expense makes it out of the question.

    That said, I'd love to have a diesel bike too.
  13. Diesels, ignite the fuel by the heat of compression....Glow plugs / intake heater grids are used to aid in cold weather starts...Small RC type engines have been converted to "diesel" by a company called Davis diesel ('ll have tp read on their site more to see how they do it...they really don't seem to beef up any of the glow engines innards...just a special head of some sort and maybe some special fuel....I'll have to read more thoroughly...

  14. DougC

    DougC Guest

    I just noticed something--
    the shipping weight of the cheapest Honda horizontal-shaft engine they have (a 6 HP) is listed as 33 lbs.

    the shipping weight of the 4.5 HP diesel is listed as ..... 75 lbs.

    Lightweight diesel??? Ehhhh...... maybe not so much...... I'd suspect the diesel is probably at least twice as heavy as a 6 hp gas 4-cycle.
    It would be cool to see the MPG figures, but you betta put full suspension on that motor-bike!
  15. JemmaUK

    JemmaUK Guest

    There is something you are missing methinks here. My family used to drive the old peugeot diesels - the commonly found XUAD 90hp jobbie...

    look at the horsepower rating and you think - oh dear, but then you floor it and the torque is amazing.

    Not to mention that diesels are simpler mechanically, plod along where a petrol would have stalled out and dont get sensitive about fuel.. admittedly its expensive as a unit engine - but if people start ordering them from outfits such as GEBE then that unit price will drop..

    Jemma xx
  16. StreetPlanes

    StreetPlanes Guest

    Diesels do have amazing torque and produce horsepower at far less rpm than similar gas engines. They also handle heavier loads and last up to 10 times longer than gas engines.

    2 stroke gas engines would be far easier to convert to diesel (fewer moving parts = fewer timing issues) but like I said before none of the 2 stroke engines used on bicycles would be strong enough to convert and would explode. Now if one could build a cast iron jug and head and add an extra ring to the piston I'd be perfectly willing to show how it can be done but cast aluminum... no way.
  17. JemmaUK

    JemmaUK Guest

  18. kevbo

    kevbo Guest

    I had one of thier kits on a Cox .051 many years ago.

    Only the head was changed. On these Cox engines, the glowplug is the entire head.

    Model diesels do not inject the fuel, they take in fuel air mix just like a glow plug engine. Ether is added to the fuel to allow compression ignition at moderate compression ratios. No glow plugs are needed. The timing is adjusted by varying the combustion chamber volume, and so the compression. You can always spot a model diesel by the compression adjuster screw on the head...usually a tee handle. The 1/2-A (.049 or .051) kits had a head with a piston backed by a compression adjustment screw. Rather than a precision fitted piston in the head, they used a teflon diaphram under the head.

    It might be because I lived in Denver (high altitude) but I could never get it to start by hand proping. I had to use an electric starter. I never had a problem hand proping glow engines, so I don't think it was my technique. It might also be that my fuel was old and had lost some of the ether.

    With the conversion, the engine had noticeably more torque. I ran an 8" prop on the diesel version, while the glow version used a 6".

    The model diesels burn fuel at a lower rate than glow engines. They tend NOT to throttle down very well though. So the tend not to be popular for sport RC, but more for control line, free-flight, and other aspects of model aviation that run the engines wide open for the entire flight.
  19. When I get the money, this will be my new motor. But it wont fit on a bicycle frame. I wonder how practical it would be to have pedals on a motorcycle. I like being able to pedal my way home if I run out of gas or the motor gets sick.
  20. I used to own a few RC 2 stroke diesels. They had variable compression with a piston at the top of the head pushed down by a screw that you turned with a "T" handle. No glow plug. The fuel was either kerosene or diesel fuel mixed with ether and oil. I don't remember the ratio of ether to diesel and oil...or did we use oil at all?... This was about 35 years ago. Back then it was the local pharmacist were we got the ether under my dad's approval.
    The one thing I sure remember was the vibration. Many times more than the glow plug RC gas engines. I think you would not want that on a bicycle.