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Post by bigscoot on Sept 6, 2014 19:10:51 GMT -5
Hello all,
I know this might be an unconventional thread but I was searching the internet for scooter forums and this seemed to be one of the most popular ones. My main reason for posting is to get a little feedback to see if what I would like to do is possible. I am a senior mechanical engineering major and am on a team that is trying to make a 50cc diesel engine for our senior design project. Our plan right now is to take an existing 50cc gas engine and convert it to diesel. At this point we are thinking of trying to use the Yamaha Zuma engine. We know there are a lot of challenges to this but we think it might be possible. We also will need to get our hands on a Zuma engine. Does anyone know where a good place to look for one of these would be? It needs to be the newer version that is a 4 stroke. Thanks for any feedback you all may have.
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Post by tvnacman on Sept 6, 2014 19:54:39 GMT -5
craigslist.org
I remember seeing a post somewhere that diesel powered scooters were blocked from being imported . With that said I think it has been done and in production , just not here in America .
I would imagine it would need to to be water cooled , high compression for ignition . It would need very tall gears due to low rpm . I would like to see this unit .
John
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Post by JerryScript on Sept 6, 2014 21:43:07 GMT -5
Curious project, would you elaborate on the goals? Only justification I can think of off hand for a 50cc diesel is the ability to run it off of a multitude of fuels.
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Post by bigscoot on Sept 7, 2014 13:34:55 GMT -5
The engine is for our Super Mileage team at school. Every year we compete in the Shell Eco-Marathon. There are a number of different categories but right now we have three cars that compete. The "cars" are small 3 or 4 wheel prototypes that fit one person. The goal at competition is to have the highest mpg's. The cars and the engines we build for them are all designed around this goal. The diesel category is only a year or two old so not a lot of teams have them. The ones that do are running 219cc or bigger engines that are close if not completely stock. We want to be the first to build a smaller one. I have been searching craigslist and eBay. Found one engine on eBay that we are considering but thats all we have found so far.
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Post by wheelbender6 on Sept 7, 2014 15:53:07 GMT -5
Your project reminds me of when General Motors made passenger car diesel motors based on modified gas engine blocks in the late 70s. It felt strange to smell diesel exhaust while following a big Oldsmobile.
Your little diesel will have a narrow power band so you will need plenty of manual gears. I don't think a 50cc diesel will have enough power to work with a CVT.
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Post by wheelbender6 on Sept 7, 2014 15:58:19 GMT -5
Try the ecomodder forum, bigscoot. Most of the posts are about aerodynamics, but there are some guys that are into engine mods on it. ecomodder.com/ |
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Post by xyshannen on Sept 11, 2014 15:16:25 GMT -5
Another good source for info on this sort of thing is over at endlessphere.com.
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Post by rockynv on Sept 11, 2014 21:46:29 GMT -5
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Post by urbanmadness on Sept 12, 2014 0:49:46 GMT -5
Why 4 stroke? Back when I was a kid, some of the guys would convert .049 engines to diesel. It only required changing the head and making a contra piston. You didn't have to worry about injection, etc. If you could run a two-stroke, I'm sure you could have a head machined out of a piece of bullet with a cnc mill (remember you are just looking for really high compression), and with a cvt, you could run lighter weights, so it could at least be tuned to make it work with the diesels extremely narrow torque curve most naturally aspirated diesels have. Your not going for speed, your going for milage. Just seems the simplest route to go. Going with the four stroke makes it a lot harder, as you will need to figure out how to increase the compression without having the valves collide with the piston so at the very least you will need to grind a cam for it. The extra compression is also going to be hard on the timing chain and it's a very tiny chain. Remember the compression will have to be in the neighborhood of 18:1 for it to light off. If you do a four stroke, your going to have to machine a head (cnc out of a bullet) with valves, valve seats and ports, your gonna have to grind a cam, and make a piston. The four stroke will have a wider torque curve, but will not make as much low end as the two-stroke. You will need some sort of injection. If you do a two stroke, you will need some sort of fuel injection and some sort of oil injection. But the head construction will be very simple compared to converting the four stroke gy6 even with the additional machine work involved with a contra piston. Either way, you will need to make head gaskets, probably out of sheet copper and you will probaly need to use larger barrel studs and tread inserts. Then with the two stroke style diesel, there are two ways to go. If you choose to go with a carbureted compression ignition, you can use a carb, but you usually have to add a little either to the diesel or you can go with a more conventional set up where the air charge is compressed, then the fuel is injected into the combustion chamber and the super heated air ignites the mixture. This does away with needing the either to lower the flash point of the fuel or the need for the contra piston. www.modelenginenews.org/faq/index.htmlwww.flyrc.com/make-your-own-diesel-conversion-head/en.wikipedia.org/wiki/Carbureted_compression_ignition_model_engine |
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Post by rockynv on Sept 12, 2014 4:34:47 GMT -5
I am still not sure the GY6 cylinder mount would be up to doubling/tripling the compression as the metal is pretty thin where the studs go in. My kid brother machines his own .049 diesel conversions which are already a glow plug compression ignited engine and close to being a 2 stroke diesel as they sit while the GY6 is far from that. You may not get it to run for very long or reliable enough to go further than a short demo run.
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Post by urbanmadness on Sept 12, 2014 8:20:11 GMT -5
I am still not sure the GY6 cylinder mount would be up to doubling/tripling the compression as the metal is pretty thin where the studs go in. My kid brother machines his own .049 diesel conversions which are already a glow plug compression ignited engine and close to being a 2 stroke diesel as they sit while the GY6 is far from that. You may not get it to run for very long or reliable enough to go further than a short demo run. you could girdle it? He's talking about using a Zuma engine. Are they interference style engines? Come on guys... a scooter rollin' coal.... California's worst nightmare! |
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Post by bigscoot on Sept 13, 2014 12:30:26 GMT -5
urbanmadness, our engine must be a 4 stroke to run in the competition we are building this for.
This is all helpful. We have been looking into the problem of valves colliding with the piston. Do you think fly cutting the pistons would not be enough? The timing chain is not something we have looked into yet.
One thing we are thinking about right now is to take possible a 125cc gas engine and sleeve and possible grind it to get it closer to 50cc. Our thoughts we this is that the bigger bottom end could hold up better to the diesel and high performance parts are more readily available for a 125cc. A whole new head may still have to be fabricated though.
We aren't worried about getting 100,000 miles out of our engine but we do want it to run reliably for competitions for years to come.
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