MJS, I'm really looking forward to this electric build, I am also thinking about making an electric scoot. I have a few frames at home. My biggest headache is getting the parts, as I have to import from the US. Do you plan to change the motor? I see you mentioned a 8Kw motor, is that whats on right now?
Yep I understand, actually I think I'm over shooting here, 11:1 or 11.5:1 is what I might aim for. If I have to weld a cam myself and grind it on a make shift jig I'll do it. I see the gx200 guys have some nice 246 degree duration cam. I'll have to figure out what our valvetrain can handle. More than likely I'll be doign that by trial and error using lift figures from the cams we already have.
So I actually ditched the pvc intake and made another short one out of a butane refill can, air speed is much better with the short setup. I also changed that uni filter for a pod style. Much better flow up top. I tried to upload the setup but I keep getting errors to load my pictures.
For sure Piston, thats exactly why I would choose the 58.5 head if I had to do bolt on's only. But I'll never be able to do the bolt on only option. Before I piece anything together, I'll cc the head calculate static and dynamic compression with the cam I'm going to use etc. I know some of you may know what dynamic compression is. But many others believe that once the static compression is high, the engine is unreliable and its going to overheat and not run good. Manufacturers have dispelled this myth years ago. It is true that the gy6 engines may be prone to failure with stock components due to them being made with poor materials, but if you install proper aftermarket components there is no reason to be afraid, once you have a good idea as to what you are doing. Anyway, cam design has a big role to play with a "high" compression engine. Piston please bless us with some knowledge on the topic. I know you told me before but I'll have to go searching, but I really want to get a custom grind on a cam for a 12:1 high compression build. Isky? Delta? Webcams?
That's a great bolt on package for sure Ricardo, plug and play no worries. That's not enough for me bro, I want to have more than just bolt ons but I know this thread isn't about that. If I HAD to stay bolt on only, I'd run a high compression 61mm BBK with a 58.5mm big port head and either a Nibbi cam (I had great results with this) or a A11 or A10 cam. I had great grunt with the A8 cam as well, spun those bearings due to low oil. A 28mm PWK carb, good exhaust pipe, a real adjustable CDI and the highest octane gas I can buy from a gas station.
You are very right here SD12, when I go about doing calculations for gearing, I always assume the CVT as a 1:1 ratio (or constant ratio). The main reason for this is at top speed even though the CVT has a given ratio, the engine is running all out and if we only consider the effects of changing the gear set, the CVT gear ratio will remain unchanged with the engine wide open and therefore we can eliminate if from our calculations as a factor. You are on point about the "torque sensing " aspect of the CVT also, but again I think that torque sensing feature of the CVT goes out the door when we talk about top speed. I'm not talking about the whole run from a dig, but only up at the top of a run. It would be great if someone could do a write up of the theory behind the CVT on the GY6 engine and the working principles of each component and the effects of changes in the system.
Hey MJS, technically, there is no reason you can't install a higher flowing head with bigger valves. I currently have a blended/ mildly ported Taida big valve head for a 58.5mm cylinder on a stock 150 block with a A10 cam and a 26mm Nibbi PWK slide carb, 105 main jet and a 40 pilot with a home made air filter tube from a butane can and a pipe. I also run a few degrees ignition timing advance to help the situation out. It is not a great performance setup but its runs for now. It is lacking severely in the compression department and that A10 cam hates it. Why this setup you may ask. I don't have a stock cam and I refuse to run that garbage stock head with the EGR. The motor runs way rich and I cant go WOT cause it just drowns in fuel cause I can't get a smaller main jet. I'm not going to bother to get one cause this will not be my final setup. The motor needs a BBK and build with a good tune to perform well. I'm thinking at least a 61mm BBK and a 2.2mm stroker crank. If I can't get a crank, I'm going to deck the block to bring that piston to zero deck height. I'll also be adding some more ignition timing. Again this is what I am going to do and I do not recommend this to anyone to use as a daily, as attempting this setup may lead to engine failure, loss of money and/or loss of limbs.
Hey Kachi, The numbers on the left should be a measure of power such as Horsepower of Kw. Concerning the RPM's, you wont see them drop off, the engine will rev, but what the graph is saying here is that at higher revs, the engine produces less horse power. That's why from the graph, I would choose the A11 as there is more area under the power curve from the start (I know the graph only starts from 6000rpm) of the curve till around 8500rpm as compared to the A9. Even though the A9 has slightly more after 8500rpm, both of the curves fall off the same and I would prefer to have more HP lower in the rev range. This is where your gear choice comes in to play. Because power drops off considerably after 8500, I would run my calculations for top speed with the engine somewhere at 8000rpm for my desired top speed so I know the engine is most capable (or has the greatest potential) to pull that taller gearing I install. I run a flat slide carb and I love it. So again there is massive theory behind both style of carbs and though I have good knowledge of both I don't think I can do it justice. Basically due to the working principle of the CVK, which works on pressure differential to lift the slide, it takes a longer time to react as compared to the flat slide/ round slide/ D slide carbs which use the throttle cable to lift the slide directly. The response if quicker. Also in my experience, CVK carbs are very forgiving on the rider. For me I prefer it as it is easier to work on, I don't have to worry about tearing the diaphragm, I hate that autochoke enrichment garbage.
Kachi, this is how I go about choosing my gear ratio. This is the way I do it and do not recommend this unless you are aware of all the variables involved. Use this guide at your own discretion and only as reference to help you make your decision. This is a rough guide as there are many variables that have cause and effect in the engine and CVT happening as we make changes. 1) Determine the cruizing speed and top speed I want to achieve? I want to hit 140km/hr Please note that our scooters were never designed to reach these speeds and I do not recommend for anyone to attempt these speeds. Also I do not encourage or recommend that anyone break the law by violating the designated speed limits. My Top Speed goal is totally theoretical and I only attempt to reach those speeds in my dreams while I race Marc Marquez for the Moto GP championship. 2)Determine the current gear ratio of the changeable gears. Think mine was 13:40 or something like that. 3)Determine your current cruising speed and associated RPM and also top speed and associated rpm. My cruizing speed =80km/hr ; top speed= 105km/hr I d not have a tach so I didnt know what the rpms were. If you do have a tach this information is valuable 4)Considering that EVERYTHING else remains the same, we can make an ASSUMPTION that speed is directly proportional to the change in gear ratio. This is not a bad assumption for a ball park. I create a table with all the available gear ratios on the market. An example below Ratio Speed Stock (13:40) 13:40= 13/40 = 0.325 100km/hr Therefore 1= 100/0.325 307.7km/hr 14:38 14/38= 0.368 307.7 X 0.368 = 113.2km/hr 14:36 14/36= 0.389 307.7 X 0.389 = 119.7km/hr 15:38 14/38= 0.395 307.7 X 0.395 = 121.5km/hr 15:37 15/37= 0.405 307.7 X 0.405 = 124.6km/hr 15:36 15/36= 0.417 307.7 X 0.417 = 128.3km/hr 16:38 16/38= 0.421 307.7 X 0.421 = 129.5km/hr 16:37 16/37= 0.432 307.7 X 0.432 = 132.9km/hr 16:36 16/36= 0.444 307.7 X 0.444 = 136.6km/hr 17:36 17/36= 0.472 307.7 X 0.472 = 145.2km/hr 18:36 18/36= 0.5 307.7 X 0.5 = 153.85km/hr So basically there are many more combinations you can get but my hands are tired. you get the point, choose the gearing that gets you close to your goal. Understand that if you ONLY make this change in gearing from stock to achieve a higher top speed, you have effectively decreased the torque multiplication of the transmission and you WILL have a decrease in acceleration. DO NOT LET YOUR SENSES FOOL YOU Conversely There are gears that further increase the torque multiplication of the transmission to increase the acceleration at the expense of top speed. This is usually used for tight race tracks where the top speed of a longer gear is unachieveable and will result in lower lap times. Again your senses may tell you that you are accelerating quickly but if everyone else racing optimized their gearing to suit the track you will be in last place. Ask Piston how much gear kits and sprockets his team walked with to a race. Hope this helps out. I added all the calculations so anyone can replace them for their own and know what is going on. Quick add in. If everything else remains the same and you increase your RPM ONLY this works the same way RPM is directly proportional to speed assuming all else remains the same. This was how I was able to get from 90km/hr to 110km/hr even though I couldn't get replacement gears for my engine. I increased the RPM, I DO NOT RECOMMEND DOING THIS AT ALL. All engines have their limits and I found mine. Dont go looking for yours.
These are awesome minimac. They entail a lot of welding and machining that most of us may not have the machinery to do. I would like to attempt something as clean as that someday though. With the idea I have everyone should be able to duplicate it if they wanted and should only require a few machined parts that they can get done at a machine shop.
No problem at all, I too mix up my theories and concepts and I depend on all of you guys if I do. I've always found that no one ever fully explained the transmission. I still left out a few parts concerning the CVT. Maybe I'll do a write up when I get some more time, there are many misconceptions out there about variator and CVT tuning that I too got caught up in before going back to basic principles and fully grasping the concepts. There are many BIG named scooter companies that share a lot of misinformation when coming to this topic. There is also a big misconception concerning a high compression engine but that is a huge topic with many variables.
I think there may have been a mistake with the gear ratios discussed above. This was already discussed in the "gearing" thread but never fully explained. 18:35 will not give you better take off or less top speed as compared to a stock ratio of say 13:40. This is simple and the concept is used by stunt riders so they can pop wheelies easier and do mad burnouts. Go look at any video of a professional stunt bike, the rear sprocket is huge as compared to stock. They do this to multiply the engine's torque. They gain crazy acceleration and loose top speed. We want the opposite. This is the same concept used in a chain block/ come along for one person to lift a heavy load. You turn the input gear about 100 times to get the output gear to turn once, equals a torque multiplier For those interested I have typed and explain in detail gear ratios and how our gy6 transmission works. Let me back this up easily as this is simple mechanical theory 40/13 = 3.077 This means for every 3.077 revolutions of this input shaft (Engine), the output shaft (Wheel) will turn once 1000 Engine rpm = 1000 / 3.077 = 325 Wheel rpm as compared to 35/18 = 1.944 This means for every 1.944 revolutions of this input shaft (Engine), the output shaft (Wheel) will turn once 1000 Engine rpm =1000 / 1.944 = 514 Wheel rpm For the same 1000 engine rpm a gear ratio of 18:35 will give you greater distance covered by the back wheel which results in an increase in top speed. Comparing ONLY these 2 gear ratios, the results are as follows: 13:40= increased acceleration, less top speed 18:35= decreased acceleration, more top speed The terms Engine and Wheel used above was only used to prove the simple concept. For our gy6 engines, the gears that we change are not actually the true gear ratio. Let me explain with a picture.
The Shaft to the top right is the clutch input, it has a small gear that drives a big gear. It will take that small gear many rotations to turn that big gear once, this is the first stage of gear reduction and torque multiplication. For this transmission, the first gear ratio is 15:42 meaning it will take 2.8 rotations of the clutch input shaft to turn the "middle" shaft once On that same "middle" shaft there is a small gear that we can't see, that drives the big gear on the output shaft to the left, this is what your wheel is driven by. This is the gear ratio that we are altering. It will take that small gear a few rotations to turn that big gear once, this is the second stage of gear reduction and torque multiplication. To determine the overall gear ratio of the transmission it would be= 2.8 (from the first gear ratio) X 3.077(Stock 13:40) OR 1.944(18:35) Stock = 1:8.6 8.6 rotations of the clutch input shaft will turn the wheel once "18:35"= 1:5.4 5.4 rotations of the clutch input shaft will turn the wheel once I hope this clears up any misconceptions of the gear ratios of the gy6 transmission.
MJS I was actually playing to try out a BLDC as an electric "supercharger", but the cost is very high where I am and batteries will cost a good bit. I was thinking to gear it to the crank for torque to help the engine get into its powerband. Unless I can get at least a The plan is to put the second engine in the space between the current engine and front upright. I'll also be fabricating bracing to triangulate the frame for added rigidity. The plan is to put the second engine in the space between the current engine and front upright. I'll also be fabricating bracing to triangulate the frame for added rigidity. I've spent some time on a dry sump idea but it is a lot easier to just place the engine right side up. It will take a lot of welding, drilling, tapping and time to do it, but it is possible. I've even thought to redirect the oil passage from through the cylinder so we can run larger BBKs but again time and money. I'll take some measurements and do up some sketches and plans for you all by Monday (I upload off of my pc at work) Thank you guys for the support