Kayla Posted November 15, 2011 Report Share Posted November 15, 2011 What about a simple 4t bottom end (SR125 or something like that) with a TZR125 barrel (no intake port to blank off and the transfers can be filled with epoxy to close them) mated to it? I'm thinking that the cylinder head could be made to take a spark plug and an injector. I know I'm really over-simplifying it, but would that be a good starting point and has anyone already thought of this and am I ten years late? Link to comment Share on other sites More sharing options...
crayons Posted November 15, 2011 Report Share Posted November 15, 2011 There's a conversion kit for tuk tuks so it most be do-able. Edit for linky Link to comment Share on other sites More sharing options...
szrdave Posted November 15, 2011 Report Share Posted November 15, 2011 What about a simple 4t bottom end (SR125 or something like that) with a TZR125 barrel (no intake port to blank off and the transfers can be filled with epoxy to close them) mated to it? I'm thinking that the cylinder head could be made to take a spark plug and an injector. I know I'm really over-simplifying it, but would that be a good starting point and has anyone already thought of this and am I ten years late? How would you get air into the engine if you're using a 4T bottom end? Link to comment Share on other sites More sharing options...
kaighn80 Posted November 15, 2011 Report Share Posted November 15, 2011 other than the use of cams why would it need to be a 2t barrel (i ask as i dont know the major difference) could it be possible to build a couple of cams that would open the valves twice as much? (obviously i know it is its just a question to open up other avenues of development) with the way things have moved on with fuel injection and ecu's theres no reason you couldn't use it to fire fuel injection twice per cycle most have the option of doing this so that the cylinders don't run lean. from what i can see its going to be overlap on the cams that will be the biggest problem, meaning that there will be combustion in the exhaust system to burn off the rest of the fuel. honda had a problem getting the emissions low enough on the s2000 so it has an air pump that puts air into the exhaust, might be an option. theres going to be a really small time span for the valves to be opened and closed it might need some really clever thinking to get around that. any one seen mike? Link to comment Share on other sites More sharing options...
Kayla Posted November 15, 2011 Author Report Share Posted November 15, 2011 other than the use of cams why would it need to be a 2t barrel (i ask as i dont know the major difference) Because you still need an exhaust port to let the gases out and I don't want any cams or extra weight on top of the engine. Hmm. I think I'm not barking up the right tree here. It's not the wrong tree, just not the right one. Link to comment Share on other sites More sharing options...
kaighn80 Posted November 15, 2011 Report Share Posted November 15, 2011 ok that make sense, how are you thinking of delivering the air to the system? are you considering using a reed valve type set up or do you have another idea? it would be good if the amount of air could be metered in some fashion if only to give the ecu something to measure and calculate the amount of fuel needed along with the rpm speed and throttle position. Link to comment Share on other sites More sharing options...
2moto Posted November 15, 2011 Report Share Posted November 15, 2011 Just start with either a snowmobile or outboard motor and go from there. Graft a gearbox type bottom end onto it, i.e. use everything from cylinder upwards and a suitable bottom end. You'll need all the electronics, sensors, fuel pump, as well obviously. Link to comment Share on other sites More sharing options...
Boozybloke Posted November 15, 2011 Report Share Posted November 15, 2011 nothing to see here but us potatoes Link to comment Share on other sites More sharing options...
spacemonkey Posted November 15, 2011 Report Share Posted November 15, 2011 Why not do it the way orbital do it? Use a supercharger/pump to shove air in like a two stroke diesel. You could use all your poppet valves as an exhaust. Or do it the other way around, use the exhaust port in the barrel and the valves at the top as inlets. I found a page by someone who did something like this years ago. I dunno what it was called though! Link to comment Share on other sites More sharing options...
Evilchicken0 Posted November 16, 2011 Report Share Posted November 16, 2011 I pasted this in the other thread in General Section Link to comment Share on other sites More sharing options...
spacemonkey Posted November 16, 2011 Report Share Posted November 16, 2011 Like a Miller cycle engine? Link to comment Share on other sites More sharing options...
2639 Posted November 17, 2011 Report Share Posted November 17, 2011 On a particuarly DIY front... Jon Molyneaux (a Cumbrian shed-dweller not concerned with standard practices) made something similar some years ago. He took an old Z1000 engine and cut the inlet cam up so it allowed cam timing of a two stroke. The exhaust cam was messed with so the valves could not open. The barrels were then piston ported. The engine was bench run using the workshop compressor in place of the supercharger. I recall a car distributor acting as a centrally mounted cam chain tensioner... but I am not sure if this was the same mad cap scheme or not. Assuming some sort of plenum was made and it ran through carbs. If so pressure would need to be equalised into the flaots to get any fuel to flow. I didn't see it run. So can't recall the fuelling exactly. Aparently the thing set the garage on fire twice. After that I know not. I rode another Z1000 hill climber type thing with so few bits it appeared unrideable. It had the clutch running off the gear lever; thus you pressed down for first and this disengaged the clutch and selected the gear. Hold your foot down to stay still. Couple of revs and release pressure on the gear lever and your away. Lovely idea, no doubt loads of work to get it to work. Hopelessly impractical :-) Anyway, best of luck. Link to comment Share on other sites More sharing options...
Benji Posted November 17, 2011 Report Share Posted November 17, 2011 Direct injection, is going to need alot of fuel pressure, this soon becomes a heavy item. The other thing is most direct injection system, use multiple injection pulses to get swirl and good combustion in the combustion chamber, so a good degree of mapping will be needed. You can even find that the orientation of the spark plug to the injector affects the smoothness of the flame fronts travel. If you are injecting you are going to need some form of air metering otherwise how are you going to know how long an injection pulse(s) you require. Anything is achievable in a shed Link to comment Share on other sites More sharing options...
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