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Kawasaki EX500 2 stroke
http://www.kawi2strokes.com/forum/viewtopic.php?f=21&t=14136		 Page 2 of 5
Author:  DGA [ Thu Jun 04, 2020 9:53 am ]
Post subject:  Re: Kawasaki EX500 2 stroke
I chose the EX500 for a couple of different reasons. I needed a twin cam, rocker motor and this is that. I originally thought I would use a current MX engine, KX250F etc, but those have half of the cylinder liner inside the crankcases and it wouldn't work easily, and few had rockers. I wanted a twin, ok, its like 40% more work to build, but it showcases that this does not need a sealed crankcase for each cylinder, and actually has much less pumping and windage in the crankcase. I needed rockers because of the short duration, you can only have low valve lift, so a rocker increases the possible valve lift through it's ratio increase, the EX500 has 1.38:1 ratio.
I have an investor interested in me doing this with a Suzuki GSXR 1000, I would do the engineering, design and prototype. Would be a fun motor I think, would sound like this engine though because of the typical 180 degree crank, it would fire two cylinders at a time. The newer 1000 cc bikes have 90 degree cranks, so that would change it a bit. But a rocker design base engine is still better, so will look into that.
Author:  H2RTuner [ Thu Jun 04, 2020 12:40 pm ]
Post subject:  Re: Kawasaki EX500 2 stroke
I've been working on (actually slacking off on) a water cooled, single block cylinder, case reed, power valve, removable head insert 750 triple top end. I do a little work on it every year, actually, too little cork on it, too stretched out.

I like ingenuity, and good design common sense in people, great ideas are the result.
Author:  DGA [ Thu Jun 04, 2020 3:01 pm ]
Post subject:  Re: Kawasaki EX500 2 stroke
Was just looking at the Yamaha R1 for this. Does not use rockers but the valves are big enough that the low valve lift would have plenty of flow anyway. The cross plane crank would mean it would be an even fire, so would sound like a V8 four stroke.
So, nobody has any questions about the 2:1 cam reduction speed and how that might work for a two stroke?
Author:  Jim [ Thu Jun 04, 2020 4:03 pm ]
Post subject:  Re: Kawasaki EX500 2 stroke
DGA wrote:
So, nobody has any questions about the 2:1 cam reduction speed and how that might work for a two stroke?

2-lobed cam?
Author:  DGA [ Fri Jun 05, 2020 9:49 am ]
Post subject:  Re: Kawasaki EX500 2 stroke
Yes, 2 lobed cams. I was originally going to alternate the valve pair openings, but after looking at the maximum lift I could get from the short duration, realized that wouldn't be enough exhaust flow. Then realized that there was enough room on each lobe that it could have two lobes. I never wanted to change the cam speed to 1:1 like Detroit does, if you think about it, the fastest you can run a cam and valve is maybe 7,000 rpm, or 14,000 crank, for this size valves. I designed the lobe shapes based on the duration I wanted, then made the ramps as gentle as possible, which isn't much. Had to make a second design after the first ones were riding off the edge of the rockers and had the valve head pairs clash each other.
Author:  H2RTuner [ Fri Jun 05, 2020 11:32 am ]
Post subject:  Re: Kawasaki EX500 2 stroke
I really like it, keep going.
Author:  DGA [ Fri Jun 05, 2020 12:27 pm ]
Post subject:  Re: Kawasaki EX500 2 stroke
One of the efficiency gains I worked on was the injection method. In an earlier pic I showed the front of the cylinders, you can see the two blue injectors, these port through the cylinder wall directly, and have a slight upward angle. Goal here was to reduce wall wetting, which is a source of emissions, especially cold start and warm up. Injectors are ported and timed to fire just as the transfers open and spray back across the incoming transfer air flow. across the top of the piston. Note you can't do this with a typical 4 stroke because that leaves a port hole in the cylinder wall that will be an oil consumption problem. I call it LPDI, or low pressure direct injection, it is direct yet does not need extreme pressures, only has the typical 45 psi as the cylinder pressures are low when the transfers open anyway, and the exhaust has cleared out.
Author:  H2RTuner [ Sat Jun 06, 2020 10:20 am ]
Post subject:  Re: Kawasaki EX500 2 stroke
Ford did extensive testing on cylinder positioning for the injection nozzle a decade ago, and using a crystal in the sleeve to light the fuel, instead of a conventional spark plug. They didn't complete their testing, but their tech notes might name available to read. These were on 4 stroke engines, but tech is tech with it, theory and application.

I figure you are looking into high fuel pressures for the EFI system, over current pressures. Unrelated, but Diesel injection systems went from low hundreds of fuel pressures, to electronic EFI using as much as 25,000 psi ( YES, 25K psi).
Author:  Ja-Moo [ Sat Jun 06, 2020 10:58 am ]
Post subject:  Re: Kawasaki EX500 2 stroke
Kinda 2 stroke....lol Just interesting in engine design.

https://www.youtube.com/watch?v=F_7J3W97d20&t=451s
Author:  DGA [ Sat Jun 06, 2020 11:05 am ]
Post subject:  Re: Kawasaki EX500 2 stroke
It seems to work great with just 45psi, and if you think about it, if there were any higher pressures in the cylinder at that point, the transfers would not flow the air charge in. I do have a small issue with flow time, as I want the entire fuel charge to complete it's squirt before the piston returns on the up stroke. I calculated for 15lb injectors, based on 110 hp I figure it should make, and those went really high on pulse width early on, so I am using 24lb now. Still idles great at 860 rpm on those with only 6% open time, so I may go to 28lb next, which are normally used on the GM LS1. Later developments would use 2 injectors per cylinder and stage them, which Microsquirt ECU can do.
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