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PostPosted: Sun Apr 26, 2020 7:04 pm 
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On the street
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Joined: Sun Apr 26, 2020 6:00 pm
Posts: 18
Location: Ecuador
Country: Ecuador
Suzuki 2-Strokes: 1990 AX100
Below are notes on my free spreadsheet of mini 2 stroke calculators. Some of these calculators have never been available till now although engineering types have always been able to figure this stuff out. The download link is at the bottom.

Maximum Average Piston Velocity Calculator
The average (mean) piston velocity is what most calculators go by instead of the maximum velocity which is fine because they maintain a set relativity to each other no matter what. I rearranged the formula also to make it show the maximum RPM needed to achieve an maximum average piston speed of 25m/sec.

Cranking Engine PSI Calculator
I came up with my own formula to estimate the cranking psi calculator going only by the compression ratio and riding elevation. Of course the more the rings are worn the less the pressure is, so the formula assumes the rings are within spec. The formula tries to mimic a cranking psi graph I found on the net which looked right from going by my own experience with engines I've owned.

Engine Compression Ratio Calculator
This calculator is easy enough in concept but getting the "above TDC mm" is a bit impossible because domed pistons throw simple formulas off since that especially has to be taken into account when figuring out the combustion volume when the piston is at TDC so I made a "piston dome cc" calculator at J19 to help. Luckily I found a good formula to use to help calculate the volume the piston dome occupies.

Trapped Engine Volume Calculator
This one was tricky due to piston dome area but I figured out how to do it. I think we should all be going by this calculation instead of the old way which basically gives the engine volume from BDC on up but without the head volume. That's what the 4 stroke engine volume calculators do. Crazy, like 2 strokes aren't important enough to have their own formulas. Go figure.

Mikuni Main Jet Crossover Calculator
The jet crossover formula is my own concoction that tries to duplicate the best information I've come across on the subject (including contacting places that sell the jets). Too many reports on the internet though are totally off and some even say the opposite of what's true.

Carb Air Velocity Calculator
This calculator is cool because it shows what your carbs air velocity is and then shows what the extremes of trail riding and racing would be best at, and what size carb you'd need to achieve that. The calculator mimics what the motorcycle manufacturers have done over the years so don't bark at me if you don't like it. Go to http://www.dragonfly75.com/moto/carbsizing.html to read more.

Pipe Cone Angle Calculator
This one is handy to use if you are gathering information on your pipe but don't have the formula for figuring out the cone angles. Of course the steeper the angle the stronger the return wave but also the shorter the return wave, and both the diffuser wave and the baffle wave need to have a certain length depending on what your goals are concerning the powerband. To really figure this all out right you need a good expansion chamber calculator based on a return wave simulator.

The link to download this spreadsheet of calculators at the bottom of http://www.dragonfly75.com/moto/various.html You need to have Excel on your computer. I give credit to James Dean, the creator of the JD Jetting spreadsheet for Keihin carbs, which I used to select the best needle for my 1989 Honda CR250, for getting me into making spreadsheet calculators. (The JD spreadsheet is no longer available in case you're wondering.)


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PostPosted: Sun Apr 26, 2020 11:45 pm 
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World Superbike
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Joined: Thu Feb 16, 2012 11:50 am
Posts: 2350
Location: The Republic of South Yorkshire
Country: England
Suzuki 2-Strokes: 2 x GT550s GT750, T200, TC200
Always nice to post an introduction before anything else. Just a bit of who, where and previous biking experience.
Other than that, welcome to the forum.

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Think of how stupid the average person is, then realise that half of them are more stupid than that.


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PostPosted: Mon Apr 27, 2020 5:17 pm 
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On the street
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Joined: Sun Apr 26, 2020 6:00 pm
Posts: 18
Location: Ecuador
Country: Ecuador
Suzuki 2-Strokes: 1990 AX100
I became bike crazy back in 1973 when I got my first bike, a Penton 125. A few years later I was racing motocross with a '75 Husky CR125 in Austin. About 10 years ago I was living in Ecuador without the ability to get a drivers license so I got a 48cc motorized bicycle which was not up to the job of climbing hills and existing in the high mountain air where I was. So I started studying and experimenting and eventually the bike was so strong it was accelerating up hills. See my site about it at http://www.dragonfly75.com/motorbike/
I had tried the 2 Stroke Wizard to make a pipe and hated the result and didn't want to spend $200 on a good pipe calculator so decided to make my own. Little did I know it would stretch into a 5 year project working sporadically on it mostly due to it being a return wave simulator (after realizing others have fake return wave simulators). I also decided to make other 2 stroke calculators such as a jetting calculator since I knew of no good cheap ones. It helped me solve an unsolvable jetting problem with my Suzuki AX100. I also made a crank balance calculator, the only one that takes into consideration all the different forces involved every 15 degrees of crank rotation.
It's a good thing I developed my calculators since now they are helping me to survive during this crisis as people are getting into perfecting their ride as something constructive to do while we are waiting for the boot of the government to get off our neck.


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