WaveDyno docs
Guides and tutorials
How to model a two-stroke engine in WaveDyno, run it across the rev range, and read what the expansion chamber is doing. Use WaveDyno in your browser with a free account. Daily run limits apply.
Your first expansion-chamber sim
Build a 125 cc motocross two-stroke in the setup wizard, sweep it from 8,000 to 14,000 rpm, and read the expansion chamber's wave diagram at the peak and off it.
Compare two pipes: what 30 mm of header does
Lengthen the header of the same 125 cc moto-X chamber by 30 mm, run both pipes over the same rpm points, and read the difference in the tuned-rpm badge, the power curves and the wave diagram: where the longer pipe gains, and where it drops off the pipe.
Tune a 50 cc moped pipe: what a longer chamber buys, and what it costs
Build a 50 cc piston-port moped engine from the 125 road race template, sweep it from 5,000 to 9,500 rpm, then change the transfer timing, the chamber length and the stinger one at a time: what a chamber lengthened for 7,000 rpm buys low down, and what it costs in the middle.
Raise the exhaust port: what 2 mm does, and what the pipe does about it
Take the 125 cc motocross engine from tutorial 1, sweep it from 10,000 to 14,500 rpm, raise the exhaust roof 1 mm and then 2 mm, and retune the pipe for the higher port both ways: what each millimetre costs at the bottom, what it buys at the top, and what a longer or a shorter header does about it.
How a 2-stroke expansion chamber works: straight pipe vs chamber, in the wave diagram
Run the 125 cc motocross engine from tutorial 1 with a straight pipe of the same length, then with its expansion chamber, and change nothing else: what the chamber does to the power and the charge, and when its suction and plugging waves reach the port, at the top of its band and either side of it.
70 cc kit on a 50 cc two-stroke: does your pipe still match?
Take the 50 cc moped engine from tutorial 3, change only the bore to 70 cc and sweep it, then open the ports to the bigger bore: where the kit adds power, where each version comes off the pipe, and what the wizard's pipe for the 70 cc would look like.
Reed valve vs piston port vs rotary disc: one engine, three intakes
Take the 50 cc moped engine from tutorial 3, change only the intake type, to an ideal reed and then to a rotary disc, and sweep each: where each intake gains or loses power against the piston port, how much mixture goes back out through the intake, and where each comes off the pipe.
Crankcase compression on a two-stroke: what 1.35 and 1.60 do to the powerband
Build the app's 100 cc kart engine, change only its case compression, from 1.48 to 1.35 and then to 1.60, and sweep each: where each setting gains or loses power, what happens to delivery ratio, and where each comes off the pipe.
Expansion chamber calculator: design a 2-stroke pipe for a target rpm, then sweep it
Use the app's pipe calculator to design a pipe for 12,000 rpm on the 125 cc motocross engine from tutorial 1 and sweep it: its highest sampled point and where it comes off the pipe against its target, and what the calculator's Max power level does to power and exhaust-gas temperature.
2-stroke pipe temperature: does a hotter expansion chamber hit at higher rpm?
Take the cooling air off the pipe of the 125 cc motocross engine from tutorial 1, then give it twice the air and a polished surface: how much hotter the exhaust gas runs, where the power changes, and whether the engine stays on the pipe at a higher rpm, checked from a cold start.
Raise the transfer ports on a 125 two-stroke: what 1.5 mm does to blowdown and the powerband
Raise the transfer ports of the 125 cc motocross engine from tutorial 1 by 1.5 mm, then by half that, then raise the exhaust as well to give the blowdown back: what moves at the bottom of the sweep, at the peak, and where the engine falls off the pipe.
A dent in your expansion chamber: how much power does it cost, and does where it is matter?
Put a 12 mm dent in the header of the 125 cc motocross engine's expansion chamber from tutorial 1 and sweep it, then make it shallower and move it to the first cone and the belly: what the dent costs below the peak, where the engine falls off the pipe, and what the model can't tell you.
What does a power valve actually do? Closed vs open on a 125 two-stroke, and what a stuck valve costs
Lower both exhaust roofs of the 125 moto-X engine by 2 mm, then by 1 mm, and compare each sweep with the open port: where a closed valve gains or loses power, where each run falls off the pipe, and what both ends do from a cold start.
Stinger size on a two-stroke pipe: what a bigger stinger does to power and heat, and does length matter?
Widen the stinger end of the 125 moto-X engine's pipe by 8 %, narrow it by 7 %, then make the stinger 100 mm and 312 mm long, and compare the five sweeps: where each version gains or loses power, how hot the exhaust gas runs, and where the engine falls off the pipe.
Intake manifold length on a two-stroke: what a longer or shorter tract does
Lengthen the intake duct of the 125 road race engine from 120 to 200 mm, then shorten it to 80 mm, and compare the three sweeps: where each length gains or loses power, how much mixture is pushed back out of the intake, and where the engine falls off the pipe.
Kart flex length: what a quarter and a half inch do to a 100 cc kart's power
Make the flex of the 100 cc kart's exhaust a quarter inch longer, half an inch longer and half an inch shorter, and compare the four sweeps: where each length gains or loses power, and where the engine comes off the pipe.