srp Posted May 2 Report Posted May 2 This Banshee HQ thread is for HQ members that want to understand how two stroke pipes are designed using math. Anybody following this thread will learn how to design pipes and have the know how to compete with the top pipe builders, at the track and on the dyno. We will discuss what software to use, types of formulas to use and tricks we do to get an advantage. Tell your friends that Banshee HQ forum is the only place to get this information. Will post some technical stuff soon. 1 Quote
kawa110 Posted May 3 Report Posted May 3 This Banshee HQ thread is for HQ members that want to understand how two stroke pipes are designed using math. Anybody following this thread will learn how to design pipes and have the know how to compete with the top pipe builders, at the track and on the dyno. We will discuss what software to use, types of formulas to use and tricks we do to get an advantage. Tell your friends that Banshee HQ forum is the only place to get this information. Will post some technical stuff soon. Sent from my iPhone using Tapatalk Quote
srp Posted May 3 Author Report Posted May 3 8 hours ago, srp said: Sent from my iPhone using Tapatalk These three images are the same two diffuser pipe, it has resonance at 10150 rpm and 7772 rpm. At 6048 rpm the belly section return wave has no support from a diffuser section. Sections in the pipe not including the main wave from the baffle have two return waves tuned to be in resonance with the header or a diffuser section with 4 return waves. A three diffuser pipe has a diffuser section supporting the belly section! 1 Quote
srp Posted May 5 Author Report Posted May 5 The three most important formulas for resonance tuning are heated speed of sound, tuned effective length and horn coefficient. (Heated speed of sound) this formula converts exhaust gas temperature to pressure wave velocity. (Tuned effective length) this formula converts true tuned length of each section to effective tuned length of each section. An example pipe with a total tuned length of 1000 mm may have a total effective length of 1400 mm. The effective length of each section gets longer as the diameter gets bigger. A tuned effective length of 1400 mm on this example pipe would be used to time and tune for resonance. (Horn coefficient) the kh factor controls diffuser angles for smooth and controlled expansion. 1 Quote
srp Posted May 7 Author Report Posted May 7 4 minutes ago, srp said: Sent from my iPhone using Tapatalk I tested resonance on what I believe is the most well known two stroke pipe, Gordon P Blair’s Grand Prix 125cc pipe. This 125cc road race pipe is in his book Design and Simulation of Two-Stroke Engines on page 444. All input data for this test matches Gordon Blair’s specifications. Rpm 11750 Exhaust duration 198 Exhaust gas temperature 600 degrees Celsius Tuned length 832 mm, total effective length calculated out to be 1181.5 mm After testing this pipe, it had very good resonance at 11750 rpm and 9315 rpm. The image is at peak power 11750 rpm. 2 Quote
srp Posted May 12 Author Report Posted May 12 I test all pipe designs with Mota two stroke simulation software. Mota shows the 4 diffuser, 3 diffuser and 2 diffuser pipe designs will make over 70 horsepower at the crankshaft per cylinder. The test engine was a 465 Cheetah Cub on gasoline. The dyno results on all three made just over 113 horsepower and 60 foot pounds of torque. These pipes were designed for the heavy rider (doughboy class), the tuned length was much longer than the average drag pipe. Designing a pipe around the chassis weight / riders weight helps the heavy rider like myself to launch without bogging. 1 Quote
kawa110 Posted May 14 Report Posted May 14 I’m 170# if I’m lucky. Should I be running a lightened flywheel?4milSnipers110 fuel Sent from my iPhone using Tapatalk Quote
gusto Posted May 15 Report Posted May 15 Looking forward to learning. Generally speaking can you explain the effects of chamber diameter and cone length ? Quote
srp Posted May 16 Author Report Posted May 16 On 5/14/2026 at 5:54 PM, kawa110 said: I’m 170# if I’m lucky. Should I be running a lightened flywheel? 4mil Snipers 110 fuel Sent from my iPhone using Tapatalk I wouldn't cut the flywheel for that build, it should rev quick. If all I had was a lightened flywheel I would run it and see how it works. 1 Quote
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