| Author | Message | ||
     S21125r |
My brother is just wrapping up a custom ’69 Suzuki T500 that he slammed and hard tailed (not my first choice in design direction but it does look cool…). He wants to put chambers on it, but doesn’t think he has room for two so he’s looking to build 2 in 1 chambers. I know it’s possible because I’ve seen the configuration on snowmobiles before, but what I don’t know is what changes from a cone/belly/stinger length/diameter once the second cylinder is added. Is it as simple as halving the tuned length so that the pulse from cylinder 1 interacts with cylinder 2 and visa versa? I know this stuff is part art and part science when it comes to application, so my baseline thought was to plug everything into one of those custom chamber calculators and then doubling the RPM to simulate twice as many pulses coming out of the head pipe. This should give us an idea of how much a stock chamber would need to change and we can then make relative changes to an off the shelf design. This should result in a shorter pipe that may help packaging, but I’m thinking there is a trade off when the reflected wave goes back up the pipe and splits – potentially loosing half it’s energy. I presume there is a way to amplify the returning wave with yet another parameter change, but that starts to get even further into uncharted territory. So... Does anyone have any resources on how this can be done intelligently? | ||
| Oldog |
years ago HP books produced a 2 stroke tuners guide that explained a myirad of things related to Expansion chambers good luck.. | ||
| Teeps |
Gordon Jenning's 2 Stroke Tuner's Handbook has been out of print for many years. They are out there but are not cheap... http://www.amazon.com/Two-stroke-Tuners-Handbook-G ordon-Jennings/dp/0912656417 Hope you like math... I would build one chamber and put a 2into1 collector on it and call it good. Even with a poorly designed chamber that bike will be quite the hand full. (Message edited by teeps on September 04, 2012) | ||
| Reepicheep |
I rebuilt a 1971 Kawasaki 250 (F8 Bison). It had the rotary valve and no expansion chamber. It pulled nearly as hard as my tuned and ported 1995 KDX-200 (225 big bore kit) which did have an expansion chamber. So I'm with Teeps... just fabricate a collector, try and keep the rough volume similar to the factory original setup, and call it good. | ||
| Sifo |
I had a 1976 GT750 with a 3 into 1 tuned pipe. I don't even want to think about how that might work. From my experience with model airplanes, the really critical thing is the total length from the exhaust port. If you can build it with a section before the expansion chamber that can easily be modified for length you could test it to see where it comes on the pipe and adjust from there. Probably easier to do on a model airplane than a motorcycle though. | ||
| Bluzm2 |
Man, don't know what happened but I just lost a whole bunch of typing.. Not going to do it over... Dirt Bike magazine had a series of articles back in the early 70's on design and construction of expansion chambers. All that math and trig helped me pass Alg 1 and Trig! Anyway, here's some Gordon Jennings stuff I found.. http://www.datafan.com/Horsepower_Blog/gordon-jenn ings-two-stroke-tuners-handbook/ Brad |
