Rotary engine exhaust design considerations?
Rotary engine exhaust design considerations?
(OP)
thread71-235689: Expansion chamber type exhaust for rotaties?
Some good information in the above thread, guys, thanks! Are there any experts that can expand on what some of the actual design considerations would be for a rotary exhaust system? I am most specifically interested in a Renesis side-port engine, but some ideas for all types of ports might be helpful as well.
Basically, we are about to build a custom header or two to dyno test and would like to know what sorts of things to try - primary length, collector angle/shape, what to do about the different side and center ports.
There's tons of papers and software written to aid in the design of 2 and 4-cycle piston engine exhaust systems, nothing for the various Rotaries.
Thoughts, ideas?
-Jason
Some good information in the above thread, guys, thanks! Are there any experts that can expand on what some of the actual design considerations would be for a rotary exhaust system? I am most specifically interested in a Renesis side-port engine, but some ideas for all types of ports might be helpful as well.
Basically, we are about to build a custom header or two to dyno test and would like to know what sorts of things to try - primary length, collector angle/shape, what to do about the different side and center ports.
There's tons of papers and software written to aid in the design of 2 and 4-cycle piston engine exhaust systems, nothing for the various Rotaries.
Thoughts, ideas?
-Jason





RE: Rotary engine exhaust design considerations?
Regards
Pat
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RE: Rotary engine exhaust design considerations?
Surely there will be some tradeoff between primary length, peak output and area under the curve. I'm just looking from some general direction on where to start so we can mock up some test systems for the dyno.
Some people are saying longish primaries with a very long/gentle collector, others are saying no collector and just run three pipes out the back of the car? Can you get a longer collector than a 12deg anywhere, or will we have to make our own?
Or am I asking for proprietary knowledge and are just better off trying some stuff to make my own conclusions?
-Jason
RE: Rotary engine exhaust design considerations?
Your exhaust doesn't care much about bore, or stroke. It does care about the volume of the charge that was intook.
Cheers
Greg Locock
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RE: Rotary engine exhaust design considerations?
The lack of any overlap reduces the value of pulse tuning to aid exhaust scavenging.
Piston engines often had no overlap 100 years ago. I think a little overlap became the norm about 90 years ago. Maybe the rotary is 100 years behind in development
Regards
Pat
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RE: Rotary engine exhaust design considerations?
As I remember, it made the 302 capable of ~14,000 rpm with the removal of the conventional valve train.
RE: Rotary engine exhaust design considerations?
Looks like they're still around.
RE: Rotary engine exhaust design considerations?
There has to be an answer as to 'how' best to scavenge those gasses.
RE: Rotary engine exhaust design considerations?
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
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for site rules
RE: Rotary engine exhaust design considerations?
One of my acquaintences has a small rotary shop and a chassis dyno, and he has done a lot of experimentation with the collector shape. The angle of the collector is absolutely critical, especially as the port overlap gets larger.
Unfortunately I haven't seen any math for determining a first cut for any of this! At least, no math that matches up with real world experience. I wish I could offer more help than this vectorial, but it seems that the people involved are not keen on giving away the secrets to their $600 headers.