Mailing List flyrotary@lancaironline.net Message #45115
From: Monty Roberts <montyr2157@alltel.net>
Subject: Exhaust lengths
Date: Sun, 8 Feb 2009 13:19:21 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
FWIW, the people at Racing Beat said that the Renesis is a very different animal than peripherial exhaust port rotaries when it comes to exhaust systems.  As I recall, they said they got only about an 8 HP improvement when going from stock (RX-8) exhaust system with cats & the works, to a full race setup with headers, race mufflers, etc.  That is TINY in comparison to the earlier engines.

 In other words, the Renesis is very non-critical when it comes to exhaust systems.  Just keep the back pressure down and you'll do pretty well.  At least that was my conclusion.  Note there is zero overlap in intake / exhaust cycles in the Renesis.

BTW I'm still waiting for someone to build & test a peripheral intake port Renesis.  I think that would be a great setup for aircraft applications. 

Tracy

Paul Lamar had a PP Renesis built. I think he got about 240 hp. He used a carb, and the bsfc was terrible. I'm not sure how good the data was. There are graphs on his web page. There used to be a youtube vid of it, but it may be only on his site now. 
 
I don't think it is worth fooling with unless you also port the exhaust. There is enough meat in the four port motor to open it up to the 6 port exhaust config, but the shape is still terrible.
 
If you look at the port interaction, the path between the exhaust and intake is so torturous that I'm not sure you would get any crossover tuning like you do with PP exh. even with the added overlap.
 
With the PP engine you have the glowing hot spaghetti problem to deal with, and the muffling issue.
 
Monty
Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster