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Removing QRC muffler

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Removing QRC muffler - Page 2 Empty Re: Removing QRC muffler

Post  GallopingGhostler Tue Apr 28, 2020 8:25 am

Welcome cggs. Here's an article from May 1967 Aeromodeller that explains the development of the QRC by its ancestor, the QZ.

Sceptre Flight Model Engine Tests  Cox 049 QZ

The rest of the engine articles including the Babe Bee are here:

Sceptre Flight Model Engine Tests Index
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Removing QRC muffler - Page 2 Empty Re: Removing QRC muffler

Post  Ken Cook Tue Apr 28, 2020 8:48 am

Not to put more confusion into the equation. Anytime you put a muffler on a engine, your restricting it which causes a loss of rpm's. When you had a Babe Bee vs a QZ for instance, the power output of both were somewhat equal. The engine themselves were different in which the QZ/QRC utilized a dual bypass cylinder vs the single ported bee. In addition, to gain more rpm's, the muffled bees used a high compression head. Therefore it took a lot of modification to just regain the power of a stock bee.

         So the Bee and the muffled QRZ without mufflers side by side would or should  offer the QZ/QRC a distinctive advantage. I also believe and this might not be factual but the early QZ when first introduced used SPI and a shim was placed under the cylinder to reduce it whereas the later QRC cylinders were designed with no SPI. This suggests to me that the exhaust timing shim when removed offers SPI back to the cylinder enhancing performance even further.

         I have several of these engines, I kept all the mufflers/shims with everything. The performance was so poor that I removed all of it just to make the engine useable for control line flying. Back then I didn't use a tach to understand the true rpm's, we took the planes out and flew them. When something like a muffler was robbing critical rpm's  it was removed.  I never have gone back to using the stock equipment but out of curiosity, something tells me to give it a go once again. I have very few engines that have satisfied my liking using a muffler for my type of flying, the end result is typical, loss of power, overheating.
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