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what to use black or red muffler

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Old 07-14-2008, 11:59 AM
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SACKRC
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Default what to use black or red muffler

GOT A 40 SPORT WITH THE RED CARB AND BLACK SHORT MUFFLER..ALSO A 50 SPORT WITH THE LONG RED MUFFLER. MY QUEsTION IS CAN IF PUT THE SHORT BLACK MUFFLER ON THE 50 TO GET THE RPMS UP.. THE 50 IS ONLY TACTING 17500 WITH AN
8.8 x9 . where the 40 will tact 19000.
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Old 07-14-2008, 12:14 PM
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Default RE: what to use black or red muffler

Hi,

Thanks for writing.....

17,500 on a 8.8x9 prop is just about right for a SJ-50 engine.

Yes, you can use the black racing muffler on the .50 engine.

However....

Same target rpm is important - you want a prop selection that allows the engine to easily get to 19K ground peak rpm or better. Then back off 800 or so rpm for flight.

Question though.....

Do you have a sport .40 ? (CAPS or SEMPRA racing engine?) Those were supplied with the SS sport racing (red) muffler.
Or is it one of the 428 engines with a carb added?
(Dub sells the 428 racing engines with an added carb quite often - but it is the race engine, not the sport engine)
Easy way to tell typically..... look at the liner. The racing engines are almost all AAC (aluminum liner). The sport engines are ABC (brass liner)

Based on the prop and rpm, it sounds like you have the 428 .40 engine with a carb added on - thus the black muffler.
That engine would have no problem turning the 8.8x9 or 8.8x8.75 prop up to and over 19k.

The SJ-50 sport engine is lower timed less rpm but a bit more torque and a great deal more user-friendly. Expect to run LESS prop to get it to turn up with the black muffler. Typically an 8.8x8.5 is a good bet.

Hitting the rpm is important or the engine will not needle properly and may overheat

Bob
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Old 07-14-2008, 02:05 PM
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Default RE: what to use black or red muffler

THANKS FOR THE QUICK REPLY.. THE 4O HAS AN ALUMINUN LINER AT 165 EXHAUST TIMING.. THE 50 IS TIMED AT 165 ALSO.. THINKING ABOUT A FULL PIPE ON THE 50 (MAC PIPE) MY THINKING IS MORE RPM SAME PROP AS THE 40. ALSO WHAT ABOUT 170 EXHAUST AND FULL PIPE ON THE 50???? DO YOU HAVE A START LENTH ON THE PIPE , POSSIBLY. OH THE 50 IS IN A MATNEY ZOOMER. MIGHT PUT IT ON EXTREME SPEED SIGHT BEFORE THE FIRST FLIGHT.. MAYBE TONIGHT, MIGHT BE THE LAST, YOU KNOW HOW IT GOES. THANKS AGAIN FOR INFO ITS APPRECIATED, SAVES ALOT OF TIME. RICH B.
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Old 07-14-2008, 02:30 PM
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Default RE: what to use black or red muffler

No problem Rich..

A little experimenting goes a long way Put the Q-500 muffler on the 50 and play with it. Between the rpm and torque it may surprise you.

As for the full pipe, I dont have a length handy here. Rather rare setup for the side exhaust engines, mainly the FIRE engines get the pipe. You may be able to pick up a visual reference on the length here.

http://www.jettengineering.com/hall/hall-delta.html

One thing that Dub does on the MAC pipes he provides is to restrict the exhaust outlet a bit - an insert into the tail pipe - to get the right backpressure and improve tank pressure. Sometimes it helps, sometimes you can get away without it. But something to consider if you want to try the big pipe on it.

Bob
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Old 07-14-2008, 03:37 PM
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Default RE: what to use black or red muffler

thanks will do . rich b.
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