Author Topic: Pipe as muffler - yes, no, maybe.... (Read 823 times)

Matt Piatkowski · « **on:** July 07, 2017, 01:00:31 PM »

Hello,
I still have old Jett60 that was run on Windy's pipe in my first plane (Intrepid XL) named Great White.
This engine is a hybrid of old and new parts, with the liner and piston being almost new (1.5 years old) and the rest being old (17 years).

I have tried to run this engine in the pipe mode and partially succeeded: on Oct.31,2016 on 12.25x3.75 APC prop. and using 12.5% Nitro Omega with splash of SIG castor, the ground RPM were 11,400 max. and 11,100 just below 2 cycle. The pipe was set at 18 and 1/8" distance from the baffle to the glow plug for 11,400 RPM., after trying 17.5, 17.75 and 18" that delivered lower RPM values.

There was an audible increase in RPM for 18 and 1/8" v/s the other distances but I did not measure the RPM for 17.5, 17.75 and 18".

When the 18 and 1/8" distance was set, I have tried also 3 blade cut Bolly (11 and 7/8" dia. and 4 or 4.25" pitch). Unfortunately the owner of this prop. who kindly lent it to me for the ground tests, did not know its pitch.

Previously, I run this prop. without pipe and got 10,100 RPM max. The pipe "added" 1,000 RPM to the engine that buzzed at 11,100 RPM. in the 2 cycle mode.

Considering the above and the fact that I "cooked" my Evo60NX in RToucan to death running it in full 2 cycle, very lean, mode with 10,400 launch RPM on 13x4 MAS prop: can I use Windy's pipe as muffler and try to run Jett60 on 13x5 prop. in rich, wet 2-4-2 mode at, say, 8,200 RPM.?

I am assuming such wet 2-4-2 mode will help the engine not to overheat that killed my EVO60NX.

How much SIG castor will be needed for my usual fuel ( Omega 5 or 10% nitro ) to carry the heat away and, at the same time, do not leave too much carbon residue on piston?

Thanks,
M

Tim Wescott · « **Reply #1 on:** July 07, 2017, 01:42:13 PM »

The "tuned" in "tuned pipe" refers to the fact that the pipe dimensions are set according to how fast the engine is supposed to run.
If you could slap it on any old engine with any old prop and have it work, it would be a "magic pipe"
A tuned pipe is not a muffler
11000 RPM doesn't sound excessive for a JETT engine, although it may be faster than you want for stunt
If you want a muffler, use a muffler. If you want a tuned pipe, set it up correctly
While lots of folks use a 2-4-2 run, lots of folks run a wet 2 and don't burn up their engines or suffer runaways

So, you burnt up (or you think you burnt up) an engine, and now you're trying to avoid doing it again. But you are (in my humble opinion) going too far, and you're applying possibly-outmoded ways of fixing the problem. Specifically, you're looking to a 2-4-2 run to keep the engine cool -- but the 2-4-2 run only works with specific engines; you can't just wedge any old engine into the 2-4-2 mold and get a decent run out of it. In particular, trying to do that with a modern Schnuerle-ported engine that hasn't been "dumbed down" will end up in endless runaways and frustration. I can't comment on that JETT engine, but I suspect that it won't be amenable to such treatment.

What's your skill level? Is there a reason you don't want to use a known-good, known-easy engine like a 46LA or (if you have $$$) a PA? Or why you don't want to ask what the accepted setup is for your Jett60 and just do that?

It sounds to me like you're doing a lot of random stuff with random engines, in a world where it's known how to get a pretty decent stunt run easily and inexpensively (using a 46LA, Tower 40, or an Enya). If your goal is to have fun dinking with engines, then by all means dink endlessly with engines. But if your goal is to get out there and fly, then give us your engine inventory and planned airframes, and someone will tell you how to put 2 & 2 together and get a really sweet 4.

Matt Piatkowski · « **Reply #2 on:** July 07, 2017, 02:59:55 PM »

Hi Tim,
I will go directly to the conclusion.
I have Ro-Jett76 that will fly one of my next year planes. This engine has the header/muffler made specifically for 2-4-2 stunt muffled run and will work with any 14x~4" two blade prop. at certain RPM.

I bet my next day dinner that I will run my old Jett60 with Windy's pipe as muffler. The only question is what prop will deliver a proper engine load and will not overheat it in the air and here I will experiment. Clarification: muffler muffles and the properly set pipe amplifies.

Another clarification:Windy's pipe I have does not have the converging part. The diverging part changes to the cylindrical part that ends with the circular cap, having a stinger in the middle. I have run my Jett 60 with improperly set pipe (that was actually a muffler) for a year in 2014 knowing very little about the C/L stunt as nobody in my club (Balsa Beavers, Toronto, Canada) knew anything about pipes. It was before I have discovered this forum.

Now, I know much more but also the scope of my interests expanded. I will go 100% electric in two years and will stop using ICE at all.
I have presently two well flying electric planes that help me to improve my pattern and I will compete at Brodak's next June in the intermediate stunt category.

Interest in ICE is just a curiosity now: I have found the subject quite difficult and confusing, especially with so many people on this forum expressing frequently either very general or conflicting opinions. If something is difficult, I usually try to discover why. Sometimes I fail (like in case of my late RToucan and EVO60NX) but there is learning even in failures. This is why I dink with engines that are not typical stunt engines.

I thank you for you comments and opinions.

Regards,
Matt

"Learning never stops and when it stops this means you are dead"

Author Topic: Pipe as muffler - yes, no, maybe.... (Read 823 times)

Matt Piatkowski

Pipe as muffler - yes, no, maybe....

Tim Wescott

Re: Pipe as muffler - yes, no, maybe....

Matt Piatkowski

Re: Pipe as muffler - yes, no, maybe....