Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

magnum with sj 50

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Old 05-29-2007, 12:33 PM
  #1  
cmopar
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Default magnum with sj 50

Does any on else have Magnum with sj 50 ?What prop ?and rpms u getting on the ground ?
I flew mine this weekend with a 8.75x9w and was tacking about 17,600 on ground .Seemed ok in the
air but i was expecting more! I was going to clip a 8.8x9.25 down to an 8 and try the ss40 jett muffler
or mac header with macs pipe but it was so nice out i just flew it how it was .

Corey
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Old 05-29-2007, 08:38 PM
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Default RE: magnum with sj 50

hey , corey

i flew mine this weekend also,,,with a thunder tiger 46,,,,,turns a 10*6 prop @ 12660 rpms not alot but looking to put a tune pipe on it in a few...what typ of motor are you running with this????
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Old 05-29-2007, 10:52 PM
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Default RE: magnum with sj 50


ORIGINAL: cmopar

Does any on else have Magnum with sj 50 ?What prop ?and rpms u getting on the ground ?
I flew mine this weekend with a 8.75x9w and was tacking about 17,600 on ground .Seemed ok in the
air but i was expecting more! I was going to clip a 8.8x9.25 down to an 8 and try the ss40 jett muffler
or mac header with macs pipe but it was so nice out i just flew it how it was .

Corey

you are doing fine with the sport jet 50.
I have run a 9x8 at 18K and 9x9 @ 17K in the cooler weather runs great flys fast.
currently the tach is broken.
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Old 05-30-2007, 08:40 AM
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Default RE: magnum with sj 50

ORIGINAL: teejames007

hey , corey

i flew mine this weekend also,,,with a thunder tiger 46,,,,,turns a 10*6 prop @ 12660 rpms not alot but looking to put a tune pipe on it in a few...what typ of motor are you running with this????
10-6? That's a test flight prop for the Magnum. Get a go-fast prop on there dude!

MJD
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Old 05-30-2007, 09:28 AM
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Default RE: magnum with sj 50

Whats the thoughts on clipping down the 8.8x9.25 to 8x9.25 and using a tuned pipe ?Think it might b out
of the rpm range for sj50 timming maybe bob will see this and chime in.
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Old 05-30-2007, 09:42 AM
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Default RE: magnum with sj 50


ORIGINAL: cmopar

Whats the thoughts on clipping down the 8.8x9.25 to 8x9.25 and using a tuned pipe ?Think it might b out
of the rpm range for sj50 timming maybe bob will see this and chime in.
Until Bob gets here, this is a quote from him awhile back concerning tuned muffler rpm's.

"Jett tuned mufflers
Just for reference, on the 40-60L size mufflers.... when used on the Jett .40/.46/.50/.60L engines (and with other engines typically)

Standard is designed for between 15,000 and 18,000 rpm (minimum and max suggested ground peak rpm)
SS muffler is designed for 17,000 and 19,500 rpm (target for the 60LX engine)
Black q-500 racing muffler 18,000 - 20,500

Usually best to prop lighter - allow more rpm. Do not lug it down below the bottom limit. "
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Old 05-30-2007, 10:16 AM
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Default RE: magnum with sj 50

Great info Mike! Im balancing a prop right now at work i cut down the 8.8 to 8.25 and i am going to
try that with the ss jett muffler tonight and see if its faster we did radar gun it on monday and it was between
108 and 112 mph flat and level i will get tach #s and speed #s to see the difference
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Old 05-30-2007, 12:12 PM
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Default RE: magnum with sj 50


ORIGINAL: cmopar

Does any on else have Magnum with sj 50 ?What prop ?and rpms u getting on the ground ?
I flew mine this weekend with a 8.75x9w and was tacking about 17,600 on ground .Seemed ok in the
air but i was expecting more! I was going to clip a 8.8x9.25 down to an 8 and try the ss40 jett muffler
or mac header with macs pipe but it was so nice out i just flew it how it was .

Corey
Thanks mike.....

Skip the pipe Cmopar.... stay with the standard jett-stream or the SS muffler.

Sounds like the engine is running ok. RPM number sound ok. However if you have a standard SJ50 engine, the 9W may be a little heavy. 8.75x8, 8.75x8.25 or 8.8x8.5 might be better selections.

On the Magnum, you may be better off with a standard blade 9x7 or 9x8.

RPM is your friend, but you need some blade area too.

I've seen a Magnum with a SJ-50 (used engine), 9x7 prop hit 130+ mph (radar) in level flight, effortlessly. Set up better it would probably have run closer to 140.

If you switch to the SS muffler, definately prop the engine for OVER 18,000 rpm. Try the 9x7, clipped 8.8x9.25 will work ok too, but clip it until you get the rpm (should be appx 8" dia). Also worth trying the 8.5x7.25 (this will hit 20K on an SS setup - works great on a Q-500, might not pull the Magnum well though). Keep in mind, the Q-500 props are not always the best choice for "larger" airframes. But sometimes they work ok.

Setting the engine is important too.....

Find peak ground rpm with the prop selected,
back off 600-700 rpm. Launch it there.

Bob
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Old 05-30-2007, 02:04 PM
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Default RE: magnum with sj 50

mjd



i plan to this weekend getting tune pipe and prop on it,,,,looking at going with 9*7 or maybe 9*8 . wonder will the tt 46 handle 30 % fuel ???? any suggestions????




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Old 05-30-2007, 04:00 PM
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Default RE: magnum with sj 50

TJ 30%fuel with high rpm most of the time make a lot of bad glow plugs a good 15%fuel will work great

Corey
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Old 05-30-2007, 06:41 PM
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Default RE: magnum with sj 50

thanks corey,,,ill stay with the 15% that i have,,,,
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Old 05-30-2007, 08:00 PM
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Default RE: magnum with sj 50

Allright since it was really hazy and a yellow and black magnum looks great on the ground and
a $%^$# to see in the air i got a bunch of taching done!!
***********red muffler*********black ss muffler********tuned pipe
8.25 x 9.25**18,200************18,700****************18,5 00
8 x 9.25*****18,600************19,100****************1 8,900
9 x 8********17,900************18,000****************1 8,000
9 x 7********18,800************19,200****************1 9,200-300
8.5 x 7******19,000-100*********19,300-400************19,400-600

These are what i got rounded to the nearest 100 with my hanger nine tach on 15 %
Hope they are inline with other peoples #s ! WOW I will also add that a full nittro pipe
is loud and sounds great hope my neighbors enjoyed it!!!
The tuned pipe is the last i tried i also set it 18,900 and hit it with a leaf blower to make it unload
on the ground. It unloaded a fair amount and sounded like it came right up on the pipe so im going to try flying it with
with this set up since it on there and then reinstall the ss black muffler to see how it does !!

Corey
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Old 05-30-2007, 08:27 PM
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Default RE: magnum with sj 50

ok thanks corey,,,what motor was this?
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Old 05-30-2007, 09:59 PM
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Default RE: magnum with sj 50

Sport Jett 50 made by Jett

http://www.jettengineering.com/
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Old 05-31-2007, 08:46 AM
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Default RE: magnum with sj 50

Be careful with the full size pipe.

Most stock pipes do not produce enough backpressure for the jett engines. Engine may go lean in the air. Dub modifies the pipes he sells. You can fly it with what you have there, just be careful. Also from the data you have there, it looks like the pipe may be set just a bit short for the bigger props.

From what you have shown, I'd stick with the SS muffler and that 8x9.25. The engine will unload over 20K in flight.
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