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07-25-2009 | 02:01 AM

#18

DarZeelon

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From: Rosh-HaAyin, ISRAEL

RE: YS 45 Muffler

Quote:

ORIGINAL: freakingfast

I can get the same numbers with a Super Tigre .45 ABC and a TT.46Pro on stock mufflers with the APC 11X6 @ 12,700.
And the same #'s APC 10X6 @ 16,350 on 10% and 15,800 on FAI fuel with the TT.46Pro and stock muffler! For me, Mr. Lee’s results are good, but not shocking.

Karl,

MJ was having doubts about the standard muffler, when he began this thread...

As to the RPM numbers you had stated...

The OS.46AX is currently; correct me if you think I am wrong, considered the 'benchmark' of .45-.47 engines. Not the performance monger; just the 'standard'...
It is definitely not the best performing engine out there, but equipped with the standard P-Box muffler in its original state and using 15% nitro fuel, it consistently spun an APC 10x6 prop, at 14,200-14,400 RPM, in virtually all the engine reviews done on it.

It achieved this performance, which calculates to 1.08-1.12 actual HP.

With the P-Box's baffle removed and spinning an APC 8.75x8.25NN Q500 prop, the same engine could only reach 16,100, which is 0.9 HP; a reduction of about 20% in the HP...
...Just when according to the 'rated' OS numbers, it should be very near to its 1.65 HP @ 16,000 peak... Now I am thinking perhaps the removal of the baffle, something most looking for the best performance from such an engine, would 'naturally' do, is what kills its top end... I finds it difficult to fathom.
I prefer the other assumption; i.e. that the rated power is either completely baseless, or achieved by the OS engineers with a full length open pipe, 20% nitro (decompressed) and with an A5 (now the#10) glow plug; not as it comes from the factory...

The OS clones of this displacement bracket, as well as other similar engines, with non-tuned exhausts, also consistently show about the same numbers on the 10x6 APC.
...This includes the TT.46Pro, by the way...

As to the Super Tigre .45 ABC engine, I have not seen it run with a 10x6 APC, but it does spin an 11x6 MA black prop, at 14,100, with its bulbous standard muffler, on 15% nitro.
The MVVS .49 showed 14,600 on the same prop, with the #3248 tuned muffler, on just 5% nitro, by the way.

[link=http://www.rcuniverse.com/forum/m_8194729/tm.htm]The tachometer forum[/link] shows significantly lower numbers for the OS.46AX on this prop.
The Clarence Lee test shows an even lower number for the YS (12,700 on the Rev-Up), but this compares with about 12,500 RPM, achieved with the OS on the APC...

The achievement of the YS.45 on the 10x6 is exemplary... Perhaps the non-tuned original YS muffler behaves like a Helmholz resonator at its tuned frequency, exactly in that RPM range; because frankly, on larger prop sizes, it is oh-hum rather ordinary, being out-revved, even by the ST .45ABC; a $65 engine, half the OS.46AX price and probably about a fifth of what this YS engine would have sold for today, had it been in production...

The OS P-Box (at least when de-baffled), does no such thing...

The TT.46Pro is very close to the OS on the MA black 11x6 prop and on the APC 10x6...

The [link=http://www.rcuniverse.com/forum/m_2082094/tm.htm]TT.46Pro tachometer thread[/link] apparently has some 'out of whack' tachs (or perhaps, 'out of whack' people), which apparently show the TT.46Pro with the normal muffler, out-revs the Jett .60LX with the JettStream...

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