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08-24-2011, 12:34 AM

#14

DarZeelon

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RE: Magnum/ASP 108

Quote:

ORIGINAL: jstanton

I still have this engine running a little on the rich side and I will go out and get a APC 15x8 prop tomorrow and try it once again. Ed, I do thank you for your help with this engine and it does start very easy. What RPM readings should I see with the APC 15x8 prop? Will it still be in the 9000 range?

I will be using Omega 10% for the next couple of gallons because I already have it on hand. I will try the 5% if I can find it at my LHS. I think they only have 10% and higher nitro on hand. I don't know if they will order any 5% for just one gallon[

]

Jim,

It probably is more than just a prop selection matter.

The ASP 1.08 is an OS1.08FSR clone and I believe it was designed to top-out at more than just 9K.

This engine is not merely an enlarged, cloned .91FSR. The .91 had a 17 mm diameter crankshaft, while the 1.08 uses a much larger 20 mm diameter crankshaft (like their current 1.20-1.60 engines).
It is a size larger than the .91 'big-block'.

It has large passages that support higher RPM and a light 15x6 prop should not really an obstacle for it. Like a 14x8, it should be spun beyond 11K!

Try loading it with a larger prop; I suggest a 16x8 of the same series (MA S-2/Scimitar).
It should spin around 9K, drawing just under 2.00 HP.

If it does not, look for possible butting of the ring ends...
It could cause overheating and make the sleeve go south very rapidly. Do use only 5% nitro fuel!
You could make your 10% nitro fuel into 5%, by mixing each gallon with 103 ounces of pure methanol and 25 ounces of castor oil (BéNOL, Bakers/SIG AA, CleanCastor - all OK).

If you obtain castor oil in the drug-store, it will likely not be degummed and will make your engine rather filthy rather fast.

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