Update on several .15 diesels...

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Update on several .15 diesels...

Postby loucrane » Sat Mar 07, 2009 10:05 am

Also to bring some content in this forum more up to date. Hated seeing no action here for so long...

Recent days I decided to compare several .15 diesels I have handy. Finally brewing a consistent and 'happy' fuel!

The engines tested include a 1950's(?)Taipan 2.5D (Aussie; G. Burford), a recently mfd CS 15 (retooled Silver Swallow), an older Silver Swallow 2.47 (same engine, just not as prettily executed), an MVVS 2.5D from the mid-1950s, an ENYA 15D-II, and a DDD converted Fox Schneurle .15BB.

Local conditions: Altitude ~5,000' above sea level, desert-dry air (5%-25% RH), temps in the 60°-75°F range.

Fuel: 30% ether (John Deere), 24% (SIG) castor, 45% kerosene, 1% AMSOIL DII.

Prop(s): APC 9-4, Master GF 9-4. (Some of the engines - the ones I have the papers for, anyway, indicate the intended prop to be an 8-4. F'rinstance, CS and SS state max RPM of 14,000. )

Simple summary: They all turn a comfortable 11,000 to 12,000 RPM, with the single and double BB engines tending toward the higher end.

All the above engines except the Chinese pair are side exhaust, and much MUCH less messy to run. The peripheral-ported CS and SS spray generously and everywhere...

The CS and SS were a bit fussy about finding initial start and run settings, but restart both hot and cold at the settings found. They were also a bit fussy about bench tank height, and improved with the top of the fuel nearer the spraybar height.

All start and run very well, good prospects for medium-size sport CL models (none are throttle-equipped.) Economy is amazing, but can be reduced to manageable by setting a bit richer.

(At an optimized lean setting, e.g., I got over 7 minutes on 28cc fuel on another diesel - a new ENYA 25D BB, on an 11-5 at ~9,000 RPMs. That's TOO much economy! E.g., contest CL stunt flight time limit is 8 minutes from flier's start signal until model stops rollng after landing. Anything done after 8 minutes is not scored - landing points forfeited!)

And, something I've been claiming for years is true of all these engines - when the setting is properly matched to the prop and fuel, vibration decreases significantly. They still shake hard coming up to RPM and spooling down when fuel is exhausted, of course, but that is brief at each end of a run.

(edit: spelling)
loucrane
 
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Joined: Mon Jul 26, 2004 2:39 pm
Location: Sierra Vista, AZ, USA

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