K&B 4050 Diesel

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K&B 4050 Diesel

Postby giffy » Sun Dec 19, 2004 9:57 pm

With the new thicker crankcase coming out it's now conceivable to make a K&B 4050 diesel.

I wonder if the OS FP .40 conversion kit would be of any use. I'd have to know the bore size of the OS.

I was running an 8-7 @ 20,000 with the glow version. I'm hoping to double the range but, expecting a decrease in speed.

I might want to make a custom liner since the 4050 has a too wide exhast port and not enough blow down time. I think they were trying to make it a stunt engine or something.

Any ideas?

Giffy 8)
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Postby dennis » Sat Nov 12, 2005 7:06 am

K&B did make a 4050 as a stunt motor for john Brodak. Not too many though and they wouldn't hit 20K ,I think.
Now as to the diesel conversion. Bob Davis makes or made a head for this motor and i bought one and installed it on the first 4050 that I bought. Great running motor and can handle some real lumber. Now for the amusing part. It got to late october that year and it was cold and we were trying a bunch of props for top rpm. I put an 11/7.5 on that and the good fuel and tached about 14K[impressive] I took off and the plane was really flat out moving when the top of the motor separated from the case never to be seen again. Probably the only converted diesel that I ever had that did it. I called Bob reported the results,talked to Wisznewski and sent the motor in and great people that k&B were ,they sent me a new motor. Got a new head from Bob and flew that one for a few years. It is still in good condition and sits waiting to be used again sometime. Moral of the story it will probably do 20K with the prop you mentioned without blowing up but a diesel on a small prop reving as high as it's glow counterpart is just as thirsty. No increase in milage
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Postby loucrane » Sat Nov 12, 2005 11:18 am

And Giffy,

Dennis' experience reminds us of another factor: The compression control adjusts ignition timing. For higher RPM we need to advance point of ignition - i.e., set compression higher, much as is practice with auto engines (spark advance) and glow engines (adjusting nitro, head spacing).

Diesels begin set with higher compression than glows, so 'advancing' timing means much more compression than glows are usually designed to live with. Another example of failures due to excessive compression for a converted glow is the legendary crankshaft failures with DDD converted reed valve Cox engines...

The lack of economy improvement may be due to the generous porting glows generally have, needed to get enough low-energy methanol into the combustion chamber. The kerosene in diesel fuel does not need as much oxygen to burn efficiently, so the excess passage volume is not a particular help.
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