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Using Pressure on a Cox .051 R/C

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Using Pressure on a Cox .051 R/C

Old 01-02-2013, 04:45 PM
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Steve Westphal
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Default Using Pressure on a Cox .051 R/C

I would like to use fuel pressure on my Cox .051 R/C engine but, I have a nipple for tapping it in on the backplate and there is the unopened nipple on the front of the plastic. Which method is the best? Thanks.
Old 01-02-2013, 05:30 PM
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combatpigg
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Default RE: Using Pressure on a Cox .051 R/C

Backplate pressure is the only way to go. A check valve tends to build excessive pressure, so it is best to go without.
Old 01-02-2013, 11:07 PM
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Default RE: Using Pressure on a Cox .051 R/C

Why do you need pressure?
The 05RC runs very rich at low revs, even without any pressure on the fuel.
Old 01-02-2013, 11:41 PM
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Default RE: Using Pressure on a Cox .051 R/C

good point Mr Cox. I've never tried backplate pressure with an exhaust throttled engine.
Old 01-03-2013, 04:37 PM
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Default RE: Using Pressure on a Cox .051 R/C

Thanks.....I think I will forget about it.
Old 01-03-2013, 04:50 PM
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Default RE: Using Pressure on a Cox .051 R/C

It won't cost you anything to try it. The pressure is higher than what you might think and tiny model engine carbs don't have compensating fuel circuits that can handle a wide range of fuel demand and system pressures, like fullsize automotive carburetors have.
Crankcase pressure is to allow you to feed an oversized venturi with adequate pressure for wide open throttle flow that a smaller bore carburetor can not support and that the engine is unable to suck on it's own without providing some "push" also.
It's a pretty ingenious way to allow these tiny engines to process as much air as possible without going the next step up to a tuned pipe.
Old 01-03-2013, 04:58 PM
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Default RE: Using Pressure on a Cox .051 R/C

CBP......I am going to leave it alone as it already screams. I haven't done a lot of inverted flying where I thought it would need it but now will abandon the idea. Thanks!!
Old 01-04-2013, 10:34 AM
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Default RE: Using Pressure on a Cox .051 R/C

If memory serves, the .051 R/C has a little muffler and a carburetor? If so the muffler pressure should help a bit.

On my exhaust throttled TeeDees I usually hook up the tank vent to a 3/16" brass tube mounted so that it's facing into the prop blast as close to the prop tips as possible. It fattens up the top end and after resetting the needle to compensate, the midrange transition's better. That's my story and ah'm stickin' to it.
Old 01-04-2013, 04:59 PM
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Default RE: Using Pressure on a Cox .051 R/C

DB.....Good idea...I might even trumpet bell the end so as to catch a bit more air....I guess it might handle that don't you think? I guess I am worried for nothing as this engine literally screams. I just thought it might help while inverted or mounted upside down. I have never owned a tach but might pick one up to see if this engine is really going as fast as it sounds. Thanks
Old 01-06-2013, 03:02 PM
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Default RE: Using Pressure on a Cox .051 R/C

What .051 RC is this engine?.... I have TeeDee with a carburator and Medalilion with sliding exhaust and NVA linkage

No matter in either case (sounds like you want to MOUNT the engine inverted) the tank pickup must be level with venturi NVA

I prefer Texas Timers fine thread NVA and bladder on my non RC Medallion .051s
Old 01-06-2013, 03:51 PM
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Default RE: Using Pressure on a Cox .051 R/C


ORIGINAL: fredvon4

What .051 RC is this engine?.... I have TeeDee with a carburator and Medalilion with sliding exhaust and NVA linkage
He probably means the '05' R/C-only produced for a relatively short time (along with the similar 09 R/C) based on the TD 049 and 09 respectively, a with proper intake R/C carb and a muffler as standard. As opposed to the earlier rotating exhaust throttle Cox setups. I don't know whether Cox made any internal porting changes to the '05' and 09 R/C versions-they did make a change to the plastic venturi housing in the '05', fitting a strengthening rib, and I think a cylinder shim was used to eliminate SPI and lower compression. The 09 silencer seems to be the same as the one fitted to the Queen Bee (which makes sense as the cylinder dimensions are largely the same)

ChrisM
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