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Building Tips and technical articles. => Building techniques => Topic started by: minnesotamodeler on September 22, 2009, 07:15:15 PM

Title: Improving Cox Sure-starts
Post by: minnesotamodeler on September 22, 2009, 07:15:15 PM
Somewhere (I can't find the thread now) Larry Renger (IIRC) recommended drilling out the Cox production engine's venturi, which narrows down beyond the NVA, to the existing exterior diameter. I tried it with one of mine, and it sounds more like a Black Widow than a Babe Bee! And still starts,  draws fuel, and needles just fine.  So my thanks to Larry, and you guys oughtta try it if you want to make your Surestarts into superior sport engines.

No official tach comparisons, sorry.  But a significant upgrade according to my ear.
Title: Re: Improving Cox Sure-starts
Post by: ray copeland on September 22, 2009, 09:02:05 PM
Ray, have you actually tried this on a plane yet or just bench testing?  I am curious about the fuel draw with the nose up . 
Title: Re: Improving Cox Sure-starts
Post by: minnesotamodeler on September 23, 2009, 12:42:02 AM
On a plane but on the ground, Ray.  But I did point the nose up, down and all around!  The mod doesn't seem to have affected the fuel draw at all. 
Title: Re: Improving Cox Sure-starts
Post by: Larry Renger on September 29, 2009, 10:15:24 PM
It will, however have affected the fuel consumption.  But with that engine you use an external tank, so who cares?
Title: Re: Improving Cox Sure-starts
Post by: minnesotamodeler on September 30, 2009, 08:18:57 PM
Right, extra power has to come from somewhere--no free lunch, huh.  So who notices an increase from 1/2 oz. to 3/4? I expect I'll do all my surestarts this way (I have 8 I guess, hard to keep track--4 on planes and 4 still wrapped up in the coffee can. I think.).

P.S. Ray, I did fly the little beastie and it did fine, loops, eights, inverted.