Glowgeek

The FG14 instruction manual says 13.47 cc.

Hobbsy

My Feedback: (102)

This could easily be checked out in a small test with and without a regulator. I mentioned this phenomenon several years ago and was told I was crazy.

It looks like Horizons specs online and the manual are different. Imagine that.

Hobbsy

My Feedback: (102)

Thanks Mike, I'll be watching for that CHI test, I use a CHI unit on my FG 11, the CHI makes a while lot more powerful spark accompanied by a very audible snap..

Glowgeek

i recently purchased an analog 1-5 psi gauge. Easy enough to see if the tank pressure drops shortly after going wot. Doubtful, but I'll test it.

Hobbsy

My Feedback: (102)

I personally think it's thermodynamics within the engine, but can't begin to explain that.

Glowgeek

i agree, and neither can I. That said, perhaps whats happening is the combustion chamber gets really hot when we try to peak the rpms. That would heat the incoming air/fuel charge to a higher temp, expand it and reduce the overall quantiy of air/fuel allowed to enter the cylinder. Once that happens no amount of needle twirling will bring the peak rpm back unless the combustion chamber is first allowed to cool down to normal operating temps. How does that sound?

Edited: When testing for peak rpm I've heard a few people say for example "Peak 8700 rpm with a pinch to 8800". This would imply to me that the engine wouldn't hold the 8800 peak rpm. Probably started getting hot and losing air/fuel charge density?

Hobbsy

My Feedback: (102)

That'll work. Many of my tachometer readings show it.

Glowgeek

Welcome my world fellas. I get plagued with all the obscure and nonsensical electrical and mechanical problems anytime I have to fix stuff. I can change the gas cap on a car and immediately the water pump will start leaking! Also, the harder it is to replace a part the higher likelihood it will be defective right out of the box or fail in short order eg my latest bout with SS bearings in my saitos. That said, I do often make things harder than they need to be in an attempt to improve upon perfection.

FlyerInOKC

My Feedback: (6)

Back in the Stone Ages I worked in a 2nd level support helpdesk of a major corporation. This translates into we were the people who actually had a clue on what were were doing and would tell the developers when they broke something. Whenever a user asked why something was happening being the wiseguy I was I answered "The computer is out to get you and you're not paranoid when its true!" Not one user ever disputed that statement.
It reminds me what a prolific R/C designer/builder who was published regularly said about build articles. He brought up the subject about how in most articles the author mentions how great the newly built airplane flies during the maiden flight without any major adjustments needing to be made. He called B.S. on these statements. He claimed every maiden flight of a new untried design was a textbook adventure in terror. He always would add lines on what it took to tame a particular design before flying so his readers didn't have to recreate his first flight.

Jesse Open

acdii

I always thought the epoxy works to help dissipate heat, and to make it somewhat water and vibration resistant. I have a CenturyJet gear control module that is uncased, and I tend to be concerned using it that it could be easily damaged just from securing it to the wing.


You posted that you couldn't find bore and stroke, so posted them for you. Not what you were looking for?

Jesse Open

Yes, and no. The potting itself usually traps heat, making the heat sinking enclosure a compromise to help relieve some of that heat..Potting is done for moisture proofing and vibration toughening in most cases. Potting is seldom needed for vibration toughening surface mount components. Potting is a means to better insulate high voltage components, the most applicable here. ..
The main drawback is it renders servicing as well as modifications near impossible. That is why some folks pay a bit more for the otherwise identical CH version of .RCexl ignitions.

With the effects of expansion and contraction, poor thermal conductivity, potting can create more problems than it cures.

Hobbsy

My Feedback: (102)

Sorry, I was alluding to the fact that the 13.47 cc and the 13.8 cc should not have the same bore and stroke, but in a similar way I had a Byron's Mustang 50, a re-badged Fuji 50 that had the bore and stroke reversed in the specs. Had this been true it would have been a nice long stroke engine. We can enjoy discussing factory misinformation. I'm sure there is more of it around.

the Wasp

My Feedback: (1)

looks like I am not going to buy that Mustang with the Saito 72, RCG's site tells it's only 111 miles away, but when I searched it (how far) I found that 111 number is as a crow flies, the road trip would be a 300 mile trip, and I ant no crow, so I decided not to make the 300 mile trip, too bad, I wanted it, the plane looked to be in good shape, and I could have put my 82 in it. after all, it's a mustang and it should be flown like a mustang, fast and wild

Jim

Glowgeek

Testing today for tank pressure showed .51 psi at 10050 rpm peak and no noticeable drop in tank pressure when the rpm started to drop off. It dropped all the way down to 9500 when left at that fully leaned hsn setting and the tank pressure was then .49 psi. The head temps were noticeably higher there. Safe to say that falling tank pressure is not the reason that the engine drops off of peak rpm when the hsn is left leaned for peak. I tried several times, letting the engine idle to cool off and got the same results.

Now, if I peaked the hsn and immediately riched it 9700 rpm it would run there for a whole tank.

So I think we have our answer ie elevated combustion chamber temp is what causes a fully leaned for peak engine to begin dropping rpm after a second or two.

Disclaimer: ymmv

Jesse Open

Glowgeek

Yes, I'm sure we all richen at least 200 from peak to fly. My post was in response to a phenomenon that occurs when checking peak output.

Jesse Open

the Wasp

My Feedback: (1)

hey guys, please tell how you drill engine mounting holes, I am always looking for a better, faster way..

so I got my engine mount holes drilled today for my 100, I tried something new, it worked great, but it only took half a year to do it LOL

first I turned down an old x-acto knife on the lathe to make a center punch that fit in the engine's mounting holes rather tightly (what ! it's the only aluminum round stock I had), I made the point of the punch only .030" long,
I set the engine on the mounts where it should be and held the engine to the mounts with 2 c-clamps, installed the punch in one of the engine's mounting holes and tapped the punch to mark the center of the hole, then I marked the 2nd hole on that same tab,

I removed the engine and removed that 1 mount and mounted the mount in the vice on my Sherline mill/drill, leveled the mount.
I have a 2 inch long pin, it's .050" thick, I mounted it in the drill chuck and used the pin to find the center of the mark that my center punch made,,,,, drilled both holes,

remounted the engine mount to the plane, mounted the engine to that mount, and center punched the other 2 holes on the other side,,, removed that mount and drilled those 2 holes,

well it took a while because I never did it this way before, actually it was a pain in the back side to do it this way, but it came out great, actually it was the best engine mounting job I have done,

I could have got it done much faster with using a hand drill, or using a drill press, but I don't have a drill press, never the less I got the holes straight and where they should be>>>>>>

tell us how you do it guys ????

Jim

FlyerInOKC

My Feedback: (6)

I clamp the engine in place and use my Great Planes tool with the cone on the end to drill with the spring loaded bit inside a 1/16" hole and then use the hole to guide a larger bit as required.

Rudolph Hart

Jim use a flat sheet of glass laid flat on the bench top for a temp firewall.Stand a plastic engine mount beam on it and tack with super glue.then you just hold the engine in position so the carb is about 1/8" off the glass and use an engine mount bolt dipped in red paint to mark the holes,drill ONE and bolt the engine to it then tack the second engine mount to the glass and do the rest.I'd rather have my short and curlies ripped out one by one than use bolts and nuts/washers etc squashing a top quality plastic engine mount beam.Use good stainless steel caphead self tappers like the one's shown in the pic above.

Normally two clicks back off peak drops about 300rpm,if you use a cline demand regulator sometimes i leave it peaked but if the engine saggs a bit going vertical one click rich solves the problem.

Captcrunch44

Hobbsy

My Feedback: (102)

I too do exactly that.

Hobbsy

My Feedback: (102)

Did you get a Posi-Loc or other, Thanks

Captcrunch44