I have been playing with airplanes for over 20 years but only recently got my first gas engine, a 3.2 FPE on a SIG Sundancer. The engine is sweet and flys the Sundancer with authority...unlimited vertical, no. On vertical, the engine begins to bog down at 10,00 feet ( Kidding!!). It does begin to load on vertical, but it's ok. Not that I'm a perfectionist, but I'd like to get maximum performance from my engine and I am not sure I'm getting what I should.

Props.... I have run a Bolly wood 22X10 most of the time and I also have run a Bolly wood 22X8. The Bolly website says the right prop is one that will let the engine run at the "rated" rpm to achieve the "advertised" HP. For the FPE 3.2, that is 3.95 HP @ 7300 rpm. My engine wouldn't turn 7300 rpms with a 12X6. I get 6000 rpm on the 22X10 and 6600 on the 22X8. I have run the 22X10 almost since I started and I like it better, the 22X8 feels like it's cavitating. The 22X10 seems faster.

Plugs....I read an article in Model Airplane News on plugs which said if the plug is black, it's rich; if brown, it's right; if white, it's lean. My plug is black but I have spent hours in my yard "tweaking" the needles and I have the needles set so that the engine runs good, transitions good, doesn't sputter in the air, idles good, etc. Am I too rich? Who knows, the engine is running good. Optimum? I wonder. My plug is black.

Carbs....at first, the engine burbled a lot in the air although it ran good on the ground. I talked to the mfg. and he suggested I remove the velocity stack because it was outside the cowl in the airflow, creating a vacuum and making the engine go rich in the air. I removed the stack and re-adjusted the needles unitl it now runs smooth, transitions good, idles good.

So, what's my complaint? None, really, the engine is running great but the rpm is not as advertised. Did you ever buy a car that would get the mileage advertised on the sticker. I never did, if it stated the highway mileage was 28 mpg, I'd be lucky to get 18 mpg. I am beginning to think airplane engines are the same. I have friends at the field with DAs that don't run as good as mine. But I still want to get optimum.

Any ideas?

Larry

I can't speak for FPE, but advertised RPMs on any particular prop/fuel combo are seldom obtained in real life. I've found that horsepower ratings are usually useless because of the size prop and RPM they use to obtain them. Experiment with the prop until you get the performance you want, despite what the manufacturer says. For example, a Zenoah G-23 isn't supposed to turn an 18-6 prop very well, but on my 1/4 Fokker Dr.1, it works great!

Dr.1

Contact FPE and see what make and sized prop they use.
As a side note I have a Sachs based 3.2 engine with a J&A Peacekeep inverted pitts muffler. I fly at 5400ft. My engine turns a Zinger Pro 22x8 @7500 rpm. The pro may not be everybodies(anybodies) favorite prop but its what I can get. I'm going to look at some 23x8 later..

If you have the D&B/Reichmuth ignition the engine is timed at about 18 degrees BTDC..Time it where it belongs, at 28 BTDC...Be careful starting it, there is no spark retard...You engine WILL run like it should if timed correctly...Been there
C&H has a hub keyed for the correct timing...[8D]

THe FPE 3.2 and up use the Syncro ignition. The 2.4 use the D&B with the Syncro CH as an option.

That does sound low, but I have never run a Bolly on my Brison 3.2. You are loosing alot of power by proping down to 6000. Find a prop that will run 7000 even if its a smaller prop like a 20x10.
Your dark colored plug may be from using too much or the wrong kind of oil.
As RCI said, check you timing.

Yeah, I have C-H ignition and have had no problems with it other than the prop blast blowing the spark plug wire off. Finally, I put a plastic tie on it and fixed that problem.

Thanks for your input.

By the way, I read someplace about some engine that you could plug into the ignition system and get rpm readout. And after a flight you could see the maximum rpm the engine reached during the flight. Anybody familiar with that? It sounds really interesting, maybe I just dreamed it.

Larry

My 3W's (75i and-106) have a tach output on the wiring harness. The tach will hold the rpm value for you. I have the tach, it's a very nice tool.

Thanks, Dan767, that sounds like a really nice thing to have. Where did you get the tach? I don't have such a connection on my ignition harness but maybe I'll contact C-H to see if it's available. I'd like to have it.

Larry

lJones;
Wow! engine bogging down on an upline I think is an indication of high needle too lean. Not good for engine. Makes big heat.