BTerry

My Feedback: (8)

RCU automatically filters out any link to ****. This is perfectly within their right, as they own this site and shouldn't be forced to advertize a "competitor".

**edit** you gott be friggin' kidding me. it even censors the words in the text! that should say
"****" but without the spaces.

edited by moderator

blw

My Feedback: (3)

I just got a reply about that site. It is filtered by RCU and will remain so. I don't know all of the reasons yet, but some of them have to do with practices of the other site.

Please don't try and get around the filter since there are reasons for it being filtered. I had to do some editing to fix up previous links.

There are members here now that are able to offer the help and advice needed. I think some of this help is being overlooked at times when it is offered.

BTerry

My Feedback: (8)

...and the foot is down, and has spoken. NOW I see why people leave these forums.

I didn't mean to offend by including that link, I should have just summarized the info.

**edit again** OK, fine. I know you are doing your job, blw, and thanks for your work. The problem is, RCU owns this forum, but the rest of us see it as a "free exchange of information". That will always create a conflict for the users when the companies who own the other forum sites and the owners of this site have a policy eliminating "competition" from their individual forums.

So, in answer to the original question, here is a method that works for me: Open the needles to at least 1.5 turns open. Start the engine (it will be very rich), and try increasing the throttle. Lean the low end until you can get a somewhat smooth midrange (4000 or so), then check the top end.
Lean the top end a bit until it runs smoothly, with maybe an occasional burble. Keep the throttle at WFO for 5-10 seconds at a time. Lower the throttle a bit until it runs rough, then turn in the low speed needle 1/16th turn at a time, allowing it to stabilize.
Then lower the throttle a bit until it runs rough again, and lean the low end again. When the low end is properly leaned I find I can pull the throttle WAY down, so slow I can count the blades (I don't fly with the idle this low, of course).

Then, I go fly. I find the high end is easier to tune and my engines seem to have a wider tolerance of high-speed needle settings. Now when I pull the throttle back on downlines I listen for popping/sputtering/hesitating/etc, and if it is still there I lean it out. When I have the engine two-stroking throughout the throttle spectrum it sounds much smoother and I find the power is more linear than when it is rough. When I get to this point I check the high speed needle by pulling into an extended vertical climb. If it leans out under the increased load it still has a bit to go (leaner by a very small amount). If it sags it is lean, if it accelerates it is a bit rich. However, my planes are so overpowered I rarely use full throttle. There is nothing wrong with leaving the engine a touch on the rich side, and manufacturers will often recommend this.

Just to keep myself honest I fly a Great Planes Ultra Sport 40 with an old OS 46SF for fun. It teaches me much about energy retention as it can only climb 150-200 feet from a level pass.

BTerry

My Feedback: (8)

By the way, "Wild Bill Kelso" is one of my favorite movie characters of all time!

rmh

I really think this should say "for about 5-10 seconds "
at one minute -in hot weather at full tilt lean - a novice can wreck the ring/piston/sleeve.

everyone has their favorite procedures

BTerry

My Feedback: (8)

That is a good point, I just liked the "tune away the four-cycling" part of it.

lcarron

Hi,

I will give a try to answer to the initial question from Chuck.
I was also sure that the 200 rpm drop was mandatory for gas engine.
After reading my brison manual carefully it state that : “Use a tachometer to adjust the high speed mixture for maximum RPM and leave as far open without rpm loss "the rich side of the setting".

The rumor about the 200 rpm is coming from the glow plug world as when you go vertical you do not want your engine leaning up and die from it.
My theory is that with a glow plug engine you do not have a fuel pump as the walbro carb does. A gas engine going vertical does not go lean
because of the sucking efficiency from the pomp.

I hope that this explanation is the right one as I really try to understand how a gas engine works. I spent so much time tuning my gas engine.

RTK

My Feedback: (1)

A "novice" with poor or no baffling would be wise to run 100 or so on the rich side, less chance of a dead stick and/or a burned up engine.
Ask any manufacturer what the most common reason for repairs are, besides crashes.

Jake Ruddy

My Feedback: (40)

The 2 most important things are temp and does it sag when you pull verticle? If it sags then you are too lean.. no way around it. If your temps are high you are either really close to too lean, your baffling is not done properly, or both.

BTerry

My Feedback: (8)

updated my post to remove the "offending material" and to post a method that works for me.

Tired Old Man

My Feedback: (1)

Any rpm drop on the high end when tuning a gasser can be accomplished by ear. If you hear an rpm reduction then it was enough. This is a starting point anyway, the rest of the tuning is derived from in flight performance, not rpm crunching. What it does in level and upline vertical flight is the final arbiter of tune settings.

As to the 200 rpm thing, you're right, it's been carried over from glow engines by glow engine flyers. We don't fly glow here folks

rmh

The reason for going lean on uplines has nothing to do with the carb on a gasser - it is simply the load of pulling against gravity as the model slows (a difference in speed indicates a load increase )
On glow engines (improperly setup ) ,the run it richer thing is because the fuel head ( vertical distance from fuel puddle to carb spraybar) changes
Also--
gassers run a much leaner, more critical fuel to air mix -as compared to glow engines
gassers run 12-1--14-1 mixes and glow 5-1 - 8-1 mixes
a nice high nitro mix on a glow engine is extremely tolerat of adjustment -especially if used with a good tank pressure setup attached to exhaust - a closed loop setup.
My next slide please ----

Tired Old Man

My Feedback: (1)

So it hasn't actually gone lean, it's just reached the limit of the amount of power it had to perform work. You want to see a lean mix, I'll show some plugs where the mixture is so lean it cooks any trace of oils off the insulator, leaving them bright white for 50 hours of use or more. That's max power out of the engine at the expense of heat and a shorter life span. Much shorter life span...

Jake Ruddy

My Feedback: (40)

Sounds like it has gone lean due to gravity slowing down the speed of fuel delievery?

rmh

no-
lean relative to work load .

Jake Ruddy

My Feedback: (40)

ahh

BTerry

My Feedback: (8)

Right. The higher work load requires more "energy" in the form of fuel, i.e. a slightly richer mix in that situation (up to a point).

So in the end, is it possible to know the "best" high-speed needle setting with the plane on the ground? Theoretically the highest load would be at zero forward airspeed.

What, if anything, does this info tell us if the prop is stalled at zero airspeed? I submit that the highest load on the engine will be at or near the minimum airspeed when the prop is NOT stalled, and not necessarily at ZERO airspeed. If the prop is cavitating the turbulent flow will decrease the total mass of air through the prop disc, thus decreasing the total amount of "work" done by the prop and engine. Does anybody else buy this argument?

rmh

sure -but difficult to measure - it is why I have adopted the "clean air " prop mounting -to allow the blades to direct air straight back -as much as possible - on many setups, the prop simply stirs and creates a high pressure poolbetwen th blade and the cowling.
some think the air actually blows thru the cowl but -of course - that ain't the case.

AirWizard

My Feedback: (3)

Dick,

Can you explain the clean air prop mounting or show a pic of what you mean?

rmh

The pic above show what I mean- not that the engine is extended as far forward as possible. Then, I added an inch thick spacer between the spinner and the cowl

If you look at later, performance oriented , prop driven aircraft - many have the props forward in long spinners and some have the spinner faired very well into the surrounding cowl -- both radial and inline and some opposed engines
some of the work is done of course, to reduce drag from cooling inlets

crazyjoseph

My Feedback: (3)

I love reading these posts they are so funny especially when dick chimes in, who by the way is usually the only one that knows what he is talking about. Be careful what info you get from these sights because often the info is very poor. for example aviation fuel gives more power, or less oil more power, or i don't need baffling, or tune your engine 200 rpm richer. ALL FALSE STATEMENTS.
I guess thats why at the end of the DA manual it says if you have a problem please call us don't get your answers online
I frequently fly in 100 degree weather I baffle all my engines and tune for the rich side of max rpms hover all day no heat problems. People are so scared of running lean that i have noticed at flying Fields 80% of the planes are running extremely rich motors
Also as the day warms up on occasion i need to richen up my low end slightly.

ljones5000

My Feedback: (2)

Off subject, but I'm surprised you can find a place flat enough in Glenwood Springs to take off. Great little town, I have been driving through there for years on the way to Aspen.

Cheers.

crazyjoseph

My Feedback: (3)

Bring your plane and look me up

Tired Old Man

My Feedback: (1)

Here's what lean does. Ambient temps similar or higher than yours every day. Baffled, sensor controlled cowl flaps designed by 30 pound brains, filtered gas and air, and pushing some pretty expensive "toys". The "brains" seem to think lean is "in" these days. But then again, I'm one of those guys that doesn't know what I'm talking about. You go ahead and run lean. The pics are of the third engine I've seen like this in four days. Ya never know, yours could join the club.

Jake Ruddy

My Feedback: (40)

haha common... thats got some life left!