stunthanger.com
Engine basics => Engine set up tips => Topic started by: Bootlegger on April 01, 2017, 08:58:55 AM
-
I am running an L A 46 on 2.5 nitro and 22 oil half/half and only getting 5.5 min of run time on 4 ounces. My next step is changing glo plug, then venture, as this one is .281 all this is with a tounge muffler and 11x4 apc prop.
Any other suggestions/help/ideas???
-
Gil
I assume you need longer run time from the "only getting 5.5 min" blurb
Most folks are going to ask what plane, what tank configuration, what length lines, what lap times, how many more laps do you need...
Some will say add Coleman fuel, at least one will say Acetone is better...most will tell you what you know....bigger tank or custom tank
-
I dont get what the dilema is here, if you need more fuel add more fuel,
are you getting the run you want every time? aside from time?
then build a bigger tank, changing anything will change the run
-
I am running an L A 46 on 2.5 nitro and 22 oil half/half and only getting 5.5 min of run time on 4 ounces. My next step is changing glo plug, then venture, as this one is .281 all this is with a tounge muffler and 11x4 apc prop.
Any other suggestions/help/ideas???
Gil,
My personal set up for the LA 46 is: 6 MM venturi. That is the one for the LA 25. I don't know what the decimal equivalent is. (Comes with a 7 MM venturi)
A 762 muffler, UNALTERED! Yes, it has a very small exhaust hole and that is IMO what gives me a 3-3/4 oz. run for the complete pattern. (At sea level)
I use a Vess (wood) 11 X 4 and 10/22 fuel. I have not had a problem with lack of power.
That's my set up and I'm sticking to it! y1
Jerry
-
Gil,
My personal set up for the LA 46 is: 6 MM venturi. That is the one for the LA 25. I don't know what the decimal equivalent is. (Comes with a 7 MM venturi)
A 762 muffler, UNALTERED! Yes, it has a very small exhaust hole and that is IMO what gives me a 3-3/4 oz. run for the complete pattern. (At sea level)
The stock 25LA venturi is 6.5mm/~0.257. If you are really using 6mm/.236, then that would be a substantially smaller venturi and use a lot less fuel. 7mm/.276 with the stock spraybar is pretty darn big, well outside the usual sweet spot range. 6.5/.257 is right down the middle, so I would expect that to work very well.
While I have thrashed the smaller engines extensively, I have never run the 46LA myself. All I know about it is observation from others and a general rules of thumb. I do know that if I had to choose between an ST46 (which I know very well) and a 46LA, I would choose the 46LA for sure.
Brett
-
The stock 25LA venturi is 6.5mm/~0.257. If you are really using 6mm/.236, then that would be a substantially smaller venturi and use a lot less fuel. 7mm/.276 with the stock spraybar is pretty darn big, well outside the usual sweet spot range. 6.5/.257 is right down the middle, so I would expect that to work very well.
While I have thrashed the smaller engines extensively, I have never run the 46LA myself. All I know about it is observation from others and a general rules of thumb. I do know that if I had to choose between an ST46 (which I know very well) and a 46LA, I would choose the 46LA for sure.
Brett
Brett
Brett, It is the stock one so I guess it it is 6.5 MM
Thanks for clarifying that for me.
Jerry
-
Put on an 11-5 prop, that will give you more mileage.
MM
MM, an 11 X 5 gives me to much speed. I'm doing a 5.2-4 lap now. Why change????
Jerry
-
Put on an 11-5 prop, that will give you more mileage.
A Gerry notes, that seems like it going to go WAY too fast, or the engine will have to backed off too far to produce full power. I think the setup he describes is the way to go, and build a bigger tank to get the desired run time. Even a Supertigre would need at least 5 ounces even on 5% and stock venturi.
Brett
-
Brett's comment about the FP 20/25 venturi ID is on the money.
I've converted quite a few FP 20s and FP 25s and all my venturis came from Tower. Despite what the technical notes on the web site say, all of mine have measured 6.55mm using a vernier caliper that has never been dropped.
I've seen an LA 46 in a Heartbeat Models Sukhoi run very nicely using the 6.75mm venturi—the small venturi from the days when the FP 35/40 came with two venturis.
My very porky—57 oz—Shoestring designed around the Brodak P-40 wing—needed the 7.1mm stock venturi using the APC 12.25 x 3.75 prop and fuel with 22% oil, 50/50 blue Coolpower and castor, and no nitro. I tried it with a 6.75mm venturi but changed up because the engine seemed to labour. The muffler was a Thunder Tiger GP 40 item—very similar to the OS 3020 with a 9.5mm outlet.
Also, I ream out the FP 20/25 venturi to 6.75mm. It's only 0.008" so I don't change anything else. If I needed more ID I would change the bell mouth slightly.
For reference, my ARF Cardinal has an ABN FP 40 with a 6.75mm venturi and a Zambelli-spec hemi head. It runs a Bolly Clubman 11.6 x 5 and the same 22%-oil fuel.
-
My LA46s will do 7 minutes on less than 4 ozs. Try a .272 venturi with a tigre needle valve assy and 5% with a Xoar 11 x 4 prop and run it a little under peak RPM...10,000 if I remember. I know the choke area is small but it still has plenty o power and never "breaks"...just a steady wettish 2. I mod these to 4-2 by raising the intake ports and they still do 7 minutes on a little OVER 4 ozs so yours should be doing the full pattern on 4 ozs...unless you have an actual fuel leak somewhere, but that would probably cause all kinds of leaning and fattening I have seen tanks start siphoning and the pilot is unaware, so one thinks he has 4 ozs but by the time you get to the lines...not so much.
-
What Needle Valve assembly are you using?
Randy
-
P A 40 from Randy Smith, do you know him??? y1 <= #^
-
I dont get what the dilema is here, if you need more fuel add more fuel,
are you getting the run you want every time? aside from time?
then build a bigger tank, changing anything will change the run
hmmmmm I would listen to him !
Randy
-
I am running an L A 46 on 2.5 nitro and 22 oil half/half and only getting 5.5 min of run time on 4 ounces. My next step is changing glo plug, then venture, as this one is .281 all this is with a tounge muffler and 11x4 apc prop.
Any other suggestions/help/ideas???
5oz tank
-
P A 40 from Randy Smith, do you know him??? y1 <= #^
Yep, that bar is .157 , and your 4 0z is normal, I would try 4 1/2 ounces. that should get you a complete pattern easy.
If for some reason NO then use 4 3/4 to 5, This is not too much fuel for the OS 46
Randy
-
I'll never understand the fascination with getting "great fuel economy" on a stunt engine! If you have a OS LA.46 that is using less than four ounces for the pattern, you aren't getting all the available power out of the engine. Yes, you can detune the engine to fit special circumstances but there are other ways to do this than by strangling down the engine. if you need to choke it down that much, you might want to consider a smaller displacement engine. Everything from the engine start, through the flight and shut off is more predictable and consistent, I think, when the engine can eat and breath like it needs to. Fuel is power and cooling. I like to get all I can of each.
Type at you later,
Dan McEntee
-
I used an excellent running LA46 on a kit bashed Tanager. Stock venturi, tongue muffler and an FP needle valve. 12.25x3.75 APC. Ran it very rich. Broke mildly at the top of loops and top of vertical maneuvers. Broke in overhead eight. Flew near 6 second laps, somehow, staying out on the lines. A friend didn't believe how slow it flew. So we timed it. Engine burned every bit of 6 ounces in a clunk tank.