Engine advice for a Seagull Cessna Turbo Skylark 182

[Jon H]

29 minutes ago, PDB said:

I am mechanically inept however a nice club member experienced in stripping engines down is going to take me through it in their workshop

 

Excellent. You could just let the guy fix it but its better to learn how to do it yourself. 2 strokes especially are pretty simple to sort out so its well worth adding that string to your bow. 

 

15 minutes ago, J D 8 said:

As you are fancying giving IC a go then get a hold of one soon and mount on a test stand and have fun learning how to get it started and tuned. Plenty of info/help how available here.

             I would say it is likely how most of us learned to operate IC.  The thrill of the first burst into life of a little motor 😀

 

Not a bad idea 👍

 

[john stones 1 - Moderator]

You buy an engine to fly, "I might crash" is a very odd reason to choose which engine or indeed an airframe or the gubbins you fit in it. 4 strokes are harder  to use ? No the basics are the same, correct plumbing, good plug, clean fuel of your choice stored correctly, stop fiddling.

 

2 strokes ? Loved every one I ever owned, but in a scale model 4 strokes nice, fits cowl better, less intrusive exhaust, cost more, yep, but over time fuel usage pays you back and they sound great. Good investment.

 

Crashings part of the game ? For some it is, same lads do it on a consistant basis at our club, however some just have the odd mishap, some rarely have any issues, choice is yours regarding which group you'll fit in.

[Paul De Tourtoulon]

12 minutes ago, john stones 1 - Moderator said:

You buy an engine to fly, "I might crash" is a very odd reason to choose which engine or indeed an airframe or the gubbins you fit in it.

Maybe it's because he drives a Volvo,,,😅

[Nigel R]

2 hours ago, john stones 1 - Moderator said:

choice is yours regarding which group you'll fit in.

 

bears repeating

[toto]

Well .....

 

I ended up going for a OS 55 AX in the end. 

 

The OS gets a good name and I considered the 46 but given the size of the model thought it may he better going with the 55 AX. Really just a belt and braces approach. It may he a little bit of future proofing as well as it may equally suit a slightly heavier / bigger kit in the future depending on what I decide to buy. It's not inconceivable that it could start its life in the Cessna and after a while ( once I'm bored with it or wreck it ) remove it to use in something else.

 

It may he that I will still go with the electric plant and save the OS 55 AX for another project. The jury is still out on that one but I have both now anyway.

 

As mentioned elsewhere, I am training in a nitro even though my intention was predominantly to fly electric once moving on to my own models but the lure of a raspy IC engine has got the better of me. The downside is now I will need the respective IC accessories to run and maintain it. ....maybe not so clever after all.

 

Cheers

 

Toto

[Nigel R]

Welcome to the noisy and oily side of RC 🙂

 

Engines are half the fun.

[toto]

Thanks,

 

Better start hoarding some rags. The Mrs has been put on alert that no fabrics have to be chucked out until they have been run past me  

 

Toto

[Nigel R]

Try to remember not to wash them at the same time as your regular underpants, or worse yet, your other half's...

[toto]

[Jon H]

If you use the laser 5 fuel i recommended before and tune your engine up properly even a 2 stroke is not that messy. It will be considerably messier than a 4 stroke, but it isnt horrendous. 

 

Just ignore anyone who tells you to tune the engine 'a bit rich for safety' and also ignore any advice to wave the nose of the model around in the air. Its dangerous and serves no purpose at all despite claims to the contrary. Running the engine rich will increase fuel consumption, increase the mess, decrease reliability and increase the chance of corrosion within the engine. None of which is helpful. 

[Engine Doctor]

While agree with most of your advice Jon , lifting the nose vertical with engine at WOT will show up any air leaks or in the fuel line from the top of the tank. This area is normally covered with fuel in a full tank of fuel and any pin holes are covered with fuel so engine runs fine masking any leaks. Now lift nose so that the inside top of the tank has an air space . If engine continues running then alls ok . If engine stops then one of two things are wrong. Either there is an air leak inside the tank (top of clunk line or bryoken rotten/ fuel pipe orcpin hole in flex pipe) or fuel suction is compromised at carb . This test doesn need doing every flight but once every now and then is a good idea as metal fuel pipes have been known to chaff or cut through silicone pipe. 

Far better a simple check done safely than a dead stick on lift off as model rotates .

Edited April 1, 2023 by Engine Doctor

[John Stainforth]

19 hours ago, Jon - Laser Engines said:

If you use the laser 5 fuel i recommended before and tune your engine up properly even a 2 stroke is not that messy. It will be considerably messier than a 4 stroke, but it isnt horrendous. 

 

Just ignore anyone who tells you to tune the engine 'a bit rich for safety' and also ignore any advice to wave the nose of the model around in the air. Its dangerous and serves no purpose at all despite claims to the contrary. Running the engine rich will increase fuel consumption, increase the mess, decrease reliability and increase the chance of corrosion within the engine. None of which is helpful. 

Jon, should I ignore the advice in the manuals for Saito 4-strokes ("The peak rpm should be obtained and then reduced by approximately 200-300 rpm by turning the high-speed needle valve counter-clockwise (richen)"), and in the manuals for OS 2-strokes (which show diagrams with the "practical best (optimum) needle-valve setting" 20-45 degrees back (rich) from the maximum rpm setting ("Lean")). I've always done this. Or do you mean something else?

 

Also, like Engine Doctor, I do the nose-up test at the start of a new session to check the integrity of the fuel tank plumbing.

[Jon H]

ED - Yea the nose up can detect that sort of thing, but it would have only prevented one dead stick in the last 20 years on my own models. Even then the engine ran half the flight before the level dropped too far and it flamed out. Landed safe in the field, no problem. 

 

John - we get stuck on terminology here so i will clarify how i use it. Rich, a condition rich of peak RPM (duh). Lean, a condition beyond peak rpm marked by significant drop in rpm. Optimum, as it suggests, optimum tuning giving peak rpm but with a very slight dead zone either side where no rpm change occurs when the needle is moved. If you tune to the richest end of the optimum range, fine, but if rpm drops then its just rich for no reason. 

 

I have a number of saito engines and none of them have the 200rpm rich of peak line in the instructions. I believe this comes from a bit of modelling folklore over in the US which horizon hobby, who import saito and write the instructions, just parrot back to the populous. While i cant confirm, i think saito have subbed out the english instructions to horizon and just include them with everything so we have imported this american influence. 

 

Running the engine rich of peak will help if you tank placement or cooling are both wrong. but, its a bodge as you are fixing the wrong problem. Top of tank, centre of carb. Cooling baffles installed if its got a cowl round it. If you have that all set nicely there is no need to run the engine super rich to compensate for these other problems. 

 

So anyway i can phrase my advice a few ways. Run the engine as lean as you can without loss of power, run the engine as rich as you can without loss of power, run the engine at its optimum tuning. They all say the same thing +- a click or two, but think you would agree, the first one will raise eyebrows where the second one will not. 

 

Language is messy and we often miss the intended meaning. 

 

Note that engines with tuned pipes or engines that are race or otherwise tuned are a different kettle of fish. The above is a guide for normal 2 and 4 stroke engines. 

[John Stainforth]

Jon, many thanks as usual for your expert clarification. Now that I think about it, I actually do more or less as you say and back off the needle valve from the max revs setting only slightly - and nowhere near the amounts suggested by OS and Saito. The only justification I can think of, for the amounts suggested in the American manuals, is that the Americans used to run their engines with much higher nitro contents than in the UK, which gives a considerably wider range of tolerable tuning adjustment than lower nitro fuels. With lower nitro fuels the adjustments are finer and more critical (in my limited experience).

Edited April 1, 2023 by John Stainforth
word omitted

[Jon H]

Its true that high nitro fuel offers a wider tolerable range of tuning, but that makes it all the more strange that they drop the rpm. If you have peak rpm set, and use the larger tuning range of high nitro fuel to wind on maybe 1/4 turn rich with no ill effect on revs, why do you then need to go even further and run it 200 rpm slower than that? It makes no sense. 

 

These high nitro/run rich recommendations are at least partially responsible for the thinking that glow engines are expensive to run, thirsty, and very messy. High nitro means richer mixture, running rich on any fuel means higher fuel consumption but its worse on high nitro, more fuel consumption means more oil on the model and clearly more expense. Its one big snowball. They are also partly responsible for reliability problems as rich/cold engines do not run reliably as the glow plug needs to stay hot to keep the thing going. 

 

There are exceptions though like i mentioned before. Nitro cars, and boats, heli's and ic ducted fan models too might need to run high nitro/rich mixtures to cool the engine and prevent burning of the piston crown. As you know when you spill some, methanol is cold due to its evaporation and running rich in those engines cools them by using the fuel as a coolant but high nitro allows no loss of performance. But if you look at it, all of those applications are tuned 2 strokes running at high and often fixed rpm with very marginal cooling. So these engines face different challenges to a bog stock 2 stoke pottering along at low revs (vs a 20000+ boat or car) with ample airflow and cooling so need to be run in a different way. 

 

 

 

 

[J D 8]

         When starting up an aircraft set up for the first time I put in about a 1/4 to 1/3 of a tank. Tune and run until empty. If it runs and throttles fine it will be good with a full tank.

[John Stainforth]

6 hours ago, Jon - Laser Engines said:

Its true that high nitro fuel offers a wider tolerable range of tuning, but that makes it all the more strange that they drop the rpm. If you have peak rpm set, and use the larger tuning range of high nitro fuel to wind on maybe 1/4 turn rich with no ill effect on revs, why do you then need to go even further and run it 200 rpm slower than that? It makes no sense. 

 

These high nitro/run rich recommendations are at least partially responsible for the thinking that glow engines are expensive to run, thirsty, and very messy. High nitro means richer mixture, running rich on any fuel means higher fuel consumption but its worse on high nitro, more fuel consumption means more oil on the model and clearly more expense. Its one big snowball. They are also partly responsible for reliability problems as rich/cold engines do not run reliably as the glow plug needs to stay hot to keep the thing going. 

 

There are exceptions though like i mentioned before. Nitro cars, and boats, heli's and ic ducted fan models too might need to run high nitro/rich mixtures to cool the engine and prevent burning of the piston crown. As you know when you spill some, methanol is cold due to its evaporation and running rich in those engines cools them by using the fuel as a coolant but high nitro allows no loss of performance. But if you look at it, all of those applications are tuned 2 strokes running at high and often fixed rpm with very marginal cooling. So these engines face different challenges to a bog stock 2 stoke pottering along at low revs (vs a 20000+ boat or car) with ample airflow and cooling so need to be run in a different way. 

 

 

 

 

Saito are very keen that one does not "over-rev" their engines with too small a prop: "Over-revving of a 4-stroke engine can cause internal damage to the engine". That might be one of their motives for encouraging slightly rich settings in general. Another reason may be that Saito exhaust pipes tend to become undone and fall off, if you run their engines too hot and lean!  The OS recommendation to back off the needle setting by 20 to 45 degrees from the peak rpm setting seems even more extreme. They too are very keen on the user running the engines rich whilst breaking them in. "During subsequent flights  [after the long-drawn out process of running in], the needle-valve should be gradually closed to give more power... after a total of ten flights, the engine should run continuously, on its optimum needle-valve setting, without loss of power as it warms up"

[Jon H]

The biggest problem John is manufacturers are dealing with complete idiots. There will always be that one idiot somewhere in the world who runs his engines flat out from the get go using some insanely small/big prop and his own 'special brew' fuel made with beef dripping, moonshine and unicorn tears as its 'better' than that commercial tosh. He then wraps the engine in a blanket and redirects the exhaust onto the head just to make sure it over heats. he's been doing this since 1974 and all the engine failures he suffers are 'manufacturing defects'.  He may or may not also think the earth is flat and the government are controlling his mind from orbit using microwaves. 

 

While the above is an exaggeration, there will always be 'that guy' somewhere in the world and they are such hard work when it comes to warranty claims manufacturers try to engineer out the idiot with safe recommendations as mechanical failures look really bad. There is also history to consider as a lot of these recommendations and practices go back to the days of bean juice as oil and the problem with bean juice is that it is quite variable in its quality. Machining tolerances of old were not as they are now, materials were not as they are now and yet there is great inertia when it comes to updating practices and recommendations. Just look at all the castor oil arguments on the forum here. 

 

On the rpm thing, again i think this is a bit of an overhand from the US market. They usually stick massive (by our standards) engines in small models, tip in 30% nitro and scream around flat out propped for maximum power. It is not uncommon over there for a 60 inch warbird to weigh 17lbs and use a 200 size 4 stroke where as here it would be 9-10lbs and use an 80 or 90. Consequently, if you do a full throttle power dive in your heavy and overpowered model you are going to rev the rod off the engine. They dont all fly like that out there, but i have enough of a laugh about it with US based customers that it seems pretty common! 

 

I also suspect that this is partly responsible for the large number of saito radial rod failures. Dont get me wrong, i dont think saito have done their finest work on some of those engines, but i do think modellers treating them like any other 4 stroke is part of the problem. There is great complexity and great mass of whirly parts inside those engines and you can just slap them about like a standard 90fs. That said, saito should know people would thrash them and they should have been built to handle it. Just my opinion on it The same could even be said about the exhaust. If they are known to fall off, maybe design a better one? The old saito engines never had an issue, its the new ones with the heavy cast mufflers that tend to suffer in my experience. 

 

So anyway, if you arent 'that guy', you can run your engines much closer to the line when it comes to fuel, oil, tuning, props etc and this brings considerable rewards in reduced cost, mess, fuel consumption, increased engine life, increased power, increased reliability, increased performance... What more can you ask for?

Edited April 2, 2023 by Jon - Laser Engines