When is an engine really fully run-in?

[Jonathan M]

...to the point when tick-over can be reliably set at about 2,200-2,500 rpm, and when it doesn't occasionally cut out (e.g. on 3/4 power at the top of a loop or at similar throttle on climb-out from a takeoff)?

 

Engine is a new SC40 in my Wot4 ARTF (was on an 11x6, now on an 11x5 to help slow landings etc).  Has now had about a dozen or so tanks through it in the air.  Starts first time with a hand-flick (only use the electric starter at the very start of a session to help clear out the after-run oil).  At full beans the rpm gets to about 10,700 on the ground (needle set to max less two clicks), tick-over currently around 3,000 reliable.  Adjusting the low-speed needle to lean or richen things - or setting a slower tick-over - only increases the likelihood of the engine cutting out in flight, so best left alone at present.  Rapidly opening throttle accompanied by the usual slight dip/delay before revs climb - but doesn't sound quite as confident or 'loose' as my well-seasoned OS 46 in another model.  Tank, clunk, fuel lines all good, fuel is currently Bektra 5 (was Irvine Sport 5 but no different in this regard).

 

Is it just a question of waiting until the engine has had another year's flying?

 

[Don Fry]

I’d expect another dozen tanks, and then you are near enough there. I tend to go with a high, reliable tickover, with an engine cut on a handy switch, fly it in on a normal approach, and dead stick a couple of feet up when you decide a fly round won’t be needed.

[Denis Watkins]

I think you know Jon, at 3000rpm, with a breeze, the model is still flying, and maybe straight past you without landing

Anyhow,  Tank, fuel lines, all good, does need checking

As the slight hesitation at throttle up, does include a slight pressure leak somewhere in the hesitation scenario

 

There are a couple of SC40s at my patch and will tickover at 2200rpm, amazingly, one lad found a 10.5 x 6, and the other on a 10 x 6 prop

[Martin Harris - Moderator]

I’ve found these engines can be of variable quality - especially the o rings used in the carburettor which can lead to tuning difficulties. 
 

Are you using a good quality glow plug?

 

What procedure were you using to run it in?  ABC engines don’t benefit from extended ground running, rich settings or extended tickover - they are best flown as soon as possible with only a slightly rich mixture, varying the throttle and keeping loads reasonably low.  

[Jonathan M]

Thanks for input chaps.  The fuel lines are all good (installed new only a few months ago), haven't checked the carb o-ring, but the engine was run-in on the bench exactly according to the SC instructions (below), putting two or three tanks through it before mounting in the airframe and having the dozen or so flights with it since.

 

The plug is a FirePower No4, which might be slightly 'cool' for my fairly modest use?  Might be worth buying a No5 'medium' or trying an OS No8 from my collection?  Otherwise I imagine I just need to thrash it around more for the rest of the season! ?

 

 

[Don Fry]

OS, SC, ASP, 2 st engines all run very well on an OS 8. 
A slight hesitancy on opening up might be a small amount of lean on the low end needle. Open it, anticlock, 1/8 of a turn. If it’s better, try a bit more. Nothing to lose if you stick to 1/8 turns carefully, as you always know where the original setting is.

 

Just read your original post, ignore above for the moment. Another thing I do, the throttle servo is set for slower speed. I can slam it open from tickover, but the servo takes a second to get to full chat. I reckon the motor transits better if it’s fuel supply matches it’s revs, and no motor transits in a second

Edited August 30, 2021 by Don Fry
Second paragraph.

[Jonathan M]

Yes, I've got into the habit of adjusting the low-end needle by small increments, down to 1/16 of a turn once I'm in the right ball park.

 

Will try the OS 8 plug next time I fly.  One thing that makes me think the existing plug is too 'cold' is the recent dead-stick on takeoff - after not perhaps having let the engine warm up quite enough!

 

I might also try setting the throttle servo to a slower speed...

Edited August 30, 2021 by Jonathan M

[Frank Skilbeck]

I've mentioned this before, but if your radio supports flight modes/phases then having a couple of flight modes means you can have one with a high idle for aerobatics and a landing mode with a lower idle, saves having to adjust the throttle trim for landing.

[Nigel R]

F4 might work better with high Nitro. For my money F5 or f6 for low Nitro, say 5pc.

 

I think they're the right numbers. In temperature terms I mean Medium and medium warm.

 

[Jonathan M]

1 hour ago, Frank Skilbeck said:

I've mentioned this before, but if your radio supports flight modes/phases then having a couple of flight modes means you can have one with a high idle for aerobatics and a landing mode with a lower idle, saves having to adjust the throttle trim for landing.

 

That's a really good idea Frank (and worth repeating).  I can easily do flight modes on the Taranis, but might wait until I've got the motor singing nicely before adding this.

[Jon H]

Running in engines with non ferrous piston liner setups is not a big deal. As already stated, ABC 2 strokes do not like being run cold so give them a good thrashing from new. $ strokes with rings take a smidge longer, but again we are talking no more than an hour in the air. 

 

Engines with ferrous piston/liner combo's need a little more care, but again an hour will do it. 

 

Engines will continue to settle and improve over a longer period of time but for all practical purposes an hour of flying should be considered sufficient to tune engine for peak power and use whatever prop you like. 

 

There is also no reason for a new engine to be less reliable than an old one. Tune it up and go fly it. Most factories ship their engines very rich on both needles to guarantee the engine will start. These need to be set right away so they are at least 90% right. Once its had a few flights you can fine tune the idle mixture and its all done. 

[Jonathan M]

Useful to hear that Jon.

 

 

I think I solved the problem(s) at the patch today!  First I swapped to the slightly warmer OS No8 plug but left both needles where they were.  Having run the engine up as usual on the ground without any clear issues, it then cut out as before in climb out, but after that also when running at full revs on the ground!  So opened high-speed needle two clicks to richen slightly.  When this proved reliable, I found that I could lean the low-speed needle by a full quarter of a turn.  This then enabled me to reduce the tick-over to around 2,500rpm reliable.  Also the engine now opens up much faster and more smoothly than before.  Then refilled and flew the entire B Cert 'schedule' in one go without missing a beat.

 

 

I think the warmer plug helped, and have certainly learnt something new (i.e. plug temperatures).

 

Thanks all for the input!

 

 

[Jon H]

I have to confess, glow plugs are easy. OS8 for 2 strokes, OS F for 4 strokes. I dont even entertain anything else! 

 

Also SC engines always came very rich on the slow run and their carb design means a rich slow run needs a more lean main needle setting than you might want. Its not a mixture thing as such, but a case of the carb being out of whack across the range. I recommend you peak the main needle and then lean off the slow run as far as you can. Set the main needle again and then give that a go. 

[Jonathan M]

Subsequent to my last flight mentioned above when everything had been perfect, I started getting problems again in the air, so decided to whip the engine off and take the tank out for a thorough inspection.

 

First problem was the random cutting out.  Once the engine was off the bearers I tried to blow through the carb tube to discover that no fuel or air was coming out the carb tube!  A good shake and then a bit of residual fuel came through, which obviously indicated a plumbing issue.  I think the fuel pickup tube was too long and must have been sucking/sticking close against the back wall of the tank, so I trimmed another 1/4" off, and for good measure replaced the standard filter-less clunk supplied with the Wot4's ARTF IC kit with a filtered version.

 

Second problem which was worrying me (and which was the original motivation behind this thread, i.e. the question of when a motor is fully run in) is that when turning the prop over by hand at the patch the engine felt very graunchy at TDC:  there's a double-click at the top which is sometimes smooth but also sometimes pretty rough-feeling, almost grinding-like!

 

So I removed the back-plate and took off the head for an internal inspection but couldn't find anything obviously wrong - except that with the head off the piston-head can be seen/felt to be tightening against the liner and lifting it at TDC.  So I replaced the head but left the back-plate off for the video below - in which the clicking can be heard but not on this occasion any of the random roughness.

 

Is there anything 'wrong' with this SC40 which I'd only make worse by running it, or should I be good to fly with it?

 

https://vimeo.com/manage/videos/617128969

 

Edited September 28, 2021 by Jonathan M

[Denis Watkins]

It is normal for a New ABC to sort of double click tightly over the compression

The motor is fine

So just sort the tank/ pipe pressure leak on the new pipes

[Nigel R]

16 hours ago, Jonathan M said:

there's a double-click at the top which is sometimes smooth but also sometimes pretty rough-feeling, almost grinding-like!

 

A really tight pinch can feel rough.

 

ABC, never run them rich, run them as normal for short periods until they hold full throttle and idle, then just go fly. My understanding is you need 10 or 20 heat cycles to get things hardened up but the first few you will also be bedding in the parts and that must be at proper temperature.

[Christopher Wolfe]

I remember running-in a few a few pylon racing ABC engines many years ago.

 

The advice at the time was to fit a a smaller prop than usual and run it to the desired revs with a slightly rich mixture and to back off the needle every 30 seconds after a short peak run.

 

I used to pre-heat the heads of really tight ABC engines with a heat gun prior to starting them.

 

Seemed to work out ok.

 

chris

[Jon H]

As a thought experiment, and to play devils advocate a little, why are engines run rich during run in? what purpose does it serve? 

 

As an individual and in your own words, what does rich running do that is advantageous to a new engine? 

 

I suspect i know what most of the answers will be but im just curious. 

[Rich Griff]

And, as a matter of interest, what is the running in procedure for a new Lazer engine please ?

[Peter Christy]

Jonathan, the point about ABC engines is that the liner will expand more than the piston when hot. The bore is also very slightly tapered at the top. When cold, the piston WILL pinch in the top of the bore. It is meant to, and if it doesn't, then engine is knackered!

 

When hot, the liner will expand more than the piston, to allow the correct clearance. Running the engine too cold ie: too rich - can wear the piston/liner fit, which is not what you want! (This is rare in modern engines, but possible!)

 

As Jon (Laser) will tell you, we use an excessive amount of oil in our fuels, so excessively rich running does nothing to help running in!

 

--

Pete

 

[Jon H]

26 minutes ago, Rich Griff said:

And, as a matter of interest, what is the running in procedure for a new Lazer engine please ?

 

No idea, never heard of Lazer engines ? 

 

For Lasers just start it, tune it, fly it. Repeat until worn out or turned into a lawn dart then return for service. Start back at the beginning and repeat ad infinitum. 

 

 

 

[Rich Griff]

Cool...

[john stones 1 - Moderator]

Mine are run in when the little tweaks on the needles stop being made, not very techy but it works for me, not keen on constant tweaking, I don't use a tacho, I don't care what the rpm is, fly it.

 

Current engine is a NGH 17 petrol, ran on floor first on recommended mix to reassure myself, stated easy, ran well, fly it, couple of minor tweaks so far on low end needle, top end not been touched. Is it run in yet ? no idea, but it's reliable so far.

[Chris Walby]

A point that Jon has made to me which goes against normal thinking, but perfectly logical is that Laser engines should be given a good thrashing!

 

That's not to say abuse it, but once warmed up and carb set correctly then go fly and don't be afraid of giving it a really good work out (not WOT all of the time, but you can if you want!). The point here is flying around at 1/4 throttle means the engine will cool off and if some doughnut is running it rich it will do it no good long term.

 

I liken the Laser engine to the very high performance, methanol four strokes engines I used to race with the use of high quality modern precision materials, essentially they don't need running in, but as soon as they are started they are running out! Just Laser engines will most likely out live the owners unlike the 8 hours between stripe downs my race engines required (you don't get something for nothing when you are after power!). 

 

PS Engines generally need to put up with a very varied group of owners that do some very odd things that sometimes have not been advised by the manufacturer and hence need to work despite all of the different conditions they will find themselves, sometimes I am surprised they run at all ?

[Nigel R]

Useful background info and run in process...

 

ABC running in

 

Iron/steel running in