Okay Guys; what's the latest on running in ABC/N taper bore engines?

Is it slow and gentle, rich mixture and low throttle, or hot and fast? I've heard a few conflicting methods and would like to know the general consensus...

Cheers,

Mick.

No consensus involved. It's fast with mixture lean enough to allow the engine to get close to normal operating temperature. If the engine is allowed to stay too cool by slow or very rich running you should buy some spare rods, you'll need them.

Denis

Dennis,

Thanks for that: sort of goes against the grain growing up with cast iron set-ups. Do you use full throttle on an un-run engine? If so, for how long do you run before stopping to allow the engine to cool?

I've been following the recommendations of Just Engines who have supplied all of my recent engines. They say start rich at 1/4 throttle then 1/2 et cetera. I have to say that I have experienced no problems following their advice but, then again, none of my recent ABC engines are that old.

I appreciate your observations,

Cheers,

Mick.

I may start the engine at low throttle (if it has one) for safety reasons but then I go immediately to high throttle and adjust the needle for a very rich 2cycle. The reason for this is to get the engine up to temperature in a hurry so that the cylinder expands enough to relieve the pinch at top dead center. I start checking immediately for any signs of stress from the engine. Even though I have an IR temp probe I trust my calibrated fingers more for checking head, bearing temperature. After about 30 seconds to a minute I would guess, when I think the engine is up to temperature I shut it down and let it cool off. I repeat this about 20 times (thermal cycling) and if the engine hasn't shown any signs of stress I'll lean it out to about 3 to 4 hundred rpm below peak and let it run for a couple of minutes looking for stress or the temperature to start drifting up. I do all of this on a slightly undersized prop to keep the engine load a little low and avoid sudden temp run up. If the engine seems to be comfy with all this it's ready to go flying with the needle set to an over rich 2 cycle for a few flights.

On ringed engines I start them at 1/4 throttle and bring them up to a very rich 6000RPM and let it run out a tank of fuel. This is trying to get the ring seated. If nothing ugly is indicated on the next tank I open the throttle with a very rich needle. If things seem to be running nice and cool I'll lean it out to a very fast 4 cycle, just breaking into a 2 cycle. If every thing seems to be good after about a half tank I'll lean it a little more and start thermal cycling as above.

I basically used this procedure on iron liners with iron or aluminum pistons. If they didn't have a throttle then I just lit them off with a very rich needle. When the ABC's first came out my first experience with them was on Super Tigre 15s I was using in control line goodyear raceing. I tried to break them in just like an iron liner. I went thru several rods before I figured out what I was doing wrong.

Denis

Denis,

Thanks for the info: I have heard about the need for thermal cycling - it just sounds a bit brutal for a new engine. Anyway, I am going to take your advice - what you have written sounds very sensible based on my knowledge of engines and metallurgy.

I have a new MVVS 91 in its box waiting to go in an Edge 540 so I will be giving it your treatment. That is despite the supplier's (Just Engines) recommendation to start off 1/4 throttle and rich.

Thanks again for the advice: I'll let you know how it went.

Cheers,

Mick.

I hadn't realized the MVVS 91 was not a ringed engine. I haven't encountered an engine that size that did not have a ring. My Webra's, Super Tigres and OSs that size or bigger all have rings.

Denis

Mick

From what I can find the mvvs 91 is listed as 91 GFS-R ABC R/C. That means it's a ringed front intake side exhaust ABC engine. If this is the case it should be run in like a ringed engine, slow and rich at first to allow for ring seating. Then thermal cycle it.

It's not unusual to use ABC technology on ringed engines anymore even though many would ask; WHY? the brass or the chrome. Actually chromeeing iron liners wasn't unusual a long time ago in hopes the liner would be more durable or to recover a worn liner

Denis

My SC 1.08 is an ABC so some of the larger engines may not have rings. With the MVVS I think it would be wise to take off the muffler and look through the exhaust to check if it's got a ring or not. If it's ringed then run it in much the same as a cast iron piston, slobbering rich for the first couple of runs then almost at the point where it breaks into a 2 stroke for a few more runs. Then some shorter runs at a rich 2 stroke to start hardening the ring. If it's a ringed ABC then it should last just about forever

Aw geez downunder
You made me go look and sure enough my ASP 108 doesn't have a ring and is an ABC. It doesn't even have an oil grove. I don't know why I didn't remember that, the engine towed around my Goldberg Ultimate for a couple of years and did a good job of it too. I also checked my new as yet unused Magnum XLS91 and it also is an ABC without a ring but has an oil grove. The oil grove is so narrow it makes the engine look like it has a fat dykes ring.

Mick

The instructions for the Magnum 91 say to start at 1/4 throttle and open to a very rich half throttle, just lean enough to allow for running without the ignitor, ala what Justengines suggested. The instructions then say after 1 minute open the throttle slowly to full throttle and begin to lean and then start temp cycling with short fast runs then cool down. My Magnum is not a very tight fit at TDC so I wouldn't be afraid of a 1 minute run at rich half throttle but I still think I would have it wide open right after getting it started.

the mvvs 91 is ABC engine and not ringed.

I had great success using the heat gun on two new non-ringed engines.
Heating the top end takes away the pinch at start-up, and does away with
the stress the rod has to endure....not to mention jamming the piston into
a too tight bore....and then yanking it back out. [X(]

I also oiled the tops of the engines. Try the heat gun on those really tight
new engines....

Dave.

Mick,

All tapered-bore engines need a rich, two-cycle break-in procedure.

One must be careful not to take lapped, meehanite (cast iron) piston, steel sleeve engines as tapered-bore engines.

They are not and they need a very rich break-in procedure, with multiple short bursts separated by complete cooling.

The aim is annealing the cast iron piston, to harden it and stabilize its size.

The hot air gun trick does wonders on tight ABC engines... mind you they are not all so tight you need to heat them up, but MVVS's can be VERY tight when new.

A few weeks ago I ran in an engine (West Eurotec 50V1) that would just seize up if left idling for more than a few seconds. That one was extremely tight, and it sounded horrible when it seized. It didn't do any damage though, but like I said, it sounded horrible and scared me for a moment there...
It turned into a screamer after two tanks. Couldn't be better, although it is still very tight when cold. But this is the way they are supposed to be.

So if it is ABC and tight, get it up to temperature ASAP... even before you run it... going gentle on it will do more harm than good!

Guys,

Some great information - thanks for the help. My MVVS 91 is definitely ABC with no ring. It's un-run: in fact, listening to what's been said I've even resisted the temptation to turn it over compression. Anyway, Just Engines are sending me an in cowl silencer for my Edge 540 which should arrive tomorrow. Friday is half-day so I'll be out the back with that MVVS giving it some! Might be able to take the model out at the week-end if the rubbish English weather sorts itself out...

Out of interest, Just Engines send an instruction sheet out with their new motors. All the ABC engines I've had from them include the recommendation to start at 1/4 throttle and run a tank through very rich before moving on to two tanks at half throttle, very rich.

I shall be doing as you all suggest though and come back after the week-end with a report.

Cheers,

Mick.

Well then I guess I've learned that GFS-R means glow, front intake, side exhaust or rear exhaust. Shouda been obvious.

Denis

I broke in my magnum 91 just the way the manual recomended, the second startup, the engine overheated quick and the con rod bushing on the crank went away, needles to say, it bothered me, I took an old crank and rod from another 91 magnum that wouldn't hold a head gasket and combined with a new A.S.P. liner, piston, ring from JUST ENGINES, made a great
91 that runs great, three 5 min. slightly rich runs and threw it in the air, no muss, no fuss, clean oil on the side [8D]

MickJC

I am running an MVVS 91 right now with a BCM Pitts exhaust. If J'Engines has supplied you with one of these please be aware of the fact that it will probably need a small modification for your engine to run right. I have found that the muffler does not provide adequate pressure to the tank. I can back the H/S needle out completley and it is impossible to get the engine too rich! I solved the problem by plugging one of the exhaust stacks with a piece of dowel secured with a very small screw. Don't block the outlet completley or the pipe will fill up with oil. Otherwise, great engine!

David,

There is a delay on the BCM silencers so I went for one of the black boxes that they show on the adverts. That works okay and is fairly quiet but it leaks oil all over the engine compartment. I have taken it off and attempted to seal it with gasket sealer.

The 91 is the first engine I've had that actually started first flick out of the box. It's had about 30 minutes on the ground it's now ready for first flight.

Very easy to handle - I don't know what the revs are on a 13x8 but it sure shifts a lot of air.


Cheers,

Mick.

We car guys use a method that's popular with the racers. It's called "Heat Cycling". You get the engine up to temp (190-200) and run it for 5 minutes. You shut it down and let it cool all the way. You then repeat the cylce two more times (total of 3, 5-minute bursts). The next 15 minute set is similar, but instead of 3, five minute cycles, it's 5, three minute cycles. After a this total of 30 minutes of run time, the engine is ready to "race tune".

It seems the engines run stronger and last longer (5-6 gallons on the good quality ones). Our engines are typically from .12-.21-.26 in size. I don't know if engines of different sizes or different applications (ie planes) would be any different.

Just another perspective. It's working good for us.

-RobH

The majority of "we car guys" advocate braking in a car engine at IDLE for several tanks before running it. I personally disagree with that method and prefer to get an ABC engine HOT by breaking it in at WOT in a large area where the car can get a straight line run at full throttle for a minute and allowed to cool a little with low throttle operating and then back out on the straightaway for several tanks. The car is run in a 2 stroke rich mode and after several tanks leaned out so WOT produces a maximum temp of about 270 degrees for extended non-stop operation.

My engines last over 5-6 years (oldest one has at least 250 hours on it in the past 5 years and still runs great), not 5-6 gallons. And yes, this part time car guy uses AIRPLANE fuel in his engines because the higher oil content will extend the engine's life considerably.

Interesting stuff. It seems a bit like 'horses for courses' guys. I suppose the main difference between car and aero engines is their operating speed and the fact that car engines run with a flywheel rather than a prop. A general engineering principal for those using machine tools - lathe surface grinders, millers - is that a high speed and light cut gives the best finish. Assuming the analogy follows, and as far as I can see the only differences are those of scale - i.e. the depth of material you are intending to remove, a car engine off-load would satisfy that criteria. Using that analogy a car engine (or helicopter?) should achieve the best running fits. This, however doesn't take into account heat cycling which seems to be one thing we are all in agreement on.

I guess you could summarise and say that if you keep the revs up and the load down, stop the engine and allow to cool when the temp increases and gradually extend the process to full speed, on load operation you will not be far away from ideal fits.

I suppose it's one of those things that's down to experience and the intended use of the engine. Watch an experienced operator "run in" a speed engine - it's frightening the revs they use.

What I find most interesting is that everyone you speak to has a different opinion on how to run in engines: what sorts out the men from the boys is that little bit more horsepower and those last few revs.

Mick

Mick,


I would not call this an opinion issue.

There are right ways and wrong ways. Most modelers would have somewhat different techniques to do the same thing.

BUT... There are wrong ways too.


About 10 months ago I went to the trouble of starting a thread in RCU, about 'break-in of tapered-bore engines', because where I fly I saw engines being destroyed outright, or winding up power-less. You can search RCU for it.

In 12/2002 I entered an article in a local R/C web site (you and your computer will need to read Hebrew, if you want to see it), about the same issue.


Tapered-bore engines; ABC, AAC, ABN, Plasma Ceramic, need a slightly rich, two-cycle, WOT, high RPM break-in.

Cast iron ringed engines and lapped meehanite piston engines need a very rich, four-cycle break-in, with relatively low RPM at lower temperatures, to break-in properly. Plenty of heat cycling is also needed in them, to anneal the cast iron.

Doing it the other way in either type of engine, will have a mild case scenario of your sport engine living 10-15 hours, before needing an overhaul, instead of 100-250 hours. I do not want to talk about the worst cases...