1967brutus

I have never been able to get my twin running the EXACT same cylinder temps, and the difference varies a bit over the throttle range. As long as it does not get out of hand, don't worry about it.
My difference alarm is set at "15 degrees from average" which in a twin means "30 degrees", and basically only activates at prolonged idle (when I have to wait at the starting line for example). I ignore it on the ground, only pay attention to it in flight and to be honest, that alarm limit is really WAY before anything goes wrong. It is mainly intended as an early warning for a failing sparkplug or the likes, because half the time I cannot properly monitor the engine by ear due to other traffic.

Also: flight (increased airflow) affects temperatures in more than one way: the propwash is rotational, meaning that on the ground, the angle of the airflow is different, and that affects the sensors, because it is unavoidable that one sensor is more exposed to airflow than the other when on the ground, and this difference gets less in the air. I don't see anything really shocking there... But maybe you're seeing a bit of blow-by: Blow-by increases the liner temperature mainly, but that can be visible in CHT.
Best advise I can give is to put temperature, RPM and throttle position in a log, and take it to the air. Fly a test routine (basically a throttle regime in whih, whatever you do, you hold a given random throttle position for 30 secs, change to another throttle setting and hold that for 30 secs, etc etc to cover the entire range as far as possible.

oh, and if peak RPM in that vid is "tuned for flight", I would try and find a touch heavier prop. Mine does 7600 peaked, and 7200~7300 tuned for flight.
On the ground it heats up fairly similarly quick like yours, but in the air I really have to push it to hit 140 deg (like 60 seconds full throttle, towing, climbing steep and low airspeed).

Cat 1

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Thanks for the advise Bert - Its running well and I will just fly it to see what it does - I do have the "skinnier" prop on it - 16X8 but not the wide blade. The wide puts it very close to your numbers..

1967brutus

Try a 16 x 8 Wide or a 16 x 10 narrow, the plane can handle the speed, and supressed RPM lowers engine temperature... (I did not test that with the Boxer, it has had the same prop from the teststand until now) but all other engines remain cooler if I prop heavier).

Also: how much runtime does your engine have in total, and after conversion? From new, 20 hrs is nothing. The rings are seated, but friction still is not at its lowest, Then I have also seen conversions that although broken in on glow fuel, still needed 10 hrs or so to stabilize. Especially when Castor oil was used previously. So chances are it will improve over time.

On the subject of "temperature", some considerations:
Personally, I hold 145 as the absolute limit, I refuse to go hotter than that, and throttle back preferrably at 135, simply because I don't want to risk an engine. I do not have any hard indication (engine damage or other signs) what the REAL limit is, and I most surely want to keep it that way since new engines are harder and harder to get, but I have seen sudden RPM loss around that temperature in the first two fourstroke conversions (.52 and .91, both ASP, both broken in on gas, back then still running 5:1 fuel/oil) and I never went beyond that.
For clarity: Engine Temperature is an indicator for, not a cause of engine damage: Modern oils can do their job easily up to about 180 degrees, Pistons easily survive 250 degrees and exhaust valves even handle 600 degrees or hotter.
It is that last one that is the stinker: Gasoline autoignites at around 400 deg C, under compression even sooner, so that valve can serve as source of ignition. Cooling of the valve happens via metal-to-metal contact between valve and seat, and THAT is why CHT is important. As long as CHT is within limits, not only will the rest of the engine most definitely be OK, but it means that the exhaust valve won't cause pre-ignition. And pre-ignition is the killer, causing thermal runaway of all parts forming the combustion chamber.

I have tried all kinds of "cooling mods", some worked, most didn't It is most definitely possible but the difference between working solutions and non-functional ones really are very small.
Saito's in general handle things much better on account of their construction (cylinder and head in one single casting, dissipating heat away from the head way better).
Although I do not have any experience, I would expect the Enya AAC construction to also perform better due to the liner being Aluminium. The steel liners of ringed conventional engines forms a heat barrier. It has little use trying to cool the engine better, focus on cooling the head.
A "cooling plate" between rockercover and head helps to a certain extent, but no miracles should be expected and results vary with the aerodynamic shape of that plate. Internal control of the airflow under the cowl also has marginal effects, but in combination, they can give unexpected results that can really be surprising.
Just as an example: The .91 was always a bit of a "heat challenged" engine, and there was not much difference between running the cowl or not.
When I cowled the engine, I attempted to direct the air entering the cowl as efficient as possible towards the cooling fins. This basically did nothing. That air guiding was mounted to the motor mount, and had a gap of maybe 2 or 3 mm between itself and the cowl for ease of removal of the cowl. No difference noticable in cooling effect.


I fitted a cooling plate between head and rockercover, that did "something" (it was measurable but nowhere near significant.

I closed the gap between cowl and air baffle, this did "something" but similar to the cooling plate, barely measurable.

Then I folded the cooling plate a tiny little bit outward and DANG.... THAT made a huge difference. I have had it at WOT for 1,5 minute and not hit the temperature alarm,

What I am trying to say, is that optimizing cooling most definitely is possible, even with our "undercooled, designed for glowfuel" engines, but the devil is in the details. Large mods and high time-consuming constructions can appear to be virtually without effect, tiny changes suh as that fold can make all the pieces of the puzzle fall into place.
What I think happened was that I focused on getting air to the engine, instead of getting air AWAY from the engine. In hindsight, the same thing occurred when I baffled the radial in the FockeWulf.
The baffling, and the cooling plates did "something" but the gamechanger was the spoiler in front of the air-exit, creating a low pressure area promoting air extraction.

Raleighcopter

Hey Bert, I'm not sure if you're aware but air conditioning cooling coil fins have a sinusoidal or a triangular section to them to increase heat transfer. More bends in your cooling plate should help with cooling.

Also, I've been goofing around with led tubes (from china) and 3d printing and have these 6" 7 segment displays that would probably make an awesome tach display for motor testing videos...

Cat 1

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Dave - Cant wait to see that clock (or Tach).. .

Got out flying tonite and as Bert predicted things are different in the air - I am still seeing the hotter cylinder 1 than 2 but only about 15 deg C at max diff.(full throttle) Most of the time they are quite close. Ambitent temp was a balmy (for spring in Canada) 28C. I could get 145C only after a long push of full throttle (+1 minute). On my "typical" flying with lots of twists and turns and vertical I rarely saw 140. Engine was running great tonite and club members out all loved the sound.. RPM telemetry verified that the "skinny" prop is not enough bite as its getting close to the "danger zone" on wind up low passes . I like how it preforms on this smaller one but don't want rods sticking out of the block..

I did find one anomaly that I didn't notice last time - After a long vertical pull and a throttle back after a hammerhead - the engine goes very rich (as expected with tank pressure decay delay) but tonite a couple of times it actually cut out - it did coast though and relight on all but one of the occasions but one time I really pushed the issue and it went dead stick. Will play with a few settings (no shortage on this setup ) to see if I can minimize this one.. other than that it ran great.

Chris

1967brutus

Yeah, they do, but that has to do with the tendency of airflow in evaporator coils to straighten out and become laminar if those fins would be flat...
It does not do much in the violent turbulence of a propwash. I messed around with that in my helicopter days, where those separate headsinks could be oriented any odd way. Did not make any measurable difference.
I also figured out that if you drill holes in the fins, the diameter being equal to the fin thickness,you actually add surface area to the fins, because the bore wall has twice as much area as the fin area drilled away. So I had a blast with the drill press and drilled oh, I don't know, something like 200 holes, adding about 15% of additional surface, but whaddayaknow, it did not do anything, because the air in those holes remains stagnant... Dang that "small scale of things"...

Basically, adding surface does "something, sometimes". increasing effective airflow works LOTS better.
Baffling (bulkhead with a silhouette cut-out) works, poorly! It only forces air through the fins at the location of the baffle. Tunneling works way better, and the closer to the fins, the better, as long as you can make sure the air has no other way than to pass through that tunnel.
What I did with my radial worked remarkably well, improving cooling a huge deal while at the same time reducing drag of the plane, increasing airspeed (and thus cooling air flow), but radials in general are fairly easy to "tunnel" due to the fact that the pushrods are in front of the cylinder. The Boxer is difficult to tunnel because of the placement of the rods and how that affects possibilities to really tunnel it in tight.. .

1967brutus

Those numbers at that ambient temperature really sounds quite good. It also means your engine is pretty well broken in.
A slightly heavier prop and I'd say you really are good to go.
The hammerhead thing, I think that is something that basically approaches the limits of the working principle, and I don't think it has to do much with your "forced tank pressurizing".
I have long since adopted the habit of reducing throttle to about half a second or so before kicking it over with rudder, and pulling it back all the way about when the fuse has turned 90 degrees, because my set-ups also have that tendency a bit. Reducing power at the end of the upline, maintaining a bit of rudder pressure but letting the tank pressure bleed off in part while still in nose-up attitude allows the system to bleed off the pressure before the fuel in the tank closes off the tank vent (which prolongs the duration of bleeding off that pressure). Unless you can find settings that manage to recognize the specific situation of an upcoming hammerhead, I would just pull back on the throttle a little bit earlier. It shortens the upline by a marginal bit, but IMHO the turn at the top is executed a bit smoother and nicer to the eye too...

I guess, at these small scales we simply cannot have it all...

John_M_

Cat, use a little bar keepers friend on the valve seat / faces and burnish the valve seats in... they leak from new, or at least mine did, just from rough machined surfaces... Blacken the seat and valve faces with a sharpie pen and then burnish them with the bkf... compression loss past the piston on a single ringed piston is common when the engine is turned over slowly... due to variations in ring tension and fit, you'll get some leakage... with a wet cylinder, and rpm the dynamic compression is what counts.

Next time you take the engine down blacken the cylinder walls and piston ring faces, then work the pistons in the cylinder... they're not perfectly mated, and take quite a number of run hours to get those rings to seat... those cylinder sleeves in the boxer are hardened, and being a single ring take a long while to bed in.

Glowgeek

Bar Keepers Friend, nice recommendation. I hadn't thought to use it. I use 3M Perfect-it ll, a final polishing coumpound for show car finishes. When lapping with light pressure It doesn't remove metal, just carbon and dried fuel components.

Saito's rings are interesting. Unlike OS, they leave radial grinding marks on the outside of the rings for faster break in......I guess? After a gallon or so of fuel burned the compression is usually rock hard, taking over 30 sec to bleed off cylinder pressure when held against the compression stroke. Of course Saito cylinders are also very close to perfectly round from the factory, which doesn't hurt either. At any rate it's easy to tell how much run time Saito rings have on them by examining the remaining grinding marks, if any.

I have been using Bowman rings as replacements on 4 strokes for a while now. They break in even faster than Saito or OS rings. Byorn at Bowman/RMJ claims that his rings are fabricated from a softer cast iron and use less tension than other factory 4 stroke rings. I like them a lot.

John_M_

Saito cylinders being made from one piece aluminum alloy with no sleeve, then hard chrome plated, they need to be honed true, as there is very little wear on the cylinder walls, those radial marks on the ring face carries oil to help lubricate the ring as it gets pressed into the cylinder wall from combustion pressures, prevents galling of the cylinder wall during the bed in process... they incorporate a lot of design / manufacturing processes from the auto industry... for the most part they are a well designed and manufactured engine... I just dislike their integral valve seat design.

OS's rings are hard; that and with the hardened sleeve, takes a long time to bed in... not suprised, bowmen's process for making rings surpasses most model engine rings mfg'ers, they have tighter tolerances and fit the cylinder more precisely, which requires less bed in time... and like you mentioned they use ductile iron, properly tempered.

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As I mentioned I did do a leak down and found a leaky exhaust valve and got that almost cured - Under relatively low leak down pressure (30ish psi) at TDC there was not much blow-by as evidenced at the case vent - A bit more on the rest of the stroke but I suspect dynamic compression is OK. And that's why it runs good. This was the side I did make a ring for (which helped a bit - old one had excessive gap) but I suspect a good set of rings would help even things out - The bore looks pristine but haven't checked for out of round.
Cylinder leakage is a odd dynamic - In my past have done 100's of leak downs on TIO-540's in a legacy fleet of Piper Navaho's and Chieftains and it was always a mystery why some would show signs of power issues with "limited" sealing issues and other could have terrible cylinders and still run fine.. we tended to lose cylinders at about 1500 hours (on an 1800 hour TBO) especially on the 350HP version. Probably had to to with the turbo and control system with some being able (and set) to just "jam more in" on some engines. I miss running Turbo'ed Flat sixes. It always made me smile and gave me goosebumps when the Boost would start rolling in - they make quite a beautiful sound!!!

John_M_

Blowby can rob performance for sure... dependant on how effective crankcase ventilation is managed... scavaging the crankcase; putting the crankcase under a vacuum is the best solution for best performance... I remember several occasions where the valve covers blew off, and crank seals blown out due to excessive blowby, just from one cylinder top ring failure.

I've seen some badly scored cylinders with poor compression leak down tests, but when running seal with very little blowby, and they have been running that way for many miles.

Cat 1

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Received the Enya 46-4C that I mentioned a while back - Its an older version and does not have the AAC construction that was mentioned before, Just conventional ringed piston in a steel sleeve. Very neat design. I have always had a soft spot for Enya's as my first RC "ride" was Enya .09 Powered.

Put it on the stand and did a quick test on glow - Having second thoughts on a conversion as it runs very well and is well behaved on glow. Has a very unique carb design (air bleed idle) that has a Choke function that operates by pulling the barrel out (linear) - it "Resets" the fuel slot and allows a large passage to the bore for priming - Very effective. I read they like smaller props than a typical 4C and this proved out - Spun a 10-7 at 11,700... Very smooth runner also.

Will have to think on this one for a while..

Glowgeek

Indeed, that Enya runs great on methanol. Personally I've never seen the advatages to converting engines smaller than 1.2 cu. in. to gas. Just me though, it's a hobby, to each their own.

1967brutus

One or two engines on their own, fully agree. That makes very little sense, especially the tiny ones from an economical POV. But what does make sense, is having ALL engines run on the same fuel. No more different fuels to bring along, no more big and heavy fieldboxes.

I remember back in the days when still flying glow, bringing 2 or 3 different fuels to the field depending on which set of models I brought. Then I would need a 30 lbs fieldbox containing 1 3/4 gallong of fuel, batteries, starters, tools, rags, cleaning stuff, spare plugs and what not..
Now I bring a tiny 5 lbs shoebox sized toolbox, one can (1/2 gallon) of fuel regardless of which planes I bring, and a small pack of wet wipes. No rags or cleaning agents. Simply because everything now runs on the same fuel.

That makes sense.

Cat 1

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I would tend to agree with this from a practical standpoint Lonnie but part of my "hobby" is playing with engines.. Sometimes I do have trouble balancing the "playing with engines" with the "getting out and flying". I need to retire so I can direct more at both.

That does make great sense Bert. I am planning a Fun Fly upcoming and if I bring all the planes I would want, I would be toting 4 different fuels... that's a Pain... My 10-1 gas setup is cute, simple and compact.

Glowgeek

Makes sense to not have to carry so many different fuels. Tinkering IS fun.

1967brutus

Are you sure we are not related? That sounds like me...

I figured that out fairly quickly, when I did the first gasser conversion (a .50 heli).
I had a trailer to transport my stuff to the field, and it did not really matter whether I brought only the methanol heli's or the big (2 metre rotor, 24 lbs) scale gassers, I always needed that trailer because of all the stuff I brought.
Then that ,50 came along, and I noticed that I could hold ALL that I needed in the trunk of my tiny Opel Corsa...

Cat 1

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...I'm in the final stages of Putting together a 1/3 scale CAP 232 (Eagle 580) -DA100 - 40oz fuel tank and a 32 oz smoke tank.. Not going to the field with 2 litres of fuel with that setup Im not even sure its going to fit in my truck :0

And Yes - We might be related - Im just waiting for the DNA family tree site to link us up - Its linked me up to half of the rest of the people on the planet

Rcplanedan

I normally run 2 planes anytime i go fly..
having one glow and the other gas is not much bother to deal with, i use the same fuel pump on both,so far so good,but would rather just deal with gas only if i can,well i only have 3 glow engines anyway...running out of glow fuel in a week or 2 so i better finish my conversion on 2 of them engines( asp fs91s )
and the other is a asp fs61 which i wont bother converting, glow fuel is $60 5lt and 95 gas is roughly $10 5lt + $30 per litre of my preferred 2 strole oil..much cheaper..and i just pump out the fuel i need from motorcycle when i want to fly and add oil,,

So lately i have been flying biplanes with saito 3 cylinder radial,s ,its now time to get the gas convertted magnum160 boxer out and finish what i started,
so i got me a seagull models super decathlon in blue and white ,i will be getting it all on the bench tomorrow and start assembly, i have to decide on what servos i should go with for this plane

Rcplanedan

Engine is just screwed on by one existing bolt on the plane,,is sitting off to one side and up a little..well i didn't think about spark plug caps, i will have to cut the owl for them and also the rocker covers, i knew that much

Rcplanedan

well the is bolted in place, required 30mm stand offs,that i put between engine and the mount, looks neat

Cat 1

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I bet that engine will be a good fit Dan.. It Looks the Part

Rcplanedan

Most definitely is a great fit chris,
and a easy fit for the fuel tank to sit right where its needed, so the engine will not have flooding issues

1967brutus

Yup... With those twins, you really want to be able to lower the tank to about HS needle level. In flight, a high tank (2 or 3 inches) is no real issue, but it is on the ground, with stopped engine, where that becomes problematic...