Taking the engine out of the box revealed a very smart looking device, with its deep purple head complimenting the black painted crankcases perfectly. The days of the natural alloy finished engine seem to be receding, given the smartly painted and anodized details that feature on most current engines now. This one looks the absolute business and as invariably on our sports models the engine is always on show, thats no bad thing, but it does remind me of my brother selecting a helicopter starter wand at the Woodspring show this year. His mate, in a very loud voice overheard by the trader and half of his clientele, shouted, useless that its not anodized bringing to mind of course how anorakish heli flyers tend to be about their kit. We plank men are not quite as insistent on having everything anodized, even down to after market transmitter sticks, as indeed are so many heli flyers, but we still like smart equipment and this engine is smart!
Joking aside then and back to the JEN 56, a swift attack with a couple of Allen keys revealed its innermost secrets. As expected, its a Schnuerle ported 40 sized ABC two stroke, except that this ones piston and liner are that bit bigger, upping the capacity to a whopping .56 cubic inches, ie not far short of 10cc capacity. One or two interesting details became evident as I stripped the engine, more about which later, but it all looks well up to current (excellent) Chinese model engine standards with mirror finished satin smooth components throughout. I often get pulled to one side when I bump into fliers who doubt the quality of the Chinese products, despite the fact that so many European and American products have been produced there for years now. In almost every instance I sense a deep misapprehension as I assure them that actually that ABC acme super whizzo forty is rather good and Ive got three of them! There isnt much junk around today in the engine field, given the plain fact that in a global market, you dont achieve success with unreliable rubbish. Boy a few ARTF kit manufacturers learned this lesson the hard way and quality is now improving exponentially in that field too, as it must for market survival. It wasnt always like that of course but you dyed in the wool types that insist buying only German or Japanese cars model engines and radio gear are missing a very big trick. If you need further convincing just take a look at the Kenny Roberts Grand Prix motorcycle teams 200+ MPH Proton which is from Malaya and the Korean car industry isnt messing about either!
Back to those interesting details that I alluded earlier then, beginning with the piston, which for all the world looked like it had a Dykes ring fitted when I peered through the exhaust port, although I knew it couldnt have by the feel of the new unit. In fact the shiny ring around the crown of the piston which looked like a steel band or ring, turned out to be a hard wearing aluminium of a different type to the main body of the piston. I have seen this construction on similar engines very occasionally prior to this one and it will be interesting to see if other manufacturers adopt the principle. Certainly after running in, the piston was completely unmarked, which is actually not the usual way of things with an ABC or ABN engine, where a matt grey ring usually shows that the piston has bedded in successfully. My engine felt absolutely splendid after ten or so minutes running so it was obviously happy, which leads me to think that this engine is going to last a long time in normal use. Other than the unusual piston and the crankshaft which was black rather than bright steel, probably as a result of a hardening procedure during manufacture, the rest of the engine held no surprises. I fully expected to see huge ports in the liner, which is of chrome plated brass construction, but in fact the porting looks quite conservative. A teflon button prevents the gudgeon pin from migrating into the cylinder wall which is good current practice and of proven effectiveness, and a single copper shim seals the head to the cylinder liner.
With my JEN 56 review engine came two of the silencer options and a manifold for a tuned pipe. Just Engines can cater for anything and everything that you can think of regarding silencers and exhaust ancillaries, offering a range of solutions for any model/engine combination that you can think of. Need a short dumpy muffler to go in the cowl of your Ultimate or CAP or perhaps you fancy a hike in performance for that pattern ship in the shape of a tuned pipe? Just Engines will have something for your needs in their comprehensive list of options, catering as they do for all comers in their specialised field.
Putting the engine together, I grabbed my tacho and a bunch of props and made off to the workshop to see if it ran as well as it looked. Just a word here about new engines and running them for the first time, which should be preceded by a sit down with a cup of coffee or whatever whilst you peruse those all important instructions. Instructions and aeromodellers seem not to go hand in hand in my experience, but as Paul Landels at Just Engines has taken the trouble to produce some very useful guidance for you in his documentation, the JEN 56s are worth reading. Pay particular attention to the section on fuels, (rec straight methanol and oil up to 5% nitro content) plugs and running in and unlike me, do NOT under any circumstances be tempted to fiddle with things and take your engine apart. Doing this not only invalidates the warranty, it should never be done with a unit that has been run anyway as fits will be altered, accelerating wear. There is also a useful area describing silencer tuning or adjustment which you will find interesting and of practical worth.
Running in a modern ABC two-stroke in is no longer the chore it used to be due to todays manufacturing tolerances. The CNC machine shop turns out repetitive accuracy and I never bench run my engines when they are destined for the nose of a model, bolting them in place on the firewall from the outset. Any engine is best left in its protective packing until ready to be used in anger in my opinion, so dont buy your engine, bench run it and then pop it back in the box, its pointless and you risk corrosion damage from the outset. Fit your engine to the model and run a tank or two through it as per the instructions, which in the case of an ABC type two stroke like this one, means a tad rich on a small (ish) prop (11 x6/7) for bursts of a minute or two. Punctuated by short cooling down periods, fifteen minutes of this allows you to set the needles and the engine can then be used for flying, remembering that it wont be at its best for a few flights. Use the throttle sympathetically and restrict full power climbs to infinity for a while and you wont have any problems at all. Do bear in mind that the worst thing you can do to a new engine is flog it around flat out on a lean needle setting until the tank runs dry or the poor thing quits.
Upon my return from the workshop, armed with a pile of tachometer figures I sat down to evaluate the JEN 56s overall performance. The engine fired up without fuss from the outset with a simple reverse flick of the propeller and as anticipated, took little running in, responding well to the throttle immediately. It was also more than willing to rev when given its head on a 12 x 4 RAM propeller, which was laughably inadequate to harness its power. Paul at Just Engines suggests propping it for around 11000 RPM on the ground, which will mean something like a 12 x 7 or perhaps an 11 x 8 or 9 in a fast small model, making use of this long stroke engines torque. My unit turned an 11.5 x 7 Bolly glass nylon at a very healthy 11600 RPM with just a few minutes on the clock, so the engine is no slouch and if you want it to lug a bigger airscrew quietly then it will do that too. How many 40 sized engines do you know that will happily swing a 15 inch propeller at nearly 8000 RPM? This JEN 56 pulled an APC 15 x 4 at 7800 without so much as a murmur of protest, although that is well over the top and you wouldnt go that far in reality. You could on the other hand certainly fit a 14 x 4/6 if you wanted to chuff around quietly with the quiet pipe option in a scale model.
The quiet pipe worked very well, despite it being more or less the same physical size as the standard muffler and it really was quiet on part throttle settings. The penalty for this lack of noise was not as high as you might think, with a drop of between two and five hundred RPM depending on the propeller fitted over the standard muffler. The needle valve proved somewhat less tolerant on settings on this pipe but it was not a problem and with a big prop at half throttle the JEN 56 hummed away like an electric motor very civilised indeed. I have not quoted any idle figures as these were as slow as you could wish for on any size propeller allied to an immediate response when the throttle was pegged, just perfect then!
So is the JEN 56 any good?
Well I reckon that you will have worked that out for yourselves by now. Paul Landels worked on this one for a couple of years, optimising the capacity to extract the most energy that he could from a 40 sized unit, with reliability allied to pleasant handling characteristics. In the end, after trying 52 to 57 internals he settled on the 56 this giving the best combination of characteristics, not the least of which was long term reliability. This is going to be a very good 3D aerobatic unit running perhaps a 13 or 14x4 Wide blade APC, which will really give you urge in your lightweight prop hanging 3D fun fly types. Time to go shopping methinks, I need yet another aeroplane!