 The MOKI 1.80 by Clarence LeeNow that the political barriers around the old Soviet Union and the Eastern block countries have began to fall and stringent exportation rules relaxed, quite a few of the engines popular in Europe but produced behind the "Iron Curtain" are now being imported into the U.S. Such is the case with the Moki engine line.
Produced in Budapest, Hungary, the Moki engines have been in production now for over 30 years with only a few making their way into the U.S., having more or less being smuggled in by visiting friends or relatives.
The Moki engines have always been noted for their excellent quality, especially for a former Iron Curtain country, their high power output, and a long life expectancy if given the proper care and treatment. The Moki engines were first brought into the U.S. in quantity by Davis Diesel Development/Model Products and first gained major recognition when Bill Hempel, Jr. took the lst place Gold Trophy at the Ist Giant Scale "Reno" style Unlimited Air Races held at Madera, CA in 1991 using two Moki 180s in his A-26 pylon racer.
In 1993, Jim Gerard of Gerard Enterpfises, was appointed the new exclusive U.S. importer. The first Moki engine we reviewed was the Moki 150 in the March '92 issue and we were quite surprised at the overall quality of the engine and the power it developed, in some cases actually surpassing some of the larger displacement size engines in its class such as the Super Tigre 3000 and OPS Maxi-30, both with 1.8 cu. in. displacement and even the O.S. Max BGX- I with 2.1 cu. in. displacement. Even so, the Moki people quickly followed the 150 with a larger bore 180 (1.8 cu. in.) engine, giving them a definite edge power-wise over the competition.
Basically, what we have with the Moki 180 is an increased bore 150 with the 150's bore having been increased 3mm from 32mm to 35mm or 0.118" with both engines sharing the same crankshaft, bearings, connecting rod, front housing, backplate, carburetor, and related prop drive parts. If a person happened to have the machining facilities, a 150 could be easily converted to a 180 by boring out the crankcase to accept the 180 piston/sleeve assembly. The only other parts required would be the 180 wrist pin and head. Those who may have read our review of the Moki 150 a little over four years ago will find our present review of the Moki 180 a little repetitious, so bear in mind that there are only so many ways of describing the various engine parts, especially when they are identical.
|
PartsCrankcase:
The crankcase would appear to be an investment casting composed of a onepiece center block with removable front housing and backcover. The machine work is well above average and some of the best I have seen coming from a former Iron Curtain country. Due to the quality of the machined surfaces, no gaskets are used between the crankcase. the front housing. and backcover, depending on the fit of the machined surfaces for crankcase sealing Some of our older readers may remember that the post WWII Dooling and McCoys had this feature. i.e., depending on the machined surfaces for crankcase sealing without the use of paper gaskets.
Crankshaft And Bearings:
The monstrous crankshaft has been machined in one piece from bar stock steel, hardened, and finish ground on all bearing surfaces including the crank pin - always a desirable feature. The finish grinding has been performed by the "old world" on centers technique which means the crankshaft is supported at both the front and back ends during the grinding operation which results in both bearing surfaces and the main journal being dead true with each other. Most modem day grinding shops use "centerless" grinding where the crankshaft is free to float, and although still quite accurate, is still not up tothe precision of "on centers" grinding. Most model engine manufacturers use the centerless grinding process, due to being both faster and less expensive.
The counterbalance is of the constant thickness design, cut away on either side of the crank pin for counterbalance action. The counterbalance would balance out the full weight of the con rod and wrist pin but no part of the piston's weight. This would seem a little on the light side, but the engine was very smooth vibration-wise, one of the smoothest if not the smoothest engine in this displacement size we have tested.
The crankshaft is supported by a giant 42mm (1.654") o.d. x 25mm (.984") i.d. steel caged ball bearing at the rear and a 28mm (I. 102") o.d. x 12mm (.472") i.d. steel caged, unshielded bearing at the front. Unusual is a 2mm (.079") reduction in the main journal diameter directly ahead of the rear bearing seat. Normally, the main journal is reduced only a few thousandths smaller than the rear bearing i.d. in order to facilitate installation of the bearing, i.e., it does not have to be pressed the full length of the crankshaft journal. Why Moki has used such a large journal reduction could only be answered by those who designed the engine.
The crankshaft intake port was timed to open 42o after BDC and close 61' afterTDC for an open duration of 199'. The closing timing was actually 2' earlier than the 150 we reviewed, but even so, could be considered rather late for the engine's intended operating range, however, this would also account for the engine developing its maximum horsepower at higher rpm with smaller prop sizes if one should want to go that route as did Bill Hempel, Jr.
Normally, with later closing timing, you can expect a tendencv for an engine to kick back and fire up backwards during starting and some fuel blow-back out the carburetor at idle, but we found the engine to be very easily hand started and no particular problem with carburetor blow-back that could affect the idle and acceleration as will be seen in the performance section.
Piston, Sleeve, And Rod:
The piston has been machined from an aluminum casting and is used in conjunction with a single .042" wide expansion type ring that has been pinned to prevent rotation and runs in a steel sleeve that has been hard chrome plated. Whereas the 150 we reviewed had a slightly "domed" piston head. the 180 has been machined flat. A full floating 8mm (.315") diameter. hardened steel, tubular wrist pin is retained in the piston by wire snap rings at either end.
Due to the high silicon content of the aluminum piston, no bronze bushings are used for the wrist pin holes. A modified version of Schnuerle porting is utilized with two transfer ports on either side of the divided exhaust port. The two transfer ports closest to the exhaust are aimed sliehtly upwards and to the rear. The rear two ports are aimed steeply upward and to the rear with no boost port opposite the exhaust. All four transfer ports were timed to open 58o before BDC and close 58' after BDC for an open duration of 116'. This was actually 4' less than the 150's 120' duration. The exhaust was timed to open 75' before BDC and close 75' after BDC for an open duration of 150' - 2' longer than the previously tested 150. This was obviously intentional and not just a variance in tolerance as the exhaust ports were also .006" taller, i.e., .358" versus .352".
The really hefty con rod has been machined from bar stock aluminum and bronze bushed at both the crank pin and wrist pin ends; another very desirable feature we like to see. A slot cut in the bottom of the crank pin end and a hole drilled in the top of the wrist pin end provides lubrication.
Cylinder Head:
The deeply finned one-piece head has been machined from bar stock aluminum and utilizes a.340" deep x .980" wide semi-hemispherical combustion chamber surrounded by a. .198" wide squish band angled at approximately 8'. The combustion chamber bowl has actually the same dimensions as the 150, but the squish band width has been increased to accommodate the increase in bore size. The measured combustion chamber volume was 3.25cc which computes to a compression ratio of 7.48:1 measured with the closing of the .358" high exhaust ports. Right in the ball park for a sport type engine and somewhat higher than the 150's 6.72:1 which could be considered a little on the low side.
Carburetor:
The Moki carburetor is a completely original design and not a clone of the 2-needle, rotating barrel type originated by Super Tigre that many of the model engine manufacturers are using nowadays. The carburetor is of the rotating barrel, fuel metering type utilizing a 10mm (.394") intake. The principle of operation is similar to that of the Perry carburetor in that a tapering slot in the stepped down shoulder of the rotating barrel aligns with a hole in the aluminum reservoir disc. Rotationof the barrel increases or decreases the length and width of the tapering slot, in turn, regulating the fuel flow to the venturi spraybar. A modification has been made to the positioning of the needle valve assembly in that it is now mounted horizontally and to the rear rather than vertically and to the rear as was the 150 carburetor. A positive barrel stop screw is used for setting the idle speed which we always like to see. Due to many fellows backing out the idle speed screw and setting the idle speed with the transmitter stick position and then using the idle trim to kill the engine after a flight, many engine manufacturers are now omitting the positive idle adjustment screw. Using the transmitter to set the idle speed can often result in servo "over- shoot" if the throttle is closed rapidly killina the engine, trying to idle the engine too slowly, etc. A lot of idle problems, especially unexplained dying of the engine at idle in the air can be attributed to using the transmitter rather than the carburetor to set the idle speed. In operation, the carburetor performed flawlessly with a beautiful tick-over idle and almost instant acceleration.
|
PerformanceOur review engine was supplied with a "Bisson" sport muffler; however, this muffler is optional equipment and not included with the engine. The Bisson sport mufflers, one of many models made, are manufactured in Canada, with Gerard Enterprises handling distribution in the U.S. A complete line of different types for all of the more popular makes of engines are available from Gerard Enterprises. These are well constructed mufflers that effectively lower the sound level with a minimum of power loss. Jim also has Mac's Products headers and tuned pipes available for the Moki engines as well as J'TEC "in cowl" manifolds. The Bisson muffler was installed on the engine for our testing. Something that always wins points was the inclusion of a Moki idle bar glow plug with the engine. It is my opinion that all engines should come equipped with a glow plug although many do not.
The recommended break-in fuel is 80% methanol and 20% castor oil (FAI) and the instructions specify that at no time should straight synthetic oil be used in the engine.
After the break-in, a mixture of castor/syn- thetic may be used as well as 5%-10% nitromethane, although the engine will run fine on no nitro fuel. At no time should less than 15% lubrication be used, which should be part castor, and then, only after the engine is completely broken in. We gave the engine our standard 30 minute break-in period with the FAI fuel and then switched to 10% castor, IO% Klotz KL-200, 5% nitromethane, and balance methanol for the testino - the same fuel used when testing the Moki 150. The Temperature of the day was a little cool at 65'F, the Humidity a little high at 50%, and the Barometric Pressure 29.98 inches of Mercury. All propellers were Zingers. For comparison purposes we are also including the power figures for the Moki I50.
| | Moki 180 | | Moki 150 | | 16 x 8 | 10,000 | 16 x 8 | 9,350 | | 18 x 6 | 9,100 | 18 x 6 | 8,400 | | 18 x 8 | 8,650 | 18 x 8 | 7,950 | |
| 18 x 10 | 7,800 | 18 x 10 | 7,700 | | 20 x 8 | 7,700 | 20 x 8 | 7,600 | | 20 x 10 | 6,400 | 20x 10 | ------- |
As can be seen by the preceding figures. the Moki 180 was only 100 rpm stronger with the 18 x 10 and 20 x 8 than the Moki 150. However. with the more practical prop sizes that would normally be used, the engine really showed the displacement increase turning as much as 700 rpm stronger with the 18 x 8 which is the recommended prop size for the engine. We were a little surprised at the small low end gain, but several factors enter the picture here. First, as you raise the exhaust port height and lengthen the exhaust duration, you also raise the engine's peaking speed where it develops its maximum horse- power at the expense of low end grunt.
Althouch the 180's exhaust duration increase was quite small, it obviously had an effect. Second, the 150 was tested with a Davis Soundmaster muffler and the I 80 with the Bisson muffler. Possibly the Davis muffler had a slight turning effect at lower rpm, and the Bisson at higher rpm. Whatever the case. the Moki 180 is a strong running engine. 'Me overall handling was beautiful with easy hand starts and no nasty tendencies. At no time did we use an electric starter, with the engine always fifing up in one or two flips of the prop following prop changes, idle check- ing. etc. The engine would hold a remarkable 1,450 rpm idle with the 18" prop sizes and we had it ticking over at 1,350 rpm with the 20 x 10 with almost instant acceleration. We were particularly impressed with the engine's smoothness - smoother than many 60/61 displacement size engines we have tested-
The engine carries a $532.00 retail price tag, but as we all know, few things actually sell for full retail nowadays. I should expect to see the mail order houses and larger discount hobbv shops selling the engine in the $325.00 range or even lower. A real bargain price for an engine of this displacement size, quality, and power.
|
