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Engine Test

Engine Test: Enya 61 CSX PRO

I have purchased this new Enya engine through Alberto Parra in Las Palmas (cheap and easy way to purchase this Engine in Europe) and bench tested and flight tested this motor.

On the bench I used the stock muffler with the internal baffle. I ran several tanks with an Eather 2-blade 11.5x5 UC carbon prop which is my standard prop with my ST-51's. In direct comparison with the ST-51 this Enya turned this prop at 9,800 rpm vs. 9,500 rpm with the ST-51. This was in fast 4-cycle mode like I would set it on the ground before launching the plane. Thus, the Enya seems to be a little stronger than my ST-51. Both engines have 7.5mm venturies and expansion type mufflers with a short silicon deflector and ran with 5% Nitro all synthetic fuel for the bench test.

In my big Grondal the Enya behaved much differently. With stock muffler and same prop the flying speed was too slow although the engine ran in fast 4-cycle. I removed the internal baffle from the stock muffler but it didn't improve the situation. I was disappointed first.

I then installed another muffler made from simple aluminium tube with 25mm internal diameter and 125 mm length. Due to the unusual mounting hole dimensions no standard mufflers fits and I had to machine this muffler myself. The exhaust tube is 9mm internal diameter. I connected a short silicon deflector.

I also put on an Eather 13x5 UC 2-blade prop and set 8,600 rpm on ground in slow 2-cycle.

Once in the air the engine ran very nice in fast 4 cycle and switches into 2-cycle in the overheads. Flying speed was 5,2 sec/lap. Because the engine is fairly new and I used all synthetic fuel the motor had problems going immediately back into 4-cycle in the diving parts of each manouvre. I hope this improves with run time. If not I will try half castor, half synthetic because castor cools the engine better. As far as I know Henk de Jong uses all castor fuel due to this behaviour.

I tested the stock muffler without baffle again but the power was lost again although muffler volume and exhaust diameter seemed to be fairly the same. Ergo: I cannot recommend the stock muffler, not even without baffle. Not only is it heavy (100g) but also very loud.

It seems that compared with an ST-51 the Enya is much louder. Many ABC or AAC engines are louder than ringed engines. I remarked the same with my side exhaust RO-Jett BSE 61 or Henk de Jongs Eli Rozenberg AAC 61 engine or Uwe Degner PA-61 on expansion muffler. All have a very distinctive harsh noise that is very different from the sweet noise that the ST-51 or ST-60 produce. I don't mean that ST-51 and ST-60 are less noisy but the subjective noise is different.

To conclude: The muffler seems to be critical with the Enya 61 CXS. It is not this user friendly in this respect as the ST-51 but has lots more torque although the stroke of both engines is the same. This surprised me but since I was looking for an engine capable of swinging a bigger prop I think I have found it.

The Enya uses about 145 ccm of fuel for the pattern which is 30 ccm more than my ST-51's need. As I said, the engine still heats up in outside manouvres and not immediately comes back but I think I can improve this with castor in the fuel and/or more run time.

I am still not this convinced that I would buy immediately a second Enya 61 CSX Pro but the performance is very promising. It starts easily by flipping the prop backwards against top dead center and has a good piston fit and very good compression. What I remarked while choking is that it draws lots of air through either the front bearing or from elsewhere. When closing the venturi and choking you can hear that it draws air from some way (perhaps though the depressurization boring from front bearing to venturi). Once in the air I haven't remarked any problems. The front bearing doesn't leak fuel, the engine stays dry.

The mounting holes are eays to modify to allow putting this engine in planes for the ST-51. The engines weighs one ounce more but this can be accepted.

Hubraum 9.85 cc Gewicht 338 g 

Bohrung 24.8 mm Leistung 1.70 HP 

Hub 20.4 mm RPM 7,500~16,000 rpm 



Maße [mm]


















Christoph Holtermann, 17.10.2007

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