The new engine
The EOS 100 is a brand new engine made by new start-up from Austria. Check their website for more info here: http://www.eos-engine.com/. The tech specs sound very promising: as powerful as the Polini 100 while lighter than the top80, with clutch and forced cooling.
I have visited their factory in south Austria soon after they launched this engine on market. I have met Roland, the chief designer of the EOS engine and he was very nice and helpful. He obviously knows his stuff but he kept things straight: “Take the engine and test it.”
So I did.
Tech data and features
Single cylinder, two stroke
20.5 HP at 9200 RPM
DLE diaphragm carb with choke
belt redrive 1:3.5
9.8 kg including the rubber mounts
So what is the trick?
I am not a fan of getting a lot of power out a small volume engine through high RPM. There is no scientific reason for that, I only intuitively think that that must be at the expense of durability. But this is not the case of the EOS! The power to cubic volume ratio is almost same as of the TOP80 which is known for its reliability. The Polini thor 100 had the same power out of the same cubic volume as well. And the Poloni Thor 130 just grew larger while keeping parameters proportional. The EOS has pretty neat max RPM, too.
The trick is the weight. The EOS is not smaller, it is just lighter..
Quality and finish
The build quality seems legit.
Nice finish, All CNC machined. Well designed – it is obvious they did a very good job in reducing weight by milling off all unnecessary material.
Some parts look like toys. The DLE carb is much smaller than the Walbro used on Moster. The connector for fuel line looks literally funny – i guess it fits a 4 mm fuel hose. I had to adapt it for 6 mm fuel lines that are standard for paramotors. The pulse hose is sooo tiny. The rubber mounts are half the size of Moster’s. The airbox is ehm… different. The motor is just different. They have engineered everything from scratch without making shortcuts or sticking to common patterns (most engine manufacturers actually use the same Italian pistons and cylinder heads). The EOS pistons are from Japan, the cylinder head from Taiwan, different carb, different airbox, clutch…
These guys did everything to keep the weight low. Getting 20.5 HP from 100ccm is nothing special. But keeping it at 9.8 kg is.
Yes, the engine is very light. Its not just numbers, you can really feel the difference. The SCOUT is light even with the Moster. With the EOS engine even litgher.
Reliability: Obviously, I cannot tell after first flights. Roland claimed having 35 engines operating for more than one year before market launch. Only one hole in a piston until now: a fault fuel bulb caused limited fuel supply and the motor ran lean.
The motor starts easily, even it was cold below freezing point. Easy pull.
Runs smooth. The engine has very low vibrations. Actually this was my concern as the unlucky shape and orientation of the exhaust makes it to come very close to the fuel tank. But the vibrations are minimal and the 2 cm gap is sufficient (could you imagine that on the Moster?). I was afraid of heat possibly damaging the fuel tank but nothing like this happened. The fuel tank remained cold.
Power and throttle response
Numbers are nice, let’s go flying. I took it to fly this morning.
I have tested the motor installed on the SCOUT paramotor with a 124 cm wooden prop that was supplied with the engine. I have flown it with my Ozone Viper 2, size 26. To match the glider’s certification i should probably fly 28, as I am 88 kg naked.
Easy start, easy take-off with about 4 m/s headwind. As measured on my vario:
- climb-out about +1.8 m/s with trimmers down and not touching the brakes,
- +1.2 trimmers up,
- +0.3 trimmers up and full speedbar.
The wooden prop seems to be pretty efficient as there was not much torque. Still, I am looking forward to fly this engine with a 132 cm carbon prop. With props, bigger is better.
The manufacturer claims the motor can be run at full power for infinite time.
They have tested it at full power for 3 hours in a paint-shop heated to 45 degrees Celsius. If so, this would a perfect engine for most pilots, even for the more hungry ones. I did not do this, because the engine is still in the break-in phase and it was deadly cold this morning.
I have tested the EOS with my Slalom 21, too. As expected, the power is not enough. No miracles happen. Take-off was fine, climb rates slightly lower:
- +1,5 m/s at trimmers down and at the first stitching
- +0,8 m/s at the second stitching
- -0,3 m/s at full trimmers all the way up and full speedbar (the Slalom has very long trimmers and is very fast!)
These are no bad numbers at all. But the Slalom is a fun wing and the more power is required in tight turns to get the fun-factor.
Throttle response: I would need more flights to judge on this. On ground the throttle response was instant. In fact, it literaly kicked hard when I pushed the throttle. I forgot to test this in flight, but why should this be different up there? I have tried some low flying and responsiveness to small throttle changes seemed smooth. I will add my thoughts after more flights later.
Fuel consumption was very good: 2 litres in 40 minutes. Most of the time at full power as I was measuring climb rates. This number needs validation after more flights.
Take it or leave it?
Yes, definitely take it.
With all the fame and glory of latest slalom competitions and glider downsizing, we still have to keep in mind that the vast majority of pilots still fly their gliders within the certified weight range. And the 20.5 HP is fair enough. The average pilot flies mostly XC cruises and this engine is just perfect of cross-country flights:
- its the lightest engine on the market and low weight is good when you launch with fuel filled up to the cap
- low fuel burn keeps you airborne longer
- low vibrations make it comfy in flight
Yes, we will be happy to offer the SCOUT with this engine installed. We will need some time to design an optimal 132 cm carbon prop to get even more of this great engine.
Should you have questions, please do not hesitate to ask: +421 907 561 083 or firstname.lastname@example.org
Update after few more flights
The fuel consumption was 3,3 litres per hour with Ozone Viper 2, size 26. I am 88 kg naked.
Engine start easy even at freezing temperatures.
I have to replace the spark plug, as it is not shielded and interferes with radio, PPG meter and SafeStart. Manufacturer has promised to use “R”-type spark plug in future.
The motor runs at slightly higher temperatures, but everything looks good.
Photos from http://www.eos-engine.com: