- Rotax 503 DCDI two stroke air cooled 50 HP basic new retail price with engine block, carbs, gearbox, exhaust, intake, and propeller $6300 (generic rough comparative estimate)
- Rotax 582 DCDI two stroke water cooled 65 HP basic new retail price with engine block, carbs, gearbox, exhaust, intake, radiator and propeller $8800 (generic rough comparative estimate)
- Rotax 912 four stroke water/air/oil cooled 80 HP basic new retail price with engine block, carbs, gearbox, exhaust, intake, radiator, oil cooler and propeller $20,000
- Rotax 912S four stroke water/air/oil cooled 100 HP basic new retail price with engine block, carbs, gearbox, exhaust, intake, radiator oil cooler and propeller $22,000
- Rotax 912iS four stroke fuel injected water/air/oil cooled 100 HP basic new retail price with engine block, carbs, gearbox, exhaust, intake, radiator oil cooler and propeller $30,000
NOTE: There are a number of other engines used on trikes. However, these are not very common and are listed at the end of this page for reference.
Below is a table that compares the different Rotax engines with the weight of the complete installation and the Cost/HP along with the HP/Weight and the specific fuel consumption.
|Engine Part||503 DCDI||582 DCDI||912UL||912ULS||912iS|
|Air Cleaners weight||.7||.7||.7||.7||.35|
|Water Cooler weight||n/a||2.2||2.2||2.2||2.2|
|Oil Cooler weight||n/a||n/a||1.1||1.1||1.1|
|Cooling fluid weight (est)||n/a||6||6||6||6|
|Overload clutch weight||n/a||n/a||included||included||included|
|Oil sump weight||n/a||n/a||4||4||4|
|Total weight Pounds||116.8||117.2||163.8||166.8||179.5|
|fuel flow at TO power GPH||6.8||7.2||6.3||7.1||6.9|
|Specific fuel consumption at TO Power GPH/HP||.14||.11||.079||.071||.069|
|Fuel flow at 75% power||4.3||4.9||4.3|
|Specific fuel consumption at 75% power GPH/HP||.072||.065||.057|
Determining what engine you purchase is based on some simple factors:
- How much power do you need?
- How much can you spend?
- How important is reliability?
- What about Max Gross Weight?
- How much fuel and oil do they use?
- What about maintenance?
- What other engines besides Rotax are used on trikes?
How much power do you need?
If you want to go fast, carry more weight, or take off on water you need more power.
If you want to go faster, you need more power. Here are some guidelines for speed. We will use HP as the guideline this can apply to any engine. If you want to Cruise at 50 MPH you need a 50 HP engine. If you want to cruise at 65 HP, you need a 65 HP engine. Cruise at 80 MPH – an 80 HP engine. Cruise at 100 MPH a 100 HP engine. It must be understood that this comparison is very general and varies greatly based on weight, wing size, carriage fairing. But it is a starting point to look at engines for speed.
Generally, you need more power to carry more weight. If you weight in at 200 pounds and want to take people your size plus a heavier trike (500 pounds) you should be looking at a 65 HP engine unless you are using a larger wing. However, a 50 HP engine with a 150-pound pilot, 200-pound passenger, lightweight/streamlined trike (400 pounds) will easily climb to 10,000 feet. Again, the overall design of the trike makes a big difference. My first streamlined and lightweight Cosmos Phase 2 with a 16-meter wing, a 50 HP engine equals the climb rate of the bigger less streamlined Airborne with a 65 HP engine.
If you want to be able to take off on water, this takes a higher HP engine. A 65 HP will do it at sea level and a larger wing, but an 80 HP is recommended for a sea trike.
How much can you spend?
OK, now the money. The four-stroke engines are about $10,000 more than a two-stroke to start. Why, the 2 strokes have less metal, much simpler and less moving parts. If you have the $10,000 extra for the four-stroke they have more power, use less gas (3 GPH vs 4 GPH), have a longer time between overhauls (2500 hours versus 300), and are more reliable with average maintenance. The Rotax 100 HP is about $2500 more than the 80 HP and the new fuel injected 912iS is about $10,000 more than the 912 80 HP.
How important is reliability?
It is said that four strokes are more reliable than two strokes. Generally, this is true with average maintenance. However, it must be understood that most engine failures are from bad air/induction and/or bad fuel/starvation. Neither of these is the engine itself.
Yes, the four-stroke, overall is more reliable, but both engines need to get good air, good fuel and good spark as a starting point. The two strokes “run great until they stop”, the four strokes are more tolerant of engine problems and provide more signals before they stop. If reliability is of utmost importance for your operation and you can afford it, the four-stroke is the preferred option.
What about Max Gross Weight?
Note that the four-stroke is about 50 pounds more than the two-stroke. For your trike, this increases the weight of the trike by 50 pounds thus reducing the usable weight by 50 pounds meaning you can carry 50 pounds less fuel, people or baggage.
How much fuel and oil do they use?
Two-stroke use more fuel than four-stroke. The two-stroke does not have as efficient combustion as a four-stroke. From general operating, a 65 HP two-stroke will burn 4 gals/hour while an 80 HP four-stroke will burn about 3 gals/hour (providing significantly more power and more speed). This depends largely on the specific operation but these are general guidelines.
Let’s do an example to look at the fuel burn. Let’s say we have a 12-gallon tank minus reserves. The two-stroke could go on a 12 gallon tank/4 GPH = 3 hours at 60 MPH or 180 miles. Pretty good. The four-stroke can go 12/3 GPM = 4 hours at 70 MPH or 280 miles. WOW, what a difference, an additional hour of flight time and an additional 120 miles. An additional 67% further on a four-stroke.
Additionally, the two-stroke must burn oil for lubrication. At a 50 to 1 ratio this is 1 quart for every 12 gallons of fuel or every 180 miles or 3 hours of flying. At $1.70 for an 8-ounce bottle, this adds about an additional 80 cents per gallon of premix and about 50 per gallon for oil injection. For a long cross country flight this must be considered. The four-stroke burning autogas must have an oil change every 100 hours or 7000 miles at 3 quarts of oil plus an oil filter is less than 1 cent per mile for oil. Using AVGAS this would be an oil change every 25 hours at about 2 cents per gallon.
What about major maintenance?
The biggest difference between the two and the four-stroke Rotax engine is the major overhaul period. Rotax recommends 300 hours for the two strokes, which is required for the S-LSA (many E-LSA take these to 600 hours), and 2000 hours for a four-stroke. Depending on how much you are flying this could be a factor to consider.
What are some other engines, besides Rotax, used on trikes?
Other engines besides Rotax are not commonly used because the manufacturers are not installing them. Manufacturers like to go with a known and well-proven Rotax brand that they have a history with, but the following is provided for your complete information on trike engines:
- The HKS700E is the most popular to the Rotax being 60 HP and 4 strokes. If you want 4-cycle virtues for less – and are willing to give up some performance – the HKS is the next best thing. Being only 60 HP, it’s not quite a 582 substitute. Besides being a little bit underpowered compared to a 582, the HKS has one drawback: it shakes a lot at idle. The result is that you tend to idle it at 2,000 (which is not really a problem) and that you need an unusually strong motor mount. Suzuki or Geo conversion
- The up and coming Raven Redrives/Suzuki/Geo its line of reduction drive kits for use in light aircraft. Power plants are available for aircraft needing 58 to 115+ horsepower designed around the readily available 1.0 liter and 1.3 liter Geo Metro/ Suzuki auto engines. These are complete engine packages that will be a cost-competitive alternative to the Rotax 503, 582, 912, 912S and 914 power-plants.
- Hirth two strokes ranging in power from 28 HP for ultralights to 110 HP for LSA.
- Verner has a JCV-360, 35hp (used by Northwing for their 103 trike) and a VM-133MK, 80hp both 4 strokes.
- Compact Radial engines MZ 34 is used as an ultralight and MZ202 (60hp) comes complete with gearbox and electric start.
- Kawasaki has a 340 or 440 used on some trikes.
- Bailey V4 200 (a nice little 4-stroke) is used by Airborne for their 103 trike
- Briggs and Stratton has 38hp and 50hp engines.
All these alternative engines are used on trikes but the industry standard is the Rotax.