So, Why Not Stick With Rotax?
Why take a chance with any new brand, even if it is a Japanese engine? Why not stick with a familiar brand name?
HPower’s Tom Peghiny relates airshow conversations with a wide range of sport aviators, not only ultralight pilots. He reports: “Not a single person wanted to compare price or weight with the Rotax 582, against which the HKS engine competes. In fact,” he adds, “they overwhelmingly said simply, ‘Thanks!’ for offering an alternative.”
A few good reasons explain why the 700E may represent a better value than the 582. On the face of it, a ready-to-fly 582 will run about $5,400 retail, while the 700E is $6,500 with stainless steel exhaust.
The extra cost comes from the parts count on a 4-stroke engine. More pieces cost more money. And to make these engines last longer, they must be built of components that can endure long operating periods.
However, on the other side of the cost column, the 700E will use half the fuel. In a year of 100 hours flying, you’ll save about 5% ($325) of the purchase price in fuel savings alone. On longer trips, low fuel consumption can increase your range, or you could carry less fuel and shed some weight. For example, a training school might use less than a full tank and pay less to push an airplane into the sky. This may be especially effective when a truly large student shows up for a lesson.
One of the strongest arguments for the 4-stroke 700E surrounds overhaul frequency and cost. A 582 will run about $1,500 to overhaul, with the cost primarily focused on replacing the crankshaft. These pricey service jobs come every 300 hours, and some 2-strokes don’t make it that long.
In contrast, the 700E goes 500 hours – a figure that may rise to 800 with experience, says Peghiny – and will cost less than $800, he estimates. “The 500-hour overhaul will be more inspection than engine work,” he maintains.
Let’s say it runs you $1,500 to overhaul your 582. You should set aside about $5 per hour for overhaul. If the 700E reaches 800 hours, that set-aside is only $1/hour. It won’t take long for that big a difference to become substantial.
Another strength is nickel-ceramic-coated cylinder walls and the oil-cooled heads, which allow the HKS to have little temperature sensitivity – a fact that will be appreciated by many designers who fight cooling problems.
Finally, some pilots think the 582 is lighter. Indeed it is, but the difference is slight after you add similar weights, like the oil tanks and the oil each needs, the radiator and its liquid, or an electric starter and gearbox. Peghiny estimated the weight increase of an installed 700E over the installed 582 to be barely 6 pounds. For most pilots, the gain in reliability alone justifies this small increase in weight.
Want More Horsepower?
First, you ought to be careful about horsepower. Bolting on a larger engine to an aircraft not designed for higher power may not be wise. If 60 horsepower is right according to the designer, using 75 or 80 might be called reckless.
At the Rotax 582 power level, the Austrian engine doesn’t have a lot of competition. “Rotax has no 4-stroke engines under 80 horsepower for pilots who prefer the different advantages of a 4-stroke,” explains Peghiny. Automobile conversions (for example, half-VWs or Subaru kits) aren’t viable solutions for this need, he feels, a situation created by the need for low weight and high power.
Adding too many experimental things at once is something most old-timers avoid. “Many problems are discovered every day in the field; problems that cannot be predicted with lab tests,” opines Peghiny.
In fact, the 700E is an all-new, purpose-designed engine. As HPower partner and technical expert Spark Lamontagne explains, “HKS offers solutions unavailable elsewhere, such as multivalve heads, integral flywheel and prop-speed reduction unit, standard dual electronic ignition and oil cooling for the cylinder heads.”
That said, Peghiny still advises customers wanting more horsepower to consider the Rotax 912. “It’s a proven engine and you aren’t a test pilot,” he says.
700E or Not 700E?
The question boils down to this: How much do you value 4-stroke operation? Many will find the cost difference trivial, and HPower observes that less frequent and much lower-cost overhauls will cover the difference over a period of ownership. Fuel savings will also speed the payback. Lower noise is appreciated by everyone.
Other pilots will reject the 700E as beyond their budget, and fortunately they have other choices. Used engines are also in the universe of possibilities for those trying to keep a lid on expenses.
However, many long-time industry watchers see good potential for the new offering. A number of airframe manufacturers have already been working with HPower and the HKS, including Kolb Aircraft, Harmening’s High Flyers (powered parachutes), Laron Aviation Technologies, Titan Aircraft, HY-TEK Hurricane and others.