Victor1+ compared to Rotax 447
• Cost about the same
• Dressed weight about the same
• Liquid cooled - Air cooled
• Muffler very quiet -
• Belt reduction - Gear reduction
• Smooth idle below 2000 rpm -
• Dual ignition - Single ignition
• Electric start - Manual start
• Reed valve induction - Piston port induction
• Does not load up at idle -
• Does not like rich mixtures -
• Rated at 48 hp at 6000 rpm - Rated at 40 hp at 6400 rpm
• Broad power band -
• Throttle response is crisp -
• Lightly loaded engine is quite insensitive to EGT variation -
• Manufacturers fuel flow rate data comparison is shown below
• Propeller thrust line higher -
• Recommended rebuild 600 hours - 300 hours
• Recommended decarb 300 hours - 50 hours
• Recommended fuel 87 octane nolead -
• Recommended oil mix (3% oil) or 1:33.3 - 1:50
• For a given horse power setting, uses less oil -
• Total upper end rebuild is less expensive -
• Replace reed valves at 300 hours - No reed valves
• No special tools required for upper end rebuild -

I reworked the latest latest Rotax 447 fuel consumption plot from http://www.rotax-aircraft-engines.com/. I removed the data for the two carburetor version and reworked the gallons per hour scale because what they had on the plot was incorrect. The new gallons per hour scale was calculated from their conversion factor. The blue line is the fuel flow for the Rotax 447 with a propeller mounted on the engine. I plotted the red line for the Victor 1+ with the data taken from the Simonini web site. The Victor 1+ was running a 2.7 to 1 reduction and a 162 cm x 114 cm propeller.

If these data can be taken as true, at the same rpm, the Victor 1+ will burn one half the fuel as the Rotax 447 while putting out more horsepower. For example, the Rotax 447 puts out about 38 hp at 6000 rpm and the Victor 1+ the same at 5200 rpm. The Rotax 447 burns about 4.5 gallons per hour while the Victor 1+ burns about 1.4 gallons per hour, which means the Victor 1+ will burn two thirds less fuel than the Rotax 447 at 38 hp. At this same horsepower setting and using the manufacturers recommended oil to fuel mix, the Victor 1+ will consume 5.4 ounces and the Rotax 447 will consume 11.5 ounces of oil per hour. If the Rotax 447 consumed the same amount of oil per hour, it would be equivalent to a 1:106 oil to fuel ratio.

At the same 38 horse power setting the Victor 1+ will burn a gallon of oil in 23.7 hours and the Rotax 447 consume one gallon in 11.1 hours. If one calculates the fuel/oil saving for 300 hours, the Victor 1+ will use 930 gallons less gasoline and 14 gallons less oil than the Rotax 447. At a modest fuel/oil cost of one dollar a gallon, one would save about $1,000 dollars over the 300 hours.

Since I run the Victor 1+ derated to 38 horse power and assuming that the time before overhaul (tbo) is based on hours at maximum horse power, one can calculate a new tbo based on 38 horse power. Piston ring, piston, and cylinder bore life is dependent upon the sliding motion of the piston and rings along the cylinder wall. At 600 hours and 6000 rpm the piston and rings will move up and down a total of 432,000,000 times. By derating the engine so that it operates at a 5200 rpm maximum and assuming equivalent wear rates, piston ring, piston, and cylinder life will be extended to 692 hours.

Also bearing loads will decrease due to limiting top engine speed to 5200 rpm. Checking in on Timken's web site one can find the following:

As you will see it in the following, there is more than just one bearing life calculation method, but in all cases the bearing life equation is :

L₁₀ = (C / P)^10/3 × (B / n) × a

L₁₀ in hours
C = radial rating of the bearing in lbf or N
P = radial load or dynamic equivalent radial load applied on the
      bearing in lbf or N. The calculation of P depends on the
      method (ISO or Timken) with combined axial and radial
      loading
B = factor dependent on the method ; B = 1.5 × 10⁶ for the Timken
      method (3000 hours at 500 rev/min) and 10⁶ /60 for the ISO method
a = life adjustment factor ; a = 1, when environmental conditions are not considered ;
n = rotational speed in rev/min.

This can be illustrated as follows :

• Doubling load reduces life to one tenth. Reducing load by one half increases life by ten,
• Doubling speed reduces life by one half. Reducing speed by one half doubles life.

But when one reduces engine rpm the connecting rod and wrist pin radial bearing loads (P) to not remain the same, they also decrease. Piston assembly acceleration and deceleration magnitude changes with the rpm squared. By entering in known values and assuming all other factors are constant and taking the ratio of the equations for two different engine speeds gives:

Where:
Life_new = Life_old × (Rpm_old/Rpm_new) × [(Rpm_old>)²/Rpm_new)²]^10/3

Life_old = 600 hours
Rpm_old = 6000
Rpm_new = 5200

Solving this equation indicates that Life_new = 1,797 hours which is almost triple the original tbo.

To reach the current fuel flow values, I had to move away from the Bing carburetor settings listed by Simonini. I found the original needle and jetting to be very EGT peaky at the most desirable engine cruise speed settings. I modified a needle to flatten the EGT over the entire rpm range and then I selected a Bing needle that was closest to the modified needle, and changed needle jets and main jets until this setup performed as well as the modified needle setup.