SKY DYNAMICS
MAXI-SUMP SYSTEM

 
   In the early 1980's the Maxi-Sump system was introduced to the world of aerobatics. Since then, many hours of dyno testing and thousands of hours of field testing have been accomplished. The Maxi-Sump system has been used throughout the world competitively and helped secure the World Championship for the United States.
 
   With the introduction of the higher horsepower Lycomings to aerobatics, there came a need for lighter components and improved oiling systems. In recent years, the very popular 180 hp Lycoming has been replaced with the later 200 hp version. Competitors looking for increased performance have opted for the extra 20 hp but have paid a weight penalty to do so, approximately 20 lbs. Most of this weight increase is due to the 200 hp intake and oil sump assembly. Recognizing this, we developed a new cast sump with a separate intake system to replace the stock Lycoming components. This magnesium sump contributes to a weight savings of approximately 8 lbs. This savings makes the selection of the 200 hp even more attractive for our aerobatic airplanes.
 
   As well as the lighter weight being beneficial, we thought from the onset that the most important design criterium was to improve the oiling system. Numerous features were designed into the unit, the first being a small, confined bottom as opposed to the large floor area of the stock Lycoming. This means that one quart of oil in the Maxi-Sump raises oil level 1.25" instead of .25" in the stock sump. This important feature helps when going from negative to positive maneuvers by allowing drainback oil to submerge the oil pickup sooner. In addition to the small bottom, a unique swinging oil pickup is available for much improved knife-edge oiling. This pickup, which swings approximately 3 in. either side of center, will help maintain oil pressure for longer periods. these two features allow for lower oil quantities for additional weight savings.
 
   On the bottom side of the Maxi-Sump, cooling fins are an integral part of the unit. Internally there are cast fingers that help transmit oil heat to the fins for better cooling.

 
   It becomes apparent that certain performance parameters will be enhanced by utilizing a better oil system, i.e., longevity, cooling, lower quantities for less weight, and, in most cases, eliminating the oil accumulator for constant speed equipped airplanes.
 
   The second part of the Maxi-Sump system is the induction manifold. Our intake is separate from the oil sump and, as such, does not let the heat of the oil increase the temperature of the inlet air. On a standard Lycoming, as the oil temperature increases, the power level decreases. Pilots flying our system have noticed that the power stays consistent over a full sequence or practice session thus relieving some of the pilot's workload. To complement the intake we have developed a four-into-one (4/1) collector style exhaust system. This type system allows for more evenly matched primary tubes. Many hours of testing have contributed to the best compromise on fit and performance for an exhaust system. It has been our experience that exhaust on the Lycoming engine is one of the most sensitive areas when seeking performance. Items such as tube length and configuration are critical. Testing and experience have shown that short tubes with no bends overscavenge an engine and a lot of raw fuel is swept right out the exhaust on the valve overlap period. For this reason, items such as oversize tubes and cylinder porting must be approached with caution such that they do not become detrimental to performance, i.e., a lot of backpressure is bad, but a little is necessary. For the homebuilder planning to build his own exhaust, dyno testing has shown that 40 in. primary tubes will be close to optimum on most Lycomings. Although the much-publicized crossover is okay for some applications, it certainly doesn't provide for equal length tubes, and unequal length exhaust runners mean unequal power levels among cylinders.
 
   Now for everyone's favorite subject -- horsepower. What happens? We are hesitant to state numbers because we feel too many manufacturers promise unrealistic hp increases without any substantial data for backup. As of this writing, over 400 airplanes are flying the Maxi-Sump system. This adds up to many hours of customer use -- mainly all aerobatic time. The mix is evenly divided between the 180 hp Lycoming and the 200 hp Lycoming. The airplane types are mostly Pitts and Lazar aircraft. These provide the basis for nearly all of our statistics, although we have manufactured systems for the Glasair, Lancair, and RV series aircraft. Aerobatic pilots using the Maxi-Sump system have reported from 6-17 mph increase in cruise speed along with increased vertical performance. Since the induction manifold places the fuel injector in the forward location, it provides a better direct ram air boost. This feature should be beneficial for the new breed of high speed, slippery-type aircraft.
 
 

TEST RESULTS

1. A. IO360A1A 200 hp with stock configuration
    Exhaust - four straight 30" stacks
    Timing - 25 deg BTDC
    At rated power of 2700 rpm
      377 ft-lbs or 193.8 hp
 
  B. Same engine as above with Maxi-Sump system
    Exhaust - 4-into-1 collector
    Timing - 25 deg BTDC
    At rated power of 2700 rpm
      408 ft-lbs or 209.7 hp
 
2. A. IO360A1A converted to IO360D1A with 10-to-1 compression
    Exhaust - four straight 30" stacks
    Timing - 20 deg BTDC
    At rated power of 2700 rpm
      390 ft-lbs or 200.5 hp
 
  B. Same engine as above with Maxi-Sump system
    Exhaust - 4-into-1 collector
    Timing - 20 deg BTDC
    At rated power of 2700 rpm
      419 ft-lbs or 215.4 hp
 
Comments: The actual scale readings should not be treated as absolutes but merely to illustrate the relative differences between engine combinations. Horsepower readings will vary with altitude and ambient conditions.
 
    Our test stand is set up to measure torque readings and actual axial thrust. We treat the engine and propeller as a prime mover and measure the total combination as a performance package. As a matter of interest, the thrust from the above combinations varies from approx. 645 lbs to 680 lbs depending on settings, engine combinations, etc.