Ross Farnham, who posts in the Van's Airforce "alternative engine"
forum (and who if he wasn't a Subie guy would most likely be a regular
on this list); has done quite a bit of testing with the IVO Magnum
"high pitch" version on his RV-6A, turbo Subie. The best "top
speed" (for what that's worth in this day and age) I could find in his data
was at a DA of 17,000 ft. and " 34 inches 5000 rpm, mixture -10%,
181 knots TAS". That really isn't too bad for the price you pay
for an IVO in my opinion. See this link for his IVO testing
information:
http://www.sdsefi.com/rv13.htmI plan on using an IVO on my RV-9A installation since it appears from
Ross's data that it should provide more than adequate climb performance and
will also cruise well in the 150-160 mph range (where I plan on spending
most of my time). An MT would be nice, but the cost is
prohibitive on my budget. Here is a summary of Ross's IVO
conclusions from his web page:
At the 90 hour engine/prop time mark we have some more observations on
the IVO Magnum:
1. We have had no issues with bolts or blades coming loose.
2. The in-flight adjustment works well. We use a 0-20 amp ammeter to
judge blade position.
3. After the first set of brushes laid down carbon on the slip rings,
brush life now exceeds 30 hours between changes
4. Despite having too low a reduction ratio for our airframe,
the Magnum offers good takeoff and climb performance. Medium
speed cruise performance is comparable to other certified aircraft
propellers. High speed performance also seems comparable
although we'd like to have a lower reduction ratio to turn the prop faster
and absorb more hp.
5. Given the speed vs. fuel flow considerations on our turbocharged RV6A,
this prop is matched well and is a viable alternative to expensive constant
speed, certified propellers. A fixed pitch prop on the turbocharged engine
would degrade performance considerably, especially in the takeoff, climb and
high altitude cruise regimes.
6. A slight vibration is set up if the propeller is coarsed out too much
for the flight speed, likely due to the blade being partially stalled.
7. Ambient temperature and altitude (density altitude) affect pitch
angles required for a given hp and rpm.
For takeoff using 38 inches MAP, 4800 engine rpm/ 2182 prop rpm we set
pitch at 3 amps fine of neutral pitch. This is at a hp of around 170, prop
torque is 409 ft./lbs. Density altitude 3500-4500 MSL.
For climb at 35 inches MAP, 4500-4800 engine rpm/ 2045-2182 prop rpm we
set pitch at 2 amps fine to neutral. This is at an IAS of 80-95 knots. Hp is
150-155, torque at prop is about 374 ft./lbs. Density altitude around 6000
MSL.
For cruise at 30 inches MAP, 4200 engine rpm/ 1909 prop rpm we set pitch
at 13 amps coarse. This is at an IAS of 130 knots. HP is around 114, torque
at prop about 314 ft./lbs. Density altitude 11,000 MSL.
We don't run the pitch past 15 amps coarse and figure that this results
in a pitch of 95 to 100 inches.
(note: italics are mine...)
Doug Lomheim
RV-9A; 13B/ FWF