|IVO MAGNUM IN FLIGHT ADJUSTABLEPROPELLER|
May 05 IVO INSTALLATION
I received the IVO Magnum 68" diameter 3 bladed prop. It looks great! I installed it and all went smoothly. I did a ground run and got 4000 RPM at flat pitch. That was a little disappointing but better than anything else so far. I did 2 high speed taxi runs to 74 kias and it accelerated quite a bit better. I shut down to inspect and get lunch and the engine would not restart. The engine computer said that it was missing a CAM angle sensor. So I spent 10 days checking the electrical system to see what was wrong with it. All those tests indicated it was fine. The manual says 1) check the electrical 2) mechanical problems (rather vague eh?). So I decided to check the compression. It was 115 to 120psi. The Spec is 171-206 psi. So I suspected the timing belt had slipped. I could not confirm this accurately without pulling the engine off. After I did, it was found to be 3 teeth off. I noticed some play in the belt even though the tensioner was still applying force but was not slid to its tightest position. I put on a new belt and tensioner even though there was nothing apparent wrong with the old ones. Now the compression is 195 to 215 psi. This reminded me to compare the readings to those I took when I first installed the engine. Then the compression was 150-160 psi. I thought it was low then because the engine had been setting for 10 years. Now I believe it was because the belt had slipped even back then. It probably slipped one tooth before first flight and another along the way. Then the third 3 weeks ago and that prevented it from starting. I installed the new belt with the tensioner fully tight so I don't think it will slip again.
I got it running Saturday and checked the static RPM with the IVO at it's flattest pitch. Three weeks ago it was 4000 RPM now it is 4500 RPM. There is so much thrust I can not hold it with the brakes! The nose dips down like it never did before. So the RPM increase is only due to the timing improvement. The 4500 PRM is about 900 more than I've seen on any of the other props. So I made 3 taxi runs to 75 kts (rotation speed) and stopped to inspect. All was looking good so I flew it. The acceleration to 75 kias was phenomenal at less than 1000 ft of runway. As I accelerated, the RPM increased to about 5300 at lift off so I pulled the nose up to hold 90 kts and keep from going over 5400 RPM (my personal limit and peak HP). The rate of climb was over 2000 fpm!. I did a few other flights and inspected between each. There is not an issue any more with acceleration or rate of climb. I increased the pitch in cruise. The IVO performed very nicely in manual mode. This weekend was very warm here in SoCAL. It was 82 deg at 4500ft. I could not exceed 18" MAP (that's only about 55% pwr) without hitting my coolant temp limit. So I could not test the high speed end too much. It appears that I have plenty of pitch control to not over speed at the high speed end but don't have good data there yet. Now I need to work the cooling system some more.
Looking back at my data from Flt 27, I see the coolant temp is up 62 deg over that test while the OAT is only up 30 deg. That seems out of line. I did make another change since then. I took 9 sq in out of the 63 sq. in. NACA frontal area and deicated it to the engine inlet using a turning vane. This may have reduced the cooling air by up to 15%. I will remove that vane and see if it goes down 30 deg. I should plan on operating in at least 10 deg hotter days than this flight. If it is 105 on the ground one can expect 90 deg at 5000 ft. So the cooling system needs some definite work. After removing the turning vane, I think my first tact will be to measure the pressure in front of and behind the radiator compared to static and see if I have a good pressure drop. I also want to put some turbulators in front of the oil cooler scoop. While I'm at it I will check out the automatic governor on the IVO.
Well folks, I had a couple of break throughs today. I solved most of my cooling problems and for the first time in exactly one year of flying was able to get it up to full power (available) at 4500 ft. At that point my
coolant was at only 210 deg. This was at 2920 prop RPM and 23.5" MAP (WOT). That works out to 85% power. In this condition I was burning 13.2 GPH and had 170 kias level flight. That's 190 ktas. I'm very pleased considering I know I have a few drag issues to deal with.
Now that I have removed several of the "improvements" I put in here is what I found. That turning vane I put in the NACA to direct part of the air into the engine induction system did effect the cooling. Correcting all data back to the 52 deg OAT day I tested back in Feb, I had been 37 deg hotter after all the "improvements". Removing the turning vane reduced that increase to 29 deg. Today I took out the thermostat and it dropped to only 8 deg hotter than Feb. In the flight yesterday I found that I had a 5 deg difference at the same power when operating at 4900 RPM (engine) as compared to 4300 RPM with 4900 being hotter. I didn't test today at 4300 RPM but those 3 items seem to account for all but 3 deg of the change.
I now have a real operable configuration. I figure I can operate in a 105 deg F day at sea level and still use full power even if that hot day condition persists at altitude. My oil is still too hot. It was up to 250 for the WOT condition. I think I need to redesign that scoop or put turbulators further ahead than I did before.
I also had the prop dynamically balanced. What a dramatic difference!!!! This IVO prop is out of balance more than any of the others that I've tested, but, based on the results, I highly recommend dynamic balancing to everyone. Vibration is commonly measured in inches/sec. That is the peak velocity of the accelerometer as it moves in a sine wave. This prop measured .68 ips vertically on the gearbox before balancing and it was 0.1 ips after. It cost me $150 but it was definitely worth it. It just gives you so much more confidence when it is nice and smooth. People have told me that the IVO would not absorb the HP that my 230 HP Subaru would put out. Well they are wrong. I can easily slow the RPM down to what ever I want at WOT. It seems to run perfectly at 5400 RPM and WOT at 4500 ft! I could not be happier!