Pistons, Elect. Ignition, LOP, & Metal props

First, who here will admit to accumulating the most hours on their metal prop while running high compression pistons and electronic ignition?

Who has had a failure or big problem with such a set up?

I'm, again, wondering how afraid I should be running greater than 9:1, Lightspeed III on the top, and the Sensenich 72FM. I've accumulated over 200 hrs like this, mostly at 2700 rpm and lean of peak.

My limited understanding is that LOP affects variables such as peak pressure and the crank angle at which peak pressure is produced. So, second, do LOP operations affect prop vibration, resonance, etc?

Thanks in advance for the assistance.

Monte

rv620mr said:

First, who here will admit to accumulating the most hours on their metal prop while running high compression pistons and electronic ignition?

Who has had a failure or big problem with such a set up?

I'm, again, wondering how afraid I should be running greater than 9:1, Lightspeed III on the top, and the Sensenich 72FM. I've accumulated over 200 hrs like this, mostly at 2700 rpm and lean of peak.

My limited understanding is that LOP affects variables such as peak pressure and the crank angle at which peak pressure is produced. So, second, do LOP operations affect prop vibration, resonance, etc?

Thanks in advance for the assistance.

Monte

Click to expand...

This is a touchy subject and I do not have all of the answers or have actually done the million dollar TESTS. This is my settup. IO-360A1B6. This is the counterweighted Lycoming Crank. Pistons are custom made and it is a TRUE 10:5:1 comp after CC-ing combustion chambers, pistons, etc / blueprinted. Slick mags with 22degree ignition timing on top plugs, 20 timing bottom plugs. Hartzell C/S HCM2YR-1BF 7666-A2. My New prop has 470 hours total time. The current engine in my -6 has around 240 hours with the 10:5:1 comp. So the Hartzell has seen 230 hours with the lower 8:7:1 comp engine. Is this approved NO. Hartzell says NO and has not tested it and probably won't. I normally run 2,450rpm in cruise at 75% or less power and 75-100F rich of peek, I don't run this settup LOP because the engine is making a lot less power and you fly slower, can't help or say anything about the LOP, etc.... I studied up on this issue along time ago and a combination like this needs much testing such as: New power setting charts, detonation survey, torsional vibration survey, prop approval / testing and cooling margin in climb survey. I don't have enough flying time to say if the prop is going to fly off my engine or destroy itself. I'm not worried about the engine its the prop. Seat of pants feeling is not like doing the Million dollar scientific tests or studies. But one thing I can say is the combination I'm running now is as smooth or smoother than some 6 cylinders and it is a whole different feeling than when I was using 8:7:1 comp ratio. My prop is coming up on its expiration / calendar to overhaul it and I'm curious to see if there are signs of any damage. Time will tell. I guess that's why they call these things experimentals. Should I be running this combination??? Probably not, but to date I have not heard of any failures or major problems from some of my other buddies running this similar settup. I am not recommending anything here, just passing on the settup that I'm running. I'd also like to hear from anyone else that is running this engine / prop combos. Thanks.