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I have flown the RV-14A demonstrator on a couple of trips getting equal or better speed/ fuel flow (the tri gear should technically be just slightly slower). It will easily true out at 171-172 Kts at 8.3-8.5 GPH at 9500 ' It has a bare bones stock IO-390. |
Stoney is obviously a talented and well thought out builder, but I have to chime in with Scott. On my way to OSH this year, N914VA had a TAS of 175Kts, 8,500', 10.2 gph at peak EGT. Again, a stock I0-390.
After an enlightening conversation with Scott about LOP operation, I will begin to experiment and see how I can fine tune engine operation. |
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Since I don't have any recent cross country flights, and since my memory isn't what it used to be, I decided to double check my self.......
Here is a post (first post in the thread) from a couple years ago showing that my stated fuel flow was off a little bit but not much. Still good speed vs Fuel flow #'s with a stock engine. http://www.vansairforce.com/communit...d.php?t=119114 |
I have just gone through an engine change on my Rocket. Not an RV but I now have a good comparison of High compression (10:1), and flow matched cylinders to a totally stock lycoming engine.
I had 930 hours on my original engine and had had the ECI cylinders off three times due to ring delimitation. The last time the engine never broke in and after 60 hours of blow by my engine started to make metal. An inspection showed a spalled cam that had been perfect prior to the last cylinder replacement. While tearing the engine down excessive crank bearing wear was evident. Was this caused by the high compression pistons or wear induced by the products of ring blow by? Probably a little of both, I had known that TBO would be reduced using the HC pistons but had hoped for at least 1500 hours not less then 1000. I decided to use brand new stock Lycoming jugs on the rebuild. After 60 plus hours on this rebuild I can say that I have lost 5 knots in cruise and burn about 1 gallon more per hour at rich of peak settings. The ECI jugs did not seem to like LOP operations and the speeds dropped way off to the point that I did not feel there were any real savings in terms of time or fuel with LOP settings. With the new jugs I can run quite nicely LOP and after a few nozzle swaps I have all cylinders peaking within 0.1 gph, a number I have never gotten close to in all my other aircraft. The engine runs very smooth and I am experimenting with increasing power levels running LOP and there is some promise that I am going to get my fuel economy back. I am afraid that that extra 5 knots is gone for good. The engine is broken in and oil consumption was one quart in 30 hours which is quite an amazing difference from the ECI jugs. At the end of the 30 hours the oil still has a gold tinge to it! I have no regrets regarding the HC pistons and the flow balancing. At the time I was serious about racing and my numbers were very good. It came at a price in terms of longevity but money spent, I will forget, race wins I will not. It is too bad that I had not gone with the Lycoming jugs from the start but at that time, 12 years ago, I had had some issues with lycoming quality and ECI had these new jugs that promised corrosion resistance. Since that time competition has upped the Lycoming quality and we all know how many folks have had issues with ECI jugs. It would indeed be interesting to see how HC pistons and flow balanced Lycoming jugs would have done. At this time I am very happy with my stock engine; there was always this little black cloud in the back of my mind while flying the non stock engine, especially in areas of rugged terrain! |
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And I am not specifically recommending against modified engines either. Just pointing out that the performance you have reported with an engine that is supposed to have an additional 25 HP is not better, and if anything worse (because of fuel flow) than RV-14's that have bone stock engines. |
IO-360 from a 177RG
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