My .02
I have been away from these forums for over 10 days now. I am just getting back to catching up on all the reading. This thread is very much in my mind as I have been dealing with these issues also.
Aussie9A has many of the same thoughts and ideas I have had in the recent past. Lest some out there chastise me for my lack of
conformity to the
Vans Ideal, I have indeed read everything I can find on the HP ratings of engines for the RV9A. I have even read all the writings by the "great V-man" from the vast NW himself. I do believe that much of his motivation for stating what he does about his airframe kits is predicated by the necessity to "CYA". As others have posted, I don't necessarily blame him for doing so. However, I do feel that the CYA mentality does provide for some challenges for us builders.
I am planning on the ECI IO340 "stroked" engine with the cold air induction fuel injection system for my 9A. I am also planning on the Catto three bladed fixed pitch prop, the James cowl and plenum and an electronic ignition (not sure which brand yet) with one magneto
(Yukon, GMCJetPilot and all the others, please note I am very interested in doing my own CYA here. I just want to work with some of the modern technology to improve performance and/or economy while doing it.)
I have talked for two years now with Richard at
America's Aircraft Engines. We have discussed the issues with the weight, HP, fuel burn, price and pretty much everything I can think of to go over between the IO-320, IO-340, IO-360. All three engines are close to a wash on price with just a couple of hundred dollars separating any of them. They are within about 15 lbs of each other in weight with the 340 weighing about the same as the 320 and the 360 coming in just a few lbs (less than 10-12) from the other two. The HP is where the three might be different enough with measurements showing that the 340 is outputting more rated HP than the 360 (according to ECI tests).
So when looking at all of these factors I am leaning towards the 340. It is a bit more in price than the other two but it out performs both of the others in rated HP. Its weight is about the same as the 320 so is favored in that category when I compare it to the HP output of the 320. Fuel burn should be reduced when throttling back to 55% to 65%. At that power loading I should be able to maintain a favorable cruise speed while leaning for minimum fuel burn. Another added advantage to running at these lower power settings should be an engine that lasts a very long time. Oh, and one more advantage to running at these power settings should be a decrease in noise and vibrations which is another important factor in the comfort category.
There are some cons to the choice of the IO-340 with cold air induction fuel injection that should not be overlooked. This engine compression is 9:1 so 100LL is the recommended fuel according to ECI. I do not like this limitation and am talking quite a bit with those in the know at ECI about possible fuel options. Another con for choosing this engine in combination with ECI's cold air induction and fuel injection is the fuel return lines and the cowling configurations needed. Both cause some complexity in the installation and construction for these systems. As far as the fuel lines, so far they have not proven too difficult. I am currently constructing the slow build fuel tanks and have the return lines in place. This has not been much of a problem. Yet to be built are the valving mechanisms that could be difficult. However, there are several individuals working on the necessary plumbing for these systems. One of these people is Robbie Attaway at
Attaway Air. Robbie has already been very helpful to me. I will be doing much more talking with him in the coming months. He is a great resource for working with these ECI systems.
My plans are to combine this engine with the three bladed
Catto Prop. This decision is mainly based upon reports of quieter and smoother operation using this prop from others who have flown with it. I am building a cruising machine for my desires to fly cross country in comfort. This comfort is much more valuable to me than all out speed. Perhaps a two bladed prop would provide a couple of more kts of speed but the smoothness and quietness of a three bladed prop wins out over speed for my needs. One other important factor with the three bladed prop is the ground clearance. My plane will live on a private grass strip. This will mean that at least half of its landings will be done on this grass strip and then taxied to the hangar on grass. With all the concerns of nose overs I want as much ground clearance as I can muster when choosing a prop.
Weight is another important determiner for choosing the Catto prop. I am not willing to add weight, complexity and costs (this is important too considering I am looking at $2K compared to $7K-$12K) in order to have a constant speed prop. As everyone flying the RV's has attested these planes do not fly like spam cans. Therefore, the three bladed cruise prop I intend to put on this plane should be very adept at providing enough climb for my needs while giving me very adequate cruise speeds. All this while shaving off somewhere around 30 lbs from that of a constant speed prop installation.
I had mentioned above that comfort was more valuable to me than speed but that is not to say that I do not value speed. Because of this I believe the
James Cowl and Plenum is the way to go on the cowling of this engine. Perhaps it may give more speed, perhaps not. Perhaps it will be an easier install than Van's cowl, maybe not. Whatever it turns out to be I am convinced that I will give them a go.
One last thing that I have plans for that is very much in the experimental realm of our endeavors. I have never been a fan of the loud roaring open header sound of a throbbing internal combustion engine. So with that in mind I also intend to work on a muffler installation as proposed by
Tony Bengalis. If successfully installed this muffler should contribute a great deal to silencing the sound and vibrations of my airplane. I have a great respect for Tony Bengalis and have no reason to believe anything contrary to what he has written about and experienced. It shall yet to be seen whether this swiss muffler system will be as beneficial as I hope, but if so, not only will it provide for a more comfortable cross country airplane but it should also be less of an annoyance to those around the airport as I take off or land.
Well, sorry for such a long post but I wanted to share my thoughts as I have wrestled with the idea of what engine to place in my airplane for the past two years or so. I am sure there are many other ideas that I have not mentioned here that have had an influence on my decision or may have an influence on you as you decide. I am sure many others will be more than willing to hit upon any or all of them. I hope my .02 has been beneficial as others wrestle with these decisions.
As always,
Live Long and Prosper!