I am finding this discussion interesting as I am in the very preliminary stages of trying to decide upon an engine. As with others, what engine I happen to ultimately select might come down to whatever good deal I happen to find when I am ready to purchase but, barring such luck, I am looking at the options that are available.
I am sure the O-235 would be a fine engine for much of the flying I would do. But, I do plan on some cross country flying, so a little extra speed would be nice. But, I am a low time pilot and I don't want a hot plane that would get me into trouble either (hence my decision to build the -9).
Now, one problem with the 235 is that Van's doesn't sell them, so I am stuck with the used market and we have read some of horror stories about that, where one ends up spending as much getting the things running properly as a new engine would cost.
Sure, I can get a new 235 certified engine from Lycoming for $22,500. No one apparently makes an experimental version of this engine, but an experimental O-320 is $21,650. Simply based on cost (unless one is a stickler for a certified engine, or if the fuel economy of the -235 is shown to be significant), the -235 can be scratched off the list of new engines.
But, one can get some nice experimental engines from Superior (including others). An XP O-320 from them is $20,900. (I am quoting carbureted, fixed pitch engines right now.) But, just for grins, what about a -360? From Superior, the price for the XP is $21,600, but includes fuel injection. A fuel injected -320 is $21,200. For just $300 more, fuel injection seems the way to go.
So, now comparing the FI -320 to the -360, the price difference is just $400. What about the sizes and weights? The Superior site lists the exact same dimensions for both engines, with the -360 between 3 to 18 pounds heavier, depending upon options.
One can get both engines with different compressions for a bit more money. I won't get into that, but if one goes with lower compression, as I will do so I can use mogas, one will end up with 150 HP for the -320 and 170 HP for the -360. OK, Van's says to not exceed 160 HP for the RV-9, but 170 HP is just a tad over 6% above that stated maximum. Given that the engine is only about 2% higher in cost, the 6% higher HP your get in return is a great deal.
So, I can see the temptation to spend something like $400 more to get an extra 20 horses worth of power. Sure, there will be a weight penalty, but apparently no more than 18 pounds. My wife and I, at least at this stage, might total up to around 300 pounds, still leaving plenty of capacity for fuel and baggage.
I am ruling out a used -235? No. Bill R?s results show that it is a very viable engine and, with expensive gasoline, the economy is very attractive, especially if would be flying locally mostly. I am, obviously, ruling out a new -235. I know that even with a tiny cost differential of the -360 over the -320, the -320 might still be the better engine to use, but if the larger engine will give better economy as some have been saying, then I may go for the -360 and trust myself to make sure I throttle back whenever I enter into a cruise descent.
Like I said, I still have a ways to go before I decide, but choosing an engine is probably as big a decision as choosing the kit and there is not always a single right answer. More thoughts about engine choice and economy of operation would be appreciated.
