stratospheric cost?
I think auto conversions will be a more viable alternative to many pilots especially with the statospheric costs of 540/550 engines and parts used in high end kit planes. A company like EPI is quite capable today of doing the whole job right. It won't be cheap but neither is a new 550.
(Edit: Massave math error, started off with wrong price for both engines)
You can get a brand new shiny Lycoming 540 with roller tappets for
$39,000 (corrected).
The "Complete 3.0 200 hp 6 cylinder firewall package" from Eggenfellner is
$25,000 (corrected), so at first blush we're talking
$14,000 (corrected) difference.
Looking down the list on the Egg site, a constant speed prop is $9,000 or $10,000. A constant speed Hyd control "BA" Hartzell is $6,500+$1,200 (Gov) = $7,700, so there is a (
$1,300 to $2,300)
(corrected) to the credit of the Lyc.
We could start talking about nickles and $1000's, but just off the bat, including the prop, we're looking at (
$12,700 to $11,700)
(corrected) difference.
Granted the Lyc needs an oil cooler, exhaust, electric fuel pump and baffle. Van's firewall kit for the RV-10/IO-540 is $4,710 ($5,910 minus the $1,200 prop gov I included above). **Assuming you don't need to buy anything else for the Eggenfellner, than the Lyc total FWF cost is about
$17,900 (corrected) more.
** (From Eggs option list)
Hot water heater pkg $595
6-Port Fuel valve $495
High pressure filter $195
E-Cowl with Hardware $1,890
Alternator op (75A v. 35A) $490
Shipping Creating $1,400
To the Eggs credit side of the ledger goes credit for the standard Van's engine mount and cowl, but it may still be a net cost if Van's credit is less. With some of the Egg options, I suspect are needed, the difference between the Lyc IO-540 FWF v Egg 3.0 is
less than $17,900 (corrected). If you go with the Egg turbo set-up ($7,000 more), so the Egg is about
$10,000 less (corrected) coin.
(Deleted comment about Lyc 540 v Egg being close in price.)
(corrected) One engine is 3.0 liter and the other is 8.85 liter (540 cu-in).
Time honored tradition of scrounging for a used Lyc core & rebuilding it, saves significant money, $10,000 for example. It's more of an option with the Lyc. Finding a used 3.0 Subaru will not save you that much money since most of the cost is in the Egg FWF kit itself.
I don't see the promise of significantly lower acquisition cost with commercial alternative FWF kits v. Lyc. (Well $17,900 is significant;
I stand corrected.) They have to make a profit. There's nothing wrong with being more expensive, if you get what you pay for. The exceptions are builders who scratch build everything with a used engine. Most people don't have the skill or time for that. Those that do, save money with sweat equity, not to mention the pride of doing it yourself.
As far as performance, I would just like to see SIDE BY SIDE comparisons, like Van has done in the past, like what they did with the Power-Sport rotary engined planes, eg, where you fill the tanks and fly side by side (with Lyc power) and measure fuel burn. Also you do a 'timed' closed course flight plan (and tank check), as well as drag races & time to climb. That would take all the calibration of instruments out. Power-Sport did them self proud, but the higher fuel burn of Wankel 's was apparent. It's great to go as fast or faster but not at the expense of significant gas burn, with prices what they are. I think turbo-charging and flying high is where the alternative engines can shine, efficiency wise. However this adds cost, weight and complexity. It does require you to fly up into oxygen mask altitudes to get that bonus. One could also argue you can turbo a Lycoming and make up the ground again.