Deadlocked on engine selection.
 

I'd like to place an order soon for an rv8 fuselage and finishing kit but I just can't settle on which engine. I've been looking into the 200hp IO 360, IO 375 or the IO 390. I think I'm sold on a CS prop. I'm looking for an ideal power plant for my plane. None of these engines seem ideal when I look at cost, weight, well proven, RPM restrictions, each has its own downside.

1.) Are there insurance implications for using "Non-vans approved" engines (ie 390)

2.) Are there insurance implications at or above 200hp?

3.) Would any of these power plants work better for the RV8 airframe /CG?

4.) Is there a significant seat of the pants performance feel vs a 180 hp IO360 or is it just a waste of money given the added weight?

Advice needed from those with experience. Thanks!

There wasn't for me. The insurance company never asked why kind of engine the plane had.

I went as far as asking one broker what they did for RV's with auto engines and was told that they lump the airframes together and don't look at the engine installed. YMMV

Like all things aviation, it is a compromise. Van says keep it light and simple. Others say you can never have too much HP. My RV-8 with a Superior IO360 and Catto prop comes in at 1062 pounds and meets or exceeds all Van's published performance numbers. More HP would add speed and climb but probably degrade the delightful handling a little. You need a "complex" sign off from an instructor for more than 200 HP. Insurance will depend on experience more than HP unless you go to a big six cylinder.

You need a *High Performance* endorsement. "Complex" is for retracts, etc.

Thanks! That helps from an insurance standpoint. From an engine selection standpoint is it better to have a bit more weight on the engine for CG reasons? Would I be able to carry more passenger weight with a heavier engine up front?

It is always best to build as light as you can because you can always add weight where you want it but it is very difficult to remover it.

Talk to the engine builders, they can pump a parallel valve 360 to over 200 HP without the added weight. The downside might be the TBO may suffer.

I'm not sure of the weight penalty of the other engines but typically all the extra HP does is help with climb, not speed. Van's list the climb rates for the -7 at between 1400 and 1900 FPM at gross (160 HP to 200 HP). How much more climb performance do you need?

consider fuel requirements?
 

...since nobody has mentioned it; I like the option of my low compression engine to use auto fuel if needed. ( could be a plus if true 100 octane is phased out in the engines life cycle.)
If you don't care, then go ahead with one of the high comp. options; heck, it's kinda like free horsepower with very little negatives.

Do test-rides
 

I suggest you get two rides: one in a -8 with 200 HP and one in a 180 HP RV-8, and see for yourself.

Then you'll also have an opportunity to talk to the owners.

I have built two -7's and I guess it won't be entirely correct to compare those two models, but for me the added weight for the 200 HP was out of the question.

I've now flown 180 HP RV-7's with C/S props since 2008 and I'm very happy with 180 HP. I haven't missed those xtra 20 HP one bit....

But that's me....

BTW: another factor is the compression: I have now had my first -7 for sale for about nine months, and about 90% of the people who've contacted me for info, have been asking wether or not the engine can be run on Mogas...
High compression would've been a showstopper for those 90%...

So I'm certainly glad I went for 8.5 compression...

You'll get more opinions than facts here, so I'll throw some more confusion in ;)

1. The basic 180HP engine (parallel valve) I think most would be considered a better start point than the 200HP angle valve (cost, complexity, heat, weight). I do not know the IO-375/390, but see where they start...
2. The difference in weight between 180 and 200 core is easily allowed for / lost via choice and location of other components e.g. battery / prop
3. "Max HP" sounds nice, but by definition you only have with 2700RPM and WOT. At low levels a 160HP RV-8 is "over-powered" by most measures. If high level cruising is a big factor, then more basic HP will give you a few more kts cruise.
4. I doubt many are so wealthy that "max speed" is the top aim, rather than some compromise between speed and cost?

All subjective and subject to your aims. My aim is to get CG as far aft as possible for what I consider "more pleasant handling" i.e. fun / formation aerobatics / display flying. Move CG forward and the aircraft (relatively) becomes a "pig" to fly in that environment. Of course, the aft CG makes it a nightmare in IFR type flying / heavy pax, so if your "mission" is long cruising legs with an AP pilot in, then fwd CG may work for you...

There are many threads on here about the RV-8 and landing, and this thread, which basically end up with the RV-8 as a multi role aircraft, and large CG range. It is a very different aircraft at the ends of the CG range, and ultimately you cannot have the best of both worlds :eek:

A rule of thumb I was told and I think valid - the RV-8 becomes (relatively) "unpleasant" to fly/land forward of 80.00". So put your solo weight into a CG calc and see where you need the basic CG to end up 80.00" or aft. Try and specify / build using other's experiences to target that basic CG ;) I am sure others will disagree :(

Engine
 

I'm not sure of how much time you put into your project each day , you might not need an engine for a few years . I have an Angle Valve and a Hartzell ( Constant Speed) came in at 1094 complete with all fairings , pants and paint .CG is at the forward edge . First flight in a few weeks , will report back .