A 160 hp RV-9A has a 24,500ft service ceiling, sans turbo!
prkaye said:
I don't know anything about turbo-chargers... are they something that can be "added-on" to an existing engine? For example, if I put an O-320 on my plane, and then later on decide I want to fly higher, can I simple slap a turbo-charger in there, or would this constitute a serious modification requiring taking the engine off, etc ?
By the way your phrased "slap on a turbo-charger" and the fact your building a RV-9A, my guess is you have not flown a turbo charged plane or may be even a RV yet? I don't know.
Besides $$cost$$, weight and complexity, to take advantage of turbo charging you need to fly at high altitudes, which require you suck O2, all the time. Do you have experience sucking O2 for hours? It's not fun, dries the nose out and you need to fill tanks, etc. etc. Than there is Vne. You can fly higher and faster but you will run into Vne, which you can consider is based on TRUE AIRSPEED, not indicated. Van publishes a single Vne indicated. However the "real" Vne drops about 2 mph indicated for every 1000 ft altitude.
Hot engine? As you climb the air is thinner. Thinner air means less cooling. Compressing induction air (turbo) and maintaining higher HP at altitude means a HOT running engine. This is why they have inter-coolers. When you compress air you heat it. You are stuffing this pre-heated air into an engine that is getting less cooling air. An inter-cooler BTW adds even more complexity, weight and cost. Bad news is cowls on RV's are small and tight, for speed, right. There's not a lot of room for the turbo, much less an inter-cooler. RV engines are also not cantilevered off the firewall far, meaning its crowded behind the engine as well, where some aircraft stuff their turbo.
Have I convinced you? Look if you want extra altitude performance, start with more sea level HP and keep your plane light. I don't know much about the new IO340 (170HP) engine, but it may be a good match. It keeps the weight down, gains a little HP boost, both a win win. It would allow higher service ceiling without running dangerously up against the Vne, but you still may have to watch it.
PAIN IN THE BACK SIDE
With a normally aspirated (not turbo-ed) engine the HP drops to protect you from exceeding Vne. There are some good threads on this and Van has published his admonishment against Turbos in RV's. Can it be done? Yes. Is the RV-9A a good match? No, of all the RV's it is the least suitable in my opinion, for one weight. I have flown several Turbo planes as a commercial pilot, flight instructor and they are pain's in the back side. They seem to be in the shop a lot. Fortunitly I did not have to pay for maintenance since I was being paid to fly them. The clubs C210T (turbo) was in the shop every 50 hours for major work on the exhaust or inter-cooler.
HOW HIGH DO YOU NEED TO FLY?
The RV is plenty fast and efficient with out a turbo. That is the beauty of it. Trust me flying real high where you can't see much loses its thrill after a while; RV's are plenty happy at sufficiently high altitudes. A 160 HP RV-9A already has a service ceiling of 19,000 (gross wt) and 24,500 ft (solo). Now service ceiling is NOT a practical altitude to fly at, you are just hanging on the prop, but 5 or 6 thousand feet lower is doable on a standard day. So you can easily cruise at 13,000-14,000 feet any time at gross weight and up to 18,000 feet solo!
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You know you have to be on a IFR flight plan above FL180. Above 12,500 to 14,500 ft for more than 30 min you need O2. Above 14,500 you need O2 100% of the time. So the RV-9A is no slouch in altitude performance. SO if you want to suck O2 than you can still climb to nose bleed altitude without a turbo. The 170HP IO340 would add slightly to the altitude performance. The RV-9 has a good wing for altitude, but its weight. Don't make your RV heavy. You will regret it. The lighter the more "RV like" your plane will fly. Weight affects takeoff distance, climb rate, max altitude and landing distance. Also the handling is heavier and not as nice. A turbo does nothing super practical for you in a RV, but can and has been done a few times. Your choice. Good luck.