Anyone currently flying an RV 10 with a 235 HP Lycoming in it? Curious what kind of performance #'s you are seeing versus the 260 HP numbers. Trying to decide to go with a 235 HP with the Mogas STC or convert it to the HC Pistons and 260HP with out the Mogas STC. Any expert A&P's wanna comment on which one will go longer with no problems? Love to get the fuel savings on the 235 HP but will I kick myself on the performance I give up?
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
RV-10 with 235 HP?
- Thread starter ddddsp
- Start date
Efficiency
In general, a higher compression engine burns less fuel for a given power setting than a low compression engine.
Put the higher compression engine in and use the power when you want and for climb and go to altitude or pull the power back for cruise. As I said, you will burn less fuel for the same HP out put. A high compression engine has better thermal efficiency.
Also, you would probably have better resale value if you ever decided to sell your plane.
Roger Ping
A&P
In general, a higher compression engine burns less fuel for a given power setting than a low compression engine.
Put the higher compression engine in and use the power when you want and for climb and go to altitude or pull the power back for cruise. As I said, you will burn less fuel for the same HP out put. A high compression engine has better thermal efficiency.
Also, you would probably have better resale value if you ever decided to sell your plane.
Roger Ping
A&P
osxuser
Well Known Member
If you are planning to run Mogas, which I don't recommend, then the 235 is the way to go, but you CAN'T run high compression pistons on it.
Mogas would probably cause a high compression aviation engine to detonate. Another consideration in a airplane like the -10 is the possiblity of vaporlock at high altitudes. Mogas has a much lower vapour point than avgas.
Mogas would probably cause a high compression aviation engine to detonate. Another consideration in a airplane like the -10 is the possiblity of vaporlock at high altitudes. Mogas has a much lower vapour point than avgas.
In response to the statement on this trend that "Use of high compression pistons will negate your auto gas STC" such statement is in error. No STC is required for auto gas in an experimental, only a builders entry that states "approved for auto gas or 100LL". You can also run high compression pistons on an O-235 you just need to buy the high octane auto gas instead of regular. The reason for high octane auto gas is because engines like those used in Corvettes use high compression pistons. Based on auto gas vs. high octane auto gas in Lubbock today you can still save over a dollar a gallon. If I didn't already have my IO-540 in the assembly process when avgas went through the roof I would have go the O-540 route myself.
Having used auto gas in various airplanes for over 30 years I never had vapor lock occur. On multiple flights hauling skydivers the turnaround on the ground was less then 15 minutes.
Russ Daves
N710RV reserved (RV-10 on main gear)
N65RV (RV-6A sold)
Having used auto gas in various airplanes for over 30 years I never had vapor lock occur. On multiple flights hauling skydivers the turnaround on the ground was less then 15 minutes.
Russ Daves
N710RV reserved (RV-10 on main gear)
N65RV (RV-6A sold)
540's
Thanks Russ. You just indirectly steered me in the direction I thought I was wanting to go anyway. That being the O-540 instead of the IO-540. I never really could figure how to justify the extra expense.
I met you at the Steinair booth at OSH and enjoyed the visit.
BTW if you're ever in the OKC area, look me up or let know ahead of time.
Marshall Alexander
RV10
wings/tanks
Thanks Russ. You just indirectly steered me in the direction I thought I was wanting to go anyway. That being the O-540 instead of the IO-540. I never really could figure how to justify the extra expense.
I met you at the Steinair booth at OSH and enjoyed the visit.
BTW if you're ever in the OKC area, look me up or let know ahead of time.
Marshall Alexander
RV10
wings/tanks
235 Fuel Savings
It's not so much a savings in fuel burnt as it is a savings in cost. I'll bet you'll average 13 GPH no matter what type of 540 you buy. Someone with an injected model might burn a little less but I don't think it's much less. Anyway, the savings is about $1/gal which works out to roughly $20,000 over the life of the engine.
Now depending on the flying you do, it'll likely turn out to be less than that because most airports don't sell mogas so you'll end up burning the expensive stuff about half the time. At least that's what I found in my lowly Warrior. Sometimes you can find an airport that sells mogas AND is a convenient pit stop (Joliet IL for instance) but those are few and far between.
I'm in Iowa City btw.
ddddsp said:
It's not so much a savings in fuel burnt as it is a savings in cost. I'll bet you'll average 13 GPH no matter what type of 540 you buy. Someone with an injected model might burn a little less but I don't think it's much less. Anyway, the savings is about $1/gal which works out to roughly $20,000 over the life of the engine.
Now depending on the flying you do, it'll likely turn out to be less than that because most airports don't sell mogas so you'll end up burning the expensive stuff about half the time. At least that's what I found in my lowly Warrior. Sometimes you can find an airport that sells mogas AND is a convenient pit stop (Joliet IL for instance) but those are few and far between.
I'm in Iowa City btw.
osxuser
Well Known Member
If you want to split hairs, technically you would then have to remove the dataplate from the CERTIFIED engine you install. The STC applies to the engine, which, as long as it remains certfied, must be operated within the manufactors specified limitations.dav1111 said:
True all, however there is a lot more heat involved with aircraft engines (Close to twice as hot) which is a factor that helps determine detonation. So while you may not have any problems running 91+ octane mogas on 9.5:1 compression, it isn't particularly wise because of the reduced margins involved. If you get it lean or get too much oil blow by you could have detonation occur. Because the octane ratings for mogas and the grade ratings for avgas differ, it should be known that 91 octane mogas is the equivalent of 80/87 Aviation grade as far as anti-knock properties are concerned.
Personally I'm more on the FI + Flowmatching, then running Lean of Peak wagon myself. But that of course is with 100LL.
I have no doubt this is true, and the vaporlock issue is one I have never experience either, but I'd be more worried about it at altitude than heat. Also consider that some peoples fuel system design/setup might leave something to be desired. I still feel that when it comes to aircraft engines, fuel is indeed cheap. (even at 4.15/gal)
w1curtis
Well Known Member
Can you site the regulation that says you have to remove the data plate?osxuser said:
What if you add a Lightspeed ignition system or SilverHawk fuel injection? What about any one of a host of non-certified engine add-ons? AFAIK, on an experimental aircraft, the only bearing any certification status of an engine has, is on the fly-off period.
osxuser
Well Known Member
Technically, the dataplate should be removed or modified if any of these modifications are done to the engine. As long as the engine has it's certified dataplate on it, it is suppose to conform to the type certificate. This includes mags, fuel delivery, compression ratio, etc... The list goes on and on. While most people ignore this little facet of the FAR's.
The dataplate could be modified with an "X" or something after the designator. (IO-360A1B6-X).
By the same notion, it must be operated with the designated within the minimum fuel grade limitations as well, unless modified by STC. All major engine maintainence must also be performed by an A&P (Replacing cylinders, overhaul, etc). If this wasn't the case, imagine a homebuilder buying a O-360 core, overhauling to factory specs, and putting it in his RV. He than crashes his RV (sacrilege) and sells his engine on e-bay to a guy with a Cessna, who then installs this engine because it's dataplate still says it's certfied.
Oops...
Seems a bit far-fetched, but it really isn't. I liken this to putting a different cowl on a Commanche vs. on a RV. The certfied airplane has to have an STC, the RV can just be swapped out. As long as that engine maintains it's certified status, it must be maintained and operated as such. Not many people do, but thats the way it is suppose to work.
The dataplate could be modified with an "X" or something after the designator. (IO-360A1B6-X).
By the same notion, it must be operated with the designated within the minimum fuel grade limitations as well, unless modified by STC. All major engine maintainence must also be performed by an A&P (Replacing cylinders, overhaul, etc). If this wasn't the case, imagine a homebuilder buying a O-360 core, overhauling to factory specs, and putting it in his RV. He than crashes his RV (sacrilege) and sells his engine on e-bay to a guy with a Cessna, who then installs this engine because it's dataplate still says it's certfied.
Oops...
Seems a bit far-fetched, but it really isn't. I liken this to putting a different cowl on a Commanche vs. on a RV. The certfied airplane has to have an STC, the RV can just be swapped out. As long as that engine maintains it's certified status, it must be maintained and operated as such. Not many people do, but thats the way it is suppose to work.
235 to high compression
High compression is not necesarily a good idea for 235. Most are narrow deck engines and better suited for the lower compression. An easy method of incresing it's power numbers,(as I'm doing to my 235) is install Unison LASAR ignition systen. The system used should be the one with 25 deg base timing. This will allow the engine to run us a tad faster that the 2575 to 2700 rpms. The engine should also be equiped with FI, though, not critical.
The ignition system manages ignition timing allowing complete fuel burn at all rpm range. The extra engine speed (125 rpms) and use of timing management calculated between 250 and 260 hp, but with low compression.
Though Unison recommends only the use of AV, for certified AC, we are experimental. The use of 100LL was mandated by the FAA in order to obtain certification (good old beauracracy).
My personal experience with LASAR was 800+ hours on my Piper Arrow, which I sold to pay for my RV10. Overall, LASAR increased climb, cruise, and top speed as well as significantly decreasing fuel consumption. I also tried MOGAS, and the performance number were even better, particularly fuel consumption.
I will be using FI as well as a C/S prop on the B2B5 engine, but with low compression.
High compression is not necesarily a good idea for 235. Most are narrow deck engines and better suited for the lower compression. An easy method of incresing it's power numbers,(as I'm doing to my 235) is install Unison LASAR ignition systen. The system used should be the one with 25 deg base timing. This will allow the engine to run us a tad faster that the 2575 to 2700 rpms. The engine should also be equiped with FI, though, not critical.
The ignition system manages ignition timing allowing complete fuel burn at all rpm range. The extra engine speed (125 rpms) and use of timing management calculated between 250 and 260 hp, but with low compression.
Though Unison recommends only the use of AV, for certified AC, we are experimental. The use of 100LL was mandated by the FAA in order to obtain certification (good old beauracracy).
My personal experience with LASAR was 800+ hours on my Piper Arrow, which I sold to pay for my RV10. Overall, LASAR increased climb, cruise, and top speed as well as significantly decreasing fuel consumption. I also tried MOGAS, and the performance number were even better, particularly fuel consumption.
I will be using FI as well as a C/S prop on the B2B5 engine, but with low compression.
