Does anyone have data or experince using 9:1 pistons in an 0-360 Lycoming with and Mogas 93 octane?
Pistons are Superior SL 15357 for:Are these H2AD pistons, used in a 360?
O-320 | -H1AD, -H1BD, -H2AD, -H2BD, -H3AD, -H3BD |
O-360 | -E1A6D |
So that would put you at roughly 96.5 octane. In cruise did you notice a difference in EGT/CHT when switching from 93 to 100LL?I have 9:1's and I've run 93 non-ethanol in one tank, but only used it after leveling off for cruise. The other tank was 50/50 avgas/non-ethanol. I run the mx in both tanks now since it's just easier to premix the entire batch.
Not sure what these words mean, but with SDS you can have pretty much ANY ignition point at ANY MP. And that (ignition curve) is the key to making the engine safe from detonation. My 8.5 engine is programmed to 17 BTDC for “high” MP.SDS is offering a starting point of 23 BTDC under higher MP
I haven't assemble the engine yet; I'm just considering 9:1.Air Guy question re: 93 with alcohol?
Are you using 25BTDC or a curve for timing ? SDS is offering a starting point of 23 BTDC under higher MP.
I have the 174 h.p. Titan in an experimental bush plane (the three letter name other than Van) that I just completed. This engine was selected so I could run mogas if desired. The 174 h.p. Is actually 8.0:1 compression and J.B. at Titan has said, although not officially recommended, customers successfully run alcohol free mogas. To date I only have 65 hours on this engine and have run a mixture of 87 alcohol free gas and 100LL and see no difference in performance or temperatures. The 87 octane is the only alcohol free gas I can get here in the high country of N. AZ. I should note that I paid much attention to building a low turbulence fuel system to minimize potential mogas vapor issues. A buddy and I built identical planes with the exception that he used the 9.0:1 Titan and I used the 8.0:1 Titan -he does have a VERY slight advantage in takeoff-we se no measurable difference in cruise.I am at a very similar research situation. thinking of getting the Titan O/IO 340 180 HP which has 9:1 compression. This engine will be used more for occasional back country trips and the ability to use 91 mogas would be a huge benefit. I have looked at the possibility of using the 174 HP version with the 8.5:1 pistons, but knowing that a guy can use all the HP he can get when in the mountains, I would prefer to have the few extra HP. I've read of a few guys using the occasional tank of 91 MOGAs in their Carbon Bubs with no issues, hence my research. I do keep several hundred gallons of 100LL at my private strip, so would mainly use it. The problem is when I visit distant friends at their strips and they only keep 91 MOGAS do to that's all they require in their aircraft. I'm wanting to order a new engine and this has been my reason for being on the fence per se.
I use a timing curve with SDS, with 22 degrees at high manifold pressure up to a max of 29 degrees at low manifold pressure. The 22 degrees was based on my testing with 91 octane before I had access to 93. I never repeated my detonation testing with the 93, I just stuck with the 91 curve and called it good.Air Guy question re: 93 with alcohol?
Are you using 25BTDC or a curve for timing ? SDS is offering a starting point of 23 BTDC under higher MP.
That's good information, and accurate if you are not willing to make any hardware/mechanical changes to the fuel system.Some good reading/information.
Unleaded Fuels Part 1
This article is the first of three that explains in more detail Lycoming Engines's position on automotive fuels. The bottom line is that it's possible to make automotive gasoline "fitfor-purpose" for aviation. However, in doing so, you deviate from "pump gas" and end up creating a low octane...www.lycoming.comUnleaded Fuels Part 2
Automotive fuel from the pump is NOT the same everywhere you go. There are summer blends, winter blends, geographical blends within the seasonal changes, varying levels and types of oxygenates (not just ethanol) and when tanks are switched over a mixture of "in between". The pump labeling is...www.lycoming.com
Difficult to say whats REQUIRED, considering the myriad approaches available and the fact that this is experimental, so technically nothing is REQUIRED in the first place. However, here's a quick summary and what I did over time and why. The only real trick here is to develop a "hydraulically correct" fuel system - which needs some knowledge of physics and chemistry.Questions for the knowledgeable ?
Airguy offered E10 pump gas requires fuel temp management and higher rail pressure than my engine driven pump and/or AFP electric pump can produce.
Assuming, seasonal / regional vapor pressure variance:
1- How high should rail pressure be to suppress bubbles ?
2- Who sells an RV compatible pump that can supply this pressure ? Apparently cars have one in the fuel tank.
3- Is bypass recirc a must at this pressure ?
4- Is this higher rail pressure acceptable to an AFP servo and splitter ?
R+M / 2"So that would put you at roughly 96.5 octane".
Actually I think the "M" rating (lower number) in the R+M/2 is the automotive octane measurement methodology that is closest to the "Aviation Lean" method used to determine the octane on 100LL. The "M" measurement uses higher rpm and warmer fuel to determine octane--closer to the "Aviation Lean" method on 100LL. The "R" method uses an idling unloaded engine and cooler fuel. This simply means using the "M" rating vs the "R+M/2 results in the 50% blend referenced above being several points lower than 96.5.
Would this difference matter?? Maybe not at lower power settings but at high power and low altitude it certainly might.
Cheers,
db
If you haven't built the engine yet Just put in 8.5-1 and you can burn Costco premium. I do. I do have SDS fuel and ignition also. And be done with it. But I do not burn regular for sure.I haven't assemble the engine yet; I'm just considering 9:1.
For the same reason you are building/flying an RV instead of just buying a Bonanza or a Mooney. They aren't really that expensive either, are they?Maybe somebody already asked this...
Why?
If one is going to all that trouble building a high compression engine, why not feed it with 100LL and get all the power one can out of it? Av gas is not that expensive in our RV's due to our generally lower fuel flow rates, and shorter trip times, as compared to spam cans.
Larry, we fly similar missions. No lead in oil is good, I cant wait for G100UL. But for me, I have no viable unleaded option at this time. Kudos to those who do.#1- no lead in plugs and oil to consider. Dipstick has clear oil for at least 25 hour
#2- I am not in a hurry. I fly 2000 to 2300 RPM @ approximately 7 GPH
#3- HP is not important, RV’s have way more than I need
My reference point is my 3B with carbureter that used 90 no alc recreation mogas.