10:1 pistons in an IO-360?

[moespeeds]

It turns out my cylinders are pre-AD ECI from 2005. They are of the good batch of serial numbers, where I can keep them to TBO with inspections every 50 hours, but my OCD will never allow that.

I called Lycon and they are recommending 10:1 ported nitrided cylinders. Thoughts? Experience?

Prop is a WW300, I'm confirming with them that it's no problem.

Engine is a Mattituck TMX IO360 parallel valve.

 

[ArlingtonRV]

The engine in my RV-8 started its life as an O-360-A1A that was sent to Lycon for rework before ever being installed. Among other things, like upgrade to fuel injection and constant speed, they installed 10:1 ceramic coated pistons.

That engine now has about 2325 hours on it and has had no cylinder related problems at all. It still runs well, has good compression, and doesn't make metal. It uses a bit more oil than I would like, but at it's age, it is acceptable.

I have a replacement or overhaul in my future and I have been debating whether to keep the high compression or go back to standard compression.

The only thing that makes me hesitate to stick with the high compression is the uncertainly of the future availability of high octane gas, whether leaded or un. At that compression ratio I can't use 91 or 94UL, I need the 100.

 

[erich weaver]

It turns out my cylinders are pre-AD ECI from 2005. They are of the good batch of serial numbers, where I can keep them to TBO with inspections every 50 hours, but my OCD will never allow that.
.

I don’t understand. If the cylinders are pre-AD, why are you concerned with 50 hr inspections?

 

[BillL]

Maybe I drank the cool-aid . . . .

You would seem to have more experience that most with the Cr.

On the "should you" due to fuel availability:I watched a video with George Braley, and based on the testing and retesting viewed by the FAA was sold on the G100UL as a viable replacement fuel. Of note was the detonation testing. IIRC, George was doing the standard FAA test, met the goal, but pushed the boost to a much higher level with no detonation. Sure sounded like it is acceptable from that standpoint.

Based on this, it would seem that there will be an unleaded fuel that is as good or better detonation-wise than current 100LL. Although, I would like to see a few hundred thousand hours on it with various uses to know for sure, or learn more about the validation testing.

If/when you take the engine down it would be interesting to see the condition of the coating - durability wise. Please post if that happens.

 

[Carl Froehlich]

SNIP
Based on this, it would seem that there will be an unleaded fuel that is as good or better detonation-wise than current 100LL.

I’m sure it will - but at what cost? We already know it will be more expensive than 100LL, and 100LL is already past the point of pain. Considering it will have the GA piston market in its hands when 100LL is banned, cost control will not be a priority.

I ordered my new CAS IO-540 with standard 8.5 pistons. The slight penalty in HP is more than made up by the flexibility to burn premium pump gas. What I really want to burn is Swift 94UL but few FBOs have yet to embrace that business model.

Carl

 

[moespeeds]

My cylinders are included in the AD.

Turns out this is all moot. Whirlwind confirmed that I cannot go above 8.5:1 with my 300RV prop due to harmonics unless my crankshaft is counterbalanced.

 

[David Z]

The difference in power between 10:1 and 8.5:1 is less than one would expect. If we were racing, where everything counts or doing competition aerobatics, that's one thing. An RV, flying around for fun...well, to each their own. Smiles per dollar will be higher with lower compression pistons and not stuck with 100 octane gasoline.

 

[RV8JD]

The engine in my RV-8 started its life as an O-360-A1A that was sent to Lycon for rework before ever being installed. Among other things, like upgrade to fuel injection and constant speed, they installed 10:1 ceramic coated pistons.
...

The only thing that makes me hesitate to stick with the high compression is the uncertainly of the future availability of high octane gas, whether leaded or un. At that compression ratio I can't use 91 or 94UL, I need the 100.

Regular compression pistons (8.5 to 1) would allow you to run LOP comfortably and increase range when needed and eliminate that pesky fuel stop.