High compresion piston for O 320

[F-PCGG]

My Long Ez is equipped with a O 320 D2A.
I fore see to replace basic pistons by 10:1 pistons but I don really know what could be the negative effect of this change.
Will the reliability of the engine be reduced?
Which effect on oil T° / CHT & fuel consumption?
Can some of you, give me some lessons learnt?

Gérard

[EZPILOT742X]

I think you'll be running hotter, shortening your TBO, and replacing more parts. I have an IO-320-E2D, which is 7:1 compression, someday I'll bump up to 8.5 or 9:1. It'll probably give me 5 knots.. maybe. I've already picked up 10 with fairings and drag reduction.

Chris

[flyingwaldo]

There is more to it than just the pistons.  Ask this question on the Yahoo Lycoming Forum and you'll get answers from engine builders with years of experience.  There was a thread recently and I believe it was said that some blocks work, some don't based on bearings etc.  I know of 2 canardians that had engines hopped up to high compression and the other modifications necessary by knowledgeable engine builders.  They are expecting almost normal TBO, we'll see....
Do they have an unlimited supply of high octane avgas in Europe?

[easyrider]

I have 9.75 comp. pistons in an O-235 and the change I noticed was increased oil temp, it went to 220 on a hot day on climb out.
I fitted a 10 row oil cooler and increased the oil line hoses to AN 8. It now runs at 190.
I also advanced the timing from 22deg. to 25deg.The HP gain was 12, 118 t0 130 and the climb out on hot days was much improved.
Easyrider

[flyingwaldo]

A quote from the Lycoming Forum engine builder:

1. It may shorten cylinder life, bearing loads will be higher and you may need a
carburetor mod, to get more fuel, to feed the extra horsepower.
I think at 9:1 you aren't straining things too much. Above that, things are
stressed a bit more and you may see reduction in long term durability.

Other than this and a note that the wrist pins need to be changed, this is all I could find on your suggested upping of the compression ratio.  Seems there is some talk of reduced TBO but what the heck for a bunch more horses!  Still gotta have the high octane fuel and we think that's going away some day.  But there are  a lot of expensive aircraft out there that need it, so who knows?  Viva la France....