G

glenn654

Well Known Member
For you guys flying w/ high compression pistons, have you had any problems such as excessive heat or cooling problems in summer, cracked heads, reduced TBO or any other problem which you think significant. Trying to decide whether to use them. Also, would you buy them again.

Thanks,
Glenn Wilkinson
 
High Compression Pistons

I have an ECI engine with Lycon 10:1 pistons.

I anticipated it would run hot, but it actually runs cool!

I would recommend Lycon to anyone who wants more performance out of a Lycoming engine.

I typically don't run my engine full out except on take off and initial climb...but if I want those extra horses to stomp a little, they're there.

Also, be advised that Lycon does NOT endorse LOP operation in their high compression engines, so normally I run no more than 100 degrees ROP. At 8,500 I typically get good speed and good economy at 24 squared, but it can gulp fuel if you lean on it!

The way I look look at this option is....a poor man's turbo without the weight of a turbo. The extra compression raises the ceiling at which you can get what the factory rates as sea level horse power. And if you throttle back at altitude you gain excellent MPH figures.

I would like to caution that merely adding high compression pistons is only part of the "package" to get more power and economy from your Lycoming or Kit engine. Talk to Kenny at Lycon for his options. Also, if you read the recent Kit Planes mag about "o" ringing case halves, I think that is an excellent idea to ensure long term no leaking or seeping of oil.

I elected to purchase a high performance I0-320 and am very very pleased with it. I liked the idea of the lighter weight of the 320 and my plane already had a 320 so the swap out was fairly straightforward.

Lycon has two dynos and my engine was (as all the custom engines Lycon builds are) run for 5 hours on the dyno.
There are a number of parameters the dyno measures, but the one that most are interested in is HP. 205 at 2710 rpm.

The engine now has about 250 hours on it, and runs very smoothly and does not use a lot of oil...about a quart every 25 hours. Kenny did recommend using Lycoming cylinders as he (at the time) felt they gave superior service life to the ECI Titan ones.

Tom Hunter
 
Come on... Seriously a 320 with 205 hp by using 10:1. I don't think so. I may have believed this if it were in the RV Musings thread but not here.

Be careful with propeller selection if you choose to go High Compression as some manufactures of props have not Tested or endorsed their props for some engine combinations. There is lots of information and past talk about this and high comp in the archives. Another consideration is the demise of 100 LL. Will your HC engine be able to burn anything less. Not likely.
 
Last edited:
jrvssgl said:
Come on... Seriously a 320 with 205 hp by using 10:1. I don't think so. I may have believed this if it were in the RV Musings thread but not here.

Lycon regularly gets around 210hp out of a 320. It is however more than just the pistons. They have their own cams and cylinders are flowed etc. My friend's 0-320 Cub motor dynos at 208hp. Don
Click to expand...
 
I have a little over 700 hours on my overhaul. I went with 9.5:1 pistons. If I had it to do over again, I wouldn't go above 9:1.
The engine was not as smooth as it was with 7:1. The Catto prop brought back the smoothness.
My estimate of hp is somewhere around 175-178. My original estimate was 175. Sensenich built me a prop based on this estimate, but I could turn it 2900 rpm. They then sent me their standard 180 hp prop with 1/4" trimmed from the tips. I turned this prop 2750.
My 3-bld Catto is (I think) 66 X 74. I also turn this prop 2750.
 
They work fine

In my current airplane and I put them in my last airplane as well. This airplane had them when I bought it, so I have no before/after comparison. I did the HC piston STC in my last airplane (Mooney) and the power increase was very noticeable. A 7%-10% increase in power translated directly into 7%-10% increase in climb rates.

EGTs run cooler with high compression pistons. I don't think they effect overall engine temperatures, except that if you're producing more power, you're also producing more heat.

I usually run mine LOP in cruise, but never above about 65% power.
 
I have 10:1 in my XP-400SRE. So, not that it compares to anything else.. but, I do have very low EGT's, low CHT's, and high oil temp. Starting cold is hard on the starter. With a battery that is 100%, and the throttle at 1/4, I can just barely get past top dead center. Once it creeps past, bang! Starts every time. Hot starts are easy. No boost pump or anything.

Still working on timing/leaning/fuel flow stuff. All cylinders peak within .1 gph. When I lean to peak EGT, if I go 5 degrees past peak the engine quits, like it is out of fuel. Somebody explain that one to me...
 
I was reading the skyranch book about case fretting and how using higher compression pistons stresses the case more. Also, they won't do much for you unless you are also porting the cyls which has the potential to cause cracks depending on where you remove metal and how you do it. On top of all of that there are limits to running LOP due to increased combustion pressures.

I've never owned a high compression engine, but after the extensive research I've done on the matter, I just decided to go with 8.5:1.

Keep in mind, I'm running a IO-540 so it's not like I'm hurting for power anyway.

schu
 
10:1's

I have a new, 120hrs. Superior O-360 XP Extreem with 10:1's in my 8A, runs great, low temps, CHT normally runs 325* oil temp 180* these are Florida summer temps in the mid 90's. The one issue I do have seems to be higher than normal oil consumption, 1 qt. in 7 hrs. Eagle Engines, builder of the engine say's that the oil useage is about normal???? I have a friend with an O-320 with 10:1's that uses a qt. in 20 hrs. I guess it is what it is????
Dick
 
You must log in or register to reply here.