Changing compression ratio

[N355DW]

I have not ordered my engine yet, and have been leaning towards the lower compression IO-375 from Aerosport so that I could use mogas if 100LL goes away.

Since I have spoiled myself for many years flying high performance aerobatic aircraft, of course I now find myself thinking of higher compression/hp ( maybe even that Superior XP 408AC!) and since I don't plan on using mogas unless I have to, I started wondering how involved it would be to lower the compression ratio in whatever engine I have, should it become necessary. I am building a 7.

Both manufacturers offer low compression versions of the same engine. Is it just a matter of changing out the pistons? I know that may be an expensive and involved undertaking, but it's cheaper than buying a new engine.

This will be a question I will ask each manufacturer of course, but I wanted to get some thoughts/opinions from the community here as well.

Thanks!

Damon

[hydroguy2]

I figure my engine will be ready for an overhaul by the time 100LL goes away.

[jrs14855]

Just change the pistons. You would want to hone tyhe cylinders and replace the rings. One days work if you're organized.

[N355DW]

Thanks, I thought that might be the case but had not ever really looked into it.

In my Extra 230 I had an angle valve with 10:1, it was around 230hp. From level flight wide open I could do a 5-6g pull and get around 1500-1800' vertical. Don't remember the speed I would get WOT level, it was 15 years ago, but I'm guessing between 160-180mph. The wing leading edge and wing itself on a 230 is very thick compared to an RV, and does create more drag. I'm may be wrong but I seem to remember weight of the 230 was around 1050lbs, so a 230hp parallel valve engine in the RV should have a very nice effect on performance.

I guess it's a holdover from competition - you can never have too much roll rate or too much horsepower! High compression it is!

[jrs14855]

Which Extra did you have?? A great airplane, one of my all time favorites, The definition of overpowered is an airplane that will accelerate to self destruction going straight up.

[N355DW]

It was Patty Wagstaff's originally. Bought it in 1994 or 1995, sold it around 1999. Serial # 12, I think. I've never flown a plane that flies as nice as that one did. Still regret selling it.

So I'll put in the big engine, take off the flaps and extend the aileron all the way in - viola! Two place 230 with baggage space!

[jrs14855]

I got to excersize 444PW on a regular basis 91-93 after Patty traded it on th 260. I also did the fuselage mod which involoved removing the wing, engine etc and welding in some additional tubing. Great airplane.