I'm looking for a "schooling" on why I'm hearing that the C85/90 @ 180 lbs & 85 hp is considered to be better engine than an 0-200 @ 170 lbs & 100 hp (specs are off Wikipedia so allow some latitude)

My understanding is because of the J3 and the type certificate and allowable props therein. If you are experimental, or if this is for another type then I got nothing for you.

On the J3, the C85 is much preferable for a number of reasons:

1) the Sensenich metal climb prop that is allowed by the type certificate for the C85 is 2" longer than all the other options on the C90
2) The C90 is static RPM limited to 85HP - you can't run at the same rpm as the C85, therefore it doesn't make full 90HP
3) The availability of the stroker STC is only on the C85 - which will allow you to get well beyond 100hp with a built up motor
4) The O-200 STC requires bullshit header tanks an unusable fuel AFAIR.

This is all from memory - I sold my J3 and moved to skywagon'n 7-8 years ago. Most of this info was gleaned from Harry Fenton's tech treasure trove for the Bowers Flybaby:

http://www.bowersflybaby.com/tech/fenton.html

I can tell you from experience that the C-90 is a more desirable engine for backcountry kinds of airplanes, mostly due to torque. The 90 spools up fast. My understanding is, that is largely a function of a different camshaft and lifters.

But I am not an engine expert.

MTV

I think what Mike is saying is correct. I’ve recently been researching pa-11s and some are built on 85 and o200. Correct me if I’m wrong but the 85/90 is more desirable because of the cam and the horsepower is more useable at a specific rpm range. Take everything you read on the web with a grain of salt. I could be full of shit.

For a "stock" engine, I believe what MTV is saying is true. I've heard it a bunch over the years. But I've also heard that the O-200 crank, rods and pistons STC creates an engine that will out perform it. I haven't gotten to be around one, but I've heard quite a few say basically the same thing.
John

hardtailjohn wrote:For a "stock" engine, I believe what MTV is saying is true. I've heard it a bunch over the years. But I've also heard that the O-200 crank, rods and pistons STC creates an engine that will out perform it. I haven't gotten to be around one, but I've heard quite a few say basically the same thing.
John

So the 0-200 crank, rods and pistons in a C90 crankcase

Check out Don Dreams Machines.

Mapleflt wrote:
So the 0-200 crank, rods and pistons in a C90 crankcase

In an 85 case. It basically makes a "stroker" C-85. Aircraft Specialty Services used to have an STC as well as Don's Dream Machines. I think it's down to just Don's now, but don't quote me on that.

John

A C-85 stroker is the engine you want. If you are experimental or OM then putting C85 pistons in with the O200 crank will give you another little bump in power. The C85 piston crown would need to be chamfered.

The O200 engine makes 100hp at 2750rpm which is a high rpm and therefore propeller options become limited and efficiency of long props goes down. It’s camshaft design is for high rpm so it lacks low end performance.

The C90 makes great power, lots of low end torque at a lower rpm due to its camshaft design. Same cubic inches as the O200 but runs at a lower rpm.

The C85 has the same bore but the stroke is 0.255 inches shorter so the displacement is less. It’s max rpm is 2575 so it has a cam that is good for low end torque, but not quite as good at the C90, and has good prop options. Getting the STC for the O200 crankshaft bumps up the placement so it is the same as the O200 but you get to keep the good cam and desirable prop options. The STC was developed because of the shortage of good C85 crankshafts. The target was not to gain power so the engine is still only rated at 85hp even though a stroker C85 puts out around 106hp.

Great intel gang, you can always count on the BCP community for a good "schooling"

This is a good chart that explains the HP Difference based on RPM.

Ok that chart answers a lot of questions for me, THANK YOU

also look at the graph of the torque values between the engines. See JimC's post on this thread (#30):

https://www.supercub.org/forum/showthread.php?29655-O200-and-C90-power-torque-curves&p=602667&viewfull=1#post602667

Hi, Does anyone know where I can find the complete article that's shown in this post? It looks like a comparison of the C series power curves. I'd like to read the article. Thanks.

Good information all. I would just add that I have found the slower turning engines C-65, C-90, Lycoming O-540 at 235 hp, and R-985 to prop easier and run cooler than comparable faster turning higher compression engines. I have flown all except O-540 without back case with starter and generator.

AlpineFlyer wrote:Hi, Does anyone know where I can find the complete article that's shown in this post? It looks like a comparison of the C series power curves. I'd like to read the article. Thanks.

Maybe PM Sticknrudder to ask where he found that.

Was reading over this topic today and added this to the KB:

https://backcountrypilot.org/images/kb/ ... 0-0200.pdf

Still looking for that other article that's photographed earlier in the thread.

I was never able to locate it either.. That picture was passed onto me, and the person who sent it didn't have the whole article either.