Join the Association!

 

Int'l Cessna 120-140 Association members and non-members are welcome to REGISTER and participate in our forums. Use your forum username to login once you have registered below. Members can log into the MEMBERS ONLY section of the site using their paid membership number and password.
   CalendarCalendar   FAQ and Forum GuidelinesFAQ and Forum Guidelines    SearchSearch     RegisterRegister 
ProfileProfile Log in to check your private messagesLog in to check your private messages   Log inLog in
Don's dream machines engine
Goto page Previous  1, 2, 3
 
Post new topic   Reply to topic    The International Cessna 120-140 Association Forum Index -> Cessna 120/140 Pilot Lounge
View previous topic :: View next topic  
Author Message
stang51d



Posts: 12

PostPosted: Fri Feb 22, 2008 8:14 pm    Post subject: Reply with quote

It's all about how big of a prop you have and how hard/fast can you turn it. Everything else is just smoke and mirrors.

Two 140s, same size of prop, one has a 85 climing at 2500rpm and one has an o-200 climing at 2500rpm, you get the same climb. The ???? is not, what does some dyno say you have, but what will it swing.
Back to top
View user's profile Send private message
gcgilpin



Posts: 1

PostPosted: Sun Feb 24, 2008 11:24 pm    Post subject: Reply with quote

The only functional difference between the C85 (with 0200 crank rods and pistons), C90 and O200 are the camshafts.

The C85 'stroker' ends up being very close to the stock C90. If a true comparison were done (ie. use two fresh engines, on the same airframe in the same weather... and choose an RPM limit ... ie 2575) you will not see any difference.

The 0200 cam is a 35 degree overlap camshaft while the C85 / C90 camshafts are 24 degree overlap camshafts. Less overlap / duration moves HP / torque to lower RPMS. C85 stroker / C90 outperform O200 up to about 2550 RPM. After that the O200 wins.

The C85 camshaft does have less lift than the C90 / O200 camshafts, however tests and calculations have shown that this is not necessarily a disadvantage but possibly an advantage. Camshaft design is not clear cut. Be careful what people tell you. Some people use the terms 'duration', 'overlap' or 'scavenging' causing the rest of us to assume they know what they're talking about. Don't be afraid to ask questions.

Oh and by the way... the old C90 530788 camshaft is not the 'end all be all'. It's torque / power curve falls somewhere between the C85 or newer style C90 (531076) and O200. Again... there are many people out there who will tell you that it is a magically camshaft... not true. It has less overlap than the O200 but more than the C85.

If you want an engine optimized for lower RPMs (ie. 2400-2550 RPM) go with C85 stroker or 531076 C90. If you want an engine optimized for higher RPM go with the O200.

Or if you just want to extract the most horsepower from your engine in a given situation (ie climb vs. cruise) pitch your prop accordingly.

From a guy who has spent way too much time researching this stuff... don't worry so much ... just fly your airplanes.
Back to top
View user's profile Send private message
Randy Thompson



Posts: 2686
Location: Olinda, California

PostPosted: Fri Mar 07, 2008 10:44 pm    Post subject: Reply with quote

I have just overhualed two C-85's with the O-200 crank STC and I have to report that they are very strong. When doing the run in I found them to have a lot more thrust than regular C-85's. They seemed to be more reponsive too.
_________________
A&P IA. Holder of STC for O-200A's in 120, 140 & 140A's. Engine overhauls on C-85's ,C-85's with O-200 crankshaft, C-90's and O-200A's
State Rep for California
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    The International Cessna 120-140 Association Forum Index -> Cessna 120/140 Pilot Lounge All times are GMT - 4 Hours
Goto page Previous  1, 2, 3
Page 3 of 3

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
Send e-mail to John von Linsowe
contact the board administrator


Powered by phpBB © 2001, 2005 phpBB Group