What are those of you experimental types doing to get more hp out of the C-90? I've seen the C-85 pistons will work with some modification and bring the comp. ratio up to 8:1 or so. Lycon had 9, 9.5 and 10:1, has anyone tried them yet?
Thanks
Tom
What are those of you experimental types doing to get more hp out of the C-90? I've seen the C-85 pistons will work with some modification and bring the comp. ratio up to 8:1 or so. Lycon had 9, 9.5 and 10:1, has anyone tried them yet?
Thanks
Tom
Tom Ford
What's your redline on the tachometer? Do you have a climb prop? Can you get to redline with it?
On old gas recip engines RPM = HP til about 4000 RPM!
-- 8GCBC: 2100A, 31136.R, 8.566, C3000A
A&P, ATP, SES, CFII, MEI
Fly with me here: http://www.youtube.com/watch?v=SXI48e1heuo
I tried using C-85 pistons in the O-200 on my other plane. I would advise against that. They need a bit of machine work to fit properly, but after 250 hours of run time I found some really interesting wear that indicated that the top ring was actually overrunning the end of the barrel and banging into the aluminum head at the top of the bore on two cylinders. I cut back the aluminum at the top of the bore a bit, then when assembling had the top ring pop out and expand above the barrel. That was really challenging to get back off the engine as the piston was locked in at TDC.
A better solution is to buy a set of O-200-D pistons, which are 8.5:1 compression and will fit the C-90 with no modifications. I'll be installing a set in my O-200 this weekend, but don't expect the plane to fly again for a few months for other reasons, so won't have any testing with them for a while. You can also go with Lycon for 9:1, or higher pistons. It seems to me that I paid something like $172 Ea for the Continental O-200-D pistons from Aircraft Specialties.
-CubBuilder
put in an 0-320
I don't know where you've been me lad, but I see you won first Prize!
Running 10:1 Lycon's, engines just run/start better with compression not to mention the hp_boost. A good polish and port seems to make significant gains. Might spend some time matching the cam to the goal RPM/prop. What about air intake venturi? That sounds like a good idea..Originally Posted by RaisedByWolves
Do you have them in your engine?
Tom
Tom Ford
Yes, everything but the venturi.. Roger was discussing it the other day (N3150 Experimental PA11), we are now considering installing one.
PM if you need specifics
frank
little_cub (at) alarmspro.com
Just an update on using the new O-200-D pistons. Continental made an change to the piston so the O-200-A ring set won't fit. It appears that they narrowed the top ring groove in the piston by .005", so the C series and O-200-A rings won't fit. You have to buy the O-200-D rings, which are a special order from Continental and $600 for 4 sets. I had heard they were going to restrict access to them by requiring an O-200-D serial number to get them, but did not verify that. Only that the Continental Distributors didn't stock them and they would be a special order from Continental. My O-200-D pistons are now with my friendly machinist having .005" cut out of the top ring groove so I can use the C series/O-200-A ring set.
-CubBuilder
Tom, Had Lycon pistons in for a while. after 10 or so hours (rings set) started to puff oil smoke, 200 +/- hour cylinders, flew 150 or so hours good power but smoke on start up and acceleration 2 hours per quart of oil, reringed it with the same results, know of a c145/0300 with same pistons and same results also a bunch of cessna 150's with the same results. the pistons are a 3 ring design so I don't know if that was the problem. Long story short I bought 4 more new cylinders with the stock pistons and have a mostly clean white plane again and 1/2 to 1 quart between 25 hour oil changes.
I have the c-85 pistons in my c-90 and always have so I don't have much experience with any other setup, but the biggest performance gain I say was in going away from the 2-into-1 sytle exhaust and either using a crossover or 4-pipe exhaust. The throttle response is also much better with either of these systems.
Does anybody know what the compression ratio is with the c-85 pistons?
Clint Busenitz
Tom you should try my prop.
Bill
I haven't tried the Lycon Pistons, but the feedback I've had from others that have tell me they seem to have a problem with seized rings around the 200 hr time frame.
FWIW, the O-200-D pistons also went to two compression rings and a single oil control ring.
-CubBuilder
Douten, were those all 10:1? And bill, ill have to come try it when crow island dries out.
Thanks for the input guys
Tom
Tom Ford
I know a friend who runs the 85 pistons in the C85/0200 stroker wth a C90 cam and it works well. CR is 8.6.... or so
Glenn
Tom, I think they were 9.5/1 but not 100% may have been 9/1. I really wish they had worked for me as they made some hp. and take Willy B up on his offer to try the prop. I need to send mine out to be tweaked a little bit for the Amphibs.
This is way out there, but a friend of mine used to build o200 Formula engines. He used 350 Chevrolet pistons. (If I remember right) Something about extra ring, weight and an oil wiper ring. That was a LONG time ago.
Tell us more. If I remember from my drag racing days SB 350 was a 4" bore and a SB 400 was a 4 1/8" bore
Glenn
Correct Glen... 4.000 and 4.125 respectively. The C-90 and O-200 are listed at 4.06 from what I can find.
Used to be a engine builder in oklahoma, Duane Blackburn that used some type of car pistons in small continentals. He built a C-90 for me in the early nineties (not with car pistons) I don't remember the combination he used or how he modified them, should have paid more attention. C90 is my favorite engine/camshaft combo and the wave of the future for me.
I picked up an 85-8 with Lycon high comp pistons for my exper bird.
The motor had approx 50hrs on the assembled unit & appeared to run fine..
Tore it down & everything checked out fine.
I now have another 15hrs on it using approx 1/4 qt of oil.
It runs beautiful & makes good power.
I don't know what the comp ratio or hp is but you can sure feel it when flipping the prop!
I like
C85 pistons in a C90 or O-200 give 8.68:1 compression ratio for a 7.0% increase in power and torque.
9.5:1 Lycons will give 9.76% more power and torque than the stock 7.0:1 throughout the rpm range on both engines.
Here are Charts of Sea Level Torque vs RPM and Sea Level Power at 29.0" MP for the stock C85, stock C90, stock O-200, 9.5:1 O-200, and 10.5:1 O-200
The anomaly in the C90 torque at 2350 rpm is due to a glitch in the Continental power curve for the C90 at that rpm.
The rpm range is 1800 to 3100, and the torque range is 155 to 220.
C85 is plotted in yellow
C90 is plotted in blue
O-200 is plotted in red
9.5 O-200 is plotted in green (ran fine on 93 octane mogas containing ethanol for the few hundred hours I ran it that way)
10.5 O-200 is plotted in black (for torque chart only -- not included in power chart)
The values for the stock engines are taken from Continental Publications. I calculated the values for the 9.5 and 10.5 O-200 based on the thermodynamics of the compression ratio. I've got a good bit of time on a 9.5 O-200, but have not flown the 10.5
With a 9.5 O-200 at 3150 rpm and a Mac 7142 prop, the J3 tops out at about 118 mph in level flight. It cruises at about 80-81 mph at 2350 rpm.
Last edited by JimC; 03-09-2013 at 08:13 AM. Reason: add Chart
Jim
Great post. Good to see you here again. Missed your informative posts.
Bill
Very Blessed.
While we're on the subject of power and torque available from our favorite little engines, several O-200's have been mounted on J3's by 337 rather than STC in order to avoid the somewhat puzzling requirement of the Univair STC to add extra fuel, to limit the fuel that can be used from the nose tank, and to limit the prop to 69 inches diameter. Re engine weight, a non-electric O-200 is 1.58 pounds heavier than a non-electric C85-12F, and is approximately a pound heavier than a C90-12F.
The 337 installed O-200's run the stock nose tank with no non-stock limitations on cg, have no requirement for extra fuel, and limit the allowable horsepower by a rpm redline placard on the instrument panel and a redline mark added to the tach. The O-200 redline rpm is usually reduced to either 2640 rpm or 2665 rpm. The prop used is usually a 71 inch Mac, generally on the order of 41 to 42 inches pitch.
So, how do the stock 85, 90, and derated O-200 compare at sea level? Here's a chart comparing the sea level power produced by the three engines at their rated takeoff rpms while at various manifold pressures (the O-200 is derated to 2640 rpm by not shoving the throttle to the stop on takeoff and climbout -- in order to comply with the panel placard and tach marking). The C85 is shown in yellow, the C90 in blue, and the derated O-200 in red. Note that at sea level and at rated rpm, the C90 produces more power than the O-200 only when the manifold pressure is below 17 inches. This also implies that the superiority of the O-200 diminishes as altitude increases. When the altitude is high enough that neither engine can maintain more than 17 inches manifold pressure at full throttle while at their respective rated rpm (derated rpm in the case of the O-200), then the C90 will outperform the O-200. At more usual altitudes, the converse is true. Assuming 1 inch of induction.loss in each engine, another way of saying this, is that the stock C90 will outperform the derated O-200 at altitudes above 13, 500 feet.
This Chart is a compilation of information provided by various Continental publications. Nothing new here.
Last edited by JimC; 03-10-2013 at 09:24 AM. Reason: to add information
JimC what is a top RPM to turn a c85 i know 2550 is what is continentals red line but would it hurt to turn it say 2750 like a stock 0200 or as you said 3100 for a short time?
Well, it ain't legal to do it on a J3, but the published Continental power curves for the C85 go up to 3100 rpm. The 85 cam is similar in timing and duration to the O-200 cam, so the shape of their power curves with respect to rpm is similar (though the 85 has reduced valve lift compared to the O-200, which chokes it at high rpm compared to the O-200).
Back in the 60's, I used to run a Mac 7438 prop on a stock 85, and it was a real warhorse on takeoff roll and climbout at high rpm. And no, I don't remember what rpm I was turning on climbout (45 years ago, and I have a 3 minute memory). It was turning up pretty good though.
BTW, I"ve seen several people ask on the forum what the rocker arm ratio on these engines is. It's 1.2
Last edited by JimC; 03-10-2013 at 01:05 AM.
Thank you for the information Jim, It has been mentioned here that a port and polish would do some good... Was this a polish to combustion side for anti knock and improved cooling or suggesting polishing ports beyond 80 grit?
Has anybody used 5 angle valve seats or full radius cuts?
at 9 or 9.5:1 cane you run 91 octane?
Has anybody welded up a flat below the sparkplug entrance to create a small flat for quench area?
last but least how about wideband 02 sensors that are now pretty cheap to see air fuel ratios?
one more....what about playing with venturi sizes?
Put a vetterman crossover exhaust on.
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