c-90 vs. 0-200 for pa-11

[vonbaxterak]

I have a j-3 converted to a pa-11 with atlee's stc. I currently have a lycoming, but would like to change to the lighter continental. I have heard you can get better horse power with the c-90 at lower rpm. The other thing I was wondering, I fly on floats so I want to use the best prop and engine combination together.

also can someone explain what they mean by " you can make your c90-12 into a c90-8, or you can put a 0-200 crank into the c-90" . I see this on various adds for continental engines for sale.

Any and all info would greatly be appreciated.

 

[irishj3seaplane]

C90 V O-200

Hey,

I had a good bit of confusion on this one too, when upgrading my J3 from an A65. I know that the 0-200 does develop 100hp when it revs out, and many do go for it, but I've been told by so many that a C-90-8 is much better suited to a J3 on floats. It develops more pull from lower revs, and also is almost as light as the old A-65. I'm using it now with a McCauley metal 1B90CM7146 and EDO 1320 floats. It a great set up, and with a good carb is an easy starter. If the elec start means alot to you, I would take a look at the 0-200 conv but I dont mind hand swinging.

Ring Dons Dream Machines, they seem to be the experts in these size engines. Google them as I cant find thier number.

Way to go with the PA-11 mods, I'd love them.



Regards,

WF

 

[Frenchy]

Hi

C-90 and 0-200 have the same bore and stroke(200 ci) ,with a c-85 it`s a bit different, if you put a 0-200 crank in a c-85 you go from 188ci to 200ci,
If you keep c-85 pistons in this set up you end up with a higher compression engine but i don`t think it`s legal ( no STC). If you can find a c-90-8 with a 74 ins. prop. you will have a light engine that produce torque at lower RPM.

Frenchy

 

[behindpropellers]

Hi

C-90 and 0-200 have the same bore and stroke(200 ci) ,with a c-85 it`s a bit different, if you put a 0-200 crank in a c-85 you go from 188ci to 200ci,
If you keep c-85 pistons in this set up you end up with a higher compression engine but i don`t think it`s legal ( no STC). If you can find a c-90-8 with a 74 ins. prop. you will have a light engine that produce torque at lower RPM.

Frenchy

Frenchy-

Adding cubic inches without changing the cam and jetting will not give you more hp. I have yet to hear of any conclusive tests of anybody putting a c-85 with the 0-200 parts in it on a dyno.

Tim

 

[Frank T]

Do a search for "C-90 Experts" and you will find a recent large thread on the C-90/O-200. The Camshaft is the big difference. If you are experimental you can run the C-90 cam and C-85 pistons in an O-200. If Std Cat. you will need a C-90 to use the "good" cam.

There are different cams for the C-90, one grind is good for more torque at the lower RPM, but you will need to run straight pipes to get the power out of it. The above thread will cover what you need to know.

Frank

 

[Alex Clark]

I have the C-90-8 in my J-3C-65 that was converted to a PA-11-90 using the Atlee Dodge STCs.

So it is a hand starter. The C-90-12 would take a starter, but that is more weight.

I have flown the same plane (same conversion anyway) with a 0-200.

The 0-200 did not have as much performance off the water. It was a little heavier and it did have a starter with a solar cell charged mini battery under the seat. It was good for about 3 or 5 starts a day.

My prop is a Sench. 76Ak-2-38. So it is really 74 inches long with a 38 inch pitch. I fly off lakes at sea level to 2500 feet most of the time so it is OK for instruction.

If it was only me flying her, I would have a 40 inch pitch for floats.

The 38 inch pitch is better for teaching docking and sailing in various wind conditions. (I can back up in lighter winds) BUT, it red-lines much too easy. And I have limited cruise speed.

For wheels & Skis, I need and am currently looking for, a 46 or 48 inch pitch. Then I could obtain some better cruise speeds and would not over-rev the engine on climb out.

 

[vonbaxterak]

Appreciate the info. I should have mentioned that I have an electrical system and would like to use a starter. I don't mind hand cranking on wheels, but on floats not as comfortable.

Is there 0ne c-90or 0-200 which will or will not take a starter, if so any one know which one's will?

 

[Alex Clark]

The C-90-8 will not take a starter.
The C-90-12 does.
The 0-200 does.

Actually I like hand propping on floats much more than wheels.

I just float out, stand on the forward float and give her a spin with the left hand on the door edge. Then I can slow taxi around while standing on the floats by reaching in and moving the rudders with my hand.

Assuming I have the mix pulled out in case I fall off the stinking float.

xx

 

[irishj3seaplane]

Good man alex,

I was thinking about that one in bed one night - taxying the plane standing on the float. I tried sailing while on it and its quite a neat trick. I'll remember to keep the fuel turned off when I try it.

I've great pictures to send you of us operating off a narrow canal. great fun.

Regards,

WF

 

[Alex Clark]

I had a student once who was rather firm with throttle use during start-up. I had the mix pulled top cut-off.
The engine was warm and it had flooded.
I was out pulling her through and suddenly she caught at high RPM. I yelled to throttle back.
The young student was a bit rattled so she gave her full throttle.

The plane took off like a shot for a 100 feet or so before she died.

I was pushed against the wing struts by the prop blast.

My favorite hat now rest on the bottom of Beluga Lake. Next to a good set of sun glasses.

 

[howieb38]

Alex:

You should write a book. Great stories as well as informative.

 

[Nathan K. Hammond]

Hi Von,

A -12, although a little heavier, does have a few good qualities. First off is the ability for an electrical/starter system, which like you said, pays for its self when on floats. Secondly, and more importantly in my opinion, is the fact you can bolt on an oil filter to the side of the case.

If you can go Experimental, the C-90 is one of the best cases to start with. It takes the longer stroke of the O-200, match that up with an early model 90 cam, add Lycon 10-1 pistons or C85 pistons (which have to have the bevel increased to clear the cylinder head), along with a couple other details and you've got 120+hp!

When Dons Dream Machines was getting their STC, they had to submit a power curve taken from the test engine. They actually had a difficult time getting an exceptable curve, because they kept over shooting the target, 85 +/- 5%. They ended up catching a curve, by manipulating the throttle (in fact they "revved" the engine by slamming full throttle and not warming it up in increments, and clicking 'Print Screen' before the engine got up to full potential.) So I have every reason to believe I'm making 100hp at full throttle (2500rpm in my case.) To justify that statement, I can run head to head with an O-200 powered Champ, and even beat him off the ground in my C85/O200 Champ, when all things are equal. Until I put it on a dyno, thats the best info I have.

My unbias opinion between a C90 and O-200, is run a C-90.

nkh

 

[JP]

You can mount an Airwolf filter on the upper left hand quadrant (facing forward) of the firewall on the -11 for the C-90-8.

It's a booger to do, but can be done.

 

[Dan Gervae]

Interesting read....how many experimental guys put the mag timing back to 28 on their o200 and what prompted the change? I gather from the AD that cylinders were cracking? Anyways...read this link....interesting Dyno test of stock O200

http://flycorvair.com/thrust.html

 

[JimC]

Sea Level torque and horsepower curves for the C-85, C-90, O-200, 9.5 O-200, and 10.5 O-200.
Calculating O-200 power from measured J3 climb rates between 300 and 7800 feet indicate that the Corvair Team data for the O-200 was wrong and original Continental dyno information was right. Also, the O-200 power curve is still increasing at 3100 rpm. Corvair Team was wrong about that too.
As an aside, the Continental data point for the C-90 at 2350 rpm is also wrong.

Climbing out an O-200 J3 with a Mac 7535 at 55mph and 2850 rpm is quite a ride. Much prefer it to climbing a 90 out at 2475 rpm.

In side by side J3 flights with 85 Stroker and O-200, the O-200 performed better in takeoff roll, ROC, and top speed in level flight. I attribute that to the increased valve lift (0.410" vs 0.381"). That said, the 85 Stroker is an impressive performer in its own right.

Dan, restoring the timing to 28° gives a substantial boost in power. The reduction only applied to certain older Continental cylinders.

 

[Dan Gervae]

Jim, I knew you'd reply:smile: you've done more research on this than anyone I know and I love to read the development of your responses over the years. It makes sense to me. I have a C90 with the 88 cam and Sensenich 76Ak-2-40 prop on my TCraft on floats so I look forward to the comparison when I finish my PA11Ex and put the O200 on it. I had access to a C90 with a GPU crank for this project, but realized it was a-16 which is basically the same as the O200 except for the case and the GPU flange mod looked a bit sketchy to me. I got a great deal on an O200 with B&C starter and 8 amp alternator with very low time so now all I need to decide is what prop....I am hoping to come up with a Catto that works well for my needs, I've also given some thought to the Lycon 9.5:1 pistons or C85 pistons....but I'm not sure yet. I believe that with the right prop this stock o200 will do what I need to power this cub if I keep it as light as possible. I have some building to do yet so I have time to think about it.

 

[JimC]

Jerry Burr has done more testing with the O-200 than I have.

That Corvair article was goofy as a three dollar bill.

C-90 will outperform an O-200 when the rpm is less than 1800, or MP is less than 21", or altitude is much above 9000 feet.

I don't like the GPU flange mod.

C-85 pistons will give you 8.68:1 compression ratio. I've had good luck with Lycon 9.5's and 0.015" overbore.

I like the MA3-SPA 10-4115 carb.

 

[JimC]

Dan, what's your static rpm with the 40?
What rpm do you see during climbout at what airspeed?

 

[mvivion]

I have a j-3 converted to a pa-11 with atlee's stc. I currently have a lycoming, but would like to change to the lighter continental. I have heard you can get better horse power with the c-90 at lower rpm. The other thing I was wondering, I fly on floats so I want to use the best prop and engine combination together.

also can someone explain what they mean by " you can make your c90-12 into a c90-8, or you can put a 0-200 crank into the c-90" . I see this on various adds for continental engines for sale.

Any and all info would greatly be appreciated.

There have been several posts here, but few that address propeller. First, since you're certified, if you go with the C-90 engine, look at the propeller limits specified in the Type Certificate: Model PA-11:http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/ec36f12e6e139c5b8625785c006c09c8/$FILE/A-691%20Rev%2034.pdf


Look under equipment applicable at number 311, which applies to the C-90 engine installation. Metal props are limited to 71 or 72 inches diameter for that engine. Wood props can be as long as 76 inches. You'll need to look at the STC for installation of the O-200 for which props are approved on that installation.

Also, note the rpm limits for the C-90: 2475 rpm. The O-200 has a higher max rpm. So, when comparing engines on those graphs, be sure to consider those rpm limits for certified aircraft/engines.

MTV
(1) A-65-3 of A-65-8

 

[JimC]

O-200 and C-90-12F crank are identical, same part #. I'm having a senior moment about the -8F crank.
At sea level, the 90 will put out more power than the O-200 when rpm is below 1800 or manifold pressure is below 21".

Monte Warne at Boss Hoss in Dyersburg, TN has a freshly overhauled Sensenich AK76-2 38 prop for sale. That is ia pretty good prop for seaplanes, though I personally prefer a Mac 7535. Either would make you happy.

MTV is correct about the TCDS diameter limits. Keep in mind that you will lose about 5 thrust horsepower if you use a wood prop. Also note that the static limits are different betwen the J3 and PA11. Need to check your STC to see which applies to you. It is possible to mount other diameters by 337, though the paperwork can be tedious.

I would not recommend using the STC for mounting an O-200 on a J3. Far too many restrictions. That is the reason I did the O-200 J3 by 337 instead.

Here are the Continental horsepower versus manifold pressure curves for the 90 and O-200 at 2350 rpm and 2750 rpm.
2350 rpm is maximum static for the 90 on the 11 (2300 is max for the 3).
2750 rpm is rated rpm for the O-200.

 

[JimC]

Dan, have you considered a titanium firewall and a gillfab floorboard to save weight?

 

[Dan Gervae]

Dan, what's your static rpm with the 40?
What rpm do you see during climbout at what airspeed?

Jim, I don't remember my exact static cause I'm always on floats with that plane...but it get 2350-2400 on takeoff at 60mph. It varies some with conditions. It is a nice set up with that c90 and 76ak40 combo....I get 97 mph cruise on floats and 8-10 second tak offs when solo. Id love to slap my O200 on there with that prop for a real worl compare....but that's more fooling around than I'm willing to do for that answer:lol: oh...I have Hanson Wilson exhaust.....I got a hanlon Wilson with the O200 I bought last week too. I figured it works good on my T so why not. It may need some modification to fit under the 11 cowl. One more thing....where did find all those HP comparison curves? That is some specific stuff....its great info.

 

[Dan Gervae]

Dan, have you considered a titanium firewall and a gillfab floorboard to save weight?

No, The firewall is already fabricated...its galvanized and not as light as I would like and the boot cowl is done and fit and drilled already and that came out nice.....its a one piece wrap boot cowl. What's a Gillfab floorboard? (Carbon fiber?)I have 2 sets of plywood floorboards, one new. And one from a J3 for a template for all the holes. Any experience with the vacuum pad mounted 8amp B&C alternator ? I got one with my O200.... I haven't looked to see if it will fit Behind the PA11 nose bowl (Wag type) that I have. Wonder how many RPM it robs on takeoff;-)

 

[JimC]

Gillfab is a very light weight open core kevlar structural material used for aircraft floorboards.

Check the weight of a titanium firewall. You may decide the weight savings (though not a stunning reduction -- titanium is about the same density as aluminum) is worth redoing it.

8 amps at 12 volts is a bit over 0.1 hp output, so it is robbing roughly about 0 25 hp away from the engine, and that implies very little rpm loss. I've put one on a Cessna 140 with an 85 Stroker.

I replotted the curves taken from the Continental Service Manuals into a single Xcel spreadsheet and graphed the data to illuminate different aspects of the original data.

The high compression numbers are just a simple thermodynamic calculation that assume no change in timing, cam, or carburetion. The actual horsepower and torque numbers due to increasing compression may be less, but cannot be more (unless you also modify factors other than compression). In other words, this is what you get if you just pop a different set of pistons into the engine. You see a lot of impossibly high hot-rodding horsepower estimates on the internet, and that bugs me. The actual numbers aren't all that high. For example, the most I've ever seen during climbout in a J3 (55 mph with Mac 7535, 9.5 compression O-200, 2850 rpm) is only 114 hp. I normally climb a stock O-200 J3 out at about 80 to 85 hp at roughly 2500 to 2665 rpm. Performance is a little better than an 85, and marginally better than a 90 turning the same prop at 2475 rpm. Above about 9000 feet, the low manifold pressure allows the 90 to come into its own, and it gains the marginal advantage.

I haven't gotten around to doing the curves for the 85 Stroker yet, but the shape of the stock 85 torque and power curves lead me to expect the Stroker to do a little better than a 90 due to higher allowable rpm and a little worse than an O-200 due to reduced valve lift. All this assumes appropriate prop choices.

 

[cubdriver2]

Jim, I don't remember my exact static cause I'm always on floats with that plane...but it get 2350-2400 on takeoff at 60mph. It varies some with conditions. It is a nice set up with that c90 and 76ak40 combo....I get 97 mph cruise on floats and 8-10 second tak offs when solo. Id love to slap my O200 on there with that prop for a real worl compare....but that's more fooling around than I'm willing to do for that answer:lol: oh...I have Hanson Wilson exhaust.....I got a hanlon Wilson with the O200 I bought last week too. I figured it works good on my T so why not. It may need some modification to fit under the 11 cowl. One more thing....where did find all those HP comparison curves? That is some specific stuff....its great info.

I don't think the HW exhaust will fit under an 11 cowl. A stock 11 exhaust barely fits.

Glenn

 

[JimC]

Dan, are you running a 76AK 40
or a
76AK-2 40 ?

 

[Dan Gervae]

It's a 76AK-2-40 but if you measure it, measures exactly 75" tip to tip...maybe because the tips are round they call it 74" I know that the -2 means they start at 76 and cut off 2" but the tape says 75"...Exactly. It really is an impressive performer. I can't wait to try my new ex 11 cub out against it as a comparison . I also have a 65hp j3/L4 and an 85 hp TCraft...I'll have to sell some of this stuff one of these days ... But as I say when asked...why do you have 5 airplanes? Because I can't afford 6!

 

[Dan Gervae]

I don't think the HW exhaust will fit under an 11 cowl. A stock 11 exhaust barely fits.

Glenn

yah...it looks tight. I'll try to modify it to make it fit

yes...it's in The house and I know that's a J3 mount. Lol

 

[Dan Gervae]

Here is the firewall and boot

 

[JimC]

Where?