O200 and C90 power / torque curves
- Thread starter gcgilpin
- Start date
I found this on Harry Fenton's site bowersflybaby.com....I have seen, and believed many opinions on this....what do the rest of you think?
Altering An O-200's Power Curve
I am looking at buying a J3 prodject. Frame and wings almost done sans covering. The engine is a 1500 hour 0200 off of a C-150. All I have been able to determine is that the power curve on a stock 0200 is not the best for a cub type a/c. It has bben suggested to change the cam to a C-90 and get the same power curve as a C-90. It seems there is a question as to what lifters you can use and if a carb. jetting change might be needed. If I get this project I may just run it as is till I get to TBO then overhaul it an make the changes then.
I am wondering if you have any thoughts on this. Have you had any experience with converting a 0200 to have a more C-90 power curve?
There has been the wives tale of the C-90 vs O-200 for years. I strive to base my answers on factual data, and avoid lending credence to the unsubstantiated claims, but there is the possibility that there is some science behind this wives tale.
Nearly 25 years ago, a veteran Continental rep told me that the C-90 cam was a bit hotter than the O-200 cam. The reason? The C-90 was in production when wood props were common, but wood props were not as efficient as metal, therefore the C-90 cam had a bit more aggressive profile to extract a bit more torque to achieve equivalent performance from the wood prop vs the metal prop. When the O-200 hit production, wood props were not used on production planes, so the cam profile was optimized for the more efficient metal props. So, while I don't have hard data to work from, the comments from a veteran Continental engineer that I trusted make the premise that the C-90 cam is a bit hotter than the O-200 cam believable.
There may be an apples to oranges comparison to the C-90 and the O-200 which may appear to be credited to the cam, when, in fact, the cam has no effect. The C-90-8 is a non-electrical engine and the O-200 is usually fitted with a starter, generator, etc. The -8 engine can weigh as much as 20 lbs less than the C-90-8. Less weight feels like more power.
A major hurdle to jump is that the C-90 cam is not a legal installation in the O-200, so you would need to obtain some sort of FAA approval to make it legal. You will undoubtedly be told that the C-90 cam just drops in, which is true in the mechanical fit sense, but it is not FAA approved.
Having said that, let's step away from theory and into the real world. To notice the benefit of the C-90 cam, all things would need to be equal in terms of engine and airframe, and in the Cub world, this rarely happens. Airframe rigging, weight, propeller, engine condition and pitot static system calibration all play a factor in determining comparison performance. A C-90 on a straight, light Cub will perform much better than an O-200 on a heavy, out of rig Cub. Aircraft trim will also play a factor in Cub performance as the trim is controlled by moving the horizontal tail via a screw jack. Due to varying aircraft CG and engine thrust line the trim position will change and affect the overall drag of the airframe.
The underlying theme here is that the C-90 cam may provide some benefit, but either the C-90 or O-200 has ample reserve power to pull a loaded Cub around on a hot summer day. Build your O-200 light and remove the accessories and you will probably be very satisfied with the performance of your Cub.
Harry
Altering An O-200's Power Curve
I am looking at buying a J3 prodject. Frame and wings almost done sans covering. The engine is a 1500 hour 0200 off of a C-150. All I have been able to determine is that the power curve on a stock 0200 is not the best for a cub type a/c. It has bben suggested to change the cam to a C-90 and get the same power curve as a C-90. It seems there is a question as to what lifters you can use and if a carb. jetting change might be needed. If I get this project I may just run it as is till I get to TBO then overhaul it an make the changes then.
I am wondering if you have any thoughts on this. Have you had any experience with converting a 0200 to have a more C-90 power curve?
There has been the wives tale of the C-90 vs O-200 for years. I strive to base my answers on factual data, and avoid lending credence to the unsubstantiated claims, but there is the possibility that there is some science behind this wives tale.
Nearly 25 years ago, a veteran Continental rep told me that the C-90 cam was a bit hotter than the O-200 cam. The reason? The C-90 was in production when wood props were common, but wood props were not as efficient as metal, therefore the C-90 cam had a bit more aggressive profile to extract a bit more torque to achieve equivalent performance from the wood prop vs the metal prop. When the O-200 hit production, wood props were not used on production planes, so the cam profile was optimized for the more efficient metal props. So, while I don't have hard data to work from, the comments from a veteran Continental engineer that I trusted make the premise that the C-90 cam is a bit hotter than the O-200 cam believable.
There may be an apples to oranges comparison to the C-90 and the O-200 which may appear to be credited to the cam, when, in fact, the cam has no effect. The C-90-8 is a non-electrical engine and the O-200 is usually fitted with a starter, generator, etc. The -8 engine can weigh as much as 20 lbs less than the C-90-8. Less weight feels like more power.
A major hurdle to jump is that the C-90 cam is not a legal installation in the O-200, so you would need to obtain some sort of FAA approval to make it legal. You will undoubtedly be told that the C-90 cam just drops in, which is true in the mechanical fit sense, but it is not FAA approved.
Having said that, let's step away from theory and into the real world. To notice the benefit of the C-90 cam, all things would need to be equal in terms of engine and airframe, and in the Cub world, this rarely happens. Airframe rigging, weight, propeller, engine condition and pitot static system calibration all play a factor in determining comparison performance. A C-90 on a straight, light Cub will perform much better than an O-200 on a heavy, out of rig Cub. Aircraft trim will also play a factor in Cub performance as the trim is controlled by moving the horizontal tail via a screw jack. Due to varying aircraft CG and engine thrust line the trim position will change and affect the overall drag of the airframe.
The underlying theme here is that the C-90 cam may provide some benefit, but either the C-90 or O-200 has ample reserve power to pull a loaded Cub around on a hot summer day. Build your O-200 light and remove the accessories and you will probably be very satisfied with the performance of your Cub.
Harry
There are two cams for the C-90. One is exactly the same as the O-200 cam, the other has a different (older) profile and has more torque at lower RPM.
However for the higher torque cam to work you need to have a very freeflowing exhaust, otherwise it actually is worse than the O-200 cam.
There was a major thread on this somewhere. Do a search for C-90 and you should find it.
BTW the two different cams use different lifters.
Frank
However for the higher torque cam to work you need to have a very freeflowing exhaust, otherwise it actually is worse than the O-200 cam.
There was a major thread on this somewhere. Do a search for C-90 and you should find it.
BTW the two different cams use different lifters.
Frank
I guess the bottom line for me is that I can spin a 76AK-2-40 prop with my C90-12f @ 2450-2475 RPMs on takeoff and produce nearly 90HP with a nice long prop and break the water in a short distance....I would have to have either a shorter prop...or a much flatter prop to be able to get the full 2750 rpms required to get 100HP from an O-200. I guess that is really what makes the C90 a better choice for me...I have read the thread called "C90 expert", and it is all very good info. I still believe that the above stated reason is why most make the statement on the "power curve" being better for our type of flying....which I'm assuming is either Float flying or short field off airport flying. JMHO
acroeric
SPONSOR
Burlington, NC
The Hot cam for the C90 is a P/N 530788 and it takes special lifter bodies. The difference is that it has 35 degrees of overlap compared to the 24 degree overlap of the O-200 and C9o standard cam.
To take advantage of the cam timing you need a very free flowing exhaust (Lusccombe 8E etc) and not a 4 in to 1 set up like on a stock cub.
To take advantage of the cam timing you need a very free flowing exhaust (Lusccombe 8E etc) and not a 4 in to 1 set up like on a stock cub.
Roger Peterson
Registered User
Sweeny, Texas
I just finished building a 0-200 up with a 530788 cam, 9.5 to one pistons and fully ported intake and exhaust. Mounted a 76AK-2-40 on it and it turns 2500 static. Really feels strong. Have the timing set at 20 deg but may try 22 deg after I get 25 hr or so on it. The static rpm is 200 higher than with the 0-200 cam. The 76AK-2-40 is really smooth and has no resonance points. Only have 2 hr on it but seems good so far.
I note in passing that the diameter limits for a 76AK-2 prop on a Continental are max 74, min 72 (many folks think it is a 76 inch diameter propeller).
Using a 1B90-71-42, on an O-200 powered J-3, I get about 2550 static, and about 2640 during climb. By comparison, a 1B90-74-41 statics at 2500 (about the same static as Roger's ?74?-40) and climbs out at about 2600, but the 74-41 isn't legal on the O-200 yet.
Based on my experience, I'd say if you have a C90 lying around use it. If you have an O-200, use it. If you have both, use the one that's most convenient.
Using a 1B90-71-42, on an O-200 powered J-3, I get about 2550 static, and about 2640 during climb. By comparison, a 1B90-74-41 statics at 2500 (about the same static as Roger's ?74?-40) and climbs out at about 2600, but the 74-41 isn't legal on the O-200 yet.
Based on my experience, I'd say if you have a C90 lying around use it. If you have an O-200, use it. If you have both, use the one that's most convenient.
Roger Peterson
Registered User
Sweeny, Texas
If you build up one like I did and put a 4 into 1 exhaust on it, Make sure you have good noise limiting headsets and put a turndown on the exhause. It does beller.
Jerry Burr
MEMBER
Sedro Woolley, Washington.
timing
Hi Roger. Do you really mean 20deg? Or 30deg and going to try 32? Jerry.
Hi Roger. Do you really mean 20deg? Or 30deg and going to try 32? Jerry.
redrooster
Registered User
western Washington
Re: timing
Yeah, that struck me wrong too.
Jerry Burr said:
Yeah, that struck me wrong too.
Roger Peterson
Registered User
Sweeny, Texas
For compression of 9.5/1 or more set you ignition timing to 20 degrees BTDC.For compression of 8.9/1 - 9.5/1 set you ignition timing to 22 degrees BTDC. for 8.5 / 1 set it to 25 degrees BTDC. Fuel burns faster if the compression is higher and if the cylinders are ported, you need less advance.
0-200/C90 Power
I'm not quite grasping this whole C90/0-200 rpm issue,90/100 hp?If you want to get out put the longest flattest prop that the engine will spin and spin it! Use a prop that puts enough load on the engine so that it pulls as high as you dare turn it.Too flat it won't load the engine,too coarse the engine won't get to max power.If you want more cruise then put some pitch in it.I turn my 0-200 2600 static with a 75/35 Mac and it works real good.I really don't care about cruise ,it's a cub.
I'm not quite grasping this whole C90/0-200 rpm issue,90/100 hp?If you want to get out put the longest flattest prop that the engine will spin and spin it! Use a prop that puts enough load on the engine so that it pulls as high as you dare turn it.Too flat it won't load the engine,too coarse the engine won't get to max power.If you want more cruise then put some pitch in it.I turn my 0-200 2600 static with a 75/35 Mac and it works real good.I really don't care about cruise ,it's a cub.
redrooster
Registered User
western Washington
Roger, I seem to recall that you were running an O-200 on your Cub with one mag & one elctronic ignition. Are you talking about setting the timing on the mag or on the electronic side? Or is this a different set-up and/or on another airplane?
Rooster
Rooster
Roger Peterson
Registered User
Sweeny, Texas
Same plane, but the electronic ign started to go south and have not had time to do some improvements and mods to it so I put a mag on both sides. Coming back from Canada I ended up coming in the last 100 miles on the mag only. Bad weather and it didn't give me a warm fuzzy feeling.
redrooster
Registered User
western Washington
Roger, thanks for clearing that up. I seem to recall also that you talked about the advance changing on the electronic side, like you maybe had a digital readout of when it fired? What was the timing range, like for example timing at idle,at cruise, climb-out,etc? And where was the one mag set?
Rooster
Rooster
Roger Peterson
Registered User
Sweeny, Texas
I have not recorded the timing under all different conditions, but it was quite close to the description on: http://www.lsecorp.com/Products/IgnitionIIPlus.htm#Display1
The set of pistons that tested 9:1 was timed at 25 deg on the mag and I used a timing light to set the electronic ign. There is also a procedure to calibrate the display to the actual timing, but I never did that. I just used it as a indicator to make sure the ign was working properly. I did not put in the pot so that I could adjust the timing while flying as I figured I would total the engine trying to get the last little bit out of it.
As I said, I am not using it right now as I want to do some redesign.
If you are interested, Klaus is great to work with and really knows what he is doing.
The set of pistons that tested 9:1 was timed at 25 deg on the mag and I used a timing light to set the electronic ign. There is also a procedure to calibrate the display to the actual timing, but I never did that. I just used it as a indicator to make sure the ign was working properly. I did not put in the pot so that I could adjust the timing while flying as I figured I would total the engine trying to get the last little bit out of it.
As I said, I am not using it right now as I want to do some redesign.
If you are interested, Klaus is great to work with and really knows what he is doing.
In case anyone's looking for the power curves here's a link that covers the A65 through to the O200.
http://www.popularaviation.com/docs/ContinentalPowerCurves.pdf
(not clear what cam the C90 curve is based on)
http://www.popularaviation.com/docs/ContinentalPowerCurves.pdf
(not clear what cam the C90 curve is based on)
Note that the C90 and O200 power curves are basically the same up to ~95 HP at ~2600 RPM (after which the C90 power curve flattens out while the O200 continues to increase).
It would follow that the torque curves are also the same since
Power (HP) = Torque (ft-lb) * RPM / 5250
It would follow that the torque curves are also the same since
Power (HP) = Torque (ft-lb) * RPM / 5250
supercrow
FRIEND
Smith Pond near Millinocket, Me
C90-0200
Hi Guys. For me, WillyB said it the way it's easiest to judge performance. I can't help you with the numbers and the power curves. I can tell you this because I did it myself some years ago. Three J-3's-no doubt all different weights, but all with no electrical systems. All happened to be on floats at the time and on the same afternoon within an hour and a half, I put my Sensenich 76AK-2-38 on all three airplanes and checked static RPM,and we flew them once around the block.Because of the unknown weights, which I believe would be within 30 or 40 lbs., because I knew all three quite well, I can't give absolute results. What we did learn was that the 0200 turned less static RPM and used more water to get off. The C-90 worked some better and actually sounded stronger going out. The 85 stroker which was on my cub turned higher static and jumped out of the water well ahead of the others. All the engines were in good shape and well taken care off. My stroker would turn 2575 to 2625 static depending on conditions. Both the others were under 2500. For me, in stock configuration, give me the 90, then the 0200-and finally the 85 which isn't a lot better than a 65 or 75. Talking changing cams, etc. give me the 85 stroker,90 and then the 0200. Remember I'm just adding info here, talking about short ponds on floats on a high density day.Thanks for the opportunity to put in my two cents. I might add that I wasn't looking for speed in my fishing buggy and I'm sure it didn't pull and cruise on the top like more prop would. As I remember, around 75 MPH was about it, but I wasn't going very far and it worked for me. My stroker was built over 30 yrs. ago, well before the popularity and legality that it is offered today, but it really got the job done as compared to the other engines. Reid
Hi Guys. For me, WillyB said it the way it's easiest to judge performance. I can't help you with the numbers and the power curves. I can tell you this because I did it myself some years ago. Three J-3's-no doubt all different weights, but all with no electrical systems. All happened to be on floats at the time and on the same afternoon within an hour and a half, I put my Sensenich 76AK-2-38 on all three airplanes and checked static RPM,and we flew them once around the block.Because of the unknown weights, which I believe would be within 30 or 40 lbs., because I knew all three quite well, I can't give absolute results. What we did learn was that the 0200 turned less static RPM and used more water to get off. The C-90 worked some better and actually sounded stronger going out. The 85 stroker which was on my cub turned higher static and jumped out of the water well ahead of the others. All the engines were in good shape and well taken care off. My stroker would turn 2575 to 2625 static depending on conditions. Both the others were under 2500. For me, in stock configuration, give me the 90, then the 0200-and finally the 85 which isn't a lot better than a 65 or 75. Talking changing cams, etc. give me the 85 stroker,90 and then the 0200. Remember I'm just adding info here, talking about short ponds on floats on a high density day.Thanks for the opportunity to put in my two cents. I might add that I wasn't looking for speed in my fishing buggy and I'm sure it didn't pull and cruise on the top like more prop would. As I remember, around 75 MPH was about it, but I wasn't going very far and it worked for me. My stroker was built over 30 yrs. ago, well before the popularity and legality that it is offered today, but it really got the job done as compared to the other engines. Reid
I recently installed a new aeromatic prop(tarver propellers) and i was turning 2390 rpm w/7147 mac prop on takeoff but now i get 2640 rpm which makes a substantial difference in performance. i could increase the rpm to 2700 with additional arm weight but the book only calls for max 2625 rpm for 5 min. so i'm a little leery to go to 2700 rpm- should i be?
Longwinglover
Registered User
Charlotte, NC
Do you REALLY think you are going to see a dramatic performance increase with an additional 60 RPM (now 75 RPM) over the manufacturers recommended limit? :roll:
John Scott
John Scott
behindpropellers
Registered User
NE Ohio
Longwinglover said:
Please....Let this dead horse of the 0-200 VS C90 VS C85 be dead!!
Longwinglover
Registered User
Charlotte, NC
behindpropellers said:
Gee, Tim, I thought that was what I was pushing for. Does he REALLY think 75 RPM (5 HP - 95 to 100) is going to make a dramatic difference in his takeoff? All this round and round about a 15 HP spread.
What is it that I said that you picked on me??
John Scott
cubdriver2
FRIEND
upstate NY
Longwinglover said:
John,I guess you never had a hotrod or were a bench shooter :lol:
Glenn
AntiCub
Registered User
North Pole
Here's a site for a corvair conversion manufacturer that set up a dyno to test their conversion against an O-200. The numbers for the O-200 are interesting.
http://www.flycorvair.com/thrust.html
and excerpt from the site above:
Phil
http://www.flycorvair.com/thrust.html
and excerpt from the site above:
Phil
I run my 9.5 O-200 at 28 degrees BTDC on mogas.
Here are sea level torque curves at 29 inches MP for the C-85, C-90, O-200, 9.5 O-200, and 10.5 O-200. Torque is in pounds-force-foot, commonly called pound-foot. Stock O-200 is in red, stock C-90 in blue. Note the bad Continental C-90 data point at 2350 rpm.
Also a horsepower chart for the stock C-90 and stock O-200 at varying manifold pressures for 2750 rpm. The C-90 produces more power than the O-200 at idle rpm and also at full power when above 9500 feet pressure altitude. Below 9500 feet, the O-200 is the better performer. The 9.5 pistons bump the power and torque up by 9.76%.
With the 9.5 pistons and a Mac 7535 prop turning 2800-2850 rpm at 28 degrees BTDC during a 55 mph climb, the O-200 J3 is quite a perky performer at roughly 114 hp output during the climb. Top speed in level flight with the 7535 is about 110 mph. With a 7142, 118 mph.
Here are sea level torque curves at 29 inches MP for the C-85, C-90, O-200, 9.5 O-200, and 10.5 O-200. Torque is in pounds-force-foot, commonly called pound-foot. Stock O-200 is in red, stock C-90 in blue. Note the bad Continental C-90 data point at 2350 rpm.
Also a horsepower chart for the stock C-90 and stock O-200 at varying manifold pressures for 2750 rpm. The C-90 produces more power than the O-200 at idle rpm and also at full power when above 9500 feet pressure altitude. Below 9500 feet, the O-200 is the better performer. The 9.5 pistons bump the power and torque up by 9.76%.
With the 9.5 pistons and a Mac 7535 prop turning 2800-2850 rpm at 28 degrees BTDC during a 55 mph climb, the O-200 J3 is quite a perky performer at roughly 114 hp output during the climb. Top speed in level flight with the 7535 is about 110 mph. With a 7142, 118 mph.
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