2 stroke compared to 4 stroke
10-26-2010 | 10:19 PM
#26
Senior Member
RE: 2 stroke compared to 4 stroke
ORIGINAL: Mikecam
With the DLE 20 out pulling the saito 125 glow I see no reason not to go to gas for everything that size. Another option!!!!
With the DLE 20 out pulling the saito 125 glow I see no reason not to go to gas for everything that size. Another option!!!!
I converted all of my 140-180 glow 2 strokes to the SAP 30cc (180) gassie 2 stroke on pipe just about 1 year ago. Never had the need to look back. Flew alot over the spring and summer and burned around 10 gallons of gasoline, 14 ozs at a time. A tank lasts around 20 minutes and that's alot of flight time.
Ran 4 strokes maybe 8 years ago, YS120 and 140. Nice engines but anemic compared to 2 stroke of equal displacement. The present day YS170 is the sole exception, making gobs of useful power but running 30% nitro most of the time. That fuel has become very pricy and the engine often uses 24 ozs per flight. The cost differential per flight is something like 20X compared to 2 stroke gasoline
10-26-2010 | 10:21 PM
#27
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From: Everett,
WA
RE: 2 stroke compared to 4 stroke
For a comparison that has a lot of examples all one needs to do is look at the old FAI F3A engines. These engines were held to a 10cc displacement for the two cycle and 20 cc for the four cycle. Now all one has to do is look at the record book to see that even with 200% advantage the four cycle engine was hard pressed to beat the 2 cycle for a myriad of reasons. So for aircraft that were/are critically judged the two cycle is the superior set up for our toys unless one give the four cycle an inordinate displacement advantage. Now in this example both engine types were competition engine. For the sport pilot the formula might not be the same.
All the best,
Konrad
All the best,
Konrad
10-27-2010 | 12:16 AM
#28
My Feedback: (16)
RE: 2 stroke compared to 4 stroke
ORIGINAL: Konrad
For a comparison that has a lot of examples all one needs to do is look at the old FAI F3A engines. These engines were held to a 10cc displacement for the two cycle and 20 cc for the four cycle. Now all one has to do is look at the record book to see that even with 200% advantage the four cycle engine was hard pressed to beat the 2 cycle for a myriad of reasons. So for aircraft that were/are critically judged the two cycle is the superior set up for our toys unless one give the four cycle an inordinate displacement advantage. Now in this example both engine types were competition engine. For the sport pilot the formula might not be the same.
All the best,
Konrad
For a comparison that has a lot of examples all one needs to do is look at the old FAI F3A engines. These engines were held to a 10cc displacement for the two cycle and 20 cc for the four cycle. Now all one has to do is look at the record book to see that even with 200% advantage the four cycle engine was hard pressed to beat the 2 cycle for a myriad of reasons. So for aircraft that were/are critically judged the two cycle is the superior set up for our toys unless one give the four cycle an inordinate displacement advantage. Now in this example both engine types were competition engine. For the sport pilot the formula might not be the same.
All the best,
Konrad
10-27-2010 | 12:23 AM
#29
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From: Eagle HeightsQueensland, AUSTRALIA
RE: 2 stroke compared to 4 stroke
Nitromethane is mostly a USA only kind of thing anyway. Everyone outside of the USA is running zero nitro or model diesel fuel or gasoline (petrol) of course.
Model diesel fuel (1/3rd kerosene, 1/3rd ether, 1/3rd castor oil) is quite rare here, and prohibitively expensive. That wasn't the case in the 80s and before but now ether is very difficult to purchase. Petrol (gasoline) models are quite popular but most guys run either 2 stroke or 4 stroke models with nitro quite common.
10-27-2010 | 12:33 AM
#30
Senior Member
RE: 2 stroke compared to 4 stroke
Funny, I cant get the local hobby shop to stock anything LESS than 10% nitro. Irun some european engines and would like to get low nitro fuel quick and easy.
10-27-2010 | 12:53 PM
#32
RE: 2 stroke compared to 4 stroke
ORIGINAL: MinnFlyer
A lot depends on the specific engine, but I generally say:
40 - 46 (2-stroke) = 52 - 70 (4-stroke)
55 - 65 = 91 - 100
75 - 90 = 110 -125
Larger than that, Gasoline
A lot depends on the specific engine, but I generally say:
40 - 46 (2-stroke) = 52 - 70 (4-stroke)
55 - 65 = 91 - 100
75 - 90 = 110 -125
Larger than that, Gasoline
10-27-2010 | 01:28 PM
#33
RE: 2 stroke compared to 4 stroke
ORIGINAL: Airplanes400
I agree with the above with the exception of a .52 4-stroke engine. I'd equate them to a 25 to 32 sized two-stroke engine. I have always used .70 4-strokes in place of a .46 2-stroke.
I agree with the above with the exception of a .52 4-stroke engine. I'd equate them to a 25 to 32 sized two-stroke engine. I have always used .70 4-strokes in place of a .46 2-stroke.
10-27-2010 | 01:57 PM
#34
My Feedback: (66)
RE: 2 stroke compared to 4 stroke
mike yes i know the 125 is 2.3 ounces more in weight but why buy a 91,100,115 when all four are with in 2 ounces of each other.
Why buy a 56, 62, or 72 when the 82 is very close in weight.
Also mike the 91 is lighter than the 100 by about .7 ounces.
my point is if getting a saito get the most power per weight, buy the 40, 82, 125 and 180 over the 150. yes the 220 is 7 ounces more but alot more engine over the 180.
wy8e said it best yes back in the day of early four strokes the two strokes where king, but pattern has change to flying slower and ata more consistent speed through the pattern big props do that.
The new YS 70 is very close if not beating the 60 two strokes with regular muffler. It will turn an 12x8 APC at just over 12,000
My saito 125's will spin a 14x10 APC over 11,000
saito 40 spins APC12x4 at 11,400 on 30%
Why buy a 56, 62, or 72 when the 82 is very close in weight.
Also mike the 91 is lighter than the 100 by about .7 ounces.
my point is if getting a saito get the most power per weight, buy the 40, 82, 125 and 180 over the 150. yes the 220 is 7 ounces more but alot more engine over the 180.
wy8e said it best yes back in the day of early four strokes the two strokes where king, but pattern has change to flying slower and ata more consistent speed through the pattern big props do that.
The new YS 70 is very close if not beating the 60 two strokes with regular muffler. It will turn an 12x8 APC at just over 12,000
My saito 125's will spin a 14x10 APC over 11,000
saito 40 spins APC12x4 at 11,400 on 30%
10-27-2010 | 02:10 PM
#35
RE: 2 stroke compared to 4 stroke
ORIGINAL: w8ye
And where are the 10cc engines in pattern today? Even the SPA is dominated by 15cc four strokes
ORIGINAL: Konrad
For a comparison that has a lot of examples all one needs to do is look at the old FAI F3A engines. These engines were held to a 10cc displacement for the two cycle and 20 cc for the four cycle. Now all one has to do is look at the record book to see that even with 200% advantage the four cycle engine was hard pressed to beat the 2 cycle for a myriad of reasons. So for aircraft that were/are critically judged the two cycle is the superior set up for our toys unless one give the four cycle an inordinate displacement advantage. Now in this example both engine types were competition engine. For the sport pilot the formula might not be the same.
All the best,
Konrad
For a comparison that has a lot of examples all one needs to do is look at the old FAI F3A engines. These engines were held to a 10cc displacement for the two cycle and 20 cc for the four cycle. Now all one has to do is look at the record book to see that even with 200% advantage the four cycle engine was hard pressed to beat the 2 cycle for a myriad of reasons. So for aircraft that were/are critically judged the two cycle is the superior set up for our toys unless one give the four cycle an inordinate displacement advantage. Now in this example both engine types were competition engine. For the sport pilot the formula might not be the same.
All the best,
Konrad
10-27-2010 | 02:28 PM
#36
Senior Member
My Feedback: (4)
RE: 2 stroke compared to 4 stroke
ORIGINAL: Airplanes400
I agree with the above with the exception of a .52 4-stroke engine. I'd equate them to a 25 to 32 sized two-stroke engine. I have always used .70 4-strokes in place of a .46 2-stroke.
ORIGINAL: MinnFlyer
A lot depends on the specific engine, but I generally say:
40 - 46 (2-stroke) = 52 - 70 (4-stroke)
55 - 65 = 91 - 100
75 - 90 = 110 -125
Larger than that, Gasoline
A lot depends on the specific engine, but I generally say:
40 - 46 (2-stroke) = 52 - 70 (4-stroke)
55 - 65 = 91 - 100
75 - 90 = 110 -125
Larger than that, Gasoline
10-27-2010 | 03:05 PM
#37
RE: 2 stroke compared to 4 stroke
I have made a comparison among the recommendations for 2 and 4 stroke for several of the ARF's and kits commercialized by Tower Hobbies.
The rate is about 30% more displacement up for an equivalent 4-stroke.
In this case: 0.52 / 1.3 = 0.40
Since you guys have plenty of experience with these engines, let me know of any inaccuracies you believe my chart may show.
The rate is about 30% more displacement up for an equivalent 4-stroke.
In this case: 0.52 / 1.3 = 0.40
Since you guys have plenty of experience with these engines, let me know of any inaccuracies you believe my chart may show.
10-27-2010 | 04:01 PM
#38
RE: 2 stroke compared to 4 stroke
ORIGINAL: MinnFlyer
There was a time I would have agreed with you, but I've got an OS 52 which I have used in several 40 size planes that was MORE than enough power!
ORIGINAL: Airplanes400
I agree with the above with the exception of a .52 4-stroke engine. I'd equate them to a 25 to 32 sized two-stroke engine. I have always used .70 4-strokes in place of a .46 2-stroke.
ORIGINAL: MinnFlyer
A lot depends on the specific engine, but I generally say:
40 - 46 (2-stroke) = 52 - 70 (4-stroke)
55 - 65 = 91 - 100
75 - 90 = 110 -125
Larger than that, Gasoline
A lot depends on the specific engine, but I generally say:
40 - 46 (2-stroke) = 52 - 70 (4-stroke)
55 - 65 = 91 - 100
75 - 90 = 110 -125
Larger than that, Gasoline
10-27-2010 | 04:02 PM
#39
RE: 2 stroke compared to 4 stroke
ORIGINAL: Lnewqban
I have made a comparison among the recommendations for 2 and 4 stroke for several of the ARF's and kits commercialized by Tower Hobbies.
The rate is about 30% more displacement up for an equivalent 4-stroke.
In this case: 0.52 / 1.3 = 0.40
Since you guys have plenty of experience with these engines, let me know of any inaccuracies you believe my chart may show.
I have made a comparison among the recommendations for 2 and 4 stroke for several of the ARF's and kits commercialized by Tower Hobbies.
The rate is about 30% more displacement up for an equivalent 4-stroke.
In this case: 0.52 / 1.3 = 0.40
Since you guys have plenty of experience with these engines, let me know of any inaccuracies you believe my chart may show.
I don't know as much as these guys, but here's what comes to my mind:
I have 3 4-stroke engines, and I use them in 3D planes and 1 nostalgic style model. I prefer 2-strokes for general sport and high speed flying. Last year a guy at our club was hell-bent on getting max speed in his Shoestring and kept leaning out his Saito and overheating it. I think that if he wanted more speed, he should have used a 2-stroke.
I don't think adjusting the valve lash is a pain, just do it once and you will have no trouble at all. As said before, if you never have to fiddle with the needles, adjusting the valve lash once a year is a big plus (I know some guys who have never adjusted the valve lash on their engines and they still run ok).
When comparing the weights of 2 vs. 4 stroke engines, make sure the numbers include the muffler. The 2-stroke mufflers are big, fat, heavy, and ugly compared to the 4-stoke mufflers.
Despite the 30% difference in displacement to power the same model: 40 2-stroke vs. 52 4-stroke, 50 2-stroke vs. 70 4-stroke, etc... you will still get much better fuel economy with a 4-stroke.
Generally, 4-strokes are much quiter than 2-stroke nitros, and much quiter than the gassers. If people put the same muffler and noise restrictions on gassers as they did on the nitros, the gassers might not look as attractive.
Ok, I've said too much already. The three moderators can straighten me out now.
10-27-2010 | 04:11 PM
#40
RE: 2 stroke compared to 4 stroke
ORIGINAL: wyo69cowboy
Depends on how big your 40 size plane is; I had a Phoenix Decathlon with an OS46; my buddy built the same plane and used a Magnum .52. This plane calls for .46 2 stroke or .52-70 4 strokes, and weighed just over 6 lbs. I never thought the .46 was a powerhouse in this plane, but the .52 will barely do a loop with it, not for lack of trying props or anything else on the .52.
ORIGINAL: MinnFlyer
There was a time I would have agreed with you, but I've got an OS 52 which I have used in several 40 size planes that was MORE than enough power!
ORIGINAL: Airplanes400
I agree with the above with the exception of a .52 4-stroke engine. I'd equate them to a 25 to 32 sized two-stroke engine. I have always used .70 4-strokes in place of a .46 2-stroke.
ORIGINAL: MinnFlyer
A lot depends on the specific engine, but I generally say:
40 - 46 (2-stroke) = 52 - 70 (4-stroke)
55 - 65 = 91 - 100
75 - 90 = 110 -125
Larger than that, Gasoline
A lot depends on the specific engine, but I generally say:
40 - 46 (2-stroke) = 52 - 70 (4-stroke)
55 - 65 = 91 - 100
75 - 90 = 110 -125
Larger than that, Gasoline
10-27-2010 | 04:55 PM
#41
Senior Member
RE: 2 stroke compared to 4 stroke
ORIGINAL: Sport_Pilot
And modern pattern is dominated by 25cc two strokes. When the weight reach's max the trend is toward two strokes. If a little lighter then a four stroke.
And modern pattern is dominated by 25cc two strokes. When the weight reach's max the trend is toward two strokes. If a little lighter then a four stroke.
10-27-2010 | 07:40 PM
#42
My Feedback: (16)
RE: 2 stroke compared to 4 stroke
Looking down through the thread, there were a couple references to Magnum 52 four strokes not having the power of a 46 two stroke.
I've seen a lot of the Magnum four strokes with less than satisfactory power.
These poor performing ones I've personally looked at had the cam timing advanced one tooth. This gave a great idle but took the engine performance down one prop size.
These engines when the piston at top dead center had the cam timing mark straight up and down. Either 6:00 or 12:00. And this was from the factory!
The proper timing position is in alignment with the push rods. Preferably with the mark dead center with the exhaust cam follower hole.
I've seen a lot of the Magnum four strokes with less than satisfactory power.
These poor performing ones I've personally looked at had the cam timing advanced one tooth. This gave a great idle but took the engine performance down one prop size.
These engines when the piston at top dead center had the cam timing mark straight up and down. Either 6:00 or 12:00. And this was from the factory!
The proper timing position is in alignment with the push rods. Preferably with the mark dead center with the exhaust cam follower hole.
10-27-2010 | 08:25 PM
#43
RE: 2 stroke compared to 4 stroke
ORIGINAL: w8ye
Looking down through the thread, there were a couple references to Magnum 52 four strokes not having the power of a 46 two stroke.
I've seen a lot of the Magnum four strokes with less than satisfactory power.
These poor performing ones I've personally looked at had the cam timing advanced one tooth. This gave a great idle but took the engine performance down one prop size.
These engines when the piston at top dead center had the cam timing mark straight up and down. Either 6:00 or 12:00. And this was from the factory!
The proper timing position is in alignment with the push rods. Preferably with the mark dead center with the exhaust cam follower hole.
Looking down through the thread, there were a couple references to Magnum 52 four strokes not having the power of a 46 two stroke.
I've seen a lot of the Magnum four strokes with less than satisfactory power.
These poor performing ones I've personally looked at had the cam timing advanced one tooth. This gave a great idle but took the engine performance down one prop size.
These engines when the piston at top dead center had the cam timing mark straight up and down. Either 6:00 or 12:00. And this was from the factory!
The proper timing position is in alignment with the push rods. Preferably with the mark dead center with the exhaust cam follower hole.
10-28-2010 | 01:00 AM
#46
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From: Everett,
WA
RE: 2 stroke compared to 4 stroke
ORIGINAL: w8ye
And where are the 10cc engines in pattern today? Even the SPA is dominated by 15cc four strokes
ORIGINAL: Konrad
For a comparison that has a lot of examples all one needs to do is look at the old FAI F3A engines. These engines were held to a 10cc displacement for the two cycle and 20 cc for the four cycle. Now all one has to do is look at the record book to see that even with 200% advantage the four cycle engine was hard pressed to beat the 2 cycle for a myriad of reasons. So for aircraft that were/are critically judged the two cycle is the superior set up for our toys unless one give the four cycle an inordinate displacement advantage. Now in this example both engine types were competition engine. For the sport pilot the formula might not be the same.
All the best,
Konrad
For a comparison that has a lot of examples all one needs to do is look at the old FAI F3A engines. These engines were held to a 10cc displacement for the two cycle and 20 cc for the four cycle. Now all one has to do is look at the record book to see that even with 200% advantage the four cycle engine was hard pressed to beat the 2 cycle for a myriad of reasons. So for aircraft that were/are critically judged the two cycle is the superior set up for our toys unless one give the four cycle an inordinate displacement advantage. Now in this example both engine types were competition engine. For the sport pilot the formula might not be the same.
All the best,
Konrad
My point is that if left to compare power (flight pull) of a high performance two cycle verses a high performance four cycle one needs to give the four cycle at least a 2 to 1 displacement advantage over the two cycle. To support this statement I point to the FAI rule book. The FAI tried many formulas to try to bring the four cycle engine close to parity with the two cycle engine. They tried the 15cc route for a few month and quickly realized that the four cycle engine needs a lot more displacement to be anywhere near as powerful, hence the 20 cc limit for the four cycle, when there was an engine limit in the F3A class.
10-28-2010 | 09:27 AM
#48
RE: 2 stroke compared to 4 stroke
Hi!
Not in Sweden!
Most of us over here uses nitro in our fuel ...but perhaps not as much as you Americans. 5-10% nitro is the norm overhere.
Not in Sweden!
Most of us over here uses nitro in our fuel ...but perhaps not as much as you Americans. 5-10% nitro is the norm overhere.
10-28-2010 | 09:50 AM
#49
RE: 2 stroke compared to 4 stroke
Most of the club members in my club run around 15% nitro. The heli guys run some crazy %s. But I run 15% only because of the 4-strokes. Before I got 4-strokes, I used 10%. I broke-in my old Irvine 15 years ago with 0% nitro and it tolerates 0-15% with only minor tuning changes required. I have not yet tried to see how low %nitro I can go with my 4-strokes. Might be a good experiment.
10-28-2010 | 01:54 PM
#50
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From: Bend,
OR
RE: 2 stroke compared to 4 stroke
ORIGINAL: w8ye
Looking down through the thread, there were a couple references to Magnum 52 four strokes not having the power of a 46 two stroke.
I've seen a lot of the Magnum four strokes with less than satisfactory power.
These poor performing ones I've personally looked at had the cam timing advanced one tooth. This gave a great idle but took the engine performance down one prop size.
These engines when the piston at top dead center had the cam timing mark straight up and down. Either 6:00 or 12:00. And this was from the factory!
The proper timing position is in alignment with the push rods. Preferably with the mark dead center with the exhaust cam follower hole.
This is very helpful to me as I just bought a Magnum 52 4-stroke for a Balsa USA 1/6 scale Sopwith pup. It specifies a .40 to .50 4-stroke or a .30 to .40 2-stroke and the plane weighs 6.5 lbs. I've not done much in the past with 4-strokes but it seemed that this engine was a pretty good match for this plane. I printed the picture you guys posted so I have that info but how do you tell when the piston is in the proper position..........TDC as opposed to the exhaust stroke??? I used to work on cars but I'm pretty stupid when it comes to model engines and it's been a long time. I would like to take whatever I have to off the engine and look before I even attempt break-in.......that way I'm starting in the right spot. All help, pictures, etc would be greatly appreciated!!!
Thanks
Andy
Looking down through the thread, there were a couple references to Magnum 52 four strokes not having the power of a 46 two stroke.
I've seen a lot of the Magnum four strokes with less than satisfactory power.
These poor performing ones I've personally looked at had the cam timing advanced one tooth. This gave a great idle but took the engine performance down one prop size.
These engines when the piston at top dead center had the cam timing mark straight up and down. Either 6:00 or 12:00. And this was from the factory!
The proper timing position is in alignment with the push rods. Preferably with the mark dead center with the exhaust cam follower hole.
This is very helpful to me as I just bought a Magnum 52 4-stroke for a Balsa USA 1/6 scale Sopwith pup. It specifies a .40 to .50 4-stroke or a .30 to .40 2-stroke and the plane weighs 6.5 lbs. I've not done much in the past with 4-strokes but it seemed that this engine was a pretty good match for this plane. I printed the picture you guys posted so I have that info but how do you tell when the piston is in the proper position..........TDC as opposed to the exhaust stroke??? I used to work on cars but I'm pretty stupid when it comes to model engines and it's been a long time. I would like to take whatever I have to off the engine and look before I even attempt break-in.......that way I'm starting in the right spot. All help, pictures, etc would be greatly appreciated!!!
Thanks
Andy
