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-   -   4-stroke to 2-stroke.... (http://www.rcuniverse.com/forum/beginners-85/3091900-4-stroke-2-stroke.html)

johndalton 06-20-2005 02:48 PM

4-stroke to 2-stroke....
 
I really didnt see where to post this since it is about motors, but I AM a beginner, SO..... I have a "Groovy 503D" made by The World Models. It calls for a 50 4-stroke, but I was wondering if I could put a 2-stroke on it, and what would be considered equal to a 50 4-stroke. This probably sounds exactly like a nube question, because it is! Is there some sort of "conversion chart" where I can find what equals to what as far as 2-stroke and 4-stroke? Any help will be GREATLY apreciated. If u need more info on the plane, just lemme know.

Thanks,
John

carlosponti 06-20-2005 02:53 PM

RE: 4-stroke to 2-stroke....
 
sounds like a 30 size will accomadate in the place of the 50 size four stroke.it says it accepts a 70 size as well which is a 40 size in the 2 stroke sizes. i would put a os 45 max on it, it would scream with that. its going to be roughly twice the ci for 4 stroke. 90 in 2 stroke 120 - 180 in 4 stroke.

2slow2matter 06-20-2005 03:08 PM

RE: 4-stroke to 2-stroke....
 
There is no way that a 30 = 50, 40 = 70, and 90 = 180? No way. More like:
four stroke Two stroke
50 46
70 62
90 75
120 90

I know you said 90 = 120-180. The 120 is the only part of that post that I'll buy. the 180 is perposterous. Of course, it all depends upon whether or not the two stroke is ball bearing, bushing, OS, GMS, or whatever. They all act a little differently. I think you'd find my chart above to be pretty close. These are basic prop comparison numbers. You'll never get a four stroke to run as fast as a two stroke--there is no practical conversion for that. So, if it's speed you're after, better go two stroke. I have a .56 four stroke that will swing a 12 X 6 prop with ease. My .46 two stroke won't even touch a 12 X 6 prop. However, proped with an 11 X 6 prop, the .46 will out run the .56 all day long.

carlosponti 06-20-2005 03:28 PM

RE: 4-stroke to 2-stroke....
 
i think you are a bit more off.

four ------- two
52 is about 30
70 is about 46
91 is about 60
120 is about 90
180 is about 120

i am talking power not prop sizes on related planes there is another factor to that. 4 strokes have more torque and accomadate a bigger prop because of it. i do have a feeling we are both wrong and they are in between what we say.

johndalton 06-20-2005 04:33 PM

RE: 4-stroke to 2-stroke....
 
Thanks for the speedy replies. I want to put an O.S. 46 LA on it. So far, from what I've gathered from what u are saying, this will do just fine. Any other tips and/or suggestions are welcome.

Thanks,
John (nube)

exeter_acres 06-20-2005 04:43 PM

RE: 4-stroke to 2-stroke....
 
relax guys...

it is a 5 ot 6 lb aerobatic plane....

a .46 2 stroke would be fine......
the LA would be OK, but I am not a fan of them...it will fly fine with that though....

johndalton 06-20-2005 04:45 PM

RE: 4-stroke to 2-stroke....
 
will it be OK, or will it do what the 4 stroke would make it do?

DBCherry 06-20-2005 04:49 PM

RE: 4-stroke to 2-stroke....
 
carlos,
Your comparison of two and four strokes was true about 10 years ago, but no longer. Four strokes have gotten more powerful over the years, and I'd have to agree with 2slow's assessment.
50 46
70 62
90 75
120 90

Dennis-

carlosponti 06-20-2005 04:56 PM

RE: 4-stroke to 2-stroke....
 
i dont get it then, have the airplane manufacturers not caught up? they still recommend a 72 size engine on a 40 size plane like my US 40 plus. i am basing it on what the airplane manufacturers give us as recommended engines for a plane. i run a Saito 72 on my US 40 plus.

manufacturers make it confusing [:@]

2slow2matter 06-20-2005 09:01 PM

RE: 4-stroke to 2-stroke....
 
Most people overpower their planes anyway. The .72 is the very upper end of the range for most ".40" sized planes. Most of them have a range of .52 to .72, or such for a ".40" sized plane. And the two stroke is a lot of times a range of say .40 to .50 or so. As I said before, I don't believe you'll ever get a four stroke to pull your plane as fast as a two stroke (practically, that is). You'd have to so over power it that it would be way too heavy, so on, and so on. Four strokes definitely have their place (and they have a lot of places in my hanger), but speed racing is NOT one of those places.
BTW, you are probably correct in your assumption--the truth is somewhere in between. It really depends upon which brand of four stroke and two stroke you are talking about.

johndalton 06-21-2005 12:03 AM

RE: 4-stroke to 2-stroke....
 
ok i am confused now...will the freakin O.S. 46 LA on a Groovy do the job? or not enough, or just right? Um....im confused!

John

campbec 06-21-2005 12:27 AM

RE: 4-stroke to 2-stroke....
 
Hi John,

The short answer is yes! The 46LA will provide adequate power. If you are going to stick with the hobby an OS 46 AX, Saito 72, Enya et al will provide more versatility into the future.

Too much power may get you into trouble but retain the ability to get out of trouble. Not enough power is looking for a place to have the accident. Within limits it is better to overpower providing the airframe is robust enough. It's all about throttle control:D

Cheers,

Colin

Cheers,

Colin

cantw8tofly 06-21-2005 12:35 AM

RE: 4-stroke to 2-stroke....
 
i have a os 52 fs surpass turning a 13x6 master airscrew on my 4 star .60. this thing screems i had an os max .61 2 stroke on it and it was too slow... i mounted the four stroke on it after i saw it fly a heavy spad that a freind built. at this time i would not change a thing......
i am a noob so i dont have much experiance with that many engines but there is no way my .52 four stroke has the power of no .30 2 stroke... it dosnt rev like the 2 stroke did but it will pull that four star straight up way faster that the .61 did

just my 2 cents

DBCherry 06-21-2005 05:04 AM

RE: 4-stroke to 2-stroke....
 

os 52 fs surpass turning a 13x6 master airscrew on my 4 star .60. this thing screems i had an os max .61 2 stroke on it and it was too slow...
As 2 slow said, it depends on some things. In this case it's most likely the props.

A larger diameter prop, which a four stroke loves, will improve vertical performance. A higher pitch prop at higher rpm will get you greater speed. And 2 strokes like high rpm.
Dennis-

a65l 06-21-2005 06:40 AM

RE: 4-stroke to 2-stroke....
 
As if I need to muddy the waters any more......

I have a World Models Zen 50, which is roughly the same size and weight as the groovy 50. World Models calls for a .52 sized 4 stroke on it, and truth be known, it would fly the plane, and probablly be enough power to make it fly most of the pattern manuvers. I fly mine with a Saito .82, which is very much overkill for the airplane, but it's still not screaming fast.


So. My input is as follows. Not really knowing what you're expecting out of the airplane, I'm guessing here. I don't think a .46 LA will do what you want. Sure, it will fly the plane, but you're going to be very limited in your vertical manuvers, and I really think you'd be working to get the plane to do a lot of the pattern manuvers. A .46 AX would be better, but it think you'll still feel the need for more power. If you want to stay 2 stroke, I'd suggest a good .51 or .61 sized engine. 4 stroke, I wouldn't go below a .72.

Just my two cents....

Andy

britbrat 06-21-2005 10:10 AM

RE: 4-stroke to 2-stroke....
 
A 46 LA will not be adequate, but a .46 AX or .46 TT Pro will work quite well, particularly with either a 12-4 or 12.25 - 3.75 prop.

2S - 4S comparisons are tremendously dependent on prop choice, engine displacement-class and airframe specifics. Many folks over-prop their 2S engines, or use props of small diameter -- in those cases a mid-size 4S compares very well with similar-sized 2S engines -- hence the growing 4S power-equivalency mystique. However, a correctly propped mid-size 2S will still outperform a similarly sized 4S. When you get into large displacements the 4S is essentially as good, size-for-size.

For correctly propped engines, 2slow2matter's comparison chart is good.

johndalton 06-21-2005 10:41 PM

RE: 4-stroke to 2-stroke....
 
you all have been great help. Thanks. I have the 46 mounted, but im gonna take it off and put my bro's 61 on it.

Thanks
John

Spaceclam 06-21-2005 11:26 PM

RE: 4-stroke to 2-stroke....
 
i think you will find that a .46 LA will perform like a .40 size engine in any other brand. Either get a Thunder Tiger or an FX or the new AX. you wont be sorry.

bubbagates 06-22-2005 06:49 AM

RE: 4-stroke to 2-stroke....
 


ORIGINAL: cantw8tofly

i have a os 52 fs surpass turning a 13x6 master airscrew on my 4 star .60. this thing screems i had an os max .61 2 stroke on it and it was too slow... i mounted the four stroke on it after i saw it fly a heavy spad that a freind built. at this time i would not change a thing......
i am a noob so i dont have much experiance with that many engines but there is no way my .52 four stroke has the power of no .30 2 stroke... it dosnt rev like the 2 stroke did but it will pull that four star straight up way faster that the .61 did

just my 2 cents
Dave,

If you really want that 4*60 to pull, change out the 52 for the OS91 with a 15X6 APC. I have that setup on mine and OMG. Really strong and not overpowered and I can stay up for 25 minutes running around at half throttle, 30 minutes if I sit and do touch and goes for the whole tank (been there, done that, have the deadsticks to prove it:D)

Fastsky 06-22-2005 08:03 AM

RE: 4-stroke to 2-stroke....
 
Re: "Either get a Thunder Tiger or an FX or the new 46 AX. you wont be sorry. < Ya, what he said! You might save a few dollars now if you go with an LA engine but engines last for years and a short while after you buy the LA engine, you will kicking yourself for not spending the extra bucks and getting a hotter engine. I have a 46FX that has outlasted several planes and its still a great engine. I recently bought the newer 46AX and its even a bit better! [8D]

gboulton 06-22-2005 03:47 PM

RE: 4-stroke to 2-stroke....
 
Well, John....this thread has certainly answered at least ONE issue...

Now we know why there's no 'comparison chart' ;)

johndalton 06-22-2005 08:27 PM

RE: 4-stroke to 2-stroke....
 
I already had the 46 LA, so no money spent extra. I am currently saving up for a 46 AX, which I heard was a better engine over all. Give ya an update asap.

John

tIANci 06-23-2005 01:03 AM

RE: 4-stroke to 2-stroke....
 
My TT46 performs (RPM) as well as a 46AX, both were new and the other guy who is well versed with engines had problems with his AX, both TT and AX were in the same plane, both inverted, mine would backflip start by turning the spinner. After selling my plane off about 4 months ago, the TT46 was sitting idle, I put it back into a plane and after it was primed the engine just fired up. Cheap and good ...

Fastsky 06-23-2005 07:48 AM

RE: 4-stroke to 2-stroke....
 
I don't own any Thunder Tiger engines but I can't say anything bad about them. When I started teaching there were some new flyers who showed up with a Thnder Tiger engine on their plane. I was surprized that the engines started as easily and ran as well as my OS FX engines. They were not finicky and they were easy to adjust for strong reliable running. Bottom line, nice engines at a very good price![8D]

johndalton 06-24-2005 03:41 PM

RE: 4-stroke to 2-stroke....
 
If anyone has a Thundertiger 46 for sale, or an OS FX, lemme know.

John


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