jimmyjames213

My Feedback: (2)

well im looking at getting a 4 stroke. the magnum .70 is 21.2 oz and the .91 is 22.4 oz
so..... is the extra power/20 bucks worth it in a .40 sized plane (also will my fuel consumption go through the roof compared to a .47 gms)
im looking at getting the new gp extra 300 but w/ toliedo in 2 weeks that could change

Jetdesign

My Feedback: (8)

I wouldn't call this advice but if it were me, I'd get the bigger engine if it's only an ounce different. Practice throttle management. Running at lower RPM will use less fuel. Bigger planes are nicer to fly, so having a .90 will be a nice thing to have around in the future.

goirish

I have 3 Magnum 91's and they are great engines. Very low fuel consumption.

jimmyjames213

My Feedback: (2)

ok i think ill get it
and if i want to 3d w/ a extra 300 (lol good luck [8D], need to learn some aerobatics first) then ill be able to
i love to overpower planes, i was just worried about weight/fuel consumption

btw what prop are you running on that 91
also what glow plug, is the fox 4 stroke good for the price ($5) compared to the os f plug (10 bucks)
o and what sized spinner

goirish

I use a 13/6 and a 14/6 depending on the plane. I have them mounted on a seaplane and a p-51 getting ready to mount the other one on a scratch built.

MinnFlyer

My Feedback: (4)

Whoa! A 70 4-stroke is PLENTY for a 40-size plane.

A 91 would be good for a 60-size plane

jimmyjames213

My Feedback: (2)

thats what the 15x4 was invented for

ChuckW

I'm flying this plane with a YS-63 and it is an animal. Of course the YS is light and very powerful. I wouldn't do anything bigger than the recommended OS .81. It'll just be more weight and probably less fun. Also, those Magnum engines sure seem close in weight. I wonder how accurate the numbers are? Also, does that include the muffler? If not, add a little weight.

jimmyjames213

My Feedback: (2)

thats what im a little confused over. i would only do the 91 if that was the actual weight w/ muffler, tower doesnt say ill look elsewhere. a magnum 91 is prob only a little more powerful than a os 81 and its not like im going to try to set any speed records with the plane (aka i wont full throttle it until the wings break off)
it just seems kinda stupid to buy a 70 when a 91 is only a oz more. its better to have the power and not need it, then to need the power and not have it.
or as other members say a underpowered plane is asking for trouble, but for a over powered plane just throttle back.

jimmyjames213

My Feedback: (2)

http://www.globalhobby.com/public/gallery/210970.asp
post the weight at 22.4 oz same as tower
but they dont menton the muffler
ill keep looking

jimmyjames213

My Feedback: (2)

what throttle setting will the plane hover with the ys 63?

ChuckW

Hmmm... you're assuming I can hover.

I'm not the greatest 3D pilot and I don't try to sit there and hover all day (very annoying to others trying to fly) but it will hang there around 1/2 throttle give or take a little using a Xoar 13x4.

rgm762

My Feedback: (4)

jimmy: will this help any?
http://www.vqwarbirds.com/products/access/MAG491.html

jimmyjames213

My Feedback: (2)

yep, thanks a lot. ive been looking all over for that

well since we now know that it is 22.4oz w/ muffler

which engine do i buy?

fcomer84

I just weighed my NIB Magnum .91 FS 1 lb. 7 oz. or 23 ounces! Engine, muffler, pipe and glow plug.

Campgems

I've got to agree with Mike. I fly a lot of magnum 4 strokes an the Mag 91 will pull a 4*60 almost unlimited vertical. putting that engine on a 40 size plane would both a waste of plane and motor. The Mag 91 likes a 14-4W APC prop, and very few if any 40 sized planes have the ground clearance for a 14" prop. Of course if you are into disposalable planes, fly them for a week end if they last that long, go shopping for a replacement on Monday, it may be the engine for you. Most all 40 size planes fly very well with a Mag or O.S 52 4 stroke A 70 is over kill, and a 91 just doesn't make sense at all for a 40 size plane. Get the 91 and then a plane the fits it.

Just remember, you have to have the plane balanced. A plane designed around a 40 size engine is going balance out with minimimual added weight with a 40 to 52 engine. Add the 70 and thats about 7 oz on the nose so add another couple oz aft to balance, it. You keep this going and soon, the wing loading is out of sight and you need a runway of about 3000 to get back down. The lighter, the better it flys.

Don

jimmyjames213

My Feedback: (2)

thats close enough for me.
i just went to the glow engine forum and asked in "club magnum" someone said a 70 os surpass wont give unlimited vertical so theirs no way a magnum 70 will
guess ill be getting the .91 hopefully the weight doesnt screw me over (that same guy said he had a 91 asp in his and it pulled out of a hover).
if it does ill have a excuse to buy a bigger plane

also what sized spinner? would a 3" be fine?

also to put things in perspective a os 81 weights 19.63 oz, so a mag 91 is three oz heavier

ChuckW

The plane comes with a pretty decent plastic spinner. Not sure what diameter off the top of my head. It should work and will likely just need trimming to fit your prop at the most.

chashint

can you post a link to the plane the engine will be going into ?

jimmyjames213

My Feedback: (2)

well im still a little confused as what to get
i would love to power of the 91 but weight is a issue
as of now if im going four stroke im going the mag 91

i was looking at 2 bangers
what about a super tiger 51 or a gms 47 (i have and love that engine)
maybe a ax 55 but if i were to go 2 banger id like to save the cash (from not buying the magnum) and buy a saito or ys for my next plane


http://www3.towerhobbies.com/cgi-bin...?&I=LXVVG4&P=0
http://www.rcuniverse.com/forum/m_84..._4/key_/tm.htm

VeeAte

I have had three .40 size planes that all will swing a 14" prop with no problems at all.

.40 sized P-51 Mustang
.40 size Super Chipmunk
.40 Sized Edge 540T


Very little difference in weight or physical size between an OS .70 Surpass and an ASP/Magnum .91.

My advice would be to search the forums and find out what other people have put in the plane you plan on buying.

If the plane needs weight on the tail with a .40 2 stroke or similar then I wouldnt put a large 4 stroke in it. Will just have to add more weight to the tail.

If the plane needs nose weight with a 2 stroke then a large 4 stroke wont be such an issue.

I did some research on CMPro's F4U Corsair .50 size and from what I read people were still adding weight to the nose with a .91 4 stroke installed.

Without knowing exactly what plane you plan on installing the engine into its a bit hard to recommend one.

VeeAte

That os 70 I had in my edge 540. It would still climb to a respectable altitude straight up. But it wouldnt pull out of a hover very well and I wasnt too impressed with the power I had in that airframe.
In other lighter .40 sized planes that same .70 would head skyward like a homesick angel.

All depends on the weight of the plane and what you want to do with it.

That edge with the ASP 91 was an animal. Take off in 10 feet and go straight up til you couldnt see it if you felt the need.

But that plane balanced with 0 weight with the .70 and was still fairly light on the wing. So I put the .91 in it for some fun.

Again that .91 would not be practical for other planes. Either too much engine hanging out of the cowl spoiling the looks. Or too much weight needed to balance it which would make the wing loading too high and ruin the handling of the plane.

Just suggestions.

Research here on RCU and other forums is your best bet to finding a suitable engine for a given airframe.

ChuckW

If I were going to do a 2-stroke in this plane it would be the .55-AX without question. The other engines are good and will fly the plane wonderfully but the extra stump pulling power from the .55 would be very nice.