Luizinho

My Feedback: (10)

I have a 90 Pattern plane. Is a MVVS 91 good for a this kind of plane ? my choices would be: O.S. 91FX or Saito 120 or MVVS 91 ? I have the MVVS .49 and I love that engine.

snap_roll

the OS91FX will do a better job as it has more power 2 weight ratio,and the displacement is bigger..

Luizinho

My Feedback: (10)

Thank you snap_roll , so do you think that the O.S. 91FX will be better than the Saito 120 ? I have been thinking in Saito, because of the cowling also. The O.S. 91FX the muffler is to big. May I can used it with a Tuned Pipe, I don't know. Also the O.S. 91FX is more economic, that's why considered the O.S.

tommy s

My Feedback: (55)

snap_roll
Why do you think the OS .91 has more displacement than the MVVS .91 ?
The displacement is the same no matter whose engine it is , a .91 is a .91 .
The MVVS .91 is one of the most powerful 2 strokes available and will swing
a very large prop as it is a long stroke engine and has tremendous torque at
low RPM's , this makes it a very good pattern engine.

tommy s

Jim Oliver

My Feedback: (1)

Hi,

You probably know this already, the MVVS can be configured as side exhaust or rear exhaust--must be done before first run and then not changed thereafter---or so "they" say.

Luizinho

My Feedback: (10)

Pattern Student ,
That is and extra point for me to choose the MVVS.

majortom-RCU

My Feedback: (40)

I'm presently flying the MVVS 77 with short pipe on a sport ARF, still in its first gallon, getting 11,100 on APC 14x6, still nowhere near leaned out. Runs strong & steady, impresses everyone who has seen it fly. I've yet to find anyone who has put the MVVS 91 on a pattern plane, but I'm eager to try it--inverted mount, rear exhaust & short pipe, all I need is a plane that the engine/header/short pipe will fit readily.

MicroMac

I am building a Infinity 90 (pattern) right now using the MVVS 91.
Maiden flight early August if I am a buzzy bee.
So can´t give you any reports yet []
If I remember right tommy s has used the 91 for pattern with good results.
I wanted a rear exhaust 91 engine, and the MVVS is a lonely swallow in that marked.



Picture: Making room for the header

snap_roll

tommy,ther's a slight difference in displacement,luzinho,if u want economic engine+quality power and cheap running,get a super tigre 90,5% nitro and u get good torque,but i think that the MVVS 91 is lighter

Rendegade

Having said that the G90 is a real powerhouse but if I was to buld another 90 sized pattern plane I'd seriously consider the MVVS just beacuse it IS rear /side interchangeable. Sort of. I hate seeing pipes poke out of my lovely, slippery ships.

tommy s

My Feedback: (55)

I've run both engines, and while the SuperTigre is a good engine for the money it
can't hold a candle to the MVVS as far as pattern performance is concerned. The
MVVS's vertical performance has to be experienced to be really appreciated. I still
have an old school pattern ship, an Illusion with retracts which weighs 9 1/2 lbs, and
a MVVS .77 pulls it straight up as long as you keep the nose pointed that way without
even straining, it will accelerate in a vertical climb. The MVVS engines are designed to
operate on FAI fuel which has no nitro so while they aren't cheap to purchase they are
economical to operate. I run YS 4-strokes in my pattern ships now but if I decided to
build a 2-stroke ship without a doubt it would have a MVVS engine. The best only costs
a little more.

tommy s

Luizinho

My Feedback: (10)

Here in South America I can get the MVVS 91 with the Aluminium Tuned Pipe for $ 270.00 from Argentina + $ 6.00 shipping to the border of Paraguay. The Saito is very expensive and the O.S. 91 FX with the Stanndar Silencer $ 270.00. So for the price, performance, durability, etc, I gess MVVS would be my best choice.

majortom-RCU

My Feedback: (40)

No question in my mind I'd rather have MVVS with pipe over OS with standard muffler. They're all good engines, but for this application I agree MVVS is the way to go.

mikehannah

Hi
I would also remember that although the OS 91fx is more powerful on paper 2.4 hp to 2.8 hp. The OS max figures are at an unworkable 15K rpm where as the MVVS develops it max power at a much more useful 11K

Mike

JasonS

I've got an old Piorun Eclipse that really needs something rear exhaust to work right. I recently had it set up with a YS .91 FZ but balance and vibration issues plagued that combo. I got it down to slightly over 8 lbs. with the YS. I think It would be a hoot with the MVVS .91 rear exhaust combo. Where in the US is the best place to get the MVVS with header and pipe?

majortom-RCU

My Feedback: (40)

Morris Hobbies is the US distributor, but they seem to be often OOS for months at a time. You might do better shopping in Canada with Dave Moen, or even Europe, now that the dollar is doing better over there. Piorun Eclipse--been a long time since that came up!

ElectRick

My Feedback: (2)

Bingo. The OS is rated at 2.8 HP at 15K (who uses props that small?). The MVVS .91 is rated at 2.41 HP at 11k.

Which HP/RPM range is more useful?

It's torque that turns the prop, not horsepower. The MVVS clearly makes it's (comparable) power at a more reasonable RPM than the OS.

I have a MVVS .91 that is going into a SA Excelleron. Looking forward to it's power.

Rick

Luizinho

My Feedback: (10)

Well, I am decided !!! MVVS 91 with a Pipe. I didn´t known that MVVS is such a great engine until now. So, what propeller shoul I use ?

ElectRick

My Feedback: (2)

Everything I've read says you want to run the MVVS .91 at around 9500-10,000 RPM to get the best torque from it. I would say something in the range of a 14-8 to a 14-10 APC prop would be close.

Rick

RottieBoy

Luizinho:

Here in Malaysian my friends are flying 2 Kyosho G trick, 66" patterns. ONe uses an OS91FX with bolly pippe. The othe uses a MVVS 91 with mini-pipe.

I tune and adjust both planes from my 2 friends.

Here my honest opinion.

The MVVS is :
as easy to tune as the OS
seems to fly the plane faster.
vertical on both are excellent and you will not want.
MVVS metallargy is definitely superior and will almost definitely outlast the OS
MVVS can use lower nitro
OS Is a btter looking engine.

verdict: it depens on what you want. .. I plan to buy the mvvs bec here it sells for US110 and the pipe and manifold is only abou 30USD!! OS is bout 50-100% more!!
btw the MVVS 91 seems to like a 13-8 or 14-6 apc. spins about 12K or first and 9K on second

maustin

My Feedback: (7)

Another vote for the MVVS 91, I have a Bridie XLT at 10.5lbs and the mvvs hauls it around like nobodies business. I've had good performance with 13-10 prop since the plane is so heavy. Also run the alum mvvs pipe.

BBM [8D]

checho4

My Feedback: (4)

HI all ,
I have a 91FX WITH Pipe , in a CMPRO LEA 110(67")PATTERN PLANE.
THIS ENGINE IS VERY VERY WELL, I FLY AT 7000¨AND THE VERTICAL POWER ITS GREAT.

MicroMac

I now have a few flights with the MVVS91/ Infinity 90 combo .
With a Krumscheid 1010 tuned pipe, preset to 550mm for rpm 9500 (KS numbers)

The MVVS started on the 4 flip straight from the box. Used a 13x8 for the first few tanks.
But I could not get the idle right with the stock glowplug (Nova Rossi??), the engine just died under 1/3 thr.
A OS #8 cured that.
Smooth low idle and starts on the first or second flip every time. I was in glow motor heaven
A Perry VP-30 changed that. Almost impossible to get the engine idle right, the engine simply drowns after 5-10 sec , even with the low end needle almost closed.
Cant rev the Perry screw out any more, the engine needs fuel on full throttle.
The motor also seems to run hotter with the pump. Maybe because the higher pressure make a more effective fuel/air mixture?
Haven´really sorted this problem out yet. I will try with a bypass from the pressure side of the pump back to the inlet side. Waiting for some T s at the moment.

For the first flights I used a APC 14x8. The Infinity is not in any way overpowered with this combo, In fact I am disappointed so far. The vertical is not unlimited as I expected. I doubt if I can do a nice vertical roll. I find this strange for a pattern plane that weight 3400 gram ready to fly w/o fuel,
I get 9000 on the ground with the 14x8 that is at least 500- 1k short of my expectation. As it is I have no other choise than putting back that APC 13x8 to get the motor on the pipe, when I hoped to put on a APC 14x10 or 15x8.

A club friend is running a OS91FX/Flair swallow with the APC 14x8 and a old Hatori pipe and get 10200rpm . After what I have read I should expect at least the same numbers from the MVVS.
I know the engine is new and not fully leaned out, and will improve over the time.....but.
I must be doing something wrong? . The engine itself seems to be in exelent condition, not runned lean and hot and not runned cold

PS sorry for my crappy E

jho

MicroMac,

I have made some very similar experiences as you have with the MVVS 91. I use this engine in a CMPRO Leo with a Hatori 700 tuned pipe and a APC 14x8 prop. For fuel I use 16% synth oil and 5% nitro. After 4 flights and some 2 litres fuel on the break-in test bed performance is still not at its max.

First of all it seems to me the MVVS engine needs quite some time to break in before it a) develops good power and b) runs reliably. My previously used MVVS 61 engine in the very beginning quit many times in flight and developed it's power only after about 5 litres of fuel had gone through it. I admit that I also had some difficulties to set up the carb.

What considers the perry pump: I had exactly the same problem. I needed to rev out the screw of the pump as far as possible and still had to close the main needle of the engine to about 1/2 turn open position. Otherwise the engine would completely drown in fuel. Then again it was very difficult or lets say impossible to adjust the idle needle. A fellow at my club said, that the MVVS carb is probably not suitable for use with a pump. I therefore removed the pump for the time being and changed the tank's position to behind the firewall which was quite difficult in the Leo.

I do not know about your KS pipe but I have my Hatori pipe set up at about 490-500mm. Maybe it's worth to try to reduce the distance carefully by 1 or 2 centimetres on the test bed and look at the revs.

What regards the OS 91 FX: I also used this engine for quite some time in a Swallow with very good results. It did not need any particular break-in time to develop fair power and was 100% reliable. I just changed to the MVVS because of the rear exhaust mode. Maybe we have to be patient with the MVVS engine.

Jan

Luizinho

My Feedback: (10)

Jho, I think you have to use 20% of oil. The MVVS manufacture recommends 20% of Oil.