MVVS .91 - rear or side exhaust , longstroke , develops max horsepower at around
10,000 RPM - lots of low end pull !!!

tommy s

PS: the newest version comes with an updated carburetor which is easier to adjust
and has a very quick and smooth transition from idle to full open.

that's a good call Tommy. Are there any available yet? Last time I emailed them they were out and didn't know when they would get any. I had to get an OS for my Epsilon.
Tom

I'm not sure , I noticed Morris Hobbies doesn't even show them on their
web site anymore and they are the US distributor located here in Houston.
I drove out to their location in the Woodlands and picked up one of the new .91's directly
from the owner but that was about 5 months ago. I also picked up a very sweet looking
custom rear exhaust header from him while I was there too. They have a lot of
equipment there that is not on their web site so I would suggest e-mailing them or
calling. They are very nice people to deal with.

tommy s

PS: I still have the new in box .91 with the custom header and the stock MVVS
header and short pipe. I might be talked out of it if you were interested.
Also have a new in box ES Composites carbon fiber tuned pipe for same engine.

I've seen the OS91FX piped to the proper length turning a 15.25X12APC 4blade at 7800-8000. Yes it isside exhaust and requires the wrap-around header and Yes I'd love to see a rear exhaust "hanno" with the built -in pump BUT it wouldn't be for $199 for sure.

Eddie

Eddie,

A few days ago, Nat posted on NSRCA list (directed to me and Randy) about the 15.5 x 12 with 25" pipe length. Are you talking about that?
Nat changed to 4-blade? How is the speed with that prop?

Why don't we all get a list of signature and submit to manufacturers for a .91 ~ 1.00 rear exhaust?
By the way, OS seems to have problem getting their pumps working (70 Ultamate causes lots of headache for people w/ higher than YS63 price).
I don't care if the manufacturer add pump (costs way too much compared to non pumped engine), but a rear exhaust is good. We can all get a Perry VP 30.

IP

Eddie you're right, the beauty part of the 91FX is that it's a cheap strong motor.

But look at it this way, how much would you pay to have a factory installed pump, header and pipe and rear exhaust?

That's what it comes down to for me.

Seems to me I read on one of the websites (maybe this one) that the MVVS engines can be configured SE or RE
as long as you do it before you run it in
WW

Yes, the cylinder bolts onto the crankcase, so can be moved round. But as suggested do this before running in!

IP
Yes that's what I'm talking about. I remembered it to be a 15.25x12 but if Nat posted it's a 15.5X12 then I stand corrected.

It flies his 2-m VooDoo Express through the entire FAI pattern with authority. Including the humpty with a pos snap on the upline.

Better downline braking and more constant speed overall. Much less tip-noise and with his properly piped setup the sound is amazing. It's quieter than anything else flying (even electric)

Renegade
I think we said the same thing. I'd too love a OS91fx RE but it won't be for $199 (we all know that).
My point was that even though the OS91 is side exhaust, it's still a viable choice AND proped/piped correctly it is a much stronger engine than a lot of people think. Definetely stronger than YS110
Eddie

Ah, Oh, now you've done it. I'm not sure your allowed to say an OS91 is stronger than a YS 110. That'll get you in trouble.

How does the MVVS 91 compare with the OS91FX?? I probably should just get the OS, however, I like to try different brands sometimes. Give someone else a shot at my money so to speak. Probably depends a lot on how it is piped. I was thinking of using one of the Jett in-cowl mufflers instead of the stock muffler. Would require less hacking of the cowl and front of the fuse.

Hi
I have an MVVS 91 but have yet to run it.
It is a very well made engine as it reputed to be an animal if run in carefully.
It is a longer stroke engine than the OS so it should throw a bigger prop.
I am told it is more powerful than the OS .
Do a search and you will find no end of threads on the MVVS and no of them had a bad word to say about the engine.
earlier version had carb problems but this seems to have been addressed.
Bare in mind the MVVS is not some cheap eastern European paper weight they have been in business since the 50s and have won alot of speed titles so they know how to put an engine together.

Mike

ps i am running mine on a pipe and a perry.

I'm not going to compare the MVVS and the OS but If you haven't run your
MVVS .91 yet you will be amazed at the power this engine has. The earlier ones
did have carb problems but this has been cured on the newer versions. They are
a little hard to start the first time because they are ABC engines and are set up
pretty tight. DO NOT run too much nitro ! They are designed to run great on FAI
fuel which has no nitro and you should never use over 5%. Be extra careful to
keep your fuel filtered as you should on any engine but especially with ABC engines
as dirty fuel plays havoc with compression. These are great engines. I think you would
see more of them except for the fact they are a little hard to get and are not cheap.
I have an Illusion pattern ship which weighs over 9 1/2 lbs and a MVVS .77 pulls it
straight up with no strain , unlimited vertical for as long as you keep the nose pointed up.
In my opinion these are the best 2 strokes I have ever seen.

tommy s

Thanks for the MVVS info. They are not cheap, however, they cost no more than the OS91FX. (If you don't include Tower's discount coupons.) I think I will give one a try. It's only money...

If you can't find one let me know. I have one NIB with 3 different headers and
two different pipes.

tommy s

Hi
Funnily enough they are about 2/3rds the price of a 91fx over here.
For once I am on the right side of the Atlantic. They are also easy to get hold of Just Engines are the UK's importer and a very helpful bunch as well.

Mike

Man you are lucky. They are $270.00 over here without header and pipe
and I've never seen one discounted.

tommy s

Well... based on a couple of scarce recommendations, I threw my money at Magnum for their OS 91FX clone. I have *NO* idea whether it's a good or other kind of choice, but I'm gonna 'speriment. Seems that's what I do.... Adding a wrap around header, a pump, and the plumbing will be similar to the OS 1.60, just smaller scale, I'm sure.

Yes - I'm doing a 90 size as a knockabout for the off season. SHould be fun.

And something to consider - also - the ST 90... quite a review on it, extolling the virtues of it's stroke and torque curve setup. They are ALL getting 'smarter', and are designing around the rpm range that we have to run to be quiet enough, but still have power enough.

Aerobob,

I had thought of giving the Magnum 91xls a try. Thunder Tiger has just come out with a 91 also. Where is the review of the Super Tigre 91 you talked about?

Thanks.

Go to the Great Planes site, look up Supertigre, you'll find it.

I went to the GP site and couldn't find anything on the ST90. Super Tigre is not a GP product. Could it possibly have been another site??

Here's a link to the review: http://www.supertigre.com/engines/supg0235-man.html

Up here the MVVS is a more economical choice than the OS

MVVS .91 - $229.00 CDN
OS .91FX - $269.95 CDN

jeffbutt, have you tried this motor? Do you know anything about it?

Thanks
Terry

After reading all the posts, i think that it would be increidible that OS develop a .91 long stroke with pump like the HANNO used to be, or YS develop their .90 size helicopter engines for using in airplanes.

This would be the best options in my personal opinion.

By the way...if OS develop a HANNO 90 size engine and it comes out at the same price as the YS1.10, i think it wold be a good option.

AN OS .90 Hanno at the YS 110 price... I'd buy a bunch! Probably would turn a 14x12 APC at 10,000 on %10 nitro... just dreaming I guess.
Hey Mr. Ogawa are you listening?
-Will B.