I have a new set of plans that call for a YS 91. I need to know what is comparable in power as a 2 stroke. I would love to get a 4 stroke but my budget won't let me.

I was thinking something like a Thunder Tiger .61 or should I look more at a Supretigre 75.

Any thoughts would be very helpful.

Thanks

The YS .91 is a very powerful engine, as powerful as most other 1.20 four strokes. You should be looking at a .75 two stroke minimum. I would go with at least a .91 two stroke.

yup

Given that comparisons between 2 and 4 stroke are difficult, I would say that the YS 91 is at least as powerful as the OS 91 FX.

You would have to go to a good 1.08 to make sure you have at least the same power.

I always look forward to reading these YS comparison posts, and how they always get bigger and better. I don't think that I'm going out on a limb here when I say that a YS 91 does not develop the same horsepower as the 91 FX. And yes I realize that due to different mechanics and torque curves it is hard to compare a 2 stroke to a 4 stroke and vice versa. I call it the 4/3rds rule, given a certain displacement YS engine, there will always be someone who will compare that engine to another 4 stroke with a displacement 4/3rds of the YS.

Also, despite the above, this in no way is a post bashing YS engines. I have the YS 63 FZ and that damn thing might be stronger than my saito 72.

Here we go again.

The YS .91 can pull a 60 size U-Can-Do 3D straight up from a hover with authority. If a .91 two stroke can accomplish the same feat, then it develops as much power as the YS 91.

Well then I guess we would have to get an opinion from someone who owns a U can do with a 91fx on the front of it. Hey I could sit here and wait for someone to respond to the above ( I probably will of course) but I know the 2 stroke makes AT LEAST as much power as the YS. It is absurd to think otherwise. I don't want to start a pissing contest but come on.

Here goes the neighborhood!

Before you guys get into a war about what's better for 3D flying I just want to let you know this is a dedicated pattern ship. I realise that a Ys 91 (or even a Saito) is ideal but just can't afford it.

I didn't mean to start a debate here just what would work well in it's place.

Thanks again.

I realize what you mean dallas. You want info, not people debating between each other. From what I hear ys engines are much more powerful than other 4 strokes of comparable size. This seems to hold up and no one argues it. So if your budget cant get you an expensive one like that, I would recommend the Magnum 1.20. It will cost about the same as a 2 stroke of the previously mentioned sized, and will have that sweet 4 stroke sound.

low on cash...Tower Hobbies .75 A bit loud and kinda a pain to break in (for some) but great power to $$$ raito.

Really a 1.20!?!

I would have thought the weight penalty would be a little too high. If I was going to go bigger displacement I would think a better size more like a Magnum or ASP 1.08.

So basically here's what I've thought of:

ST 75
ST 90
GMS 76
Magnum 1.08
ASP 1.08

Supertigres may be hard to come by

GMS & ASP don't have the greatest reputations

Magnum 1.08 might be overkill

What do you guys think?

Cdallas2.......

I've seen several NIB ST G90's for sale in the swap shop. Most have been well below $150, and I got one for $100. Combined with a $30 perry pump it would be a great engine. Plus, it is the same size as the .75.

just a thought,
Beau

I think the Magnums are excellent, reliable, strong as any FX engines. I now own 5 from .25 to .91, the .91 being my favorite. I don't own a YS, so I can't compare. My .91 will swing a MA 14x6 "K" at 10.5K with 5%Nitro, 18%(50/50) with the stock exhaust, and 12K with a mousse can pipe. The plane I have it in is a SPAD Fun-Fly weighing 8.75 lbs. It easily hovers, and will rocket out of sight until you can't see it anymore.
The Mag .91 is in a .61 case, and the 1.08 is in a 120 case. So the .91 is the way to go IMO. On the Fun-Fly, I have a 16oz tank, and have the timer set for 25 min, and land with plenty left over.
IMO the Magnums are a best buy!
You can save a few $ and get an ASP series 3:
http://www.goldscallop.com/viewitem.asp?idproduct=220
They're supposed to be identical.

I'd like to see some YS rpm figures if anyone has them, I'm told they have loads of power.

The YS .91 can swing a 15x8 apc at 9300 rpm on YS 20/20 fuel. That's over 13 lbs. of static thrust.

20% nitro? Will it run well on less? Raise the compression maybe? I don't know what it'll do with an APC prop(too pricey cause I break too many), I did run it with a 16x6 MA K prop, and I think the rpm was over 9K w/MCP(but wouldn't swear to it), but didn't like the spin up time. I think the 2 strokes, this one at least, is better off revving a little higher.

The thrust figures were from thrustHP? 14x6 @12K 12.7lbs thrust(stock muffler), and 15x8 @ 9.3K 13.1 lbs thrust. That puts both right in the ball park power wise. The YS and 20$ fuel, requiring much more cash to get there though. Of course with dif prop mfgs, the numbers don't directly translate, but I think the .91 2 stroke will more than accomplish his goal, and if a MCP will work with his airframe, the 2 stroke will exceed the requirements.

Tower-75 or MVVS-77 would be nice-

Magnum 91 would be tempting also- What does your ship weigh?

james

....if $$$ is a bit tight....look at the Tower Hobbies .75,
....they're only $99.95....and are powerful....

GMS ringed .76? Just like the TH .75, but ringed. To your door for $85 from:
http://www.gmsengines.com

He's a member here. Reliable and trustworthy.

[QUOTE]Originally posted by Richard L.
The YS .91 can swing a 15x8 apc at 9300 rpm on YS 20/20 fuel. That's over 13 lbs. of static thrust. [/QUOTE

That would be approximately equal to a 1.08. But if that fits then maybe a 2 stroke 1.2 would also. OS, Magnum, ASP, TT all make either the 1.08 or 1.2 size. ASP and Magnum are the same engine, but early ASP's had high comperssion requireing low nitro fuel. That is the only problem with early ASP engines.

Engines that require low nitro are not a problem, they are a blessing, I have approximately 65 two strokes and all run great on 5% nitro. It's the only two stroke fuel I keep.

Razor:

It's not started yet but should weigh roughly 7-1/2 - 8 pounds.

Now don't forget I'm not going to be 3D'ing this thing so static thrust really doesn't do much for me.

Tower engines are pretty rare up here since most Canadians don't use U.S. based suppliers. Duty and other fees make it cheaper for us to buy them here, so Tower is out.

I think a 1.08 - 1.20 is overkill and to heavy so they're out.

I guess I'll go with the Magnum .91 or the ST 90 whichever I'll get the better deal on.

Thanks for everyones help and input.

Sounds like a TT .91FS is just the ticket.