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HomeAircraftHelicopterHelicopter Main Discussion › OS 70SZ-H Ring
07-17-2002 08:39 AM  16 years agoPost 1
Coeper

rrNovice

Pretoria South Africa

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I just installed the OS 70SZ-H Ring engine in my X-Cell 60.

I used to have the OS61 SXH (not the WC) in the heli. I think the book says that the OS 61 produces 2.0 bhp @ 16000 rpm. (The "WC" 2.2 bhp @ 16000 rpm ) I am running 20% Nitro and 22% Synthetic Oil, Cool Power fuel (Specially mixed for me by Morgan), with the OS A5 Glow Plug. This engine was running perfect with enough power to do all the aerobatics I am capable of.

I thought that the OS 70 @ 2.5 bhp @ 16000 will show a big difference in power. (I know that the engine is not run in yet, and I am running extremely rich. I only have about one-and-a-half litre of fuel throug it.)

Is there anybody that also have a OS 70SZ-H Ring in their Heli?

The power difference between the OS 46 and OS 50 was huge. (In my Raptor) I noticed it immidiately even when the OS 50 was being run in and extremely rich.
Should'nt the power difference between the 61 and the 70 also be this apparent?

Regards

Peter

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07-17-2002 12:47 PM  16 years agoPost 2
Steve Campbell

rrElite Veteran

Baton Rouge, LA

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So, you're saying that there isn't much of an apparent difference? Interesting... But give it some time; it may surprise you when you are ready to lean it out.

I too have an older 61 SX non-WC in an X-Cell. Personally, I like that one better than the "new & improved" WC version. They changed the carburetion to get more top-end power (to make the 3F types happy), and in the process took away some of the mid-range smoothness.

After my recent (and continuing) experience with YS plank engines, when/if it becomes necessary to replace this 61 SX, it will definitely be a YS. A pal has a brand-new ST II in a Fury that has impressed us greatly...

Steve

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07-17-2002 03:18 PM  16 years agoPost 3
alawel

rrVeteran

Springfield Oregon

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I have the 70 in a Robbe Nova. I have ran about 1 gallon and a half through the thing and still running quite rich, I think it's making about the same power as my WC with a performance specialties piston and liner. Right now it's pulling 10 to -10 degrees without bogging. The Muscle pipe seems to be working well so far, even in the 90 plus degree heat.
Alan

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07-17-2002 07:30 PM  16 years agoPost 4
FlyinBrian

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USA

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Hi,

So far I have a gallon and a half on one. Its running at 9.3 to 1, 1550 hover and 1750 for everything else. Its still pretty rich running on 20/24, fuel consumption is higher than my os91sxh. I used a zimmerman os91 muffler on it, I also tried this muffler on a 61 wc and did'nt notice a bit of difference except for the sound. I believe the 70 needs a bigger muffler, the 90 muffler may be overkill but its better than being too small.

Its developing more power than the os61sxh wc it replaced, it is also smoother running in a hover (I have allways had an occasional annoying tail kick on the sxh wc). When I replaced the motor I did'nt change anything else on the heli and flew it the week before, full collective would bog the 61 down quite a bit and so far the 70 does'nt seem to mind at all. It has a gv-1 in it so you can expierement a little even with the motor dirty rich as long as you dont push it hard during the breakin period.

It seems happy on 9.3 to 1 but if the fuel consumption does'nt improve I will go down to 9 to 1. I also still have to play around with different head speeds to find out what it likes.

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07-17-2002 09:41 PM  16 years agoPost 5
Tyler

rrElite Veteran

Chicagoland area

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OS 70
Where are you guys getting these engines? I would buy one, but don't want to buy from the dark side, if you know what I mean. What is the best price you have found?

I would like a nice compromise between the 61 and the 91. I would have to run 15%, though. I hope it like lower nitro fuel.

Thanks,
Tyler

Enjoy things that money can buy IF you don't lose the things money can't buy.

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07-17-2002 11:01 PM  16 years agoPost 6
alawel

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Springfield Oregon

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The last I heard was that Heliproz would have them in October. I ordered mine from Cyberheli, less than a week delivery. It was the first time dealing with Cyberheli and I wouldn't hesitate to do so again. After shipping I think I paid around 250.00.....Your right I think this will be the engine for the folks that don't want the big block fuel consumption, or don't want to mess with gearing, both were motivating factors for me. I'm using the 61 muscle pipe, and as I've said, so far so good. I hope to get a gallon or so through it this coming weekend, should be able to start leaning on it soon.
Alan

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07-18-2002 03:02 AM  16 years agoPost 7
Chris.C

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Hong Kong

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Hi

Just got the 70 and I am wondering what is the best gear ratio for it. I think 9.5:1 is definitely too high for it. May be 9.3:1 or 9.0:1 is the way to go. Hirobo puts out a new Freya kit for OS 70 and the gear ratio is 11 to 95.

Anyway, I am going to put the new engine in my XLPro first with 11T pinion to see how it works.

How about Nitro %? Is it best with CP30% or what?

Thanks, Guys.

Chris

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07-18-2002 06:42 AM  16 years agoPost 8
alawel

rrVeteran

Springfield Oregon

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I'm running my 70 in a stock Nova, I think the gear ratio is in the 9.3ish range. I'm still running so rich that I don't think it's even coming onto the pipe, head speed is still pretty low, around 15-1600. I'm using 15% cool power and it's working great. I plan to start leaning on the engine this Friday and get the head speed up a bit, I'll know more Saturday night because I should have another gallon or so through it.
Good luck with your new engine, keep us posted on your progress. We should start a 70 users support group
Alan

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07-18-2002 08:14 AM  16 years agoPost 9
Coeper

rrNovice

Pretoria South Africa

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Thanks to every one for all the replies!

I am going to put another two litres ( +/- 0.53 US Gal) of fuel through it this weekend. I will then start to lean it out a little. (I hope the power will be with me then.)

I will keep you posted

Regards

Peter

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07-22-2002 12:13 AM  16 years agoPost 10
alawel

rrVeteran

Springfield Oregon

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OS 70 update
I've flown about two gallons through the 70 now. Out of the box I had to lean the low end a quarter turn, at about the two gallon point an now have the low end richened back to the factory settings. I'm using idle-1 at 80% throttle and it's making as much power as the 61 wc at 100% throttle. The muscle pipe seems to be working well on it.
Alan

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07-22-2002 02:51 AM  16 years agoPost 11
Chris.C

rrVeteran

Hong Kong

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I break in the engine in my Eagle with 93:11 ratio. Already run thru' 2 gallons of CP30 with OS8, Hatori 90 muffler. Hovering and top end is good but the fuel consumption is terrible: about 9 minutes.

I already lean the top needle to less than 1 1/2 turn. May be it is not fully break in now.

Chris

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07-22-2002 07:23 AM  16 years agoPost 12
Coeper

rrNovice

Pretoria South Africa

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Ran another litre of fuel through my 70..... it seems to be developing a little more power now.... maybe the 60's Western Pipe is killing it?......

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07-22-2002 11:22 AM  16 years agoPost 13
Slider

rrApprentice

Waukesha, WI

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I would think the muffler could be the culprit Try finding a compatable 80 size Hatori. I am not sure if the SB-14 or SB-15 will work with the OS 70, but you really need a different muffler. Heck, the YS 80 is only a 72 and they run a huge muffler.

My $.02

-Mark

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