quote:

ORIGINAL: STG

Dang, I forgot all about the bad 70 four stroke that OS has come out with. I guess I was just expecting the best from them & wanting some new 2-stroke technology to hit the market.

Thinking about it, if OS were most concern about offering top performance they would have made the new .46ax maybe a .53 or a .56--maximized its displacement?

--------------

I have been thinking about the right prop for this motor and looking at its spects it shows max power to be a 9000 rpms and usable RPM rage to be 9,500 max. Not surprising as with its light weight it has to have small transfer ports which will cause the motor to go to sleep at high RPM. I would guess that the port timing compliments the small transfer ports making this a very torquey 120 2-stroke.

This being said, people that put something like a 15 x6apc on this motor will end up disappointed to find out it does not turn it any faster than a .91FX ( low 10's).

A 16 x6 will most likely be the a good prop to maximize thrust and still have the good forward speed, but I would guess it will pull a 17 x6apc with a little bit slower spool up. I am thinking a good 17 x6 Pro Zinger would be a very good prop as it would load the motor closer to 9000 rpm and still have fast spool up. Too bad that a 17 x6 is kind of an odd prop size.—cannot find it in a Pro Zinger or a wood Scimitar.?

A 17 x6 will be necessary if a semi tuned exhaust is used on this motor you will want to run it no higher than 9500 rpm to get max power.


Looking at Jett's 120 motor they show performance to be

BSE 1.20L R/C with semi tuned muffler AAC
16x8apc @9,200 27.8oz

http://www.jettengineering.com/

quote:

ORIGINAL: Dr Nitro

STG,

quote:

Maybe I will pay the 5oz weight penalty and get a Turbo Jett for a 108FSR. I am pretty confident power will be similar.

5 ounces of weight is generally insignificant for an aircraft that would be of size enough to accept a YS 110. You could help make up for it by use of lighter servos, lighter battery, and so forth. The OS 108 is one of those that is on the good list in my book, they're very nice engines. Forget the Jett muffler (and depending on your application) use a Macs header with a moose can pipe, very light and effective.

quote:

The education you guys are giving me on O.S. is really spoiling my fun. I have had nothing but great running motors so far.

O.S. 25fx --only mabey 1/2 gal thru
O.S. 46fx --8 gal thru
O.S. .91FX - 7 gal thru
O.S. 108fsr - 10 gal thru
O.S. 1.6FX- 10 gal thru

Did not mean to spoil your fun. For the past few years I have been paid to test run engines for a model fuel company. Since I have my own private flying field and am out in the middle of nowhere and retired, I can do this till my heart's content and not bother anybody. Mostly I run them on the several engine test fixtures, then a few of them I will actually fly on one of my planes or heli's. I even have a set of load beams to mount on car engines and a ducting system to cool the head when I test run them. I have gone through lots of engines, some were good , some were junk.
I use as a baseline, the average 40 size two stroke will run 15 minutes (at varying throttle positions) on 8 ounces of fuel. My goal is to get 400 hours on an engine or 100 gallons, whichever comes first. I have had numerous engines make it past this mark and a few that did not. To be be fair, I do a few things that the less experienced modeler does like shut them down for the day and do nothing to them until they are run the next day, I also run them a bit lean but only to the point where the rpm's are peaked, not past peak and generally use a prop that is on the small end of the scale for the given engine. I do run them on a fuel type that is intended for that design or recommended in the instructions. and always two identical engines are run identically at the same time, one with a competitors brand fuel and one with the company I'm contraced by, just for comparison.
Anyway, to make a long story short, I have run the engines you mention above and a bunch more of the OS line, this is what I got before the engines just simply wore out:
25FX- got to about 6 gallons
32SX- got to about 20 gallons after the first set of sleeves
40FX- got to about 20 gallons
46FX- (early ones) about 6 tanks
46FX- (later ones) about 40 gallons
OS 50- (airplaneversion and heli versions)- could not get past 10 gallons without it puking the bearings, longevity testing suspended on the modern OS 50
61FX- got to about 65 gallons
OS70 Heli-got to about 3 tanks on both engines, rods gave out. replacement engines made it to about 15 gallons
91FX- got to about 35 gallons
160FX- (after several tries and replacement motors, testing was abandoned)
OS 120 Surpass III- bearings failed around the 15 gallon mark, heads warped around the 50 gallon mark
OS 91 Surpass- got about 80 gallons before it was just plain worn out
OS 70 FL- after about two gallons of frustration, testing was abandoned.

As a comparison, heres some of my test engines that are in either the 400 hour club or 100 gallon club
Fox 35 CL, 40 bushing, 40BB, 45, 46, 50 and 74
Enya- 25, 40's (all the 40's), 50SS, 50CX, 60 (all versions) and 4-strokes: 46, 53, 90, 120 (old and new) and the 155 (everything tested)
Irvine- 46, 53
Super Tigre (italian)- 34, 40, 45, 51, 75, 90, 2300, 4500 (no chineese ones tested yet)
K&B (Pre Mecoa)- 40 (4011), 48, 61
Thunder Tiger- 25, 40, 42 bushing, 46, 61, 65 bushing, 120 and 4 strokes: 91 and 120 (everything tested)
Magnum- 46 (the only model tested)
Webra- 50
YS- 45, 53, 91AC
Saito- 56, 65, 72, 80, 91, 100, 120, 180 (everything tested)
Moki 135, 180 (everything tested)
MVVS 40, 49, 77, 91 (everything tested)
Rossi 45, 53 (everything tested)

Now heres some that did not make it to the club:
Anything Mecoa
Anything Leo
Anything MDS
Anything OS (modern)


Don't flame me guys, these are just the results experienced. In all cases, fuel should not have been an issue since failures in the OS line on one fuel were very soon repeated on the other, which indicates design problems.

quote:

ORIGINAL: bob27s

quote:

ORIGINAL: STG

Looking at Jett's 120 motor they show performance to be

BSE 1.20L R/C with semi tuned muffler AAC
16x8apc @9,200 27.8oz

http://www.jettengineering.com/

This OS120 looks pretty kewl. Going to be a good engine.

Just of inforomation,
The Jett BSE-120 is 21oz without them muffler. 27.8 with the jett-stream muffler included, glow plug and spinner nut.
It is the same phycial size as the OS91FX and the Jett 90L.

Anyone have any footprint/size or mounting/muffler bolt pattern info on the new engine???

Bob

quote:

ORIGINAL: Dr Nitro

quote:

Lets hope that OS did something right for a new product (for a change). The last 9 OS engines I bought new were returned for service a minimum of one time. Three 46FX's and two 32SX's spit the nickle. The OS 70 heli engine could not keep a rod or bearings in it. The 160FX went back twice and was still junk after second brand new replacement. OS 50 could not keep bearings in it. And finally the wonderful new lightweight 70 four stroke that was a gift, it would'mt run worth a hoot. These engines all went back at least once and every time Hobby services was given the opportunity to return my money and keep the engine, which of course they refused. Only one of these engines I have now and that is one 46 FX that I forced HS to fix the peeled sleeve with a steel sleeve and a ringed piston (from the heli engine) and it still runs fine. The remaining engines went to ebay.

ACK!!

What fuel are you testing? I'll stay away from that stuff!!!! LOL

< Message edited by coveredup -- 10/1/2005 7:41:25 PM >

(in reply to Dr Nitro)

quote:

ORIGINAL: STG


Bob, I think the turbo jett is maybe 1/2oz or so less for the 1.20 size? Do you have any idea if the current web pricing is up to date $399.00 for 120, or am I going to be in for a shock if I inquire?

quote:

My math shows 24,000 hours or 6000 gallons of testing on just the ones that "made the club". That's sure a lot of testing.

quote:

If you read the complete post you also saw Doc was running two of each engine, with a competitor's fuel on the second. I don't think the fuel is the cause of the failures.

I see the same thing here with all different fuels. The only obvious difference is Joe Average with the lean run now and then and castor blend fuel gets somewhat longer engine life than Joe Average with the lean run now and then and all synthetic oil.

Bill.