Align 91H (OS91HZ) Temp/Breakin questions

[kcgraves]

Come to the people who know.
I have a Freya with an Align 91H non-pumped engine. Newer Black Head Version. This is basically an OS 91HZ Black Head engine. Has about 13 tanks through it of basically hovering. Throttle curve is 0-60 which is about 1650-1750 RPM tops.

Started with both the High needle and Midrange needle at 2 turns out (by the book). After about 10 flights the glow plug blew out the front after about 11 minutes of casual flight. I might have cross threaded it 2 flights previous when I took the plug out to clear the engine lock. Flight 11 same thing after 10-11 minutes. Check the head and the top two threads were gone. Got a new head. Also a temp gauge. And I know do not adjust the engine based on temp. I just wanted a sanity check.

So just took it out for six 3:30 minute flights. After each two I let it cool off. High needle is about 1-3/4 out. Checking the temp after each one. First one was about 250 degrees on the black head near the body (side by carb screws). Next one was about 250-260. Tried one with High at 2 turns and it was about 200. Last one, with the high back at 1-3/4 came to about 305 Degrees. This was the second of two flights, no cool down. The mid speed is still at 2 turns out.

It purrs pretty good between 1-1/2 and 1-3/4 turns with fairly good response. So before I destroy this engine I need a sanity check. Does everything sound within reason?

Thanks.

[blax1]

I thinking about this Kieth aren't you supposed to check temps at the back plate, if you can keep your finger on it for a period of time all is good, but if you cant hold your finger there at all its to lean, never used a temp gauge, so I don't know much about them, but checking the temp on the cylinder head and barrel wont give you the right indication because that where the combustion is and it will be extremely hot anyway............

Interesting subject, I'll be very interested in what the others say?

[blax1]

With regards to bolts, I took off one morning with the Caly brought her up to a steady hover at eye level to check he over before cutting her loose but it was running very erratic and there was fuel pouring out of my OS50 Hyper, landed straight away, shut her down, looked at fuel lines OK, couldn't see hole or leaking fuel tank, pulled canopy off, got Allen driver checked back plate all tight, held her up to the light looking through engine cooling fins, very wet, got Allen driver again checked head bolt all loose and two missing :eek:
Got new bolts red locktite, tightened them up, and ran it on myh bench at home got it hot and re-tightened before loctite had cured, did the same with my OS91SX-H C-Spec they were loose as well, but none had fallen out....YET!!!!

That's my story mate, yep lots of people will say you shouldn't use loctite on motors but I'll deal with it when I have too.... :)

About 5 more tanks on both engine all perfect now............... :cool:

[kcgraves]

Hi Raplh. Putting my finger on the backplate is what I have always done with my 50s. About 10 sec. or so before it feels too hot. The OS/Align has an aluminum heat sink over the back plate. It says machined in but I think it is a separate piece since it appears to be nice shiny aluminum. I have read lots of horror stories lately of people destroying 91 engines. Burned pistons, broken cranks, etc. So I bought the temp gauge and am being careful with this one. Also people seem to be all over the place with mid and high settings.

http://www.osengines.com/engines/osmg1975.html

Putting my finger on that with the needle 1-1/2 out is extremely hot. Temp gauge on it when the head read about 300 it was about 270. This was after about 3 minutes of flight.

One other thing I just remembered was the main tank at this time was almost dry, clunk had to be exposed, and the engine had just started making a noise the it died. The header tank was full. The two times the glow plug blew out the main tank was almost dry also and I was just about to bring it in. Don't know if that has any bearing or why it would die when the header was full. Never had a 91 before so this is new to me. The 50 was more plug-n-play (fly).

Cheers,
Keith

[heli-cuzz]

Hi keith,
You want to adjust the fuel/air mixture so that your engine runs at an optimal temperature which is generally somewhere between 225-250 degrees Fahrenheit for most nitro engines. Much over 250 degrees could cause a lot of damage and also shortens the life of your nitro engine.
Check your nitro engine's temperature often to keep it at optimal temperature for longer runtimes and overall better life for your nitro engine. If the running temperature is less than 200 degrees you need to turn your high-end needle adjustment clockwise to lean out the mixture a bit to get the temperature up a little. If your temperature is above 250 degrees you would bring it down by adjusting the high-end needle to richen the mixture by rotating the high-end needle counter-clockwise. The ambient temperature outside and the elevation according to sea level will adversely effect the nitro engine's temperature so adjust accordingly.

[kcgraves]

Hi Brian,

That is what I normally do with the 50s. Finger on back plate and adjust as necessary. The 90 just seems hot to me. But maybe I'm trying to rush it. If I leave it about 3-4 clicks lean from 2 full turns it seems to be fairly happy and stays around 240. Any more rich and it has no power. Any more lean and it gets way too hot. So I guess for now I'll leave it where it is, a couple clicks clockwise from no power.

On the empty main tank problem. I was thinking this morning on the drive in to work that it might be a fuel line leak. The noise was kind of a sucking sound on the muffler side so maybe I'm losing back pressure and the engine is starving for fuel, gets way too lean and dies. That is when my temp was over 300 and also around the time my two glow plugs popped out. Have to check all the lines and clunks.

[Ots]

Hi keith,
You want to adjust the fuel/air mixture so that your engine runs at an optimal temperature which is generally somewhere between 225-250 degrees Fahrenheit for most nitro engines. Much over 250 degrees could cause a lot of damage and also shortens the life of your nitro engine.
Check your nitro engine's temperature often to keep it at optimal temperature for longer runtimes and overall better life for your nitro engine. If the running temperature is less than 200 degrees you need to turn your high-end needle adjustment clockwise to lean out the mixture a bit to get the temperature up a little. If your temperature is above 250 degrees you would bring it down by adjusting the high-end needle to richen the mixture by rotating the high-end needle counter-clockwise. The ambient temperature outside and the elevation according to sea level will adversely effect the nitro engine's temperature so adjust accordingly.

225 - 250 by the time you get it down and get to it to check it, I suppose. My experience has shown that the sooner I get to it the warmer it is. I have been running a bit cooler than what you're recommending but I figured it was probably hotter in the air working hard than what I get to measure when I finally get to it.

So I guess there's a question in there somewhere! Lol! So if you see 225 - 250 when you get to it do you think it was hotter in the air?

[kcgraves]

225 - 250 by the time you get it down and get to it to check it, I suppose. My experience has shown that the sooner I get to it the warmer it is. I have been running a bit cooler than what you're recommending but I figured it was probably hotter in the air working hard than what I get to measure when I finally get to it.

So I guess there's a question in there somewhere! Lol! So if you see 225 - 250 when you get to it do you think it was hotter in the air?

That is probably one of those "depends" questions. In the air there was movement adding to the cooling of the engine. On the ground, depending on how fast you get to it, there is little or no air movement around the engine. My 50s are running around 200 Degrees by the time I get to them, finger on the back plate for about 10 sec. Yada, Yada. But one has about 70 tanks and the other close to 200. Well broken in.

I wasn't stopping my 91 when I brought it down. Just lowered the RPM, with the trim lever, way down then stopped the blades and measured the temp.

You could always have someone put their finger on the back plate while you hover it at eye level to check it. :eek:

[blax1]

^^^^^^^^ LOL Good luck with that....................... ;)



Have you read this?

http://www.osengines.com/faq/product-faq.html#q14

Shame they don't mention numbers

[kcgraves]

Shame they don't mention numbers

That was one of the first places I looked after going through the manual. Nothing. The only thing I could find were several online posts that said 200-270F. Low 200s being better. All the temp gauges say to consult the engine manufacture's specs. :confused: Be good if they gave you some.

Been doing some searching on my engine running hot and quitting when the main tank is empty. Seems to be a common problem with the bigger engines and it is a back pressure or restrictive fuel line problem. Time to take it apart and check everything. Also the fuel filter might need to be bigger if it is restricting the flow.

[vermonster]

no wonder why that model engine has a heat sink mounted on the rear back plate........:rolleyes:

[kcgraves]

OK, new head and I replaced all the fuel tubing, drilled out the inlet on header tank. Small piece of plastic I could see inside. Also the three hole stopper on the main tank looked like someone had used the second hole and plugged it with a small piece of copper rod. I pulled that out and put some aluminum tubing in it then a capped of piece of fuel tubing. Finally got a chance to take it out today and everything seems fine. Engine was more consistent and the temps stayed pretty even. No big swings.

Black Head - 200 degrees
Just behind the head - 210 to 220
Back plate (alum. heatsink) 150

That aluminum heat sink gets extremely hot because it is aluminum and also may not give an accurate temp reading because it is shiny aluminum but the rest of the engine is in the low 200s so I think it is fixed. No more 250 to 300+ temps. And the glow plug is still nice and tight.

[vermonster]

Glad to hear..........Sheeeeeesh :D

[blax1]

Great news Kc

Hey I remember a loooooooooong time ago there was a discussion on here about that plastic dimple inside fuel tanks left behind from the manufacturing process that was obstructing the fuel flow............bummer how simple was that... :cool:

I made a point of checking the temp- on my OS50 on the weekend, after a good 10 minute flight, I landed and straight away put my finger on the back plate, hot but bearable, left finger on there for 15 seconds maybe more, no trouble at all, but it was a cold morning, I'll probably have the Avant up this week I'll check her as well, I expect similar results..

Good news Kc GO FLY>>>>>>>>>>>>>>>>> :)

[Ots]

Temping the hottest part of the engine I can find from the bottom (since I'm lifting the heli in the air) after getting to it as quickly as possible I typically find 180 to 190. The backplate is hot but I can count to ten with my finger on it. This may be on the fat side of perfect, but I really let full-stick verticals decide for me. If it's got that "get there right now!" kind of vertical performance and it doesn't sound "tinny" when flown then I'm all set.

[vijendrasnv]

Hi,
You want to adjust the fuel/air mixture so that your engine runs at an optimal temperature which is generally somewhere between 225-250 F for most nitro engines. Much over 250 degrees could cause a lot of damage and also shortens the life of your nitro engine.
Thanks.