OS91SZH running Hot

[gadawg58]

Seems I have to run my OS91 non pumped very rich to keep the engine from getting too hot.I live in Atlanta and the temp today was 95. I am running over 2 turns out to keep the engine at around 200. At that setting I just about can't see the helicopter for the smoke which makes me think that it is too rich. I run the OS #8 plug and its in a Raptor 90 SE. I have the GV-1 set at 1900 head speed and at over 2 turns out it is a little sluggish. At 1.5 turns out is runs great but temp it at 250 at the end of the flight and the backplate is very hot. Any ideas?

Thanks,

George

[LAMAR COOLEY]

gadawg58,
What brand and nitro % of fuel are you running ?
Regards

[gadawg58]

Running 30% Nitro and have tried both the Cool Power and Bryon. The engine runs a little cooler with the Byron 30%. Still more smoke than what I see on video's and running way richer than what most people are running at. May have something to do with the heat and humidity here in Atlanta?

[FlyJ]

Same problem still looking for a solution. The exhaust is blinding!

[d3sbo]

i had something like that on another motor and found adding head shims worked but i dont under stand why

[d3sbo]

why

[gadawg58]

i had something like that on another motor and found adding head shims worked but i dont under stand why
I'm already running all the shims that shipped with the 91szh. I can get it to perform really well but the engine temp is about 250 after the flight which I think is too high...still a lot of exhaust even at that setting. When I get the temps down to the low 200's the head will bog some and the exhaust is blinding. Going to try a new pipe and re-tune... currently running the hatori sb-18jk. Will try an MP5 when they are back in stock.

[DavidH]

I can get it to perform really well but the engine temp is about 250 after the flight which I think is too high...still a lot of exhaust even at that setting.

Why do you think that is too high of a temp? If the engine is performing well and not going lean and slowing down. Then it really does not matter what the temp of the engine is. Also the engine can be several different temps just according to where you check it with the temp gun your using.
As for smoke from the exhaust. Never use the smoke to judge the mixture on the engine when using 30% fuel. Most of the fuels that are 30% heli use a low viscosity oil. This type oil will have the same amount of smoke when the engine is way to lean as it will when it was to rich. From my experience all the different brands of 30% heli fuel that have a low viscosity oil will smoke the same no matter the needle settings.

David

[gadawg58]

I thought it was too lean based on others posting temps in the low 200's...even 190. Also, the backplate is real hot,too hot to hold my finger there for more than about a second but the heli does have a ton of power there ... I check the temp at the head near the glow plug and on the bottom side of the head...both are close to the 250 mark when I have the needle set where it makes the most power. Won't running it that hot shorten the life of the engine? I will say though at the 250 temp the glowplug looks fine when it comes out and I get about 30 flights before having to replace the plug on average. Let me know if you think it is safe to fly at that high a temp. Also, temp outside is in the mid 90's.

Thanks for your response.

[Neriyah]

i had something like that on another motor and found adding head shims worked but i dont under stand why

adding shims you changed the ignition time of the engine, pretty much the same as using a hotter / colder plug.

[DavidH]

I thought it was too lean based on others posting temps in the low 200's...even 190. Also, the backplate is real hot,too hot to hold my finger there for more than about a second but the heli does have a ton of power there ... I check the temp at the head near the glow plug and on the bottom side of the head...both are close to the 250 mark when I have the needle set where it makes the most power. Won't running it that hot shorten the life of the engine? I will say though at the 250 temp the glowplug looks fine when it comes out and I get about 30 flights before having to replace the plug on average. Let me know if you think it is safe to fly at that high a temp. Also, temp outside is in the mid 90's.

Thanks for your response.


I don't know what temperature a motor operates at. I have never used a temp gun or sensor on an engine for the 20 years I have been in the hobby. I just set the needles and fly the model. If the engine sounds fine and is producing power. Then I do nothing. If it doesn't sound or run right, then I make adjustments on the engine. I can tell you from experience, identical engines, in identical helicopters will run different. At one time I had three identical models that would fly off the same program in the radio. The biggest headache were the engines would not be the same. So I just adjust them to run the best they would run.
So what one engine temp is on a temp gun and another engine on temp gun. They will be totally different numbers even thou both of them are adjusted perfect.
Only thing I have used a temp gun for in RC is to check the temp of a tail servo after a flight. LOL I had to borrow a temp gun . I was doing some testing to see how many flight consective I could get on a servo before it might reach critical mass. <G>

David

[gadawg58]

Not running hot any more...no more 30% Nitro here in Atlanta! Guess its time to fly the TREX450 and 600e again!