Doomking

My Feedback: (38)

Does anyone know what's a good running temperature for the zenoah g62 taking it with a laser thermometer pointed at the head where the plug is, running on the ground after warming up with cowl on?
i have a reading of around 250-260 deg F. .....is that too much?

thanks for your help....

fabio

w8ye

My Feedback: (16)

That's as high as you want to get

Doomking

My Feedback: (38)

So does that mean that I am running lean or ok? The plug was new when started a couple of weeks ago and the ceramic on the inside is a tan color......
what would be ideal temp?

w8ye

My Feedback: (16)

You are not necessarily running lean. 225-250F is a good range while in flight.

There is a big unknown here . . .

It is more important - the temperature the engine is running in flight with the cowl on?

After using the hand held infrared monitors at work for most of my working life, I decided that a hand held was not so meaningful for model flying applications.

You actually need a more or less permanent thermocouple mounted between the fins on the rear towards the exhaust that you can tele-monitor in flight?

But I could never eyeball the temperature while flying. I'd have someone else either monitor the temperature or do the flying for me?

In my hot rod car situations, I used a thermocouple to a monitor inside the car will driving down the road and also stopped at red lights etc.

av8tor1977

My Feedback: (6)

Yeah, readings taken on the ground after a flight are pretty much meaningless. The cheap and easy way to go is get a Venom recording temp gauge but I just searched for one and couldn't find one. Does anyone know if they quit making them? Tower and others used to have them...

AV8TOR

Doomking

My Feedback: (38)

So head temp on the ground is really that inaccurate?
so best way to set the carb then is with the tack.....lean it until rpm drops and then back it off 200-300 rpm.....correct?

thanks
Fabio

Doomking

My Feedback: (38)

try here av8tor.... Few left.
http://www.ebay.com/itm/like/360900748651?lpid=82

By the way where would you mount the monitor screen? Inside the fuse? How would you read it?

fabio

Truckracer

My Feedback: (19)

For gassers, while there is a relationship between temperature and mixture its best if you separate the two for tuning purposes. Think of it this way, cooling is controlled mostly by airflow through the cooling fins and the way the engine runs is controlled by mixture.

Mixture controlled the temperature much more on glo engines but there is really no need to carry this line of thinking over to gassers.

On gassers, I prefer to tune to maximim RPM and back off ever so slightly .... maybe 50 or 100 RPM and this is done mostly by ear. I just want to know that I am not lean from peak setting. Most of the additional tuning is then done after the engine is flown a few times. Tune until it runs the way you want it to perform. You can also do plug readings that will tell more of the story.

av8tor1977

My Feedback: (6)

I definitely agree with all this. The only thing is that unless you do a "clean cut", the plug color readings will be "muddied". A clean cut is a bit difficult to do with an airplane. You have to run the engine for a while at full throttle in flight, then cut the engine off without idling it down, then dead stick land it and check your plug reading. So two problems with that. Todays airplanes are way overpowered and it is difficult to run them at full throttle for long without over stressing the airframe and/or encountering control flutter. Then, after you get through that, you have to kill the engine and make a successful dead stick landing. THEN, you can read your plug and the results won't be tainted by idling the engine down to land and taxi back in. If you can't tune by ear, then tuning by a tach is the best choice. You don't need to go down 200 rpms rich like a glow engine; just slightly down as suggested by Truckracer.

AV8TOR

Truckracer

My Feedback: (19)

I agree regarding plug readings. I get to where my plug readings are what I expect to see for my style of flying. These are quite a bit darker than the text book, just slightly tan photos you often see posted. If an engine is running as expected, I rarely bother looking at a plug at all. For those who care, a plug from a warbird will look very different than one from a 3D plane. An IMAC plane would be somewhere in between.

Doomking

My Feedback: (38)

Thanks for all replies.
last week took the p-51 to the field. After running the engine on the ground which it sounded good, with good transition from idle to full I took off, lifted the gear made right turn, still at full throttle and by the downwind the engine started acting up, holding half throttle stick the engine was racing up and down on its own.
Turned for final and landed with engine still running and fluctuating high and low holding same stick position.


At the pits checked the engine. I turned the needles back to factory settings, Low 1 1/2 and High 1 1/4 + or - 1/4 turn.
Started the engine again had good transition and with the tack I tried to set the high needle but no matter what I did strangely I could open or close the needle few full turns and the rpm remained around 6400, so I decided to back it off to factory settings.
Low needle richened a bit from factory to have a good transition.


Few things I noticed during this whole process which confused the heck out of me.....
when I tried to lean the engine for max rpm, could not get it to go faster than 6500 rpm and after shot down, smoke was exiting the muffler stacks......running too hot maybe? Head temp at that point was around 320 deg.


Cannot hear the difference by hear like I can with glow engine. It does not race up or down no matter how much i open or close the HS needle. Using the tack but I seems be stuck between 6200- 6500 rpm.


Was the erratic fluctuation during flight because low needle setting incorrect which affect the low and middle of the engine tuning?


Sorry for the somewhat confusing explanation. I am paranoid now and I am afraid to take the plane up if it's going to be fluctuating up and down again.


Thanks for all the help


Fabio

STUKA BARRY

Sounds to me like you have an air leak problem not a needle setting problem. As far as temps go, remember, Zenoah's are industrial engines designed to be cowled in chainsaws, weedeaters, concrete cutters, etc. swinging a propeller on the front of a model airplane will never give it the stress it was deigned to take. Yes, an improperly tuned engine will run hot, but temps on a properly tuned engine with a clean carb screen running filtered fuel shouldn't be a concern. I always laugh to myself when I see a modeler with a laser thermometer, thinking he's attempting something with a false parameter. The sparkplug will tell the big picture, but you have to use the methods prescribed in this thread which is hard to do. I hope you find your problem.

Doomking

My Feedback: (38)

Thanks for the reply Stuka.
this past Sunday i tested the engine at my house.
with little richer setting than factory about a quarter turn, the engine is running perfect with strong top end and good transition.
I did this for about twenty minutes aggravating the whole neighborhood, it did hesitate once fluctuating up and down with the stick a middle throttle, which opening the low end needle seemed to correct it.
Now I have to take up in the air and I hope it will still as reliable.

i will take a pics of the plug just to have a general idea...
thanks for all your help

fabio

w8ye

My Feedback: (16)

You may be putting too much emphasis on reading the spark plug?

OK, so you looked at it ! The correct spark plug was the correct color. Time to forget the spark plug. You are going to ruin the cylinder head to be looking at the spark plug two three times every day.

It is time to concentrate on how the engine sounds in flight and to the throttle response.