iflynething

I have been flying this engine on my Sig Somthin' Extra for a while, and not that it is getting that hot, but I'm just wondering what should be to you guys the head temperature of it......

BTW, I am flying it on 15% Omega fuel with a APC 11x7 prop...if that helps any.....

Also BTW, What would you say the temp would be on a OS 40LA with 15% fuel also and a 10x6 prop??

Again.......when I was at the field yesterday, a guy had a temp gun and we got an average of about 160-165 degrees......I was thinking that that might be in the norm.....but just to make sure....here is this post.......THANKS ALOT....

iflynething

goodness people......I have about 13 people that have looked at this and no replies.....GOLLY....hlep me out a little here.......LOL.........I have got around 160-165 but just want to get some other opinions on what they are running on their engine......or anyother engine like this on anyways.....THANKS

jacs

I can answer if you want.

Is this in farenheit or in degrees?

I freind said once that if you pu your finger in the back of the engine (crankcase) and you could hold it there for a short time the engine wasn't to hot (old trick from a helicopter pilot, 40 years flight everything).

Hobbsy

My Feedback: (102)

This is Bax's answer to a similar question.

First off, relying on temperature to tune your engine is a sure way to insure a short life and to make sure that it won't be tuned correctly. A smoke trail is also not necessarily an indicator of richness or leanness. Smoke is as much determined by the oil percentage and oil type as well as the exact mixture setting.

You have to tune the engine by sound and performance. At full throttle, the engine should be running just rich of peak RPM. If the engine's running rich of peak RPM and is overheating, then you have to augment the engine's cooling, either by going to a lower-nitro fuel, more oil, better cooling airflow, or a different exhaust system that won't hold in the heat.

The fact that you mention that when you lean the high-speed needle the engine runs better and you can get a good midrange leads me to believe that the high-speed needle is, indeed, too rich. The actual number of turns on the needle is irrelevant if the engine's running well. Normally, most engines run with the needle about 1-1/2 turns out when leaned as much as possible, but every engine is different. If the engine runs best at 1 turn, then 1 turn it is.

Proper set up would start out with a very rich idle needle, then you lean the high-speed needle for full-throttle operation, and then lean the idle mixture as necessary to get a good idle and transition.

jaka

Hi!
Yes follow Bax advise ...this is how too set any engine ...By ear!
Forget about head temperature...it is not necessary know that on a airplane engine (on a racing car engine yes.... if it's in world champ competition). It's like asking how much amp your glowplug draw- totally unnecessary question to ask.....will not help you in anyway.
Just set the highspeed needle a little rich and fly it!! Enjoy!
Don't mess with head temperatures ...even in pylonracing we don't do.
As for props your 11x7 is a little too big if you use it on a 7,5cc (.46) engine.
Better try a 11x6 for sport flying and a 12x4 or 12,25x3,75 for hovering (at sea-level that is).
Naturally APC props!

Regards!
Jan K
Sweden

Hobbsy

My Feedback: (102)

Air cooled engines are at the mercy of the elements, so on a 100 degree day your engine is going to run hotter and on a 40 degree day it will run cooler.

iflynething

It's so funny that.......when I went flying Tuesday, everyone said the exact same thing....that I should try another prop.....and that's exactly what I'm going to do...but first I'm gonna see if I can snag one from someone at the field and try it out before I spend that money for a prop.....(a prop isn't that much, but if I don't have to spend about $2.50 for each APC by trying one first, then that's better)......I was thinking about going down to a 11x5 or 6 or so.....I'll ask around at the field and see what I can find........

BTW, I would like to move to that 12 dia. prop but I don't have the prop clearance and I don't want to buy more landing gear.......

This plane already rockets STRAIT up for about 600 ft. but I would like the vertical performance to be a little better and get or try the 12 first.......I dunno.......

THANKS ALOT GUYS FOR REPLYING.....I really appreciate it.......






Oh yeah.....I was reading something about the head temp. and they said it should be like 300 and something degrees.....and if you go ver 400 then that is hot.......I couldn't figure that out.......wouldn't that be a little too hot....??.........to my knowledge......that temp that I took was in farienheit (however you spell it..)

Homebrewer

My Feedback: (8)

Mike,
Use the search function on this forum and you'll find a fairly recent discussion about this same issue. In fact, the older thread may still be active.

For airplanes, don't use head temps as a method of tuning an engine unless you have problems with overheating caused by a insufficient cooling in a cowled application.

To tune an engine, set the high end needle to max lean rpm at wide open throttle, and back off the mixture setting about 400 rpm richer than max lean rpm. You'll be fine running your engine at this setting the other time and you won't have to worry one bit about overheating as long as you verify the mixture setting before each flight with the pinch test (pinch fuel line briefly with engine at WOT and engine should speed up 400 rpm and come back down after released-if it does you are ok.


By the way, I tune with head temps for my RC car because it is impossible to tune a car engine 400 rpm shy of max lean rpm like an airplane. I keep my head temps between 250-275 deg F. My engine runs better at the higher temps and I don't mind if it shortens its live. Most car engines tuners recommend a temp of around 225 deg F. I personally would not run an engine under 200 deg F.

iflynething

THANKS ALOT.....I usually can tell by the head temp if I am running lean or not......I think the reason that the temp. is so low because I don't think that the engine is fully broke in yet, so I'm running it a little rich until I'm sure that it is fully broke-in.......

BTW, I also think that the head temp. is so low because this engine has so much power for the Somethin' Extra, I only have to run it on half throttle for just about the whole time that I'm flying......that might have something to do with it.....the only time that I put it at WOT is when I take off and rocket out strait up for what seems like forever.......

jacs

Good you have learned the first thing that people should do, don't fly your engine on full gas the hole time. It's like driving your car flat out the hole time. I have around 50-60% throttle (depends on which prop) at liftoff and stays around there for the hole flight.

CheezeyPoof

Right now owning a temp guage is as usless as a roll of flightline. Everybody is sucking these things up with absolutely no standards at all from the engine manufacturers. They are a ridiculous tool and a waste of money at this time. It gives you a number which you have nothing to compare too! For example you get done with a flight, aim the idiot tool at the head and it tells you 300degrees. Well so what. You don't know if thats good or bad.
If the engine gets to hot in flight, your going to know it whenyou lose power and you land with the throttle stick full forward barely at an idle. You know what we really need is tire balancer. I do fly most of my planes on full throttle from the moment I lift off until its time to land. I have been doing this for years at altitude and 90plus degrees and they all run fine. If the engine gets hot there is something wrong with your set up and 99.9% of the time its running to lean for which there are many reasons why and a temp guage is not going to help you.
You want to get your engine running like a swiss watch? Since you have a Somthing Extra, I assume your engine is exposed and easy to get to. Tune it in as best you can. Now while the engine is running, carefully pull the fuel line off the carb. If the rpm increase before the engine dies, your low end is to rich. If the rpm just goes down and dies, your low end is to lean. I go for a slight increase.
This is not a barnyard trick and is in some manuals that most people overlook. I spend an extra couple minutes doing this on each plane I fly and they rung fine the rest of the day. Sorry but I am not going to rely on a temp guage to tell me if my engine is too rich or lean. Who ever is is filling you full of it.

Homebrewer

My Feedback: (8)

I agree that a temp guage for airplane engines is as useless as 50 yards of flightline and 50 gallons of propwash. Just run it 300-400 rpm shy of max rpm and don't worry about the temps. This is how folks have been doing it for decades before IR temp guns came out.

iflynething

Well, that is what I do......my engine has so much power that I usually fly at half throttle becuase of that....I dont' know if I said that already or not....but I dont' HAVE to fly at full unless I'm doing a climout on take off roll.....

Homebrewer

My Feedback: (8)

Actually, there is nothing wrong with flying your airplane at wide open throttle the entire time provided it is set 300-400 rpm shy of max lean rpm. ABC type engines when originally designed, didn't have a carb, just a venturi, and were designed to run at WOT the entire time.

Several of my airplanes only see low throttle operation during start and taxi. Once lined up on the active, its usually full throttle the entire time. I guess I'm a speed junkie ;0)

iflynething

I am also a speed person, but I do like to fly kind-of a long time....so if I fly at half throttle then I will be able to stay up for like 15 min. (even though I only stay up for like 10 min.)...........I do really like to go really fast, and that is when I put it at WOT and do a fly-by and then strait up for what seems like forever.......I know that my engine has been broken in so I am running it a little leaner so it is running a little hotter.....

BTW, thanks for all the replies.....I was just wanting to get an idea of what it should be................THANKS ALOT...