Question about CHT Vs EGT gauge.

[scottessex]

Idiot lights are for cars,
I want to know what is going on in an aircraft engine.
At least spot early signs of trouble, or give you a few more seconds to pick out a good landing spot.!

 

[Alan_Cheatham]

On my three cylinder, water cooled two stroke my instruments monitor 4 EGTs, one for each cylinder and one for the collected exhaust gases, 3 CHTs, coolant temp, and tach. The reason I monitor so many parameters is because on a multi carbureted engine, as most aviation two stroke engines are, you essentially have multiple engines connected to a common crankshaft, each one doing it's own thing.
Each parameter tells me something about what that "mini engine" is doing, EGT the mixture ratio, CHT if there is proper coolant flow or maybe a trapped air bubble in a cylinder, coolant temp the ability of the radiator system to get rid of waste heat. By monitoring all these parameters I know a lot more about what is going on with the engine and if something is not correct.

 

[CPL22]

Scott, have you ever thought that lots of "idiots" are idiots cuz their "aeronautical budget" is not enough to make ends meet? Most pilots love A380´s avionics, however, it´s not possible in loads of cases..

I just wanted to put on record it´s possible to adjust the mixture with the tachometer (as manufacters like Cessna says) as well as that both gauges are not installed in the whole airplanes so.. would you stay on the ground in that case?

I´ve never used a 2 stroke, this is why I opened the thread.. to learn how to manage it as I noticed that they don´t work like 4 one. I know as well as you it´s better to fly with good equipments, nevertheless, in my opinion, a qualificated pilot has to have resources when it comes to flying in "bad conditions" every now and then.

 

[Alan_Cheatham]

One other thing, on my engine I installed an in-flight mixture control, and although I designed and machined it myself it is basically based on this system,

http://www.greenskyadventures.com/bing/manualMixPrelease.htm

The ability to turn a knob and change the mixture to whatever the engine needs is in my opinion invaluable on a two stroke powered aircraft, certainly worth the effort and $60 I invested.

 

[CPL22]

It looks great! Where is exactly located? Could you explain to us how to build it by ourselves?

 

[brett s]

I just wanted to put on record it´s possible to adjust the mixture with the tachometer .

Not on a 2 stroke, that's what everyone keeps trying to tell you - a 4 stroke engine is an entirely different situation.

If you try to set your mixture on a 2 stroke using only rpm, your engine lifespan will probably be measured in minutes rather than hours. The first time you've got it too lean at a high power setting it's toast...

 

[CPL22]

I know I know, I meant on a 4 stroke cuz someone asked me for the way to do it..

As far as your explanation, it´s crystal clear since some post before, however, nobody explain to me why. A 4 stroke is entirely different in terms of procedures to adjust the mixture but I want to know the reason. Maybe it´s just cuz my English is not good enough, in that case accept my apologizes.

 

[Alan_Cheatham]

Ok, here's the bottom line. If someone wanted to fly on a two stroke engine and just didn't want to spend much or any money on instrumentation to monitor the engine what one thing would be essential to it's safe operation? My answer is, In Flight Mixture Control. The problem with setting the mixture on an aviation two stroke, and mixture setting is THE basic key element in the equation, has the do with how it's set. Land the aircraft, pull open carbs, change jets, needles, etc, etc, which means you can't be running the engine while you are changing the mixture and that is the problem. What I have learned from using my mixture control is that I can set the mixture accurately by just listening to the engine, feeling the vibration, observing the rpm change, all possible because the engine is running while I'm doing it. Anyone who has flown R/C aircraft, which are mostly two stroke powered, would know how much more difficult it would be to adjust the engine mixture correctly if they couldn't do it while the engine was running. Manual mixture control turns the aviation two stroke into a big R/C aircraft engine, as far as mixture adjustment goes.

But, I still believe in monitoring the piss out of the engine.

 

[akoschier]

Scott,

Show me the turbine which has a TIT.
The only TIT's I know of are pyrometers looking through a saphire window onto some ceramic or platinum target.
There are EGT'S though on all engines I have seen.

avk

 

[brett s]

Every turbine engine other than APU's I've worked on had one of some variety - PTIT (power turbine inlet temp) on Lycoming T-55's, ITT on PT-6's.

 

[scottessex]

When I was in the military, running C-130's (Allison T-56A-7) you had to keep the TIT below 810 degrees on all four engines, otherwise it would jump chocks. You can take 2 engines up to 910 at a time.
Also during start up the TIT was very critical that you did not get a hot start. Otherwise you had to do a hot start inspection on the engine.

 

[JEFF TIPTON]

TIT gauge is also found on many turbocharged piston engine; such as the TCM TSIO-360 series. They are typically limited to 1650 Fahrenheit.

 

[ferranrosello]

CPL 22, the main reason because the mixture control of 2 stroke engines is different from 4 stroke ones is the engine lubrication.

The oil system in a 4 stroke is much better than in a 2 stroke. In 2 stroke engines the oil is in the fuel. So when the mixture is lean you not only have problems with detonation and thermal stress, additionally you have a serious lack of lubrication in all engine parts, but especially in the cylinders.

Because of this problem the EGT in a 2 stroke is more critical than in a 4 stroke. But it doesn’t mean than in a 4 stroke the mixture is not important.

Usually 2 stroke engines are simpler and cheaper than 4 stroke ones, and are used in light machines with reduced endurance. So is not normal to have the EGT indicator in a 2 stroke. Instead of this, the mixture is adjusted always in the rich side. The EGT in 4 stroke engines manage the mixture control operation in order to save fuel and to avoid engine contamination. In a 2 stroke engine you can’t use the EGT in this way. The mixture needs to be always rich if you don’t want to have engine failures.

From my point of view the EGT indicator is not necessary in engines without manual mixture controls. Rotax 4 stroke uses a kind of carburettors than ensure a reasonable good mixture adjustment in a wide range of density altitudes, and is not possible the manual control. So what is the sense of EGT indicator in them?

Ferran

 

[scottessex]

So what is the sense of EGT indicator in them?

so you can monitor your mixture, because it will change with altitude and temp. The rotax uses BING altitude compensating carbs, and they do work well.

When properly jetted you may have to rejet between winter and summer, depending on the temps you fly. (on a 2 stroke)

 

[GyroDoug]

Mixture Contol for Rotas 912

Mixture Contol for Rotas 912

I could have sworn I had seen some company advertising a mixture control setup that was made for and could be added to the Rotax 9 Series engines. Does anyone know what I am talking about and whether it would be a good idea or not?

Gyro Doug

 

[Joe Pires]

is it the Hacman that green skys advertises? http://www.greenskyadventures.com/bing/HACmanorder.htm

 

[GyroDoug]

is it the Hacman that green skys advertises? http://www.greenskyadventures.com/bing/HACmanorder.htm

Joe,

That's not the web site I remember visiting when I first checked it out, but I think that is the product I was thinking about. Doe anyone have any experience using that on a Rotax 9 Series? And what about Ferran's comment that it is not possible to manually control mixture on these machines?

Gyro Doug

 

[Vance]

Hello Felipe,

I feel you do very well with your English.

You are quoting from a manual for a low specific power engine. In order to get more horsepower per pound or dollar many engines in experimental aircraft are tuned for a higher output.

In my experience this makes the line between best performance and a lot of expensive broken pieces much thinner. The EGT allows you to recognize trouble as it approaches rather than after it has sucked the life from your wallet.

High fuel consumption is annoying on a two stroke and this makes getting the mixture just right alluring. It is easy to get seduced into going too far.

I do not have an EGT on my Lycoming O-290 G because it is a big lazy engine that destroys itself slowly. It is not at all hard to tell when things are not quite right and so far there has been time to bring it back to its low output best. For an engine that is tuned for a higher specific output I feel that an EGT gage can be useful.

Aviation is another wonderful way to change money into noise. I feel that an EGT gage used well can allow you to make noise for longer with the same investment. In my experience it is money well spent.

Thank you, Vance

 

[amphib]

security blanket

security blanket

Quote:
So what is the sense of EGT indicator in them?

For that warm fuzzy feeling! Whether or not I have a mixture control, it's very reassuring to know that all systems are "Go" before I overfly any "hard" terrain (where an engine-out could ruin your whole day) It's not a guarantee, but real-time real data does make me feel a whole lot better than "the engine sounds ok".


Neil

 

[CPL22]

Taking into account that there could be plenty of engine malfunctions during the flight, do you mind describing some of them and how to difference each one using engine parameters gauges? (for instance, on a Rotax 503).

Once the inditacion is in "red arc", how much time can your engine works before break down? Maybe this question is so relative and have no answer, anyway, I would like to know your opinion about it.

Cheers.

The EGT allows you to recognize trouble as it approaches rather than after it has sucked the life from your wallet.