EGT Rotax 912

[Greg Vos]

I’m toying with the idea of removing my EGT sensors from a 912, after all with the carb version we have no means to adjust the mixture in flight like we do with the Lycoming or other aircraft engines
I have owned a M16 that I flew to TBO that did not have EGT sensors, with not a days problems, yes it’s nice to have.
What are the thoughts from you guys who fly Rotax 912 with carbs ?
My thinking is we still have CHT & Oil temps,

 

[Eric S]

I’m toying with the idea of removing my EGT sensors from a 912, after all with the carb version we have no means to adjust the mixture in flight like we do with the Lycoming or other aircraft engines
I have owned a M16 that I flew to TBO that did not have EGT sensors, with not a days problems, yes it’s nice to have.
What are the thoughts from you guys who fly Rotax 912 with carbs ?
My thinking is we still have CHT & Oil temps,

My 80 hp 912 only has water and oil temps. 800 hrs and running great.

 

[wolfy]

All my time with 912 is without EGT.

wolfy

 

[Sv.grainne]

No egt's on my 912ul

 

[Gyrotriker]

1200 hrs on my old MTO without egt

 

[Chook]

I’m toying with the idea of removing my EGT sensors from a 912, after all with the carb version we have no means to adjust the mixture in flight like we do with the Lycoming or other aircraft engines
I have owned a M16 that I flew to TBO that did not have EGT sensors, with not a days problems, yes it’s nice to have.
What are the thoughts from you guys who fly Rotax 912 with carbs ?
My thinking is we still have CHT & Oil temps,

Greg, one of our guys flying a 914 TAG failed to detect EGT unbalance on departure climb out at 300'. Turns out one of his "on condition" fuel lines was fragmenting internally which caused a restriction into the carby fuel feed. This resulted in a lean burn in 2 pistons which promptly started disintegrating.
Result- forced landing onto a busy highway and a A$10,000 repair bill.

Regards.....Chook.

 

[Aerofoam]

Greg, one of our guys flying a 914 TAG failed to detect EGT unbalance on departure climb out at 300'. Turns out one of his "on condition" fuel lines was fragmenting internally which caused a restriction into the carby fuel feed. This resulted in a lean burn in 2 pistons which promptly started disintegrating.
Result- forced landing onto a busy highway and a A$10,000 repair bill.

Regards.....Chook.

I'm really not qualified to make remarks on Rotax engines, but shouldn't that have been showing up on head temp. too?
Or did it happen so quickly that the head didn't have time to heat soak?

 

[Chook]

I'm really not qualified to make remarks on Rotax engines, but shouldn't that have been showing up on head temp. too?
Or did it happen so quickly that the head didn't have time to heat soak?

Time taken to get from ground to 300' with a Steve Paulette modified 914 in a TAG is probably only seconds. If you are watching the instruments he may have spotted it - but he didn't. When your engine is losing power, vibrating and spluttering cause there is metal being sprayed inside the crank case and you are at 300' in a gyro, then you become a bit busy with getting it down safely which they managed to do.

I still think EGTs are handy because they display changes so quickly as compared to water and oil temp changes and would not remove it if is already fitted. Could I detect the change in time as I fly outside the cockpit mostly trying to avoid things, debateable in my case.

Regards.............Chook

 

[rcflier]

I'm really not qualified to make remarks on Rotax engines, but shouldn't that have been showing up on head temp. too?
Or did it happen so quickly that the head didn't have time to heat soak?

The CHT is on one cylinder - one side only. If the other side/carb leans, you won't know it.

We had a Calidus 912ULS that melted a piston because of a clogged air filter.

I have a 4 cylinder EGT meter with sensors from a scrapped Cavalon - wondering if I should mount it instead of my VSI
(which is nearly unuseable and have annoyed me much during schooling. Looking at it when I shuld have been looking at height).

But then I would have to use some lookout time to check it...

 

[MilesW]

The CHT is on one cylinder - one side only. If the other side/carb leans, you won't know it.

For the 912, the recommended install is both sides. Left front, right rear. ie dual CHT's. The heads are tapped accordingly. This has always been so.

 

[rancherman]

RCflier, back in my racing days, and before electronics... we'd run minimum 1 sensor per bank, some guys were running a sensor on each cylinder. It was a real cluster to wire and keep an eye on 8 gauges!!

I have no idea what's available these days, but a meter that could take multiple signals, averaged them for general health, but automatically switched to an outlier (high or low) with a flashing red light...
In my eye would be ultimate!

 

[Aerofoam]

When I was building off road desert rail type cars, we would put the loudest most obnoxious buzzer known to mankind on the oil pressure circuit.

 

[wolfy]

The CHT is on one cylinder - one side only. If the other side/carb leans, you won't know it.

We had a Calidus 912ULS that melted a piston because of a clogged air filter.

I have a 4 cylinder EGT meter with sensors from a scrapped Cavalon - wondering if I should mount it instead of my VSI
(which is nearly unuseable and have annoyed me much during schooling. Looking at it when I shuld have been looking at height).

But then I would have to use some lookout time to check it...

Don't know how a clogged air filter would melt a piston, you need a lean condition to melt aluminium.

wolfy

 

[Abid]

Greg, one of our guys flying a 914 TAG failed to detect EGT unbalance on departure climb out at 300'. Turns out one of his "on condition" fuel lines was fragmenting internally which caused a restriction into the carby fuel feed. This resulted in a lean burn in 2 pistons which promptly started disintegrating.
Result- forced landing onto a busy highway and a A$10,000 repair bill.

Regards.....Chook.

On condition fuel line?
There is no such thing. You use high quality fuel line and you change all rubber hoses including all fuel lines made of rubber every 5 years regardless of condition as mandated by Rotax. You cannot pull over in aircraft. One of the best rubber fuel lines to use in my experience are Aeroquip pushlock hoses

 

[rcflier]

Don't know how a clogged air filter would melt a piston, you need a lean condition to melt aluminium.

wolfy

The carb would feel a lower pressure and automatically lean the mixture as if it was flying at a higher altitude...

At least that's what happened. The Bing64 is a Constant Velocity carb.

The engine went to Norway to Edge Performance. Thomas showed us the filter was the culprit.

 

[rcflier]

For the 912, the recommended install is both sides. Left front, right rear. ie dual CHT's. The heads are tapped accordingly. This has always been so.

I know it's tapped for that. But where to find a dual CHT instrument? I would feel safer having that.
OTOH, right now I've run out of funds. I have changed too many parts, so my bank account doesn't like me...
That's why I am thinkung of installing the 4-cylinder CHT instrument...

 

[Brent Smith]

What do you gain by removing the sensors, Greg, and what do you lose? I've always felt that more information available is better even (or maybe especially) if it's always good. EGT response is more timely than CHT response, generally. Recommend you keep them.

 

[WaspAir]

The carb would feel a lower pressure and automatically lean the mixture as if it was flying at a higher altitude...

At least that's what happened. The Bing64 is a Constant Velocity carb.

The engine went to Norway to Edge Performance. Thomas showed us the filter was the culprit.

I thought cv carbs provided an indirect slide operation (vacuum sensitive) to prevent stumbling with rapid throttle motion. Are you saying they also control mixture for altitude compensation? No jetting?

This is all news to me (a Lycoming guy) so I'd like to know.

 

[rcflier]

I have to be away a few days. Let's investigate this unfortunate accident next week.
I'll ask Thomas of Edge Performance if he'll clarify.
I have a few documents that explain the workings of the Bing CV carb.
I haven't had the urge to read them both - I just sat them aside for the future.

 

[Abid]

I know it's tapped for that. But where to find a dual CHT instrument? I would feel safer having that.
OTOH, right now I've run out of funds. I have changed too many parts, so my bank account doesn't like me...
That's why I am thinkung of installing the 4-cylinder CHT instrument...

You only need to monitor the hottest CHT. No need to monitor both. The hottest CHT is going to depend on pusher or tractor installation.
In new 912s past 2014 the cylinder heads are directly water cooled. You monitor only one and it’s the same water temp everywhere.