Rotax 582 EGT numbers

Rasool

Junior Member
Joined
Jul 14, 2016
Messages
114
Location
Greensboro, North Carolina, USA
Aircraft
Magni M-22
Total Flight Time
220 fixed wing, 210 gyro
Recently I have encountered an odd problem with the EGT readings on my EIS for my Rotax 582. The EGT numbers run close for both cylinders at low RPM, but then diverge widely at higher RPM (see pics below). I am assuming (hoping) this is a faulty probe issue, and am planning to switch the probes between cylinders to test for this. Any other ideas, thoughts, coomentary?

Thanks,

Russ
 

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Yes, Bing carbs. So are you suggesting that one cylinder is running very rich, and that this could account for the significant exhaust temp differences at higher RPMs?
 
Yes. I had a similar problem and cured it by R and
R carbs, twice, and finally found problem with enrichment circuit which I was not using.
 
OK, nice to meet another Russ.

l have temperature probes on both exhaust manifolds, if that is what you are referencing. I do not have a separate piece of equipment to manually check the exhaust temperatures.

I thought that I would check the chokes to make sure one was not stuck slightly open (or closed?). I do not know what you are referring to as the "enrichment circuit". I am new to the maintenance and care of two stroke aviation engines and have much to learn.

I should also mention that the aircraft (single place Dominator) is grounded in the hanger, as it is on blocks while I replace the mains tires. So it will be a few days before I can toy with the engine again.

Russ
 
A Bing 54 carburetor doesn`t have a real "choke" (a butterfly that blocks the air inlet and creates suction for fuel).
These carbs instead have an "enrichener" circuit that just floods the engine with more fuel. It is activated with a LEVER
just like a choke so many folks just call it the choke. It just works totally different than a choke.
 
OK, I get it. I have played with these levers recently as I was having some difficulty with starting the engine. So it is possible I did not fully close the "enrichener" on one cylinder. Oddly enough, as I recall the levers are actually labeled as "CHOKE", which reinforces the misconception.

Tires arrived today and I am having them mounted. I will head up to the hanger in the morning to put the wheels back on so I can roll it out and see if I can figure out what is going on with the engine. I appreciate the input.
 
Plug color, unlike electronics, does not lie. Run the engine on the ground for a minute or two at the RPM where the EIS shows the discrepancy. This may involve high RPM, so be sure the aircraft is very well secured, your hearing is protected and you are located in a safe place (such as the seat, with a finger on the kill switch).

Switch it off directly from this RPM (i.e. don't throttle down to idle before shutdown). Then pull both plugs (let it cool first if you like). If the low-temp cylinder's plug is black, then that cyl is indeed running rich at that RPM. If it's brown, then mixture is OK and the fault is in the instrument.

It's true that the Bing "choke" lever doesn't use a butterfly to restrict airflow, but it gets to a similar place by adding fuel. Increasing the denominator of the air-fuel ratio instead of decreasing the numerator.
 
We just cured this problem on a 582 at the ROTOR flyinn. the egt were off about 100*. we balanced the carbs and it solved the problem.
 
You can find them cheaper if you look
 
Thanks for all the great input, guys!

I got the wheels back on yesterday afternoon and was then able to roll the Dominator out of the hangar and work on the engine. I cranked it up to be sure the problem was still there and it was. So I fiddled with the entichenment levers to make sure they were fully closed, which they were, ran the engine again with no change. I had heard the same suggestion Doug made, and ran the engine at 3200 RPM for 2-3 minutes, then shut it down and pulled a plug from each cylinder and they both had that nice brownish tan color. So then I switched the EGT probes between cylinders. This took a little time, since the probes were reluctant to be removed, especially the probe on cylinder #2, which was the one showing the low EGT's on the EIS. But once completed, cranked it up, and low and behold, everything looked great! Both EGT numbers remained within a few degrees of each other, right up to 4200 RPM and 1000 degrees EGT. Is it possible that the probe on the rear cylinder (#2) had some carbon buildup that was interfering with an accurate reading? In any case, the EGT numbers match up nicely again, as they had before.

My father taught me many decades ago, that you could often fix most anything by taking it completely apart, and carefully putting it back together again. I watched him do this many times and have done the same myself. Of course, this was far from a complete disassembly, but removing and re-installing the probes appears to have solved the problem.

Thanks for the many suggestions. Dave, the carb balancing tool is not expensive and it would probably be a great addition to my toolkit. My two hangar mates also have Rotax two strokes and we share our tools, so one of these would cover all of us.

BTW, I decided to have the local lawnmower shop install tubes on my tubeless tires ($13 each) as this seemed like a good investment, based on comments I have read on the forum. Unfortunately, they chipped the paint off the edges of the wheels while removing the old tires. I am going to try and find an automotive touch up paint that best matches my royal blue color, since I have a couple of other spots that also need attention.
 
Two Great Truths of troubleshooting:

1. It's usually something stupid.
2. Electric guages are frequently less reliable than the devices they monitor.

Congrats on the quick fix!
 
Just a little heads-up from my recent experience, even though it`s a little off-topic. Rotax says to only use spark plugs that have a non-removable top tip. I didn`t understand why and the screw-on
BR8-ES was available at the local AutoZone. I deliberately fouled the threads and screwed the aluminum tips on with pliers.

Well after 25 hours of flying,tiny sparks must have been occurring in the tiny gap BETWEEN THE THREADS which acted like EDM and eroded material. Two of my screw-on tips had no threads remaining
and when I pulled the cap up off the plug, the aluminum screw-on stayed captive, up inside the cap.

THIS COULD CAUSE YOUR ENGINE TO QUIT IN FLIGHT IF WIND JUST HAPPENED TO LIFT ALL FOUR CAPS OFF THE PLUGS. I will ALWAYS use solid tips as ROTAX directs.
 
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