ROTAX 582 - High EGT

[Gannet]

I am looking for the technical solution to a problem.

My 582 which recently started showing hotter EGT readings (655° C) on the Skydat panel. Up to now, grinding away at circuits may not have brought about the conditions for overhot EGTs. First step was to raise the carb needles one notch, which dropped the EGT to no more than 600, but fuel burn appears to be over 25 litres an hour!

Rotax maintenance manual advises that high revs with lower throttle settings to be avoided. There is not much to do when flying except to up the revs until the temps reduce.

Has anyone had a similar experience, or any ideas on how to reduce the EGT without requiring an Oil Company sponsorship?

[KFA]

Hi PC. What type of plane are you flying? If it was normal before and it starts changing then something is wrong or is going to go wrong. Did you check things like the carb rubbers and so on that might have a crack in them and lean out the mixture? I would first strart by asking what has changed to bring about the condition before making adjustments to your settings. Let us know of the outcome.

[Gannet]

Thanks for the prompt response. Alas, the aerie is a BB.

As it has been used exclusively for training, all flying has been in the circuit so far. Only recently have we gone cross country and it has then been set up in the cruise. When we do this, both EGTs steadily climb. With a 15 - 25° difference in cylinder temps, 1 starts flashing first at 650°, usually within 5 - 7 minutes of take off. At this point, we increase power to high revs, which quickly brings the temps down.

The rubbers are secure - no leaks evident.

Apart from the season, nothing has changed externally on the engine, the aircraft or it's operation, except that we are now starting to cruise.

Could it be a full blast of winter's colder air almost directly onto the air intakes, making a leaner mixture, which may also account for the temps only rising now, instead of during the warmer summer? Fitting a deflector plate in front of the forward air filter may solve this.

[Mogas]

Further to what KFA says, the only thing that will cause the EGT to rise is a lean mixture. Remember that the fuel air mixture works on the weight of the air and fuel, not the volume.
A few things to consider:
Air
Colder air is denser and thus heavier.
Never allow ram air to affect the intake on that Bing carb.
Fuel
The float level controls the mixture to a large extent, did anyone reset the float levels?
Good luck and let us know what you find.

[Boet]

Your petrol filter is dirty. Replace it.

[KFA]

PC. Send me a pic of your engine setup please. Pic with the top cowl off will do. I think I know what the problem is, especially if you were only plodding arround the circuit before.

info @ saplanes. co. za or give me or Rick a call.
my nr is 082 601 eight nine 7 0
Regards
Stefan

[nickjaxe]

They do vary between summer winter, only true indication is at 75f oat.

Nick.

[georgeh]

I noticed the same thing on my Shadow about 2mths ago, normally on a cruise with Rpm at 4000, the minute i increase the revs it drops. Is this not a symptom of a worn needle and needle jet? I'm used to my EGT at 525 to 550, when i saw it at just under 600 i got worried, but remembered reading about this on the forum before. Gave power and EGT dropped nicely. Now i know to stay away from 4000 rpm or be prepared for it. I certainly dont think this has anything to do with blocked fuel filters or float levels as you would then have high EGT all the time.

[Gannet]

Thanks for all of the input so far, Guys.

I hope to be back at the hangar this week and will post the pics requested. All of the suggestions will be considered, but the one that I am favouring is to eliminate the ram air onto the air filters.

By a process of elimination, we will find the answer!

[Gannet]

I would like to report some positive progress, but alas...

The Rotax maintenance manual notes that incorrect jetting may cause hotspots. I found that the aerie's jets were 158, instead of the required 165 typically required on the coast. A quick flurry of activity and two new 165 jets were duly installed. High volume ground runs and a few prolonged high speed taxis and all good!!

First flight test and EGT's off the scale before 200 feet on the climb out!! Exciting!

I will reset the needle positions again, which certainly solved the problem previously, then accurately check on fuel burn, as this was really high when previously operated in the third notch.

[JohnCWE]

Have you checked and made sure you do not have an air leak on the air intake behind the carb's,maybe one of the oil feed caps has come adrift if you are not using autolube, This causes a very lean mixture at reduced throttle settings.
Have you got the circlips on the needle's below the plastic guide in the carb piston? put the circlip in the very bottom slot to start with, is the rubber 'o'ring on top of the needle?
You egt can be up to a max of 630 deg C or 1200 deg F, but try to run around 50 degrees below that for best power output by adjusting the needle clip position
I also suggest you check the carb float level under load conditions, run the motor at full power for 5-10 seconds or so and shut it down and check your carb float level, must be 12 - 14mm below the top rim of the float bowl when the floats are removed
( start a take-off run withn the brakes engaged.)
don't worry about heating etc, the time is to short and you need to drop the level in the float bowl to the operating level quickly, just shut off the mags with the throttle fully open still. could be that your feul pressure is below the required 3 - 5 lbs and the carbs are starving, is your pulse pump within specs and is the pipe from the crankcase to the pump shorter than 400mm, is the pump installed with trhe bleed hole downwards?
I found the the floats float so that the top of the float is level with the tip of the brass pins that guides them when the setting is correct but it's best to mark it 12mm down and see that it is correct after the full power run-up
Do you have the correct grade of feul?
Have you mixed new feul and replaced the feul in the tank, when pre-mixed feul is left for more than 4 weeks it affects octane rating somehow, hence always mix your feul just before your flight
I hope this solves your issues, I've just been through it also, I could not even climb to circuit height
Sterkte ouboet
J

[Gannet]

John - thanks for the extensive comments and suggestions. The AP had suggested that we go back to bottom setting on the needles again and start from there. No problems when done previously, except for the exotic fuel consumption! I will also do the check of the fuel level in the bowls.

I hope to report some positive news soon!

Thanks Guys.

[Gannet]

Final update on the issue. Needles raised to bottom notch, newly installed flow meter removed - now EGTs do not go above 600, 550 - 575 in the cruise! Fuel consumption in the region of 15 l/hr! Sweet!

Thanks to all who contributed to helping solve the problem.

[Mogas]

Glad you came right and thanks for posting the followup!

[JohnCWE]

You might just check and see if you can run with the needle up 1 notch, your egt's should hover around 600, 550 is a bit low but you also need to watch the temp in normal mid throttle cruise,
Your head and water temps may also be very low now
I've moved mine to the second notch but my needle's have 4 notches, not 3.
I now find I have to descend with either very little power or with power, not sort of 1/4 throttle,
Why did you remove the flow meter?