EGT issue

[924549]

Hi. I have a 582 grayhead in my Kitfox. I pulled the carbs off (Bing 54's) to give them a good cleaning and to change the idler jets. I was not happy with how it idled so I change the idler jets from 55's to 45's. Engine runs great. My EGT before the change ran 1 cyl at 1000 and the other at 1100deg. About 100deg difference. Now it runs at 1200 deg on both and I think that is max's. I have not flown it yet since the change. These readings are from static run up test on the ground. Elevation here is 1960ft.
I would appreciate your feed back and suggetions.

Thanks
Pieter

[Dorsal]

Good article on EGTs in October Sport Aviation, you may want to take a look.

[akflyer]

Drop the clip on the needle one more notch. What is your max static RPM? What is your RPM on take off and climb out?

[jtpitkin06]

You should definitely read the Sport Aviation article on EGT. Then you won’t be so concerned about the EGT number. It is only a reference and not an absolute.

[avidflyer]

His engine is a 2 stroke and EGT is very important on those engines! They are not like a 4 stroke at all when it comes to EGTs. The article in the Sport Aviation was interesting, and makes me think I'm worrying about EGTs on my Jabiru to much, but don't try to apply it to 2 strokes or you will hear that deafening silence in short order. Take care, Jim Chuk

[924549]

Drop the clip on the needle one more notch. What is your max static RPM? What is your RPM on take off and climb out?

I have a inflight ajustable IVO prop. Static and climb out I try to keep at 6200 to 6500rpm.
When you say drop the clip 1 more notch do you mean raise the needle? I would like to try and keep my EGT around 1150. I do not like running at max.

Pieter

[jtpitkin06]

It appears that richening the mixture improved the operation of this particular 582 two stroke engine. This would imply the engine was operating far lean of peak. So far lean of peak that it was running rough. The initial enrichment raised the EGT, but you don’t know if you are still on the lean of peak side or on the rich of peak side. All you know is the EGT is higher and the engine runs better.



Let’s say you were 150 degrees lean of peak before adjustments. So you enriched the mixture. Now you might be 50 degrees RICH of peak which would be fine. If you only look at the EGT it looks to be 100 degrees hotter leading the operator to think the engine is under more stress. In truth, the engine might be operating just fine. It could have lower CHTs and less stress.



On the other hand you might now be at 50 degrees below LEAN of peak. Better than 150, but still on the lean side and not where I’d like to be with a two stroke. This is why EGT is only relative reading and not an absolute. Two very different conditions give exactly the same reading; while a dangerous condition before the adjustment gives a seemingly safe reading.


Hotter EGT is not always a bad thing… even on a two stroke.


You might try another test ground run with a richer still needle to see if the EGT drops while observing the CHT.

JP

[HuDuGuru]

I haven’t read the Sport Aviation article on EGTs, but if it has anything to do with the long running debate concerning lean of peak EGTs and Lycoming, then most of the information should be completely disregarded as it pertains to this post. A 2 stroke should never be operated lean of peak (at least not if you want the propeller to keep turning). A part of the reason two strokes have a reputation for being unreliable is because people treat them like 4 strokes.

Rotax factory jetting tends to be on the conservative side (rich). If the engine was actually running lean of peak with stock jetting in the carburetor, then it’s a sign of other issues, either broken carb boot, leaky crank seal, weak springs between the Y pipe and expansion pipe… etc.

There is nothing wrong with leaning out the idle jet by going to a #45 from a #55, but if you’re concerned with the EGT, switching to a #50 would be the obvious solution. Many 582 owners do this as it smoothes out the idle and makes starting easier. I used a #50 in mine from day one.

I wouldn’t change the needle position until you find the idler jet that works best for you. Some 582s experience high EGTs between 5600 and 5800 rpm, if this is the case switch to a 274 or 276 needle.

Since you have an in-flight adjustable prop try to use the maximum rpm range. Max rpm for a blue head 582 is 6800 rpm, I’m not sure if the grey head was the same. Propeller loading plays a large part in your EGT readings. Reving to maximum rpm (or at least close to max) should help keep the EGTs down by reducing load and increasing fuel flow. The metering system in the Bing carbs works much better when the engine is operated across the full rpm spectrum.

[avidflyer]

HuDuGuru, I was in agreement with everything you said until the end. Reducing the prop load will not lower EGTs, it will cause them to go up on a 2 stroke. At least that has been my experience and what every expert I've read said. I've owned and flown behind 7 different 2 strokes. Add 5 more to that number of other people's planes with 2 strokes that I've flown. The only time I've had an off field landing was when a fuel filter plugged and the engine started spitting and would only hold about 4500 RPM. I was able to set down in a neighbor's hay field with no damage done. One other thing that should be mentioned in this whole discussion though is the accuracy of the EGT gauge. One should always compare the color of the spark plugs to the EGT reading you are seeing. White or light gray is to lean, black is to rich. Chocolat brown is nice. Being a bit to rich will carbon up the engine over time, way rich will run lousy. Being to lean will cook the engine in short order. Take care, Jim Chuk

[akflyer]

I set my prop for 6200 on take off. This is about the peak HP and TQ for the 582. I will keep bumping in the pitch as I level out for a max straight and level RPM of about 6500. If the EGTs are going too high in cruise, then bump in MORE pitch and it will drop the temps.

DO NOT run a 2 stroke Lean of Peak or you WILL burn it down. I have a buddy that refuses to proper plug readings when tuning his race sleds. He just leans it out on the main till it burns down, then he fattens it up one jet size and rebuilds.. NOT what you want to do on the plane!! The final word on the EGTs will be your plugs. Your looking for a nice golden brown. Black and you too rich, white and your too lean.

I read the article in sport aviation and as they stated, there are errors in every installation. This is why you need to mark YOUR gauge where you get the nice plug color at and then try to keep the EGTs around that range.

I have the IVO inflight adjustable and inflight mixture adjustment. Basically, one turn of the knob on the dash is equivalent of raising or lowering the needle one notch. The mid range needle will effect the EGTs from 2500 RPM to over 6000 RPM.