IO-550 richer and hotter #5 cylinder

[rogerl]

who owns it

Edited March 15, 2021 by rogerl

[omega708]

I'm no expert, but I certainly wouldn't expect a higher CHT on a cylinder that is running a richer mix.  A leaner mix would cause higher CHT, until you're on the lean-of-peak side of the equation. The fact that it's taking more leaning to get the 50 degree drop on #5, I would question the temperature sensor on number 5.  How hard would it be to move that sensor to another cylinder and see if the problem moves with the sensor?  

[Cruiser]

As for the higher CHT you can search the forum for discussion about cooling. If your baffles are original I would say 50°F higher than the rest is exceptionally good. Most run much hotter than that.

 

I don't think your LOP issue and the CHT issue are related completely. The IO-550G has tuned induction and is a very good LOP engine. Normally, it will peak within .2 gph on all cylinders although my #5 CHT is also the last to peak.

 

If you are using the JPI to discover peak and LOP, your technique may influence how the JPI responds. Most common fault is leaning too fast. You will not get accurate data.

[carusoam]

A couple of things to consider...

1) Your #5 cylinder is behind the generator? That blocks the air flow... We are discussing CHT issues right?

2) You are not alone as many Eagle and Ovations have the same challenge...

3) There is a union of international hanger elves that may have created a solution...

4) At least one of the little Pixies took a picture of the solution and posted it...

5) A search for the key words 'Pixie hole' may find a photo or two...

6) That's all I know about that...

The topic surfaces every now and then...

http://mooneyspace.com/topic/3680-high-cht-on-5/page-2?hl=+pixie%20+hole

I am only a PP, I don't know any pixies or anything about the hokey union mentioned above...

See if that is the situation you have,

-a-

[carusoam]

Roger,

The EGT peaking is ussually a separate issue from the CHTs...

If the EGT of one cylinder is out of the grouping of the others, it could be an injector that needs cleaning.

Many IO550s have tight EGT spreads without going to the extent of getting GAMIs.

It may make sense to check the GAMI spread first.

If they are off, consider cleaning, flow testing or balancing the fuel injectors...

Then back to CHTs...

Let us know if you need guidance to the GAMI spread procedure.

Best regards,

-a-

[Jeff_S]

My #5 is also the last to lean, but well within tolerances of LOP operations. And it is not the hottest cylnder, even though no pixies have visited my hangar (that I'm aware of!).

[kmyfm20s]

My #3 cylinder is the hottest in climb and #5 is the hottest in cruise but only about 20 degrees hotter than the rest. I will probably see if the Pixie's will go to work just to get things closer.  My #1 EGT is first to peak and #6 is the last and is very good running LOP.  My #1 CHT and EGT are a lot lower than the rest especially when running LOP, does anyone else notice this on there planes? I see one the thread about the Pixie hole that it is the lowest as well.  I find the baffling is very efffective in keeping the cylinders in my Eagle. The other day I was doing some full power runs with in the red box and my CHT would not go over 335 degrees.

[kmyfm20s]

Rogerl, have you check your engine log book to see if past owners played with the injectors? They might have richened up your #5 in attempt to have it run cooler but at the expense of LOP operation.

[duke]

I don't personaly know any pixies, but my hangar elf must because one pixie hole showed up on #5. Made a big difference. now runs close to the rest.