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IO-540 #6 running hot

dahugo

Member
Just got ahold of a great RV-10, very few hours, new everything, glass panel, etc.

Engine has about 250 hours on it. When at cruise and running LOP, our #6 cylinder consistently runs 380 degrees or so, a full 70 degrees more than the coolest (#5). Numbers 1 through 4 are generally within 20 degrees of #5.

Last oil change we swapped injectors from #5 to #6 hoping that would clear up the problem, but it had no effect.

So, is this something common in the IO-540? Is this something a set of GAMI's could fix? Or am I probably looking at a baffling issue?

Any thing anyone could do to point me in the right direction would be helpful.
 
I would swap CHT thermocouples between cylinders 4 and 6 to see if it may be an indication problem before you get too deep into troubleshooting/fixing.
 
As you go rich to lean, in what order do the cylinders' EGT peak?
I'd expect this result if #1-5 were well LOP, while #6 is close to peak.
 
Exhaust leak?

Photo's of the installation would help.

Something is not right, either instrumentation or the install.

Monkeying with injectors is a very bad idea as Dan pointed out above.

GAMIjectors in our -10 made a world of difference, we found you had to supply upper deck pressure from the air box though like the Rocket guys do. So before you go down that path contact me for info.

I will be at GAMI in Ada in just over a week, so if you get some GAMI Lean test results and get in touch I can work through it with you and have John-Paul Townsend look after the rest for you. (Turbo upper deck type)
 
So, is this something common in the IO-540

I only have a sample of 1, however LOP, 2330 RPM, 22.5" MP, 8100' PA, 32* F OAT I have the following CHTs:

1 - 295
2 - 294
3 - 311
4 - 319
5 - 319
6 - 324

Total spread is 30*. I attribute the small rise in #6 to the fact my oil cooler is behind it, and on the day this data was logged the cooler door was open. I do have a plenum.
 
Mark,

Thanks for the data, but I would like to know the airspeed while you were pulling the data.

IMHO, your conclusion that #6 is higher because the oil cooler "robs" (my term) cooling air from Cyl#6 isn't supported until you check the Delta P (top to bottom) across the baffles.

The manufacturer cooling spec's for Lyc and Tele-Cont, are listed in Delta P, measured in inches of H2O across the baffles. If you place your piccolo tube over #6 and still have, say, a net 6" H2O across the baffles, (not running at max power) the problem lies somewhere or somewhat else.

FWIW

mjb
 
My #6 has been consistently 20 degrees hotter than the others. Other 5 have all been within 5 degrees of each other. My oil has been running really cool, in fact its hard to get it to 185. So I blocked off about a 1/3 of the oil cooler with tape last oil change and my oil temp is now right at 200 and my number 6 cylinder head is now only 10 degrees different from the rest. I'm getting em close!

I think I'll try completely blocking off my oil cooler and see if I cant get all cylinders dead on.:) I'll report back after the dead stick.
 
What are the other cylinder temps?

...When at cruise and running LOP, our #6 cylinder consistently runs 380 degrees or so, a full 70 degrees more than the coolest (#5). Numbers 1 through 4 are generally within 20 degrees of #5...

Hugo:

Dumb question - are you seeing 450 degrees F, in cruise, on #5?

Next dumb question - isn't that hotter than advised by Lycoming?

"...8. For maximum service life, maintain the following recommended limits for continuous cruise operation:
a. Engine power setting ? 65% of rated or less.
b. Cylinder head temperatures ? 400˚ F. or below.
c. Oil temperature ? 165˚ F. ? 220˚ F."

Lycoming Tech Tips 2015
 
Mark,

At that speed, you have 19.1" dynamic pressure. Even if you're at 60% pressure recovery, you should have about two times the manufacturers spec'd cooling delta P in the upper cowl.

I haven't seen your supply to the oil cooler, but typically with a SCAT hose, they're so draggy, I would suspect at least 6.0" H2O would be "seen" by #6.

Do you have the (interest) ability to plumb a manometer or equivalent to the top and bottom of your baffles?

mjb
 
Hugo:

Dumb question - are you seeing 450 degrees F, in cruise, on #5?

Next dumb question - isn't that hotter than advised by Lycoming?

"...8. For maximum service life, maintain the following recommended limits for continuous cruise operation:
a. Engine power setting ? 65% of rated or less.
b. Cylinder head temperatures ? 400˚ F. or below.
c. Oil temperature ? 165˚ F. ? 220˚ F."

Lycoming Tech Tips 2015

Read it again. #5 is 70 deg lower than #6.
 
Mark,

At that speed, you have 19.1" dynamic pressure. Even if you're at 60% pressure recovery, you should have about two times the manufacturers spec'd cooling delta P in the upper cowl.

I haven't seen your supply to the oil cooler, but typically with a SCAT hose, they're so draggy, I would suspect at least 6.0" H2O would be "seen" by #6.

Do you have the (interest) ability to plumb a manometer or equivalent to the top and bottom of your baffles?

mjb

Sent you a PM as this is a bit off topic for the OP.
 
Just a comment...

There really isn't any reason to be concerned about the difference in temperatures between individual cylinders. In reality, they are each an individual single cylinder engine. The CHT of a cylinder has no significant effect on the operation of another cylinder.

Our real interest is the temperature of each cylinder in absolute terms. Here the OP is concerned with a single 380F CHT in LOP cruise...an operating state which results in cooler CHT. Indeed, the other cylinders are operating in the low 300 range, which most of us would consider normal for LOP ops. The OP's #6 indicated temperature is, in absolute terms, quite high for this operating state.

Note I emphasized "indicated", because like Mike, I'd check instrumentation first.
 
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