Do I have a CHT problem?

[carrollcw]

Here is a pic from my recent test flight (post injector tuning):



As you can see, my EGT's are very tight and peak together, but I have a pretty large CHT spread (approx 55 deg) between cylinders 1 (coolest) and 2 (hottest). What gets my attention is the fact that the spread exists during all conditions (idle, climb, ROP, LOP). Would this be an indicator of a separate issue besides baffle? If it was a baffle issue, I would think that the temps would be fairly tight on the ground and then diverge once flying, but that isn't the case. Any ideas?

[AltonD]

1. Did you put the washer between cylinder #3 and the rear baffle?
2. Have you cut down the air dam in front of #2?
3. Based on fuel flows, and recent OAT, it would appear the CHTs are a bit elevated. Leaned out and in the summer might be a bit toasty.


Good job on the EGT. They are all peaking at the same tim3, which is more important than value. You seem to have both.

[carrollcw]

Originally Posted by AltonD

1. Did you put the washer between cylinder #3 and the rear baffle?
2. Have you cut down the air dam in front of #2?
3. Based on fuel flows, and recent OAT, it would appear the CHTs are a bit elevated. Leaned out and in the summer might be a bit toasty.


Good job on the EGT. They are all peaking at the same tim3, which is more important than value. You seem to have both.

1 - Yes
2 - Yes
3 - I am actually running fairly rich in order to keep #2 cool enough (I have an O2 sensor installed). That is my concern. I am trying to get #2 cooler, but I think this might not be a baffle issue.

Re the EGT peaking at the same time, that is the result of the fact I have individually tunable injectors. There is a VAF thread about it ("My GAMI spread is Zero"). Amazing technology!

[jabarr]

What is your power setting in the above flight? 16.6 GPH is a LOT of fuel and EGTs of 1100 are extremely low. (yes, I know absolute numbers can be misleading) . What do the spreads look like with a normal cruise setting?

[carrollcw]

Originally Posted by jabarr

What is your power setting in the above flight? 16.6 GPH is a LOT of fuel and EGTs of 1100 are extremely low. (yes, I know absolute numbers can be misleading) . What do the spreads look like with a normal cruise setting?

WOT and the snapshot is at 1500'. I agree, I don't think the EGT's should be so low with the CHT's so high. That fact combined with my O2 sensor info lead me to believe I am running really rich.

EGT's go up to about 1250 when running LOP and hottest CHT at about 360. I never cruise ROP.

[AltonD]

How many hours are on the engine?
How far from the cylinder are the EGT probes located?

I always run ROP. I have ran LOP a time or two. When I did, CHT was much lower than when running ROP.

[LettersFromFlyoverCountry]

I think the first course of action is to swap the probes in 1 and 3 and see what it looks like.

[carrollcw]

Originally Posted by AltonD

How many hours are on the engine?
How far from the cylinder are the EGT probes located?

I always run ROP. I have ran LOP a time or two. When I did, CHT was much lower than when running ROP.

About 120 hours, they are all evenly spaced - I think they were at 2" away.

Due to the tuning of my injectors, I can run anywhere from barelyLOP to 200 deg LOP. At 30 deg LOP, I am close to 380 deg CHT, obviously as I get leaner I get way cooler.

[krw5927]

Any chance your timing is way advanced? This would create high CHTs in general.

[Aggie78]

Originally Posted by LettersFromFlyoverCountry

I think the first course of action is to swap the probes in 1 and 3 and see what it looks like.

Bingo...this is the first thing that came to my mind as well.

First thing is to find out if there may be an indication or sensing problem.