A cooler #2

[mulro767]

I've been watching my #2 cylinder on my IO-360 using my JPI.  It's shows a differential at cruise of 70 degrees CHT.  The EGT is about 30 degrees cooler.  In climb, with cowl flaps open, all temps are relatively even.  It's just at cruise where I see the differential.  

Today at 5500' and 50 degrees LOP I recorded the following:

1) 1390/368  2) 1373/338  3) 1428/371  4) 1400/366

Look normal to you? I realize #2 is up front and should be cooler, but the lower EGT has me concerned and a normal CHT differential would be 25-45.  70 seems a bit high.

I'm hoping it's something minor like a cowl flap adjustment or a small baffle leak.  

Any ideas?

[Cruiser]

IF you are running LOP then the balance between cylinder fuel flow will make an impact on each cylinder temperature based on how close to peak it is operating. From your numbers #2 peaked first, then 1,4,3 so the CHT on #3 should be the highest since it is closest to peak EGT. Your #2 peaked first and is the leanest (furthest from peak) so it should be the coolest. 

The closer your GAMI spread (the difference between FF among all the cylinders as they peak) the closer your CHTs will be. Any GAMI spread less than .5 gph should be OK and since you are already operating 50°F LOP it would seem you are good.

[mulro767]

Hmmmm???  That makes way too much sense.  I have GAMI's but no fuel flow on the JPI so no GAMI spread.  Thanks for the insight Cruiser!

[KSMooniac]

Quote: Mulro767

I've been watching my #2 cylinder on my IO-360 using my JPI.  It's shows a differential at cruise of 70 degrees CHT.  The EGT is about 30 degrees cooler.  In climb, with cowl flaps open, all temps are relatively even.  It's just at cruise where I see the differential.  

Today at 5500' and 50 degrees LOP I recorded the following:

1) 1390/368  2) 1373/338  3) 1428/371  4) 1400/366

Look normal to you? I realize #2 is up front and should be cooler, but the lower EGT has me concerned and a normal CHT differential would be 25-45.  70 seems a bit high.

I'm hoping it's something minor like a cowl flap adjustment or a small baffle leak.  

Any ideas?

[mulro767]

Yep I wrote them down backwards alright.  30 degrees CHT sounds much better doesn't it?

[jetdriven]

Our #1 runs hotter with a zero GAMI spread.  385 in cruise and the next hottest is 3 and 4 with 360.  #1 is 330.    I trimmed down that air dam baffle in front of the cylinder about 1/4".  I'm trimming it again.