Surefly + Powerflow Pirep, #4 CHT mystery in M20C

[Hank]

1 hour ago, DXB said:

Accurate, except that the Surefly does not advance timing at high MP/rpm combinations, so it was not part of my CHT issue on takeoff. In principle it may contribute to CHTs in cruise up high, but then the extra power dividend from advancing the spark should let you pull throttle back for better cooling while getting similar performance as with fixed timing at higher MP (this seems to fit my experience but I haven't tried to quantify carefully).  

Powerflow produces more takeoff power, right? That will exacerbate poor atomization / mixing in the carb, leading to higher power differential and greater imbalance. Cocking the throttle plate reduces this, as good as we can do without fuel injection. Adding some carb heat will also help, but not on takeoff!

[DXB]

Just now, Hank said:

Powerflow produces more takeoff power, right? That will exacerbate poor atomization / mixing in the carb, leading to higher power differential and greater imbalance. Cocking the throttle plate reduces this, as good as we can do without fuel injection. Adding some carb heat will also help, but not on takeoff!

yes, what I said

[Oscar Avalle]

Interesting discussion. Now, everything starts making more sense. I will try that approach once I get my plane back from the paintshop

[carusoam]

Working the throttle plate could provide enough change to indicate there is some room for improvement...

FF, Timing, fuel jets, engine OH, Paintshop?
 

Wait a minute...

I thought I was in charge of taking threads off course...

Best regards,

-a-

[jamesm]

Thanks for the update.

Curious to know what manifold pressure and rpm's are you seeing on takeoff roll with throttle ~1/2" from from firewall? I have been plagued high cht temps on usually #2 & #4 is most of time hottest 420° ~ 430°. I switched engine monitors about 2 years ago replacing G3 with a CGR30P. For  few years before that I added CGR30C and insight  G3 was my setup.The  cht and egt probes are insight. which I believe the G3 cht probes are "J" type thermocouples. When had the Insight G3 installed I was seeing extremely high cht's on cyl#2 and especially cyl  #4. About 7 months ago I  installed the Surefly electronic ignition left side mag as well. With standard oem '67C exhaust. I have spare left side Mooney engine cowl  and left side louver from a engine cowling from c182/c210. I have been tempted to see the affects on my cly 2&4 cht's. Though I  haven't mounted the louver to spare Mooney engine cowl yet.

James '67C

[spectre6573]

I can share that before my surefly, I had good cht’s of 20-30 degree split front to back cylinders when leaned. My EGT spread was usually 80-130 degrees and I would have to fly at 2500 rpm and max MP when I was cruising above 10000 feet (I live in the southwest and we have rocks). Now that I have 40 hours in the surefly and flying in the lowers teens like before. My #4 cht likes to stay close to 400 degrees while my #3 is a little warmer than before. However, I have found out that I do not need to fly at 2500rpm up high anymore and can now do 2300 rpm and see the same air speeds as I did previously while burning 6.8-7.0 gph and also allows me to lower my CHT’s back to where they were before with a very nice egt spread of 30-40 degrees. before the surefly, I could change my temps pretty good with cocking the throttle plate to get them more even but now it doesn’t matter anymore in cruise. Just some info to share.