Managing Cylinder Head Temperatures

[Tjtolton]

[pjsny78]

#1, and #3 run the hottest on my plane. in cruise it settles around 335 or so. the only way i get temps like you are describing is if i would close the cowl flaps and i am climbing, however i was always told anything under 400 is ok.

 

[Cruiser]

Locate the CHT probes and determine how the CHT is being collected. My guess is your #3 cylinder probe is different than the other three cylinders. The OEM panel CHT gage is on #3 cylinder in the J model and therefore you may be getting slightly different readings on that cylinder compared to the others due to the type or placement of the probe. Since CHT is listed in your LIMITATIONS section of the POH it is a primary piece of equipment and required for flight operations. It cannot be disconnected or removed.

 

Check your baffles. They are extremely important in providing uniform cooling. Small gaps can cause significate variations in cooling.

With modern engine monitors use it has become the common standard to use 380°F as the limit for normal operations and anything above 400°F should be a warning signal to do something different i.e. bring tempuratures down.

[PTK]

Check and make certain your baffles are in order. They most likely are and the "discrepancy" on #3 is most likely probe related as Cruiser said. What monitor do you have? It was my impression that the monitor gets its info from its own set of probes separate from the OEM CHT gauge on #3. On my EDM800 they are all within the ball park. I don't have an outlier like your plot shows.

I have it alarm at 390! I know this is ultra conservative but I like to be. On occasion it will alarm during an aggressive climb and readily responds to an air speed increase. I trail the cowl flaps in climb.

[flyby201]

You have a "J" and it appears from your graph that you have an engine analyzer.  Have you tried running Lean of Peak?  Running LOP will lower your CHT's considerably and cut your fuel burn.  When I was running ROP my CHT's were running well over 400 deg (esp cycl #1).  I'd have to fly with clow flaps open and slow down to keep them below 400.  Switching to LOP ops, all CHT's will run below 360 deg maybe more like 340's depending on % power, OAT, etc.  Speed loss is only about 5 knts or less.  At least that's my experience, YMMV.

[PTK]

Steven, I don't think you should be required to cruise slow with open cowl flaps just to keep CHT's in check! ROP or not! Am I understanding you correctly? 

[Piloto]

Quote: flyby201

You have a "J" and it appears from your graph that you have an engine analyzer.

[Piloto]

[ToddDPT]

We have a J and #3 always ran away from us having to open the cowl flas in cruise, etc. We had the baffles checked and made minor adjustments to them. This helped some and kept the temps from climbing too quickly, but we still had trouble with #3 getting away from us.  Since it wasn't fixed we took it to Lycon and they ended up concluding that our #3 was running much leaner than the others. Since we have enrichened #3 (and it took 4 sequences each getting better each time) we don't have a problem anymore staying below 360. 

[Piloto]

Quote: flyby201

You have a "J" and it appears from your graph that you have an engine analyzer. Have you tried running Lean of Peak? Running LOP will lower your CHT's considerably and cut your fuel burn. When I was running ROP my CHT's were running well over 400 deg (esp cycl #1). I'd have to fly with clow flaps open and slow down to keep them below 400. Switching to LOP ops, all CHT's will run below 360 deg maybe more like 340's depending on % power, OAT, etc. Speed loss is only about 5 knts or less. At least that's my experience, YMMV.

[jetdriven]

Quote: ToddDPT

We have a J and #3 always ran away from us having to open the cowl flas in cruise, etc. We had the baffles checked and made minor adjustments to them. This helped some and kept the temps from climbing too quickly, but we still had trouble with #3 getting away from us.  Since it wasn't fixed we took it to Lycon and they ended up concluding that our #3 was running much leaner than the others. Since we have enrichened #3 (and it took 4 sequences each getting better each time) we don't have a problem anymore staying below 360. 

[Tjtolton]

Thank you one and for sharing your experiences. I have run in the past a gami prescribed test to determine the spread in fuel flow over which all the cylinders reach peak. It was a spread of about 0.7 gph. Three of the four cylinders reached peak at the same fuel flow. The hot running No. 3 was part of the population of three with the same fuel flow.  Only the pilot side fore cylinder ran richer than others peaking last. I have not had a chance to look at each particular CHT probe connected to our EDM-700. We have made a first attempt at sealing any air leaks around the interface with the upper cowling then confirmed  that light could not be seen when looking through the oil filler access door.   This attempt for a better seal was done before our latest data set that I attached was collected.

[ToddDPT]

Jetdriven,

I wish I had more info, but honestly my diagnostic abilities and understanding of the mechanics side of things is, at best, marginal.  It's something I want to learn more about, but whatever Lycon suggested and did fixed our problem.  And how I understood the solution was posted in my previous post.

[smccray]

Quote: Cruiser

Locate the CHT probes and determine how the CHT is being collected. My guess is your #3 cylinder probe is different than the other three cylinders. The OEM panel CHT gage is on #3 cylinder in the J model and therefore you may be getting slightly different readings on that cylinder compared to the others due to the type or placement of the probe. Since CHT is listed in your LIMITATIONS section of the POH it is a primary piece of equipment and required for flight operations. It cannot be disconnected or removed.

[Cruiser]

Quote: ToddDPT

Jetdriven,

I wish I had more info, but honestly my diagnostic abilities and understanding of the mechanics side of things is, at best, marginal.  It's something I want to learn more about, but whatever Lycon suggested and did fixed our problem.  And how I understood the solution was posted in my previous post.

[jetdriven]

Quote: smccray

My engine monitor is being installed soon- I'm looking at the probes tonight. The #3 probe on the JPI is different than the other 3 CHT probes.  Due to the limitations, I'm sure no one here would recommend flying with probes 1 and 3 swapped just to rule out a probe specific problem since that wouldn't be legal. 

How old are your baffles?

[flyboy0681]

Number 3 on my '83 J was consistently running over 400 degrees per the EDM 700, and because of that I always flew with the cowl flap open and fairly rich. It was looked at during the recent annual and determined that the probe was bad. $120 later the new probe shows the temp to be in-line with the remaining three cylinders. Now I can fly fast again without worrying.

[preinke]

My #4 is always hotter than the others in a 77J. My oil temp is always hotter than I would like also. I have pursued this from the time I bought the plane - new baffle seals, overhaul cooler , check vernatherm, overhaul cylinders,etc . Tom Rouch (Top Gun) said there were longer cowl rods (mines at max adjustment length) . Has anyone changed out their cowl rods ? If so part nos ? Below is a link to a novel way to measure the differential pressure to obtain a relative measure of cowling performance. It's been on my todo list .

http://www.littleflyers.com/engserv/enginecooling/coolpressure.htm 

Paul