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High EGT's and CHT's

C

Carsten

I'm New Here
I'm experiencing high CHT's and EGT's during climb-out, which I have not noticed before. Two days ago I did a test-flight to record engine data on my GRT Horizon HS, and was able to open the files and read it last night. I am looking for suggestions as to the cause of the high temps.

Here's the test-flight data, all at mixture full/in, OAT 34F.
After takeoff, at 1,000' ASL just before pulling back on throttle and RPM, I have CHT's (F) (#1,2,3,4) 451, 413, 453, 423, and EGT's 1490, 1572, 1486, and 1479.
FF was max 15.9 gph, with an average of around 14.5 during the climb.

At 1,000', at 24 squared, temps settled in at 423, 407, 422, 387, and EGT's 1407, 1445, 1397, 1403
with FF 8.1

At 1,000', at 20 squared, temps settled in at 369, 376, 178*, 338, and EGT's 1338, 1372, 1317, 1306,
with FF 6.8

Some other data:
RV-7a, approx 750 TT eng and airframe.
O-360-A1A, c.s prop.
Carburetor was originally Marvel Schebler MA4-5 10-4164-1, which was replaced approx 300 hrs ago with a 10-3878, with no discernable difference in temps.
Mag timing has been checked, both withing +/- 1 degree.
Mixture cable has been checked, its correct, with carb's micture level against it's stop when mixture control full forward.
I've checked for induction leaks, around induction tubes and carb/sump gasket, but haven't found any.

Any suggestions on what the root cause might be? What to do next, how to fix it?

Thanks!
 
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Not too many things that will result in 450* CHTs in a plane that normally is below 400. You should post what is normally seen in those configurations.. Most likely culprit for sudden onset CHTs in this rang is too much ignition advance. Cerainly other causes, but this would be at the top of my list.

The oddity here is the EGT. excessive advance should drop them. That said, the result of too much advance is often detonation and THAT will raise EGTs.
 
sansoneservices said:
Inspect your baffle seals. They DO wear out and are often overlooked. It's helpful to use a borescope when the cowling is in place. Look for positive contact between the cowling and seals
Click to expand...
Yeah, I view them every time the cowling comes off. They have no tears or cracks. There are slight baffle rub marks on the inside of the cowling all around, so they seal well.
 
Carsten said:
I'm experiencing high CHT's and EGT's during climb-out, which I have not noticed before. Two days ago I did a test-flight to record engine data on my GRT Horizon HS, and was able to open the files and read it last night. I am looking for suggestions as to the cause of the high temps.

Here's the test-flight data, all at mixture full/in, OAT 34F.
After takeoff, at 1,000' ASL just before pulling back on throttle and RPM, I have CHT's (F) (#1,2,3,4) 451, 413, 453, 423, and EGT's 1490, 1572, 1486, and 1479.
FF was max 15.9 gph, with an average of around 14.5 during the climb.

At 1,000', at 24 squared, temps settled in at 423, 407, 422, 387, and EGT's 1407, 1445, 1397, 1403
with FF 8.1

At 1,000', at 20 squared, temps settled in at 369, 376, 178*, 338, and EGT's 1338, 1372, 1317, 1306,
with FF 6.8

Some other data:
RV-7a, approx 750 TT eng and airframe.
O-360-A1A, c.s prop.
Carburetor was originally Marvel Schebler MA4-5 10-4164-1, which was replaced approx 300 hrs ago with a 10-3878, with no discernable difference in temps.
Mag timing has been checked, both withing +/- 1 degree.


Mixture cable has been checked, its correct, with carb's micture level against it's stop when mixture control full forward.
I've checked for induction leaks, around induction tubes and carb/sump gasket, but haven't found any.

Any suggestions on what the root cause might be? What to do next, how to fix it?

Thanks!
Click to expand...

We have some instrumentation issues. CHT #2 changed only 6deg from climb to cruse, the other cylinders 40+
#3 obviously isn’t working right.

CHT’s that are over 400 degrees above ambient is beyond my experience. What do they read before you start it compared to ambient?

The fuel flow for 2400RPM 24”MP seems impossibly low.
The fuel flow for 2000RPM 20”MP is rich.
 
Mikeyb said:
We have some instrumentation issues. CHT #2 changed only 6deg from climb to cruse, the other cylinders 40+
#3 obviously isn’t working right.

CHT’s that are over 400 degrees above ambient is beyond my experience. What do they read before you start it compared to ambient?

The fuel flow for 2400RPM 24”MP seems impossibly low.
The fuel flow for 2000RPM 20”MP is rich.
Click to expand...
The ambient is 44, the CHT and EGT probes all show 33 and 34.

Good info on the FFlow, thanks.
 
Planecrazy232 said:
You're way lean. I've got a O360 CS 6A and see 18+ GPH on climb.
Click to expand...
16 GPH is not WAY lean for a 360. My 540 drinks 24-25 at full power with CHTs well below 400. A 360 is just 2/3 of a 540.

Straight from the O-360 operators manual:

part throttle consumption: "fuel flow @ 2700 RPM = 16.3 GPH."

from the performance table: "29"@ 2700 = 16.7 GPH"

from the minimum allowable fuel flow chart: 14.8 GPH @ 100% power"

Being 4% lower than factory flow and above the min flow rates DOES NOT cause 450* CHTs on an otherwise normal engine.
 
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Not sure why your temps would change like that after 300 hrs, but my experience with the 3878 carb was that it was very lean at WOT, unless it has the Mooney mod. If the carb has an M stamped after the number it has the mod which makes it equivalent to the 4164-1. It made big difference to mine when I did the mod. Fuel flow went from 44 L/hr to 62 L/hr (11.6 g/hr to 16.4 g/hr). It does look like #3 probe has an issue. Check the crimps and connections.
 
Carsten said:
The ambient is 44, the CHT and EGT probes all show 33 and 34.

Good info on the FFlow, thanks.
Click to expand...

Although I’m rarely right about this, given the uncertainty of some of the measurements it’s worthwhile to put one CHT thermocouple in a cup of boiling water verifying it is at or below 212F. There is a possibility that the instrumentation is configured for the wrong thermocouple curve J vs K.

To verify the mixture setting fly it again at 24/24 and sweep the mixture slowly from full rich through peak EGT and record that data
 
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The only engine condition you know the air-fuel ratio is at peak EGT. Just pick a condition of altitude, rpm, and MAP and tweak the fuel flow .1 mph at a time and allow the engine to stabilize while either recording the data, or get it from a data card and plot. This will definitively tell where your engine is operating. This is required for solid progress in an organized manner.

Once you have defined the mixture condition, now you can use the data to draw conclusions of the cooling air flow (baffles), ignition timing and if the F/A ratio range allowed by the carb is reasonable. Addition of airspeed is handy for the cooling air flow, so record that as part of your sweep.

If you want to know the max torque (best power) point, fix MAP, RPM, and adjust the MIX until you get max airspeed. Record this and compare to your sweep.

With this data, post here and the group can refine the understanding to the high CHT's.

IMO, Until the data is known then next steps to final cause(s) are guesses and you will be chasing your tail for a solution. It seems like a cooling air flow (baffles etc) issue, but that is one of the guesses. Let's eliminate the carb, timing, and mixture issues first.
 
BillL said:
The only engine condition you know the air-fuel ratio is at peak EGT. Just pick a condition of altitude, rpm, and MAP and tweak the fuel flow .1 mph at a time and allow the engine to stabilize while either recording the data, or get it from a data card and plot. This will definitively tell where your engine is operating. This is required for solid progress in an organized manner.

Once you have defined the mixture condition, now you can use the data to draw conclusions of the cooling air flow (baffles), ignition timing and if the F/A ratio range allowed by the carb is reasonable. Addition of airspeed is handy for the cooling air flow, so record that as part of your sweep.

If you want to know the max torque (best power) point, fix MAP, RPM, and adjust the MIX until you get max airspeed. Record this and compare to your sweep.

With this data, post here and the group can refine the understanding to the high CHT's.

IMO, Until the data is known then next steps to final cause(s) are guesses and you will be chasing your tail for a solution. It seems like a cooling air flow (baffles etc) issue, but that is one of the guesses. Let's eliminate the carb, timing, and mixture issues first.
Click to expand...
You should be seeing 17.5-18.5 at full power, 2700 rpm for you 180hp ---that should keep temps where they should be, everything else being solid.

Ron
 
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