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-   -   CHT Overheating issue (https://vansairforce.net/community/showthread.php?t=174812)

gmcjetpilot 09-08-2019 07:26 AM

What happened to OP 727TT? Ha ha.

Dan what are you going for, long or short cowl. Is there some significant cooling difference? At this point nothing he can do about changing the cowl (economically) at this point except open cowl outlet.

Looking at the CH temperatures 411F is not terrible. But again retard timing a degree or two (if magnetos) and open main jet mixture (even if plug color is good) will cool the engine. All the other low hanging fruit should be tried.

Where are you 727tt?

ALagonia 09-08-2019 07:52 AM

Quote:

Originally Posted by DanH (Post 1372349)
Do you have a spool-type prop extension, or an extended hub propeller?

I don?t know how to answer this. I would need pictures to identify what I have. I have a Catto three blade prop if that helps.

ALagonia 09-08-2019 07:54 AM

Quote:

Originally Posted by RONSIM (Post 1372347)
14 seems low, to me:confused:

Ron

How do you increase the fuel flow?

N941WR 09-08-2019 08:15 AM

Quote:

Originally Posted by ALagonia (Post 1372356)
I don?t know how to answer this. I would need pictures to identify what I have. I have a Catto three blade prop if that helps.

Does your prop extension look like this one from Saber?


(Click to enlarge)

gmcjetpilot 09-08-2019 08:22 AM

Quote:

Originally Posted by ALagonia (Post 1372357)
How do you increase the fuel flow?

Open up the jet in the carb. Again get the carb part number (dash number will very). Find out if you have a lean version of the carb. You can buy richer main jets for the MS 4-5 carb. It does not matter what the plugs look like. If you are running the lean version of the O360 carb.... This is a well known issue.

Quote:

Originally Posted by ALagonia (Post 1372356)
I don’t know how to answer this. I would need pictures to identify what I have. I have a Catto three blade prop if that helps.

You have a fixed prop. How long is the prop extension. Measure the distance where the prop extension bolts to the engine crankshaft to the where prop bolts to the extension. Not sure why Dan wants this but I suspect the longer cowl has slightly better cooling. However you can as was originally suggested open up more cowl exit air area.... that will cool your engine as well.

I asked before what is your OIL TEMP? If you are running high oil temp as well check to see how many rows your cooler is. You may have insufficient cooler size. Oil keeps the CHT down.

Did you check your Mag timing? 25 degree is the spec... I would make sure it is at 25 deg or less. Again seriously 24-23 degree will help CHT.

ALagonia 09-08-2019 08:23 AM

Quote:

Originally Posted by N941WR (Post 1372359)
Does your prop extension look like this one from Saber?


(Click to enlarge)

I believe it does. Not at the airplane right now To confirm but that is what I believe it looks like.

gmcjetpilot 09-09-2019 12:28 PM

Quote:

Originally Posted by ALagonia (Post 1372364)
I believe it does. Not at the airplane right now To confirm but that is what I believe it looks like.

Measure the prop extension (Saber).between the flywheel (really the ring gear assembly) and back of spinner plate sandwitched between extension and prop.

Long = 2.25"
Short = 1.75"

Why Dan needs this not sure. Good luck and when you get serious about re jet of carb Jet me know. Also check timing (or not up to you).

ALagonia 09-09-2019 12:49 PM

Quote:

Originally Posted by gmcjetpilot (Post 1372362)
Open up the jet in the carb. Again get the carb part number (dash number will very). Find out if you have a lean version of the carb. You can buy richer main jets for the MS 4-5 carb. It does not matter what the plugs look like. If you are running the lean version of the O360 carb.... This is a well known issue.

You have a fixed prop. How long is the prop extension. Measure the distance where the prop extension bolts to the engine crankshaft to the where prop bolts to the extension. Not sure why Dan wants this but I suspect the longer cowl has slightly better cooling. However you can as was originally suggested open up more cowl exit air area.... that will cool your engine as well.

I asked before what is your OIL TEMP? If you are running high oil temp as well check to see how many rows your cooler is. You may have insufficient cooler size. Oil keeps the CHT down.

Did you check your Mag timing? 25 degree is the spec... I would make sure it is at 25 deg or less. Again seriously 24-23 degree will help CHT.

I will check the carb part number
My oil is definitely not running hot.
Not looking to change the plenum/cowl so the distance is irrelevant to my attempts to cool my CHT down.
We did check the mag timing and it is right on spec.
Looks like the carb is the next area to look at.
Thanks for your help

ALagonia 09-09-2019 03:28 PM

Quote:

Originally Posted by gmcjetpilot (Post 1372362)
Open up the jet in the carb. Again get the carb part number (dash number will very). Find out if you have a lean version of the carb. You can buy richer main jets for the MS 4-5 carb. It does not matter what the plugs look like. If you are running the lean version of the O360 carb.... This is a well known issue.

You have a fixed prop. How long is the prop extension. Measure the distance where the prop extension bolts to the engine crankshaft to the where prop bolts to the extension. Not sure why Dan wants this but I suspect the longer cowl has slightly better cooling. However you can as was originally suggested open up more cowl exit air area.... that will cool your engine as well.

I asked before what is your OIL TEMP? If you are running high oil temp as well check to see how many rows your cooler is. You may have insufficient cooler size. Oil keeps the CHT down.

Did you check your Mag timing? 25 degree is the spec... I would make sure it is at 25 deg or less. Again seriously 24-23 degree will help CHT.

The carb had the enrichment kit done to it so it is not the lean version. When discussing the EGT?s it seems fuel is not the cause. So I guess I am left with air. Cowl flap or trim a little off of the bottom cowl? I am told to do this trimming where the exhaust exits the cowl. How much to trim off?

maus92 09-14-2019 06:09 PM

Quote:

Originally Posted by ALagonia (Post 1372641)
The carb had the enrichment kit done to it so it is not the lean version. When discussing the EGT?s it seems fuel is not the cause. So I guess I am left with air. Cowl flap or trim a little off of the bottom cowl? I am told to do this trimming where the exhaust exits the cowl. How much to trim off?

Increasing fuel flow on takeoff will help with CHTs; its effect on EGTs is secondary. Re-jetting the carb to get FF to 18GPH-ish seems to be a standard tool to reduce CHT.


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