Cht??

I have a RV6 with Superior XP 0360 Kit engine with Hartzell con spd prop. I have a VM 1000 eng monitor and 50 hrs on the eng. As the amb temp goes up I see the CHT up to 430 to 450 on take off clime out. I would like to no if this is normal or do I need to look at carb rejeting or other mods?

Thanks
Donnie Mefford
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one thing at a time

First get the carb number, you should have the FAT one. (I recall MA4-5 part number 10-4164-1)

Is your CHT calibrated?

What cylinder'(s)? ALL? Just #3?

What are your oil temps?

Climb out: What airspeed? How long (time altitude) are you climbing? Power setting?

Anything over 400F CHT gets me nervous, but 450F CHT is a no-no to me even though it's not red line. CHT should never go above 435F in my opinion and according to Lycoming for long life.

Good Luck, I am sure you will get good advice. If it is just your #3 cylinder consider a washer spacer on the screw used to hold the baffle onto the cylinder. This increases the gap at the top of the cylinder (where the baffle normally touches or rides on the fins). The # 3 fins are very shallow against the baffle; adding the gap at the top helps more air feed down to the cylinders lower fins. The cylinders head fins are asymmetric. Trust me it works.

I assume the baffle is sealed well, you are not sporting super high compression pistons, advanced timing and flying in 120F ambient day conditions. I also assume you are using "bayonet type" and not spark plug ring CHT probes.

Here is an article from Lycoming: Lyc CHT article

George

Hot

i have to agree with George on this one, except i don't like to see anything over 410 on CHT. If it's all four cylinders chances are the engine is running lean, if it's one i would suspect a baffling issue.

Allen B

Yes absolutly

Allen Barrett said:

i have to agree with George on this one, except i don't like to see anything over 410 on CHT. If it's all four cylinders chances are the engine is running lean, if it's one i would suspect a baffling issue.

Allen B

Click to expand...

I agree I never go above 400 CHT, or at least I try to. If it goes too high I lower the nose. The 435F is a Lycoming number for max climb CHT goodness. They also give 400F as a CHT for long life. I guess some "hot" installations flown in hot temps have no choice but to go above 400F. My old RV-4 I had a hard time keeping it warm enough, and ran in the low / mid 300's? G

Me too

gmcjetpilot said:

I agree I never go above 400 CHT, or at least I try to. If it goes too high I lower the nose. The 435F is a Lycoming number for max climb CHT goodness. They also give 400F as a CHT for long life. I guess some "hot" installations flown in hot temps have no choice but to go above 400F. My old RV-4 I had a hard time keeping it warm enough, and ran in the low / mid 300's? G

Click to expand...

See, you guys, George and I agree of lots of thing!!!

I absolutely agree... Not over 400 degrees.

With 50 hours, I'd expect that oil usage has stabilized and the engine is broken in. Follow the advice given and also search there was an excellent note about using an AS indicator as a way to tell the effectiveness of your baffling. I'd use this as a last resort (just due to the complexities of doing it). First would be check the rich/lean stuff, then the baffles I especially liked the extra washer on #3 baffle and it lowered CHT's by 20 degrees - in another thread on the similar topic). If that doesn't help, check to make sure the baffles are as efficient as they need to be.

I have a RV6A with a O360 A1A Lycoming, 650 hours. I live in Victoria, TX where present temperatures are 85 - 90 F. Climb temperatures to 7500 ft average 435 F. I don't let it go above 450. I lower the nose. At cruise temperatures average 410 F. If I lean 100 F on the rich side the temperature climbs to 420 F. This seems to be on the high side of everybody elses experiense. I don't have a washer as per above advice on #2 cylinder baffle so I will install one.

Gus

Donnie, are all of your cylinders that hot, or just one? Also, what speed are you using for your climb-out?

My experience was that the #1 cylinder was cool and #3 was hot, particularly on climb-out. The temperature spread was significant (50f?) I brought the cylinders into relative balance with a 1" or so air blocker in front of #1. Now there is a 10F or so difference.

Also, a steep, low speed climb-out will really raise temperatures. In fact, some of the higher readings I see are on really cold and dry days where the airplane and engine are performing well, encouraging me to climb out much more steeply than normal. My normal climb speeds are 120 knots or so, and I have no temperature issues at those speeds.

First make sure you gauge is right, then it's time to look at your baffles to see if there is a problem with sealing or gaps. If you don't have a multi point CHT it'd be a good idea to switch the probe to the other cylinders to try to establish baselines for all.

Superior XP-360 is not a Lycoming

I provide this data to improve the information, not to make any argument about what one should do, since I simply don't know. Don't shoot the messenger.

Superior says maximum CHT in cruise is 430 and maximum is 500. This is for the XP-360 Plus, although I think they have the same cylinders as the regular 360, the difference being the roller cam.

h

Just curios, what ignition system are you running. It sounds like you have a serious timing problem.

We have come to appreciate that keeping CHTs under about 380dF has very positive effects on longevity. In the climb, if CHTs get above 350-360, it is a good indication that you could use more fuel flow. Take off EGTs at sea level in the 1275-1300dF range will result in much lower CHTs than most of you are reporting. This may require re-jetting the carburetor or turning up the umetered pressure on injected set-ups.

Walter Atkinson
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