VetRepp Posted August 22, 2022 Report Posted August 22, 2022 I'm curious what others see and what is normal or acceptable. I routinely see @ 80-90 temp difference in my EGT (#4 highest and #1 lowest); and 40-42 temp difference in CHT (#5 highest and #1 lowest). I have a IO550 G-PL (i.e. 310 conversion), and typically run ROP (Leaning with G1000 - cyl #6 peaks first, although I rarely use it to lean anymore because it invariably results in a FF of @ 16.8 to run 100 ROP) - 2400 rpm, 23.6 MP , no pixie hole . Just curious, Thanks for input Roger Quote
carusoam Posted August 23, 2022 Report Posted August 23, 2022 CHTs within 50°F are pretty good… If you post graphs from your JPI…. You can see if anything is strange going on…. If all six cylinders are behaving the same… or one stands above or below the others…. CHT #5 usually stands out… best with the pixie hole, but not perfect… Comparing raw EGTs is a bit tougher… they are very sensitive to distance down the tube variations…. Most valuable data… Gami spread… If you have odd CHT spreads… they are an indication of some worn baffling seals…. There is some good easy reading that can be found at the Savvy website… Best regards, -a- Quote
DonMuncy Posted August 23, 2022 Report Posted August 23, 2022 My most frequent reason for a CHT spread is faulty probes. 1 Quote
PT20J Posted August 23, 2022 Report Posted August 23, 2022 Type of CHT probe is also important especially if you have a non-primary engine monitor and have to keep the factory probe in place. In my case, the sparkplug gasket probe read about 40F higher than the factory probe, and when I replaced it with a gasket probe under the factory probe it read about 20F lower than the factory probe. I recall a Lycoming document (but I don't remember which one) that said that a CHT spread greater than 50F indicates poor baffling. Skip Quote
Pinecone Posted August 23, 2022 Report Posted August 23, 2022 I am trying to determine the CHT on my #6 (252). On the JPI 700 it reads 40 degrees higher than the other cylinders much of the time. But sometimes it is close to the same as #5. Quote
StevenL757 Posted August 24, 2022 Report Posted August 24, 2022 (edited) On 8/22/2022 at 5:26 PM, VetRepp said: I'm curious what others see and what is normal or acceptable. I routinely see @ 80-90 temp difference in my EGT (#4 highest and #1 lowest); and 40-42 temp difference in CHT (#5 highest and #1 lowest). I have a IO550 G-PL (i.e. 310 conversion), and typically run ROP (Leaning with G1000 - cyl #6 peaks first, although I rarely use it to lean anymore because it invariably results in a FF of @ 16.8 to run 100 ROP) - 2400 rpm, 23.6 MP , no pixie hole . Just curious, Thanks for input Roger A few observations and suggestions… Except for takeoff and up to 1000’ AGL, and landing, your cruise RPM with the 310HP conversion should be 2550RPM, not 2400. There is no appreciable performance or benefit to your engine’s life by reducing to anything other than 2550. I don’t buy some folks’ argument of “2400 reduces cabin noise” to properly justify the RPM adjustment downward. It changes the tone of the engine, but rarely - if ever - have I observed a reduction in actual cabin noise. If you have to get a decibel meter to determine the difference, you either need another hobby, or a better headset. 2550RPM is the optimal setting that has been flight tested and proven over time to deliver the most-optimal engine performance. Without getting into a LOP/ROP discussion, consider switching to LOP ops ASAP. Although that engine is designed to run both ways, I’ve seen more issues caused by ROP ops…particularly cylinder replacements. This isn’t an argument either about fuel burn or a few more knots. You have a tuned induction engine that is designed to run LOP, so take advantage of that ability. 80-90 degrees’ spread on the EGTs are a bit much, but not entirely unreasonable. Your CHTs should be pretty even in cruise. Lower altitudes in the Ovation (generally under about 7,000) tend to produce more inconsistent CHTs than up higher. I would inspect your baffle seals’ condition and determine whether excessive air is getting out of the upper deck. Chances are you still have the original baffle seals. Properly-installed seals keep the airflow around the upper deck more even. Generally, between about 7,000 and 15,000, the CHTs are a bit more even, although #5 will usually be hotter by about 20 degrees over its cousins. A pixie hole - as you pointed out - would help bring #5 down a few degrees. Hope this helps. Edited August 25, 2022 by StevenL757 Reorganized content 1 Quote
Pinecone Posted August 24, 2022 Report Posted August 24, 2022 10 hours ago, StevenL757 said: A few observations and suggestions… 80-90 degrees’ spread on the EGTs are a bit much, but not entirely unreasonable. I would inspect your baffle seals’ condition and determine whether excessive air is getting out of the upper deck. Chances are you still have the original baffle seals. Properly-installed seals keep the airflow around the upper deck more even. Hope this helps. What do baffle seals have to do with EGT????? CHT yes, EGT, how? Quote
mooneyflyfast Posted August 24, 2022 Report Posted August 24, 2022 EGT spread is irrelevant. Ignore CHT spread as long as all are acceptably cool. Quote
StevenL757 Posted August 25, 2022 Report Posted August 25, 2022 13 hours ago, Pinecone said: What do baffle seals have to do with EGT????? CHT yes, EGT, how? 10 hours ago, mooneyflyfast said: EGT spread is irrelevant. Ignore CHT spread as long as all are acceptably cool. Yes, I'm aware. I re-organized my remark to make it read more accurately...thanks for pointing that out. 1 Quote
carusoam Posted August 25, 2022 Report Posted August 25, 2022 Proof…. It happens to the best of them… Best regards, -a- Quote
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