JimB Posted February 10, 2020 Report Share Posted February 10, 2020 I am just sitting here analyzing some old flight data and just curious what everyone has for an average difference between cylinders 1 and 3? My CHTs tend to run nice and cool (lower 300s) but I do have about a 45 degree split between 1 and 3. Seems a little excessive? My baffling and seals actually look really good so i'm not certain what I could do about it. EGT is also lower on Cyclinder 1 so I could check my injectors and swap them around. I'm not overly concerned about it but just curious since Savvy says I'm on high side of this particular item. Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted February 10, 2020 Report Share Posted February 10, 2020 My Cht #2 is ~30-40° cooler than the rest. 1 Quote Link to comment Share on other sites More sharing options...
Yetti Posted February 10, 2020 Report Share Posted February 10, 2020 Number 3 runs the hottest. That is why when Mooney did single point monitoring on the hottest cylinder. Quote Link to comment Share on other sites More sharing options...
Guest Posted February 11, 2020 Report Share Posted February 11, 2020 Accuracy of the indicator is first. Do all cylinders share the same type of thermocouple? Clarence Quote Link to comment Share on other sites More sharing options...
JimB Posted February 11, 2020 Author Report Share Posted February 11, 2020 1 hour ago, M20Doc said: Accuracy of the indicator is first. Do all cylinders share the same type of thermocouple? Clarence I have a relatively new JPI 900 and before that I had a single cylinder CHT gauge so i dont really have a reference. The indications have been pretty consistent since the JPI was installed. I'm going with the assumption that its accurate but I guess if it's off 10-20 degrees that would make a big difference. Quote Link to comment Share on other sites More sharing options...
Guest Posted February 11, 2020 Report Share Posted February 11, 2020 1 hour ago, JimB said: I have a relatively new JPI 900 and before that I had a single cylinder CHT gauge so i dont really have a reference. The indications have been pretty consistent since the JPI was installed. I'm going with the assumption that its accurate but I guess if it's off 10-20 degrees that would make a big difference. In the case of the 900 all probes should be the same type, earlier 700’s that retained the OEM CHT probe have different probes and different readings. Check the positioning and fit of the inter cylinder baffle as well as the positioning of the Mooney baffle under the warmer cylinder. Clarence Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted February 11, 2020 Report Share Posted February 11, 2020 10 hours ago, JimB said: I am just sitting here analyzing some old flight data and just curious what everyone has for an average difference between cylinders 1 and 3? My CHTs tend to run nice and cool (lower 300s) but I do have about a 45 degree split between 1 and 3. Seems a little excessive? My baffling and seals actually look really good so i'm not certain what I could do about it. EGT is also lower on Cyclinder 1 so I could check my injectors and swap them around. I'm not overly concerned about it but just curious since Savvy says I'm on high side of this particular item. I have a 68F and it’s similar. Mine might have a bigger spread actually. At one point I had my cht probes swapped to see if that changed it but it didn’t. #1 gets real good airflow, #3 doesn’t. Weird thing for me is that #2 is pretty close to same temp as 3, yet it’s in the front like much cooler 1. The airflow is crazy in there. I have a lasar cowl closure which may or may not make a difference. Quote Link to comment Share on other sites More sharing options...
carusoam Posted February 11, 2020 Report Share Posted February 11, 2020 Jim, You have a great instrument, but... It may depend how and who did the installation... There are only four CHT wells... and with the ship’s gauge you have five thermocouples... Verify where the four JPI thermocouples are sitting... One of the TCs is probably a piggy back device... adding a 25°F error into the calculation... Or it may even be a TC spark plug gasket that adds 50°F of error... Then there are lots of opportunities for variation from cooling challenges... seals, gaps, holes... Often, the ships gauge remains in its specific well... PP thoughts only, not a mechanic. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
JimB Posted February 11, 2020 Author Report Share Posted February 11, 2020 7 hours ago, Ragsf15e said: I have a 68F and it’s similar. Mine might have a bigger spread actually. At one point I had my cht probes swapped to see if that changed it but it didn’t. #1 gets real good airflow, #3 doesn’t. Weird thing for me is that #2 is pretty close to same temp as 3, yet it’s in the front like much cooler 1. The airflow is crazy in there. I have a lasar cowl closure which may or may not make a difference. Thanks. I'm sure your upgraded cowling does make a difference. Mine is all stock. I really like my analyzer but it does make you question every single nuance that for the past 50 years has probably been going on and everything was fine. Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted February 11, 2020 Report Share Posted February 11, 2020 I have a 68F and it’s similar. Mine might have a bigger spread actually. At one point I had my cht probes swapped to see if that changed it but it didn’t. #1 gets real good airflow, #3 doesn’t. Weird thing for me is that #2 is pretty close to same temp as 3, yet it’s in the front like much cooler 1. The airflow is crazy in there. I have a lasar cowl closure which may or may not make a difference. Do you still have the sheet metal piece that partially covers #2? In my case I think if I made it a little larger it would raise my cooler #2 to be closer to the rest. If I thought it was important it would be rather simple to fabricate a new piece. I wonder if that piece changed over time? Edit: actually it’s #1 that has the cover, #2 just has the intake filter. 1 Quote Link to comment Share on other sites More sharing options...
Browncbr1 Posted February 11, 2020 Report Share Posted February 11, 2020 There is an SB that is basically a piece of aluminum that is riveted to the baffle right infront of cylinder #1 to restrict airflow on #1. Being a CB, I simulated this with aluminum tape. I applied 3 or 4 layers of aluminum tape covering the #1 aluminum cooling fins from the baffle to about 3” up. You need several layers, as rain will beat through just one later. Now, my temps have little to no spread in cruise. In climb, #3 is still hottest, but not as big of a spread as before. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted February 11, 2020 Report Share Posted February 11, 2020 3 hours ago, ArtVandelay said: Do you still have the sheet metal piece that partially covers #2? In my case I think if I made it a little larger it would raise my cooler #2 to be closer to the rest. If I thought it was important it would be rather simple to fabricate a new piece. I wonder if that piece changed over time? I didn’t know about either of the mods to #1 or #2, thanks. Is there a reason to want them closer together or is it fine as long as they are all 275-350 ish? Quote Link to comment Share on other sites More sharing options...
JimB Posted February 11, 2020 Author Report Share Posted February 11, 2020 Yes. Thanks. That is very interesting. https://lasar.com/service-bulletin-kits/service-bulletin-kit-182-scoop-kit-engine-cowling-mod-m20-182-000 https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-182.pdf?t=1524853948115 Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted February 11, 2020 Report Share Posted February 11, 2020 I didn’t know about either of the mods to #1 or #2, thanks. Is there a reason to want them closer together or is it fine as long as they are all 275-350 ish? No reason I can think of unless you have OCD. 1 Quote Link to comment Share on other sites More sharing options...
59Moonster Posted February 11, 2020 Report Share Posted February 11, 2020 Physical location of each can also play into it. If they aren't equal distant from the same reference point it could lead to cooler or hotter temps. Quote Link to comment Share on other sites More sharing options...
EricJ Posted February 11, 2020 Report Share Posted February 11, 2020 5 hours ago, Ragsf15e said: I didn’t know about either of the mods to #1 or #2, thanks. Is there a reason to want them closer together or is it fine as long as they are all 275-350 ish? I have the same issue, with #2 cyl about 40F colder than the others. The only cyl that gets lead fouling is #2, probably because it is the coldest. So for that reason I'd like to figure out how to get up with the rest. 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted February 11, 2020 Report Share Posted February 11, 2020 20 minutes ago, EricJ said: I have the same issue, with #2 cyl about 40F colder than the others. The only cyl that gets lead fouling is #2, probably because it is the coldest. So for that reason I'd like to figure out how to get up with the rest. First, Check to see if it is EGT driven... The EGT is typically the source of heating... Airflow is the source of cooling... The two together are the source of CHT... Got some JPI data? A different fuel injector could/might help... PP thoughts only, not a mechanic... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
EricJ Posted February 12, 2020 Report Share Posted February 12, 2020 3 hours ago, carusoam said: First, Check to see if it is EGT driven... The EGT is typically the source of heating... Airflow is the source of cooling... The two together are the source of CHT... Got some JPI data? A different fuel injector could/might help... PP thoughts only, not a mechanic... Best regards, -a- EGT and CHT are both about 40F low, on the JPI. It's pretty consistent. Swapped injectors between the hottest (#3) and coldest (#2) cyls with no effect. I just figured it was a lazy cylinder for whatever reason, but lately have been seeing people using different, field installed, baffling and now more people describing the same issue. 1 Quote Link to comment Share on other sites More sharing options...
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