Well this couldn't have been good for my engine.

[ragedracer1977]

Question for you guys.  Is there any way this issue could have cause my engine to run hotter???

i took it up for a flight today, first since installing the new boot.  CHTs were 25-35 degrees cooler than they’ve ever been.  I normally monitor #4 as that’s my hottest.  I flew on Saturday and #4 was running at 400-405 in a 100mph climb and was typically 375-380 in cruise.  Today with similar weather (little warmer actually) #4 was at 375-380 at 100 mph climb and 350 in cruise.  

All cylinders showed similar reduction in temperature.  I’m trying to figure out why. Nothing else changed.  Could it have been due to ingesting HOT air being right by the muffler? Maybe pressurizing the cowl in ways it wasn’t supposed to be? Maybe both?

Thoughts?

[Andy95W]

This doesn't really surprise me, actually.  The reason that air flows through the cylinder fins is actually the pressure differential between the top of the cylinders with air pressure coming in the front vs. the low pressure area underneath the cylinders caused by air being pulled out the cowl flaps.

Your leaking boot put high pressure air below the cylinders, which lowered the pressure differential.

[MIm20c]

30 minutes ago, ragedracer1977 said:

Question for you guys.  Is there any way this issue could have cause my engine to run hotter???

i took it up for a flight today, first since installing the new boot.  CHTs were 25-35 degrees cooler than they’ve ever been.  I normally monitor #4 as that’s my hottest.  I flew on Saturday and #4 was running at 400-405 in a 100mph climb and was typically 375-380 in cruise.  Today with similar weather (little warmer actually) #4 was at 375-380 at 100 mph climb and 350 in cruise.  

All cylinders showed similar reduction in temperature.  I’m trying to figure out why. Nothing else changed.  Could it have been due to ingesting HOT air being right by the muffler? Maybe pressurizing the cowl in ways it wasn’t supposed to be? Maybe both?

Thoughts?

100mph is really slow for climbing and low cht’s

I do think the air filter provides restriction so a hole that would allow slightly pressurized but warmer air might be too lean with the fixed jet size on climbout.  

[ragedracer1977]

6 minutes ago, MIm20c said:

100mph is really slow for climbing and low cht’s

I do think the air filter provides restriction so a hole that would allow slightly pressurized but warmer air might be too lean with the fixed jet size on climbout.  

I usually climb at 115, this was just a point of reference.  

[carusoam]

Brice,

Good catch, and great pics!

Not sure which way the air would flow....

• most likely air outside the rubber boot would be drawn in towards the vac generating engine.  
• Not much air being drawn in through the filter.
• high pressure air in front of the filter will still want to come in.
• probably getting a combination of clean and dirty air entering the engine.

Thanks for sharing.  Probably a good idea to send a copy of the pics to the mechanic for their benefit.

And thanks, Doc.  For sharing the mechanic’s side of the scene.  Everybody wants to learn from an experience like this.... another step in the endless trek of continuous improvement.

Best regards,

-a-