Lycoming combustion air actual IAT?

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Jeffd

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Anybody aware of any data indicating actual air temp at entry to the cylinders?
Outside air temp surely is increased due to ram rise?, exhaust / hot oil heating of the intake plenum?
My engine is a stock IO-360-A1A. Not sure if fuel injection into the cylinder head cools the air significantly.
Thinking I may install a temp probe in one of the intake tubes to know for sure. Won’t have a “before/after” as I have already wrapped the intake tubes, and exhaust is presently off for ceramic coating.
Thanks for any thoughts!

Jeff
 

Dan Thomas

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Sep 17, 2008
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Anybody aware of any data indicating actual air temp at entry to the cylinders?
Outside air temp surely is increased due to ram rise?, exhaust / hot oil heating of the intake plenum?
My engine is a stock IO-360-A1A. Not sure if fuel injection into the cylinder head cools the air significantly.
Thinking I may install a temp probe in one of the intake tubes to know for sure. Won’t have a “before/after” as I have already wrapped the intake tubes, and exhaust is presently off for ceramic coating.
Thanks for any thoughts!

Jeff
Ram rise is so small as to be negligible. The Lycoming's sump heats the air somewhat. The fuel injected at the intake port will reduce the temperature enormously. Evaporation absorbs much heat. It's the major factor in carb ice formation.
 

TFF

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Memphis, TN
The race car guys instrument everything. In general, the air is moving fast, so while the air will pick up some engine temperature, there is not a lot of scrub time. Some heat is designed in for carburetors to keep the fuel in suspension. For a Lycoming it’s moving about 150-200 miles an hour through the intake tubes. I have a friend with a carb temp probe, and it is a lot cooler than I thought. Minimizing radiated heat is good, it’s does not have near the effect of cooling the air before it enters the system like a turbo intercooler. It probably is better for life of components over power.
 

Victor Bravo

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Are you looking for temp data to conjure up a temperature/density-based performance upgrade, or just cuirious to know what the temperature is?

If you have port injection, as Dan says you're already removing a bunch of heat from the intake charge by that alone.
 

Jeffd

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Overland Park, Kansas USA
Are you looking for temp data to conjure up a temperature/density-based performance upgrade, or just cuirious to know what the temperature is?

If you have port injection, as Dan says you're already removing a bunch of heat from the intake charge by that alone.
Just looking to see if increase in air temp is significant. Installing a probe in the intake tube would provide some indication, although it would not indicate cooling due to fuel vaporization at the fuel injector location.
 

TFF

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My friend’s carb seems to run about 10F less than ambient. The hard part is getting more density before the fuel is metered. What is squirted out of the injector matches this. Cooling will give no more power after the fact.
 

Map

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I have one data point from measurements I did on a Columbia 400, with a TCM TSIO-550C.
It was during a full throttle climb. At lower altitudes the Intake temperature was around 20 to 25F higher than OAT in the left intake tube and and 33 to 40F higher than OAT on the right side. This engine has twin turbos and two separate intake tubes feeding them.
At high altitude (to FL250) the difference between intake air temperature and OAT increased to 36F left and 54F right.
If you are wondering, the max compressed air temperature (between compressor and intercooler) was in the 300F range, the intercoolers reduced that down to around 110F.
 
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