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Different IO-540 Oil Sump Designs...Why?

Vans101

Well Known Member
It seems that Lycoming has (at least) two different oil pan designs for the IO-540.

The first design is a system where the intake tubes are cast into the oil sump so this means that the engine oil is dripping down on to the outside of the cast intake tubes that run through the oil sump.

The second design has two separate cavities for the oil sump and intake system where the oil sump is its own cavity above and the intake cavity is a completely separate cavity below.

Does anyone know why they would have the intake tubes run through the oil sump?

Was one a first generation design and then they changed their thought process or was it a carbureted engine verses a fuel injection engine design??

Do they still make both systems?

What are the advantages/disadvantages to each design?

Anyway just curious if anyone has any intel because it seems like such different thought processes.

Thanks
 
For a long time, carb'ed auto engines would run an exhaust passage through the intake manifold with the purpose of heating the air fuel mixture after the carb. The advantage is that heating helps to better atomize the fuel, with more even air fuel mixing, and provide smoother running engines, especially in cooler weather. The down side is that warmer air contains less O2 for a given volume than cooler air, due to differing densities and therefore slightly less power production for a given displacement.

FI engines can better atomize fuel and this practice generally went away with port-based, FI engines.

200* oil constantly flushing over the intake plenum will add a decent amount of heat to the air fuel mixture.

Larry
 
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So was one design used for carbureted engines and the other design for fuel injection?

For the engines that have the new aftermarket "cold aid induction" how much performance gain is there for the mod?

Is the mod available for both the intake tubes in the oil sump and the intake system below the oil sump designs?
 
So was one design used for carbureted engines and the other design for fuel injection?

For the engines that have the new aftermarket "cold aid induction" how much performance gain is there for the mod?

Is the mod available for both the intake tubes in the oil sump and the intake system below the oil sump designs?

The cold air sumps, I believe, were developed to allow folks to extract a bit more HP, by eliminatng the heating. I suspect that they have a larger plenum area and this is the primary reason for the increase HP. Pure speculation on my part. The std sump has a very small and inefficient plenum relative to the auto world. Unclear if there is still enough warmth to help with carb'ed engines. To be clear, the difference is not night and day, especially with summer temps. You may not even notice the lack of heat with a carb.
 
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