Turbo Boost and FE

[GasSavers_Gollum]

Oh but the arena of engine power and how it relates to thermodynamics is complex!

For the sake of simplistic aregument, I'm going to use made up numbers to illistrate my point.

Say your air intake temp is at 90 degrees, and the exhaust temp is at 900 degrees and you're actually making 50hp. If we lower the intake temp to 70 degree, all other things being equal, we're now making MORE power.

If we raise the compression and the exhaust temp goes up to 950, we've now INCEASED power.

If we reduce the fuel and lean the engine out it's now making LESS power but it's raised the exhaust temp.

All of these change the thermal efficiency of the engine. So you see power and efficiency aren't always related to the temperature different of intake and exhaust.

A turbo is said to make an engine more thermodynamically efficient because it's converting heat to power, making use of the temperatures the engine is already creating. It will raise the exhaust temps considerably, but it raises the power MORE susbstantially, hence the increase in power.

What this is really doing is increasing the VE of the engine. Naturally aspirated engines are lucky to reach 95% from the factory, while naturally aspirated engines are doing something wrong if they can't hit 110% from the factory.

Wasted fuel energy DOES equate to heat in the exhaust, but there's many other factors that equare to heat changes of the engine both on the intake and exhaust. A turbo modifies both, and helps the engine become more efficient under load, hence extra power.

If a turbo trully improved wasted fuel energy THAT much (which is almost strictly about chamber temps, timing, compression, mixture, and quence) then it would see a DRAMATIC fuel efficiency increase... which I've never seen with documentation to prove it. The dramatice thermal dynamic improvements turbos are giving an engine result in an increase in air for the given volume and heat being generated, thus more fuel. If you can get the turbo to increase air volume without creating too much heat you WILL truly see a slight improvement of wasted heat energy, but it's because of the air temp/air volume ratio more than anything else.