Gas mileage and headers

[John_Calabrese at ENGELHARD.COM]

<<
Does anybody know why oxygenated gas doesn't give you more hp???!
Horsepower is a (rough) linear function of air(oxygen) through the engine.
Its why we do sooooooooooo much better on alky.
>>

It has to do with the BTU content of the fuel.  We don't do sooooo much
better on alky, without sacificing mpg.  The btu content of alky is around
30000 kJ/kg, while gas is 47500.  We also do better on alky because it
burns colder, and you can run higher compression, and almost need to run
higher compression to get the burn rates high enough for optimum
efficiency.  plus, the VE is increased with alchohol due to the high
evaporative cooling, which cools the intake charge for more power as well.
It really isn't a fair comparison

As far as the mpg going down after header install, it could be the oxy
fuel, or it just could be the fact that you torque curve has been shifted.
Depending on the design of the header, you can lose bottom end torque, and
with OD at highway speeds, your operating in that range.  Less torque
requires more pedal input and more gas.

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