Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Article: adding a turbo to improve efficiency

Duffman · 05-10-2008, 12:15 AM

Lost Cause,
Holding engine displacement, ignition timing, A/F ratio, RPM and compression ratio the same in a gasoline engine the power produced is proportional to the cylinder filling (AKA Volumetric efficiency VE). Because we are holding all the above constant, friction and all the other losses are constant as well and we are really only adding fuel with the increased air (constant A/F Ratio) so power will be proportional. So to put out X hp at say 2000 RPM engine A may require 50% cylinder filling. In reality 100% of the cylinder is full it is just at 1/2 pressure, hence it is operating under vacuum. Most NA engines cant exceed around 85% VE due to restrictive intake ports and cam timing. A turbo can easily exceed 100% VE becuase it is compressing the air (boost) but again really 100% of the cylinder is full but the pressure is above 1 Atmosphere so we can say it has exceeded 100% VE.

Does this help?

05-10-2008, 12:15 AM	#80 (permalink)
Duffman Master EcoModder Join Date: Mar 2008 Location: Edmonton, AB, Canada Posts: 531 Thanks: 11 Thanked 12 Times in 11 Posts	Lost Cause, Holding engine displacement, ignition timing, A/F ratio, RPM and compression ratio the same in a gasoline engine the power produced is proportional to the cylinder filling (AKA Volumetric efficiency VE). Because we are holding all the above constant, friction and all the other losses are constant as well and we are really only adding fuel with the increased air (constant A/F Ratio) so power will be proportional. So to put out X hp at say 2000 RPM engine A may require 50% cylinder filling. In reality 100% of the cylinder is full it is just at 1/2 pressure, hence it is operating under vacuum. Most NA engines cant exceed around 85% VE due to restrictive intake ports and cam timing. A turbo can easily exceed 100% VE becuase it is compressing the air (boost) but again really 100% of the cylinder is full but the pressure is above 1 Atmosphere so we can say it has exceeded 100% VE. Does this help? Last edited by Duffman; 05-10-2008 at 12:24 AM..