Also, iirc, turbos help with exhaust scavenging and help with reducing pumping loss from intake stroke.
https://sites.google.com/site/shooti...ine-efficiency
Also have to look at the technology behind it.ball bearing takes less friction than journal. Comp wheel and turbine shape. Exhaust housing size etc. Just slapping one on isnt going to give you mpg.
Forgive my android writting
Quote:
Originally Posted by serialk11r
This is pretty iffy. The 335 and the 328 are the same engine pretty much but the 335 has lower compression and twin turbo. The 335 has poorer fuel economy. Fuel economy goes up if you decrease the engine size and then turbo to make up for the power loss, because it decreases the friction you have to deal with.
BMW engines are all Valvetronic equipped except the high performance Sxx variants. This means off load boost actually can help thermodynamic efficiency.
As people have already figured out with the best BSFC at 80% load rule, increasing power production stops increasing efficiency before the engine hits full load. A usual throttle plate controlled engine might see a slight improvement in thermodynamic efficiency from a turbo at an operating point where the throttle is nearly fully open, but the valve timing is set up so that the engine is not at maximum torque output.
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