Quote:
Originally Posted by jamesm
'increases volumetric efficiency' and 'requires no tuning' are inherently incompatible statements.
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I haven't read the whole thread so forgive me if this has been said already.
I have to disagree with this statement. Here are my reasons. 1) If you increase the runner length, then that will improve volumetric efficiency due to an increase in velocity of the air stream at lower revs. NA engines usually have VE of 80-90%, so long runners could improve it to maybe 85-95% depending on engine. My guess our car is closer to the high end of the VE range due to 4 valves/cylinder and advanced flow dynamics from using advanced computer designing. Remember - Short runners improve volumetric efficiency at high rpms and long runners at lower revs, which is why you see that the peak hp is 500 rpms sooner with the long runners. This is evident with some makes i.e Mazda RX8 original design, and the old Mazda 787B rotary that had intake runner "stages" to go from long to short as the rpms climbed.
2) why would tuning be required? They're not changing anything about the air/fuel ratio. The maf/map are still calculating the amount of air entering the engine.
If I'm wrong on this feel free to correct me. The rest of the thread with all the e85 stuff is out of my knowledge range...:-)