Quote:
Originally Posted by Sean.Heihn
Using the valve timing numbers:
http://www.mr2.com/files/mr2/techinf...ata/1nzfxe.pdf
I think he means effective intake draw volume, since the displacement is always 1497cc. The 1NZ-FXE varies intake draw from 898cc down to 539cc. And since you're compressing less volume, your effective compression ratio is lower than your physical. Something like 7.8-4.68:1 vs 13:1. |
That's not how it works. All cars come with cams with well over 180 degrees advertised duration but they manage higher VE than you'd expect even at low speed because air doesn't flow through the valve so easily when there's not much lift. Compared to a normal car the Prius might be comparable to a 9:1 compression ratio. Race engines have way more duration than the 1NZ-FXE, it doesn't mean they have low volumetric efficiency. It just means they peak out their volumetric efficiency at a higher rpm. There's a reason why people spend lots of time on headers and intake tracts, it's not as simple as "the valve closes, that's when air stops flowing".