Quote:
Originally Posted by El Duende
Oh it doesn't happen? Well, I'm not referring to the slowing of exhaust flow, I'm talking about recirculation of spent gasses. Wait... So that means that backpressure does exist! 
Hope I'm not truly burdening your mind, because you're not burdening mine. |
So you're talking about EGR flow? (Rhetoric.)
What you're suggesting is that the exhaust is drawn back into the cylinder after having exited, which isn't true. What actually happens is that as the exhaust exits the engine, pressure in the exhaust channel builds as the flow slows, due to expansion and cooling, and this prevents the scavenging effect that you feel is so necessary.
Of course, I'm sure it never occurred to you that some automakers have actually designed engines with this in mind, because it's more efficient to just leave some of the exhaust gasses in the cylinder than to recirculate them via EGR flow... Of course, if there is exhaust gas left in the cylinder, that would reduce the dynamic displacement of the engine, meaning that less fresh air is drawn in, thus less fuel is necessary to maintain the same AFR, and a higher throttle angle must be used to generate the necessary amount of power to maintain the vehicle's speed, reducing pumping losses.
Do you have any links or data which backs up your claims?
I wasn't expecting flame-age for not having links readily available, but I really should start keeping a file of them. I often give information that could be covered by them, but can't provide the link for a point of reference. It's a bad practice that I need to break.