Quote:
Originally Posted by JohnnyGrey
Oh, I did, but the streets weren't empty enough to really take any meaningful measurements.
So for engine-off, closed throttle:
1. - The intake stroke works against the vacuum
2. + The vacuum returns the power on the compression stroke.
3. - Vacuum works against the the combustion stroke.
4. 0 Exhaust valve opens when chamber contents are about equal to what the manifold pressure was, air rushes in through the exhaust valve and gets pumped back out on the exhaust stroke.
Net effect: -1
|
It isn't that simple AFAIK. Depending on how your car's IAC works (totally open or closed or somewhere in between), as well as the engine's CR, and difference in combustion temperature to temperature when the engine's off, and consequently the moles of air retained in the cylinder after the exhaust valve closes, you'll end up with some difference in pressure between vacuum and atmospheric. It isn't quite -1.
