04-12-2004, 01:49 PM
Thank you for the scary, irrelavant diagrams RJ! :wink:
I think I get what you guys are saying though. The vacuum is created between the pistons and the throttle body, and it's really only there because of the restriction of the throttle body. Diesels don't really have a throttle body that restricts the airflow, so there's no (or little) vacuum. Also makes sense that when the throttle is stabbed, vacuum drops to close to zero, and it's at it's highest at idle when the restriction is highest (I said that backwards before). I like it! Thanks!
Now as far as the difference between suction and a pressure differential, I guess I missed that one. Sounds like semantics to me, but I don't really know if I have to completely understand that. A piston, when moving down, with intake valve open, is creating a low pressure area that demands the "sucking" in of more air. TB restricts that, so the space between the top of the piston and the TB never reaches atmospheric pressure, ie, a vacuum. Good enough. Feel free to explain more RJ if I'm really missing something there.
I would like a vacuum gauge on my E30 come to think of it, sounds like it'd be fun to watch instead of the road... 8)
I think I get what you guys are saying though. The vacuum is created between the pistons and the throttle body, and it's really only there because of the restriction of the throttle body. Diesels don't really have a throttle body that restricts the airflow, so there's no (or little) vacuum. Also makes sense that when the throttle is stabbed, vacuum drops to close to zero, and it's at it's highest at idle when the restriction is highest (I said that backwards before). I like it! Thanks!
Now as far as the difference between suction and a pressure differential, I guess I missed that one. Sounds like semantics to me, but I don't really know if I have to completely understand that. A piston, when moving down, with intake valve open, is creating a low pressure area that demands the "sucking" in of more air. TB restricts that, so the space between the top of the piston and the TB never reaches atmospheric pressure, ie, a vacuum. Good enough. Feel free to explain more RJ if I'm really missing something there.
I would like a vacuum gauge on my E30 come to think of it, sounds like it'd be fun to watch instead of the road... 8)