Does having more compression create more vacuum?

[DanMan7]

Hey everyone. My old engine had 2 bad cylinders. Is the amount of compression in the engine related to how much vacuum is created in the engine? I'm really curious about this. It WOULD make sense if it is related, because I can't think of any other way that vacuum is created other than from the cylinders and valves.

Another thing, is, I don't know if any of you remember me saying this, but when I was idling with my old engine, when I turn on the headlights or heater the engine would go down in rpms. I'm thinking that when I finish putting in the newer engine with 24k miles on it, that since the compression is perfect in that engine, and if it creates more vacuum, would the additional vacuum compensate for the problems I had with idling? I was thinking with the additional vacuum, that the MAP sensor and EGR sensors that depend on vacuum to get readings would allow to send information to the computer, which would actually increase RPM when I turn on accessories. I'm just really curious about this. Seems like it would work.

Any input would be appreciated!

Boy, after working on the car as much as I've been the last day or so, it's so easy and fun to work on. I couldn't believe that the engine just weighs over 100 pounds...it's so light! BUT I'm glad I bought an engine hoist anyway...makes it a lot easier to ease the engine in and taking it out of the car.

[Crvett69]

vacuum is mostly controlled by the cam of the engine. we have a race car with 15-1 compresion but the cam has such high overlap that we only have about 12 inches of vacuum at idle. reason engine idles down is that the stuff you turn on causes the alternator to drag the engine down as the more stuff thats on the more it has to generate to keep up and that requires more hp to turn it. on most cars they have enough hp that you don't really notice it much but the metros only make 55hp to start with

[GM Line Rat]

Originally Posted by DanMan7

Another thing, is, I don't know if any of you remember me saying this, but when I was idling with my old engine, when I turn on the headlights or heater the engine would go down in rpms.

Turning on the headlights and/or Heater blower motor is most likely causing by a larger load to be put on the Alternator and therefore, the engine idle drops a small amount....It's normal.