I seem to recall having heard that the health of engine can be reflected in the vacuum reading at idle. For instance an engine registering -10 is stronger and healthier than an engine registering -8.
Is there any truth to this, and/or is it measurable?
The reason I ask is today I notice that at idle in EvoScan I was registering -8; but last week it was registering -8.5? Is there any correlation to engine health/well being vs changing vacuum pressures (or am I even more OCD-paranoid than I previously thought)
Thanks.

 

i think you want to have at least -20 vacuum at idle.

 

No, vacuum at idle can have numerous reasons to be different.(ie camshafts)

I'm also guessing you are logging psi. Because when people talk about vacuum, its usually measure in in/hg.

 

Just to be clear, we are using the same measurement, psi not in/hg
Ninja Edit: that's what I thought

 

I'm working on new MIVEC maps, but idle is untouched anyways, so it had me wondering...

 

Engine vacuum varies based upon atmospheric conditions as well. The lower the atmospheric pressure, the less vacuum the engine will pull at idle, generally speaking.

I see about -7.5 psi (with a zero'd boost reading with the car off) at 4500 ft.

But this "urban legend" is generally a correct assessment given your camshafts haven't changed and you have no vacuum leaks.