I was wondering if this is normal with turbo cars. Bascially the vaccum fluctuates up and down on idle, it is like it is vibrating. The range is tiny but it fluctuates on a steady pace. All lines are tight and this is on my DEfi BF series boost gauge. Anyone have this or info on this?
TIA

 

whats ur rpm @idle? is it fluctuating as well?

 

I think its normal, Mine does that sometime, especially when the motor is cold, it fluctuates in .5 psi range between 18-17 in vac. My car is completely stock. spike to 20psi tapper to 17 and hold all the way to redline. I wouldn't worry about it.

 

I have the same gauges also. At idle my needle move up and down just a tiny bit. Seems normal.

 

autometer boost guage here. Vacuum bounces within .5 psi at idle as well. Its normal.

 

slight fluctuation is normal... at idle on a cold motor it should be slightly different than that of a warm motor... A warm motor should see at most 1 PSI fluctuation... Don't worry if their is a vacume leek you will either see the vacume loss or hear the leek. Normal leeks can see an excess of 5-8 psi of loss if not more... depends on the size of the leek

 

do you have any mods.. Usually with my bov and my intake.. i notice more of a difference

 

why does it vaccum at idle?? I've been wondering this for awhile. I know that this is a stupid noob question, and I have done a search and didn't really find the answer, so any help would be appreciated

 

Well, I'm no automotive engineer but I would guess the gauge measures vacuum at idle because the engine is "sucking" in air. Under boost it measures pressure because the turbo is forcing air into the system.

 

I have the Greddy gauge. It came with a Orifice to help prevent idle fluctuations.

 

Greedy Gauge