Vacuum/boost

[66yostagea]

Just checking to see how much vacuum you get when backing right of at say, 100kph.? S1,RS4.

Edited November 29, 2010 by 66yostagea

[zoomzoom]

My gauge shows about 0.75 to 0.8 bar less than atmospheric pressure, even more if its a downhill slope

[66yostagea]

My gauge shows about 0.75 to 0.8 bar less than atmospheric pressure, even more if its a downhill slope

Whats that in "inches of Mercury"?

[zoomzoom]

About 22-23 inHg vac.

[66yostagea]

About 22-23 inHg vac.

I only get to 18. Is that bad? Does it mean a leak somewhere.

[dirtyRS4]

Whats that in "inches of Mercury"?

inHg = 0.491098 psi, or 2.036254 inHg = 1 psi.

Fkn lol, hugh

Edited November 29, 2010 by dirtyRS4

[RubyRS4]

About 22-23 inHg vac.

I'm about 20-21 inHG vacuum.

[66yostagea]

Yes, but if you only get 18 inches, does it mean there is a leak??

[StealthX]

Yes, but if you only get 18 inches, does it mean there is a leak??

Does it idle and boost fine? i.e. no black smoke or missing?

Auto or manual?

[QWK32]

Yes, but if you only get 18 inches, does it mean there is a leak??

seriously though, yes it could mean you have a small vacuum leak, it could also mean your compression is slightly lower i.e worn rings. and lastly it could mean that you idle timing is retarded. to be honest i wouldn't worry about it, you'll find anything around 18-22 is considered normal. is your idle rpm stable?

Edited November 29, 2010 by QWK32

[zoomzoom]

I only get to 18. Is that bad? Does it mean a leak somewhere.

17 - 18 inHG would be idling for me. I would expect more vac on the overrun.

There could be many reasons. Cracked vac lines is an obvious one. Is your aux air valve letting in too much air? If you have a consult cable, checking the timing at idle is a good way to see if the ECU is retarding the timing to account for too much air entering at idle.

I also have a restrictor on my valve cover to manifold PCV so that may account for my higher vac number. That, and an engine in good condition *touch wood*