Vacuume on start up

[terrybullwon]

quick one, have done a bit of searching but nothing like what i was looking for.

Right on cold start up i am only seeing about -17 -18 psi on idle. Its normaly on about -20psi to -21psi.
When i start driving around 1500rpm to 2200rmp i see the full -21psi to -22psi.

Just wondering what over people get???

Cheers Guys James

[Ross]

I think you're meaning -20 in.HG, or inches of mercury (probably goes to -30?)... I'm not sure on the conversion rate, but my guage goes to -700mbar.

On idle @ start-up I see -350mbar at the mo today, not sure why - it's usually sitting on -400 on idle. Rev the enigne to about 1500-2000 and it's about -500. Lift off at mid-range RPM and it's around -500 to -600; lift off at high-rpm and it's about -600 to -650.

Hope this helps?

[terrybullwon]

Yeah thats right ross i get the same running consistancy ( got my coat on now and just about to walk out the door)

your running a huge turbo though? should i be seeing more vacuume

[Jamo]

Yeah thats right ross i get the same running consistancy ( got my coat on now and just about to walk out the door)

your running a huge turbo though? should i be seeing more vacuume

I wouldn't imagine so as the turbo shouldn't affect vacuum on idle ( off-boost )

I've seen between - 0.5 to 0.7 bar off boost on the Coupe never checked the Avant mind.

[terrybullwon]

right so it could only be
isv hoses
vacuume hoses from the inlet man
or vacuume hoses running to the ecu

If i have a small leak

[blown_vr6]

You wont pull as much vacuum on a cold engine (especially in this ambient temperature) due to compression being lower before the rings seal properly - as she warms up you compression/vacuum will increase.

[UrS4boy]

You wont pull as much vacuum on a cold engine (especially in this ambient temperature) due to compression being lower before the rings seal properly - as she warms up you compression/vacuum will increase.

Agree. (I was just going to post that). On my AAN engine, I have both an analogue vacuum/boost gauge (Autometer Phantom) and a digital gauge (TDS-1 from Kevin Day in the US). When the engine is first started, I see about -11 inches of Mercury (Hg) on idle. As the engine warms, driving like a member of the "pipe and slippers" crowd, I see about -15 in Hg. After driving hard and fast (hot engine) and then backing off, I see about -20 in Hg.

HTH

Dave F.

[Jamo]

I wouldn't imagine so as the turbo shouldn't affect vacuum on idle ( off-boost )

I've seen between - 0.5 to 0.7 bar off boost on the Coupe never checked the Avant mind.

Reviving an old thread I'm seeing the same on the new engine 0.55 bar vacuum at idle up to 0.8 coming off throttle.

Seems same as the old Coupe I'm happy with that.

[driftin jo]

If you engine is healthy and as yours is new then it will be, it is going to have more friction when cold and thus the ISV is allowing more air to pass to maintain idle so you would expect less vacuum until warm, this is normal for a healthy engine.