PDA

View Full Version : Negative Manifold Pressure???



Legnum Boy
27-01-2005, 09:09 AM
Ignore me, just being blonde ..... again.. :$

simpsonm
27-01-2005, 12:23 PM
Isn't there negative pressure at idle in the intake manifold. You often see the boost guage go into the negative at idle.

Legnum Boy
27-01-2005, 02:06 PM
Correct, but should you then remain to have negative pressure after the engine has been switched off?
Like I said, just me having a blonde moment.... ;)

enigma
27-01-2005, 03:29 PM
Isn't there negative pressure at idle in the intake manifold. You often see the boost guage go into the negative at idle.

I would hope that you always see the boost gauge ro -ve at idle! If you dont you have a problem!

I normally get -500mb at idle, but when it was poorly this was down (up?!) to -200mb........a sure sign it was dying!

So what does everyone else see at idle? I noticed in Dereks car he is hitting -610mb!

Legnum Boy
27-01-2005, 06:09 PM
Mine is -450mb at warm idle. :)

nick-f1
27-01-2005, 07:23 PM
I have fitted an imperial gauge ie: it reads in psi for boost and inches of mercury ( ins/hg) for vacuum ( -ve pressure), much more sensible for me! At tickover it reads 22 ins/hg and throttling off this increases to 27 ins/hg! And as the scale only reads to 30 ins/hg I think thats bloody good!

AllBeItMine
27-01-2005, 07:37 PM
-20psi at idle - goes up to around -27 to -30psi whilst engine braking.

enigma
27-01-2005, 08:44 PM
-30psi? :eek: :laugh: