Normal Vacuum On Idle

[Kwyjibo]

I noticed in another topic someone was saying their vacuum is dropping to -60mmhg on idle. According to my boost guage mine is sitting at -40Cm/hg(-4.5 to -5.5 on standard guage) or around abouts and just wondering if I might have a leak somewhere? Engine runs fine and boosts ok.

Does anyone know what it should be sitting at with no accelerator input?

Any easy ways of finding vacuum leaks?

Cheers,

Adrian

Edited January 23, 2008 by Kwyjibo

[paulr33]

it should be around -550mmhg on idle

-40cm/hg is approx -400mmhg so its about right

[Kwyjibo]

it should be around -550mmhg on idle

-40cm/hg is approx -400mmhg so its about right

Ok it seemed like the variance was a bit high, I did a search and whenever other peoples standard guage was sitting above -7 like mine people said there was a vacuum leak.

[paulr33]

if its leaking it would expect it to show sea level pressure so -0 or thereabouts

like mine was when it was leaking it was showing -60mmhg, which is almost absolute pressure (ie: its leaking to the atmosphere)

so it essentially shows sea level pressure instead of vacuum - under vacuum it should be a fair whack off 0

[vinnie32GTS4]

my guage is showin -0 on idle...i bought the car as it is and ive noticed that the guy who owned it before me has installed a t-piece inbetween the vaccum hose between the wastegate accutator and what ever that goes to...is this why it would be showin -0 because my car runs fine????

[Kwyjibo]

my guage is showin -0 on idle...i bought the car as it is and ive noticed that the guy who owned it before me has installed a t-piece inbetween the vaccum hose between the wastegate accutator and what ever that goes to...is this why it would be showin -0 because my car runs fine????

I just realised the previous user has put in T-piece that runs to the standard guage and then also runs through to the dash(probably to the other guage). None of these connections are have fastners on them so I might buy some and see if that helps. It seems a very slight is coming from where it connects to the plenum.

[RPR33]

I have two skylines in my driveway and one sit on -20inhg and the other at -16-18ish inhg, the second one has a front mount! would that have any effect on the vac? I have checked it for leaks like 20 times. and came up with nothing, I hope that it does'nt mean the engine has less compression?

would it?

Sweet it was just my gauge!!!!!

Edited February 12, 2008 by RPR33

[Munkyb0y]

ive got a related question.

at idle (warm) my boost gauge shows the normal ~20 vac (psi gauge). on cold start when rpm is around 1100 it used to show less vac, like 15 or something, till the revs dropped, but now it sits on 20vac at cold start. not sure which of these is normal.

the factory gauge shows similar figures.

if i rev it at cold start, the gauge moves up accordingly. all other readings while warm etc seem fine.

cold start and idle are spot on. no idle hunting, etc.

which one of these readings do you guys get at cold start? 20 vac, as when warm? or higher. eg 15 vac?

Edited February 12, 2008 by Munkyb0y

[joeyjoejoejuniorshabadoo]

mine cold/warm same/same

[Munkyb0y]

thank you joey joe joe

[WogsRus]

yeah mine sits about same -16 to -18 mm HG depending on external conditions, no leaks, have been pressure tested. Car same warm or cold

[Munkyb0y]

cheers

[Gtrgodzilla67]

mine sits on -21-22 on cold or warm,

[GTScotT]

ok to the person who says his car shows 0 cept when off boost and its t peiced of the actuator line, this is normal, as your only showing positive pressure on that line as it comes off the turbo hosing itself, t it off a line from the manifold instead, eg blow off valve line and it will show correctly

[RaZ_TuRbO]

-19/20 vac is normal for a car with standard cams. If your cars reasonably standard and you have a vaccuum of -16 or less id be thinking your timming belt may have some issue e.g off by 1 tooth.