Average Vacuum while driving

[93GSX4me]

Ok so I've searched dsmtalk.com and dsmtuners and only found obscure references to owners average vacuum readings at vertain points ie idle and driving

At Idle I get around 12-23 Vacuum readings
while cruising with no load ( maintaining - not accelerating ) 15-20

Pretty much an average of 18-20........

Is this normal ? What is a normal vacuum while under no load ? I need to know what to reference while looking for leaks.... If this is average then ill be wasting time looking for leaks that dont exist .

This concerns only 4G63T ( turbo - not 420A with turbo conversions !!!!! )

 

[eboy0]

When i'm decelerating, it'll hit as low as 25vac, I idle around 13(bouncy).

 

[95AWD6Bolt]

Yea that seems around normal, at least for what I have seen. If your that concerned about a leak, get a boost leak test done.

 

[DiamondStarAwd]

I am around 23-25 when I let off the gas as well.

 

[brute]

Idle is around 13-15inHg. Engine decel is 20-21inHg.

 

[xioca]

Idle is around 13-15inHg. Engine decel is 20-21inHg.

Same here.

 

[Defiant]

When i'm decelerating, it'll hit as low as 25vac, I idle around 13(bouncy).

Bouncy? Check your belt timing.

Vac should run around 18 at idle.

Cruise will depend on load and throttle position.

 

[93GSX4me]

Idle = 18-20
Cruising No Load = 18-21

Pretty much the same until I start to accelerate , the of course it goes up to 0 then boost

 

[kmoore]

Bouncy? Check your belt timing.

Vac should run around 18 at idle.

Cruise will depend on load and throttle position.

Thats what I get at idle: 18
Decel= 25
Cruise @ about 2000 rpm= 15

 

[Crazyjoker77]

well instead of starting a new thread ill post here

anyway i have a 98GST and i've recently started having some wierd vacuum issues. I use to get about 18"hg at idle(850-900rpms) but now when i come to a stop i sometimes get as low as 15"hg usualy but it slowly creeps up to 15"hg from 19"hg over about 8seconds or so also during this time my idle gets a little lower(usually around 680-700) if i tap the gas it goes to -22 while it decels till it hits idle then slowly goes to 16 or so.

I've done a boost leak test and found i do have one from the biss screw (no cap or o ring =/ but hasnt been since the motor put in)

now only thing that comes to my mind is that the idle might be what is causing the lower vacuum cause i have had a idle control system CEL come on a few times (4 over 15kmiles)

also i recently moved there is quite a bit of elevation change 2700 to 1000

so im just wondering if i should be concerned because i know i should have 18+ vac at idle and what should i look for to cure my problem.

also this doesnt always happen (most of the time) but sometimes ill go for a drive and ill have normal vacuum and my idle will sit around 800 and not fall.