i know the vaccum pressure on my gauge is supposed to read between 18 and 20 right when i'm idle in neutral? so if when i'm idle in neutral it reads 15 does that mean I have a vaccum leak? it's been this way since i can remember, and I believe it has something to do with why when i hit the gas it feels like the feeling you get when you step on the brakes with just a little air in the brakeline..there's like a slight delay before the rpm's go up..also I think this may have to do with the problem that I only spike to and hold 16 psi no matter what bov I have in..the only way I get the psi to stay higher than that is with my mbc. anyways, any help would be appreciated..i've tightened every clamp and hose I can see and it's still this way...

 

It sounds like you've modified your car; do you have cams? The overlap on the cams changes, so the vacuum changes.

When the car is cold the vacuum is less in my (stock), and runs about 16 when cold. A vacuum leak usually makes the car stumble and run poorly as well. Does your car do this?

 

all i have right now is a hallman mbc...but that was so that I would be able to boost 19psi instead of 16 as i was before i installed the mbc....my car does studder a lot when the clutch is engaging from a stop..and it feels like no matter how much more gas i give it..it will still studder each time from a stop to 5-10 mph...like I said it feels almost like I have the same feeling as air in my brake lines..like i have to wait longer than normal for the clutch to engage because i'ts not getting enough gas when i hit the throttle..

 

bump?...barely any time goes by and 32 views and only one person responds...please any help would be great

 

Mine reads 15-16 in.hg of vacuum at warm idle (~850 rpm) -- stock.

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bump for before bed..hoping for more info through the night

 

Same, mine runs 15-16in/hg of vacume at 850rpm when warmed up. During engine braking in 5th or 4th gear from highway speeds I see upwards of 25in/hg.

 

me too. It just drops for a bit then picks up but it stays between 15 to 20+ up and down

 

what boost gauge do you have?
i get 15-18 at idle. i have autometer gauges and im thinking about changing it up when i get money. mines off 1psi.

 

I have the Defi D-series.

 

has anyone else had the problem of only boosting 16 psi and holding there from the factory? i mean obviously my mbc will fix this..but I should at least spike to 19 psi from the factory but I dont..I've tightened all the clamps and hoses I can see plus the lower intercooler pipes I could get to...so I dont know what else could be wrong

 

unless my gauge just reads wrong..but then if it's 3 psi off..when I had my mbc on and it was reading 20 psi..then it would have really been 23 and I should have been detonating all the time..

 

Where do you live? If you live at high altitude, that seems about right. I live in Denver and get max 17 psi in 3rd, my car is still stock. At idle my vac reads at 15-14 as well.