low vacuum, is it normal?

[DeadlyScone]

My car at idle(900rpm) has about -13psi and at OT about -11psi. I was wondering if this is normal or way off what it should be.
Thanks for the help.

 

[biowolf]

That is actually exactly what mine is but I read -19 is the correct vacuum pressure for idle you may have a vacuum leak

 

[mirage j]

most of the time vac leak is at the brake booster also 900rpm 13 is ok unless it was higher before then vac leak

 

[DeadlyScone]

That is actually exactly what mine is but I read -19 is the correct vacuum pressure for idle you may have a vacuum leak

so you are saying it should be -19? or how do(if anyone wants to chime in) you know the appropriate vacuum for your set-up and car?

 

[genegoesfast]

It has a lot to do with idle rpm, cam setup(large cams will pull less vacuum) I'm running hks 272s at 1000rpm idle and get -13/14

 

[DeadlyScone]

It has a lot to do with idle rpm, cam setup(large cams will pull less vacuum) I'm running hks 272s at 1000rpm idle and get -13/14

i doubt it has anything but stock cams. So then i guess that means i would have to BLT and fix all if any leaks and that will tell me my base vacuum?

 

[mirage j]

wow i got some new info on this after watching a tune done on a friends car, he had really low vac 9hg untill the timing/fuel trims where tuned properly then it like 18 at 800rpm

 

[1983gsp]

Bc272's dialed straight up @ 1000rpm I get 18-20inhg. Boost leak test and see what that gets you.

 

[sciondan]

18 to 20 at idle is were you want to be. If you don't have a vac leak then check your timing.

 

[DeadlyScone]

18 to 20 at idle is were you want to be. If you don't have a vac leak then check your timing.

ignition timing correct?

 

[MichaelSuch]

Check your mechanical timing, if you are a tooth off then it will throw a lower vaccuum as well. But check for any boost leaks before pulling off timing covers. That's most likely the issue.

 

[DeadlyScone]

Check your mechanical timing, if you are a tooth off then it will throw a lower vaccuum as well. But check for any boost leaks before pulling off timing covers. That's most likely the issue.

i'am pretty positive that i just have a vacuum leak, which explains allot of the power loss and richness of the car. Can you buy BLT's or do you have to make them? any good places you recommend?

 

[mirage j]

quick question could the iac cause low vacuum also

 

[DeadlyScone]

quick question could the iac cause low vacuum also

Interesting thought. I wonder.

 

[biowolf]

Deadlyscone did you find your problem? Just curious as I have the same problem and I know my mpgs are suffering

 

[SpeedTech720]

It's usually way cheaper to build a BLT from parts from homedepot or menards or borrow one from someone close than buying one.

I believe there is a write up on vfaq too

 

[DeadlyScone]

Deadlyscone did you find your problem? Just curious as I have the same problem and I know my mpgs are suffering

no, i'am going out today to buy the materials needed to make a boost leak tester. Wish me well, .

It's usually way cheaper to build a BLT from parts from homedepot or menards or borrow one from someone close than buying one.

I believe there is a write up on vfaq too

do you have a link? I was going off this one website and video specific for dsm's

 

[talon91500]

Like most people are saying. Do the boost leak test and see where your at. My vac is at
20-21hg at idle. Now i have no boost leaks on any of the piping, But maybe a little around the TB it self. So for the most part very small leaks shouldn't make a huge difference. If it does then there is a bigger problem. But most of these small problems you just have to start eliminating very thing you can to find the issue.

 

[SpeedTech720]

Visual Frequently Answered Questions - Home Page This is probably the easiest version otherwise you can put and air tool fitting on it too by drilling and treading a hole in the end

sorry IC Pipe Tester is the right link it's under intake

 

[mirage j]

ok how i built my boost leak tester was to us a tire air valve and bore a hole in the ic pipe and installed valve in it permanent and all i have to do now it block turbo intake and put air pressure to the valve and listen

but you really should do a vac test because boost leak won't make low vacuum because vacuum is created behind the tb not infront

 

[DeadlyScone]

Went to home depot, Western Nevada supply, and O'Reilly Auto Parts. Spent a total of 20.18 w/ tax and got to work on my BLT(my first one). Here is a couple pic's.

I'am going today to test it, since i don't have a compressor i have to go to m moms house

 

[SpeedTech720]

Just make sure you use an accurate air gauge when testing.

 

[2g_4g63]

My car at idle(900rpm) has about -13psi and at OT about -11psi. I was wondering if this is normal or way off what it should be.
Thanks for the help.

i got the same exact reading on my after market boost gauge. its normal because the altitude that we live in. i didnt understand it at first either.

 

[DeadlyScone]

i got the same exact reading on my after market boost gauge. its normal because the altitude that we live in. i didnt understand it at first either.

Ya, but it still shouldn't be that low. Plus i know i have a boost leak anyway :/

 

[DeadlyScone]

Found my boost leak(more like boost-be-gone), The top of the TB was blowing out air as fast as i could put it in . I bought a new gasket for it last night and will probably install it tonight.