boost gauge question

[jmv]

So, i've had problems with my vac reading in my car for quite a while. I finally found the cause of lots of my leak-like issues, and the car felt sooo much better once i replaced the wga. My vac reading was still ~18 at idle though. I began to kind of think it was just the gauge. Well i've got silicone vacuum line on the way to replace all the 5/32" stuff on the intake mani and for the wga and bypass valve and whatnot, but i wanted to ask you guys a question.....

How do you have your boost gauge connected to your vac source?? My stewart warner gauge came with some miniscule plastic tubing and a system for attatching it to the gauge that i didn't really understand (the gauge has male threads on the back, instead of just like a barbed fitting for a vac line like i would have figured it would have). Also, some people reccomended against using the really tiny plastic tubing stuff that they provided. So i bought this kit that was designed for stewart warner gauges on volkswagens i think (i'm not sure i can find it still). It came with a thicker line, a 'restrictor' tee (which i didn't use, i just used a regular tee), and a plastic fitting to screw onto the back of the gauge. Well at the time it seemed a little odd that the place where the vac line connected to the fitting could move around and stuff. I guess it was designed to rotate so you can easily thread it onto the gauge. But anyway at the time it worked and i didn't even realize my vac reading was incorrect, i was mostly just worried with the boost pressure. after the wastegate actuator install, i've been trying to figure why my vac reading still isn't right, and was curious if you guys had any input on my method of attatching the vac line for the gauge.

Thanks guys,
Jason

[mspHtown]

my stewart warner gauge reads about 18 hg/in. i hooked up a vacuum gauge to the manifold and it read perfectly 21 hg/in. so i think the gauges are slightly off.

[volcombro16]

You should buy DEFI easiest installs by far

[jmv]

my stewart warner gauge reads about 18 hg/in. i hooked up a vacuum gauge to the manifold and it read perfectly 21 hg/in. so i think the gauges are slightly off.


see i've gotten conflicting reports. Other people have the same result as me, where you get 18 vac at idle, then others have had full 22. I actually did see the most vac i've ever gotten the other day, it was wet and i broke traction in 2nd and the revs were climbing very fast, when i let off the gauge hit 22. It slowly crept back up though. Usually when i let off from hard acceleration, i get about 20 momentarily, then it climbs back up to 18.

I'd love to grab some defi gauges but i don't have the funds right now.

[Alejo_NIN]

right now i have autometer, i know i have no leaks at all and my vac runs at 18-19

[SeR_Cyclops]

i have an autometer C2 and i get always 20 somtimes 23-25 depends on the temp btw i love it its awesome

[Brian MP5T]

20

[mspHtown]

see i've gotten conflicting reports. Other people have the same result as me, where you get 18 vac at idle, then others have had full 22. I actually did see the most vac i've ever gotten the other day, it was wet and i broke traction in 2nd and the revs were climbing very fast, when i let off the gauge hit 22. It slowly crept back up though. Usually when i let off from hard acceleration, i get about 20 momentarily, then it climbs back up to 18.

I'd love to grab some defi gauges but i don't have the funds right now.


sorry i didnt specify, my gauge reads 18 at idle. after letting off the accelerator from high rpm, my vac reading is like 20.

[ChopstickHero]

my SW vac boost gauge reads about 18-20 hg/in during idle. when i'm driving and let go of the throttle it will read exacly 20 hg/in. when i'm boosting and then shift, i see the vac go to at least 22 hg/in. I find altitude has some effect, when i drive into the mountains, i get a lower reading (a consistent 18 hg/in). when i go out to the beach (sea level), i get a higher vac reading (usually a consistent 21-22 hg/in)

[volcombro16]

my boost guage was reading 25-28 with stock side mount then i put my front mount on and it went to 22

[Brian MP5T]

^^ I believe that its fucked.. Get a second opinion..

[Wbriggs19061]

lol yea my autometer has been at 22 through out all the mods..

[Alejo_NIN]

doesm't altitude has anything to do with vac reading?

[Brian MP5T]

doesm't altitude has anything to do with vac reading?

No,

[jmv]

anyone in the austin area wanna come hook up their boost gauge to my car?? haha.

[BOOSTR]

In general a reading of 17-22 at idle suggest a normal engine. As long as your car is running well and the vaccum at idle doesn't go below where its at now, I wouldn't worry about it or buy a more expensive gauge.

[jmv]

well the whole thing that got me concerned about it was my unichip experience. I had weird bucking issues, and even when the bucking went away for whatever reason the top end didn't feel as strong as it should, according to JDM Sam. The harness fried later and its not in the car now, but i want to try and make sure my car is all sorted before (and if) i get it fixed and try to put it back on.

[hotrodf1]

I have the Autometer as well. Great gauge. I pull about 22-24"Hg at idle.

Also comes with the plastic tubing and a little tee with rubber booty type deal. At the gage end, you are supposed to use a regular compression nut and insert thingy. You just slide the nut onto the tube, then the spacer insert and tighten it onto the gage - being careful not to over tighten or you will force the tubing shut. The more you tighten, the more that little brass spacer crushes onto the tube (eventually collapsing it). Autometer includes all the necessary fittings, etc., it sound like SW didn't???

[mspHtown]

No,


yes it does...

http://www.anver.com/document/vacuum%20lifters/atmospheric%20pressure.htm

[hotrodf1]

yes it does...

http://www.anver.com/document/vacuum%20lifters/atmospheric%20pressure.htm


And the instructions for the DSM AFC from SplitSecond mention that the "0" on the gauge will not be accurate if the barometric pressure changes. Thereby shifting all your values to one side or the other I think.

[Kypatrick]

My MSP is stock, except for a SRI, and Mine reads 24-26 at Idle. I have an Autometer Carbon Fiber.

[Kypatrick]

Ok, I did some thinking in the Porcelain Library!
Im thinkin everybody is having different Vac readings due to their idle RPMs.
Im sure not every car idles the same. repost your vac reading with Idle RPMs to see if my theory works.
mine reads 24-26 at about 500-600 Idle RPms