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Discussion Starter · #1 ·
Please pardon my ignorance but I've never owned a turbo before. I installed a boost gauge today and the readings go from -20 psi (20 psi of vacuum) after letting off the throttle to about 10 psi (I haven't taken it on the freeway but I have to rally lay into it to get 10 psi of boost. Does this seem reasonable or could my TCV be bad.<p> Noah
 

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Re: Correct boost behavior (nbwallace)

Assuming that you have an "R", your boost should be about 14 max unless you have a tune
 

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Re: Correct boost behavior (jstro)

I would adjust wastegate, many cars came out of factory with the wastegate incorrectly set<p>Edit: Correct stock boost should be 14.7 max
 

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Re: Correct boost behavior (nbwallace)

What is the ambient temperature during your 10 psi runs? If it's 80-90+ fahrenheit and you have a stock intercooler, you're not likely to see full boost.<p>What kind of gauge did you install?<p>If you're going to adjust the wastegate, I would suggest rigging up a proper pressure testing rig so that you can set the wastegate to open at 8 psi, rather than simply blindly adjusting the rod arm. If you bought a mechanical gauge, you should be able to use the gauge, the T that you used to tap the manifold, and the tubing that came with the gauge (or purchase some additional tubing) to make your rig.<p>How many miles on the car? When were the sparkplugs last replaced?<p>Cheers,<p>J
 

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Discussion Starter · #5 ·
Re: Correct boost behavior (soupandspoons)

The car has 51K on it and I changed the plugs last week. This morning it was 65F and I got it up to 10 psi or so. Should it be idling at -15 psi? I have a HD TCV that I haven't installed yet. I'm just trying to get a feeling for when the car should go on positive boost I don't know if I've laid into it hard enough to actually get full boost.<p>I have the IPD gauge and it seem to work quite well. I need to get ignition power for the lamp.<p><br>
 

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Re: Correct boost behavior (nbwallace)

Mine idles at around -20 inHg. Note that inHg (inches mercury) is not the same as psi (pounds per square inch). 1 inHg = 0.4912 psi. Does the IPD gauge measure vacuum in inHg or psi?
 

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Re: Correct boost behavior (nbwallace)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>nbwallace</b> »</i></TD></TR><TR><TD CLASS="quote">It measures in psi.</TD></TR></TABLE><p>I always thought that vacuum is measured in Hg not psi. <IMG NAME="icon" SRC="http://www.vwvortex.com/zeroforum_graphics/screwy.gif" BORDER="0"> <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/smile.gif" BORDER="0">
 

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Discussion Starter · #9 ·
Re: Correct boost behavior (s140s)

Perhaps you're right. I have no idea. I'm a PhD physicist I should know. But at the accelerator labs we measure vacuum in Torr and usually in the realm of 10^-8 or 10^-9. It would be good to know that my off throttle vacuum reading is ok. By the way, anyone know where I can tap ignition switched power in the driver's side fuse box?
 

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its the fuse for cigarettle lighter but you have to look at the diagram to know which one.<p>The vacuum sounds just fine and I bet your problem is wastegauge that needs adjustment, you need a pump with gauge to adjust it to 8psi.<p>-20hg is good for idle, when I cold start i get <br>-10 and then it falls between -20 and -15 at idle
 

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Re: Correct boost behavior (nbwallace)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>nbwallace</b> »</i></TD></TR><TR><TD CLASS="quote">Please pardon my ignorance but I've never owned a turbo before. I installed a boost gauge today and the readings go from -20 psi (20 psi of vacuum) after letting off the throttle to about 10 psi (I haven't taken it on the freeway but I have to rally lay into it to get 10 psi of boost. Does this seem reasonable or could my TCV be bad.<p> Noah</TD></TR></TABLE><p><br>Completely normal. <p>I was in your neck of the woods yesterday at Ferguson's buying a sink. Gotta love the wagon. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/wink.gif" BORDER="0">
 

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hey man, I just installed the ipd today as well. car reads -10 psi at idle and gets to 12 psi with full throtle. if im in nuetral or just rev the engine, boost snaps to 0 immediately. <p>Everyone else. will warmer temps cause the 14 psi stock boost to drop slightly to my 12 psi readings? I have the wastegate tweaked and ipd's HD TCV.
 

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Also, I just checked on the gauge in the garage to see if the lighting was working. It appears that the gauge is constantly lit up and doesn't go off. I checked the ipd video again and im tapped into the correct fuse.<p>Which one are you tapped into. im assuming that either wire could be the ground/positive.
 

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Re: Correct boost behavior (s140s)

I would suggest NOT adjusting the wastegate until you have determined that everything else is oeprating properly. They can be a little low but not typically 5 psi low...
 

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Re: Correct boost behavior (nbwallace)

A turbo car always has negative vacuum at idle, -15 to -20 is about right in Volvos
 

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Re: Correct boost behavior (s140s)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>s140s</b> »</i></TD></TR><TR><TD CLASS="quote"><p>I always thought that vacuum is measured in Hg not psi. <IMG NAME="icon" SRC="http://www.vwvortex.com/zeroforum_graphics/screwy.gif" BORDER="0"> <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/smile.gif" BORDER="0"> </TD></TR></TABLE><p>Vacuum is typically measured in Torr, named after Torricelli, an Italian physicist. Inches of mercury are another common unit used, but it doesn't matter. Vacuum is measured in units of pressure and you can use any such unit you want.
 

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Re: (stormchasin_racin)

Did you ever figure out your boost levels?
 

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Re: (badams1897)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>badams1897</b> »</i></TD></TR><TR><TD CLASS="quote">According to some people I know that have boost gauges they see 14-18PSI on a stock tune with JRL Mod. </TD></TR></TABLE><p>Sure, 14-18 psi range makes sense depending on conditions, not sure why you'd mention JRL mod as it would have no affect on the boost levels.
 

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im right under the 15 mark for WOT but im worried about my idle vacuum readings which are far lower than JRL's suggested amount. During warmup the vacuum is right at 8 and after warmup it drops to just below 10. Could this be a sign of my vacuum lines collapsing and need to be replaced with silicon lines?
 
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