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boost gauge question

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10+ Year Contributor
Nov 25, 2009
Honeybrook, Pennsylvania
my first boost gauge install and was dry fitting it today and had some questions. it is a vac/boost gauge. when i hooked it up as described in the vfaq and started the car the vac read 20 in-hg and i pumped the throttle from under the hood a couple times the vac went to about 10 in-hg but never went to the boost side of the gauge. My question is is this normal when there is no real load on the car? it is a 98 gst spyder with a completely turbo system so im guessing ( again completely a guess) i should see maybe 10 psi max. Will i see a boost reading when i put the car on the road? ive seen i couple posts saying the 20 in-hg is a normal reading was really wondering about the boost. im realistic and am not looking to see boost readings of 15+ psi just looking for a reading in general.
where did you T into? should be into the FPR line, no, you wont see boost until you put a load on it aka driving.
No, typically the car will not build boost in neutral. Nor do you want it to.

thats what i wanted to hear was just curious to see if the gauge was working and everything before i got into making a place to put it (thinking of putting it in my ac vent area above the hvac controls).

i t'd it off the throttle body vaccum line as per the instructions in the tech guide on this site.
If you rev it close to redline in neutral, you might get 5-6 psi. Enough to hear a bov. But not a whole lot. The engine normally wont build much boost without load.
nah not even close to redline just gave it a couple pedal punches. may get to working on the gauge install soon make it a bit of a downtime project. i dont drive the car in the winter/after the top down weather disappears.
-25 should be about maximum vacuum at idle, and stock boost should be anywhere from 10-12psi, in gear.
thanks thats about what i was getting. i havent installed as of yet i think this is going to be a winter project as its a spyder and i generally store it.
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