does the intercooler and down tubes from the intercooler experience a vacuum when the bypass is open?
I need a point to measure boost only no vacuum.

 

When the throttle body is closed, everything past it to the cylinders is below atmospheric. Why do you need to just measure boost?

Matt

 

just get a boost gauge that only shows boost

 

I have it is a digital one but when the manifold is under Vacuum it puts on a warning light on the gauge as the gauge thinks there is something wrong it is only supposed to read boost.
besides how can the intercooler and charge pipes from the SC be under Vacuum if the supercharger is spinning and making boost even though the bypass is open?

 

if the bypass valve is opened, that means that any boost that's made by the charger is vented to atmosphere.

 

Sorry, wrong answer!
The bypass returns pressure to the intake duct between the throttle body and the supercharger while there is vacuum present on the bypass valve diaphragm.

Profpatpending, suggest you view the warning light as an economy indicator..

 

you'd think i'd know that since i've taken it apart, but i forgot....:impatient

my bad

 

Your gonna have to either - live w/ the red light or switch out the guage. Got a pic to share of the guage?

I'm running a VDO Boost guage which gives very entertaining needle action do to the 0-15lbs scale. I'm always afraid the needle will shoot off the face of the guage.

 

I sure do.
ah well.

 

I recommend the VDO ultra lite series -30/+30 vacuum/Boost Gauge because I believe analog gauges read more accurate mid scale rather than maxed out.
The only minor problem is that eventually the red bulb cover bleaches out and the color doesn't match anymore.

 

That's AutoMeter's Ultra-Lite series, and I suggest their mechanical gauge #4301 indicating boost (to 20 psi) and vacuum (to 30 in. Hg). Boost should max at about 16 psi with 15% pulley.
http://www.autometer.com/cat_gaugede...id=3149&sid=11

 

Actually boost with a 15 = 14.5lbs of boost.

Whats really nice about the autometers is that they match up nicely to the stock guages. I wanted max entertainment. You can not appreciate this guage until you floor it!

 

Now I ask myself...... WHY DID you type VDO stupid

Thanks WEEGIT, I hate spreading bad INFO around.

 

I used the Autometer guage and it works great, tapped in in the vacuum line going to the fuel regulator. The car is not always under boost. It is only under boost when it is under load. If I am cruising ona level highway it usually shows about 10lbs of vacuum.

 

Chocolate, it is not 10 pounds of vacum, it is like atmospher - mercery- something vacum. only goes in pounds when going from 0-and up, it should say something like h.a.v on one side and them pounds on the other side! JUST FYI

 

0.4911541 PSI. Who knows why they use split units....

One atmosphere is 14.7 PSI at sea level, and 20 deg C, I think.

Matt

 

Get rid of that digi and get a DEFI
and for those who want a lot of action you dont need a low number boost gauge, you just need more boost :P 19%

 

Also, remember it's measuring gauge pressure so you have to add atmospheric pressure to get the actual pressure.