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when the car is at idle what should the guage read. and what does it mean if the guage goes down or up. whats the difference between the two...please explain, im lost. thanx for any feedback
 

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When At idle or light pedal, your gage is reading vacuum. When you're at WOT, the gage should start at 0, and work it's way up to 12 lbs of boost by redline. At idle, most cars are betrween 12-20 vacuum.
 

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stiggonometry15 said:
when the car is at idle what should the guage read. and what does it mean if the guage goes down or up. whats the difference between the two...please explain, im lost. thanx for any feedback
Idle in the SS is about 18 psi (vacuum, meaning below zero). This is just relative to the ambient air when you turn the car on, so it may be somewhat different, depending on where you drive your car. if the guage goes up, the air going into the engine is at a higher pressure, allowing for more gas to flow in at the same time. More gas that can be burned (as a result of the increased pressure) leads to more power produced, and as a result, a car boosting at 12 psi is producing a lot of power compared to a 18 psi vacuum. As the SS is supercharged, you will notice an immediate change in the psi reading whenever you hit the gas pedal. I've noticed that if i'm in gear without my foot on the pedal, the engine will produce a vacuum greater than the idle vacuum, but i'm not exactly sure what that means or why it happens... like SVT said, at WOT, the boost will increase to 12 psi, but it probably won't start at 0 - from experience, anywhere from 5 to 10 psi, depending on the rpm and the gear you're in. Anyways, hope that helped!
 

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It might help your understanding if you think of it this way: an engine is nothing but a big air pump. The more air (and fuel) it sucks in and burns, the more power you get.

A normal engine "sucks" air in from the surrounding environment. Think of the engine as trying to sucking air out of some container, and think of the throttle as the valve or opening to that container. So for example, if your engine was at 4000rpm (pretty fast, so it's "sucking" a lot), and your foot is off the throttle (ie no air can get in), you'd expect to see a pretty high vacuum on your gauge (maybe 14psi vacuum). Likewise, if you're idling with yout foot off the throttle, the engine is'nt quite "sucking" as hard, so you'd expect to see a bit less vacuum, maybe 12psi vac. On a normal engine, when you step on it, you're basically completely opening up the box, so no matter how hard the engine sucks, there's plenty of air for it, so you'd expect to see zero pressure.

Supercharged engines are a bit different in that instead of the engine "sucking" air in, the supercharger is there to more or less ram air down the engine's throat. This means a lot more air (plus more fuel), and more power. On a supercharged engine, when you step on the throttle, you see POSITIVE (boost) pressure. So instead of just 0psi, you actualy see 10 or 12psi of boost... that's the supercharger compressing air and forcing it into the engine.
 

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smartmts..you should get your boost gage looked at if you're immediately reading psi when you hit the gas. I drove 3 SS's so far, and two of them, the gage starts at 0 (like it should) at WOT, and build to 12psi with engine rpm. The one, however, jumped around like crazy when i touched the gas, which is a false reading. I used to own a supercharged mustang, and my gage worked well. Some of these gages, are bad.
 

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No you wont ever see 0 at WOT. the car does not build boost its not a turbo. Get some supercharger knowledge. I have installed gauges in Redlines at 1500 rpm in 5th gear so you can watch it climb. The boost is at 3psi that low and its instant. There is no LAG. If you disagree then drive any Supercharged vehicle with a gauge you will see that you are wrong.
 

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GoofyGuy said:
No you wont ever see 0 at WOT. the car does not build boost its not a turbo. Get some supercharger knowledge. I have installed gauges in Redlines at 1500 rpm in 5th gear so you can watch it climb. The boost is at 3psi that low and its instant. There is no LAG. If you disagree then drive any Supercharged vehicle with a gauge you will see that you are wrong.
Agreed. You'll see boost as soon as you step on it. You shouldn't see 0psi at WOT.
 

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DanM said:
Agreed. You'll see boost as soon as you step on it. You shouldn't see 0psi at WOT.
Unless the belt slips REALLY BAD!!! ;)

BTW has anyone had problems with their belts slippin??
 
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