exhaust restricting turbo.
Apr 2, 2008 | 04:27 PM
#1
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From: colorado above 6000 ft.
exhaust restricting turbo.
Are any of you turbo guys seeing your boost going up from the exhaust being too restrictive. Lately ive been seeing close to 12 psi.
Apr 2, 2008 | 04:37 PM
#2
Apr 2, 2008 | 04:46 PM
#4
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12 Second Truck Club
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From: colorado above 6000 ft.
Thats what I was thinking, back pressure should slow the turbine wheel and make less boost. just trying to figure why I am seeing a lttle more boost than normal. you think running strait meth would have anything to do with it??
Apr 2, 2008 | 05:17 PM
#6
I wouldn't think so....you're tuned for the meth, correct? Shouldn't make any difference. Are you taking the boost readings off your gauge or off the MAP sensor? The gauge is subject to atmospheric conditions and will vary based on outside barometric pressure. The MAP sensor is absolute and is not subject to the same conditions.
Apr 2, 2008 | 06:09 PM
#7
No on the meth, and the freeing up the exhaust. Turbos HATE any downstream restriction (and we're talking to the level that the number of bends you have in an otherwise free flowing pipe can matter). Meth can net you more power if you turn up the boost, but does nothing to increase the boost.
The only thing I can think of that would increase your boost is a malfunctioning wastegate.
The only thing I can think of that would increase your boost is a malfunctioning wastegate.
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Apr 2, 2008 | 06:12 PM
#8
You lost me here chief. Your gauge is driven by the same sensor as your MAP sensor. You aren't pulling you sensor reading at the turbo shell are you?
Apr 2, 2008 | 06:16 PM
#9
The gauge references manifold pressure to atmospheric pressure. So for a given manifold pressure, you can vary atmospheric pressure and the reading on the boost gauge will change because the difference between the manifold pressure and atmospheric pressure will change. The boost gauge is relative.
The MAP sensor is absolute, meaning that it compares manifold pressure to some absolute pressure, which means that you can vary the atmospheric pressure all you want while keeping the manifold pressure the same and it will always read the same pressure.
Example....if I'm here in Phoenix at 1200 ft elevation and making enough boost to give me a reading of 195kpa on the MAP sensor, let's say it shows 12 psi on the boost gauge. Now I drive to the coast, where I'm at sea level. I make the same run and have the same MAP value of 195kpa, only now my boost gauge reads 10 psi because it is referenced to atmospheric pressure. When the atmospheric pressure is greater, the difference between manifold and atmosphere is lower, and the boost gauge reading will be lower.
http://en.wikipedia.org/wiki/Vacuum_gauge
The MAP sensor is absolute, meaning that it compares manifold pressure to some absolute pressure, which means that you can vary the atmospheric pressure all you want while keeping the manifold pressure the same and it will always read the same pressure.
Example....if I'm here in Phoenix at 1200 ft elevation and making enough boost to give me a reading of 195kpa on the MAP sensor, let's say it shows 12 psi on the boost gauge. Now I drive to the coast, where I'm at sea level. I make the same run and have the same MAP value of 195kpa, only now my boost gauge reads 10 psi because it is referenced to atmospheric pressure. When the atmospheric pressure is greater, the difference between manifold and atmosphere is lower, and the boost gauge reading will be lower.
http://en.wikipedia.org/wiki/Vacuum_gauge
Zero reference
Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other ad hoc reference. When distinguishing between these zero references, the following terms are used:
* Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure.
* Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted.
* Differential pressure is the difference in pressure between two points.
The zero reference in use is usually implied by context, and these words are only added when clarification is needed. Tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute. Differential pressures are commonly used in industrial process systems. Differential pressure gauges have two inlet ports, each connected to one of the volumes whose pressure is to be monitored. In effect, such a gauge performs the mathematical operation of subtraction through mechanical means, obviating the need for an operator or control system to watch two separate gauges and determine the difference in readings. Moderate vacuum pressures are often ambiguous, as they may represent absolute pressure or gauge pressure without a negative sign. Thus a vacuum of 26 inHg gauge is equivalent to an absolute pressure of 30 inHg (typical atmospheric pressure) − 26 inHg = 4 inHg.
Atmospheric pressure is typically about 100 kPa at sea level, but is variable with altitude and weather. If the absolute pressure of a fluid stays constant, the gauge pressure of the same fluid will vary as atmospheric pressure changes. For example, when a car drives up a mountain, the tire pressure goes up. Some standard values of atmospheric pressure such as 101.325 kPa or 100 kPa have been defined, and some instruments use one of these standard values as a constant zero reference instead of the actual variable ambient air pressure. This impairs the accuracy of these instruments, especially when used at high altitudes.
Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other ad hoc reference. When distinguishing between these zero references, the following terms are used:
* Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure.
* Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted.
* Differential pressure is the difference in pressure between two points.
The zero reference in use is usually implied by context, and these words are only added when clarification is needed. Tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute. Differential pressures are commonly used in industrial process systems. Differential pressure gauges have two inlet ports, each connected to one of the volumes whose pressure is to be monitored. In effect, such a gauge performs the mathematical operation of subtraction through mechanical means, obviating the need for an operator or control system to watch two separate gauges and determine the difference in readings. Moderate vacuum pressures are often ambiguous, as they may represent absolute pressure or gauge pressure without a negative sign. Thus a vacuum of 26 inHg gauge is equivalent to an absolute pressure of 30 inHg (typical atmospheric pressure) − 26 inHg = 4 inHg.
Atmospheric pressure is typically about 100 kPa at sea level, but is variable with altitude and weather. If the absolute pressure of a fluid stays constant, the gauge pressure of the same fluid will vary as atmospheric pressure changes. For example, when a car drives up a mountain, the tire pressure goes up. Some standard values of atmospheric pressure such as 101.325 kPa or 100 kPa have been defined, and some instruments use one of these standard values as a constant zero reference instead of the actual variable ambient air pressure. This impairs the accuracy of these instruments, especially when used at high altitudes.
Last edited by thunder550; Apr 2, 2008 at 06:27 PM.
Apr 2, 2008 | 06:24 PM
#10
The gauge references manifold pressure to atmospheric pressure. So for a given manifold pressure, you can vary atmospheric pressure and the reading on the boost gauge will change because the difference between the manifold pressure and atmospheric pressure will change. The boost gauge is relative.
The MAP sensor is absolute, meaning that it compares manifold pressure to some absolute pressure, which means that you can vary the atmospheric pressure all you want while keeping the manifold pressure the same and it will always read the same pressure.
The MAP sensor is absolute, meaning that it compares manifold pressure to some absolute pressure, which means that you can vary the atmospheric pressure all you want while keeping the manifold pressure the same and it will always read the same pressure.
At one time, my PCM, my guage and my meth controller all worked off the same digital signal from my GM MAP. All worked read the same values at the same time. All of the digital gauges I've had ran off a MAP sensor.
Just saw what you added there -- are you talking about a mechanical gauge (which would read a pressure diff)?