[BH1]

Where, in the engine, does a boost gauge measure boost pressure? How does it measure boost.

[brettman]

MAP, forced induction uses a 4 wire 3bar map. On mine the MAP (along with a vacuum/boost hose) is mounted on the rear of the blower housing, for and analog gauge.

[vhha.cl]

this hose go to the bypass actuator ??

[brettman]

No, threw the firewall to the P3 gauge in the vent.

[BH1]

Originally Posted by brettman

MAP, forced induction uses a 4 wire 3bar map. On mine the MAP (along with a vacuum/boost hose) is mounted on the rear of the blower housing, for and analog gauge.

Thanks brettman. The reason I ask is because I had my car dyno'd yesterday, as I felt like it had lost some power. Turns out I was right.

Anyway, after the run, they told me how much boost I was making. I didn't ask them at the time, as I had many other questions, but I got to wondering later how did the computer (plugged into the OBD port) know the boost pressure of my LT4 supercharger?

Is the sensor in the supercharger, as on your whipple, or is the data measured from some other location? My question is just for my edification. These things interest me.

[brettman]

Not "IN" the SC, ported to the inside, below the IC's. I understand that the OBD is just as good. I elected to use another way (analog) The plan is to see which one is more accurate (too much time on my hands..lol)
The MAP is a sensor (open to SC case) reads vacuum/pressure.
Hope that helps.
Did you find your power lose?

[BH1]

Originally Posted by brettman

Not "IN" the SC, ported to the inside, below the IC's. I understand that the OBD is just as good. I elected to use another way (analog) The plan is to see which one is more accurate (too much time on my hands..lol)
The MAP is a sensor (open to SC case) reads vacuum/pressure.
Hope that helps.
Did you find your power lose?

Don’t know what’s causing the power loss yet, as it’s making the expected boost. Taking it back next week for them to dive into it.

I believe I read that you have a P3 gauge as well. I use mine to watch the IATs. I thought, because mine isn’t wired analog, that the boost readings isn’t that accurate. I’d be interested in your findings.

[brettman]

I hear Ya, (yes/no.. opinions) I will do tests in the spring (I have snow)
Your IAT is important, just like AFR..(My tuner thought that AFR was) "A" after, "F" food, "R" rest....My Dyno sheets confirm. That is important, guys are bleeding them lean, for power.

[BH1]

Originally Posted by brettman

........ That is important, guys are bleeding them lean, for power.

Yes they are. Since I like to participate in mile events, I’m having them add LT4 injectors and fuel pump while it’s there; as a safety precaution. It’s a relatively long time, at full throttle, to be running lean.

[TJay74]

There are two types of boost readings, electrical ( the 3 bar MAP sensor) and mechanical (tapped into the vacuum line). Technically they both should provide the same information. One can always be used to check the other and make sure the one is accurate.

[SpaceCadet]

To help clarify; the two types of pressure measurement sensors are Absolute (measures atmospheric pressure and manifold pressure) and Gauge (just measures manifold vacuum/pressure)