boost gauge help, aem digital gauge Options

[garin]

i have a 2nd gen 3sgte swapped in a 1995 celica. i installed an aem digital boost gauge. i have the gauge grounded properly an the positive side is connected to the radio fuse. i tried tapping into to locations to get a vacuum reading. first the map sensor line and second on the timing belt side of the the engine, on the intake manifold. i get wrong readings in both cases. i check the aem pressure sensor and everything checks out fine. any suggestion, or wisdom is greatly appreciated.

[match220]

i have a 2nd gen 3sgte swapped in a 1995 celica. i installed an aem digital boost gauge. i have the gauge grounded properly an the positive side is connected to the radio fuse. i tried tapping into to locations to get a vacuum reading. first the map sensor line and second on the timing belt side of the the engine, on the intake manifold. i get wrong readings in both cases. i check the aem pressure sensor and everything checks out fine. any suggestion, or wisdom is greatly appreciated.

you shouldn't tap into the map sensor line. The map sensor needs a dedicated vacuum source to output the correct voltage to the ecu based off of the pressure. Most things that connect to vacuum will have a pressure sensing disk thing or shifting diaphragm that will change the vacuum/boost on the map sensor(or boost gauge), and thus change the voltage reading that the map sensor outputs based off the vacuum/boost. I'm not saying that this is the culprit for your incorrect readings on your boost gauge, but it does need a dedicated line to get the most accurate reading.

This post has been edited by match220: Mar 30, 2013 - 10:49 PM

[garin]

yea i switched it to the other side of the intake manifold.

[match220]

yea i switched it to the other side of the intake manifold.

in theory, the center of the intake manifold is supposed to output the most correct reading since it is equally affected by all cylinders, I don't have a way to test that, but it makes sense. I have my map running off the side because I'm about 1 foot short of hose, but I plan on moving it to the center. I believe the 5sfe had the map sensor hose going into the manifold close to the center, and I found a nipple on the center-bottom-rear of my gen3 3sgte manifold that was the same size of the map sensor manifold port...since I bought the engine in parts I don't know what went there though. Since the boost gauge is just for looking at and not for the computer to read I would put it on it's own vac source near center.

You could always drill and tap a 1/8 npt threaded hole and put a new nipple on, just connect an air compressor line to an open vac port and have a friend blow puffs of air out every couple seconds so you don't get aluminum in the engine.

This post has been edited by match220: Mar 30, 2013 - 11:08 PM