6G Celicas Forums

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.

Use any nipple from the intake manifold. What do you mean wrong readings? What are you comparing it to?

it reads 22 psi at idle... not 22 inhg. im thinking it is a constant voltage issue? the gauge calibrates itself each time the key is clicked.

It's an electronic boost gauge? (I mean with the sender?) That's why I like the mechanical ones, it's probably a faulty sender or a bad connection somewhere. Check them pesky grounds.

i suppose that is good advice. only got this one to match my aem wideband.

still no luck when the car is on, but not running it reads 35 on the sweeping light display and 0 on the digital display. when the car is on it reads 22psi at idle...

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

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

but would that cause the gauge to read 22psi at idle?

are you sure it's psi and not kpa? my car is 33 kpa at idle according the the autronic display. If your aem boost gauge is like my aem wideband gauge (which I want to sell if anyone is interested) it has a selector switch on the back where you can change the output to the gauge display or to the aftermarket ecu that you are running

there is no selector switch on the back.

i figured it out. i used the ignition fuse for power. i just uninstalled everything and rewired it. everything works now. power has to be constant, because the gauge calibrates itself at each key turn. not sure if im s fan of these gauges.

This post has been edited by garin: Mar 31, 2013 - 8:18 AM

My aem wideband controller/gauge is the same way. I had it wired to a ignition switched power source and it takes a couple seconds to come on before it shows the a/f ratio, so now I turn it on before I turn the car on. I like certain things about it, but I have my eye on another one that has signal and signal ground output wires for aftermarket ecus. The output of mine is inaccurate without the signal ground.

these gauges seem to be nice, but quirky at the same time.

yeah, I like the look. But as a high quality wideband meter it sucks. I never thought of AEM being incredible, just something that gets the job done, their aftermarket ecus have a lot of dumb tuning flaws but can still be worked with by AEM tuners that know how to work with them. The wideband meter has a signal out, but since it doesn't have a signal ground output then aftermarket ecus cannot accurately determine the voltage output of the sensor. The more expensive wideband controllers output a signal positive and a signal negative. It isn't a big deal on the gauge, the gauge displays an accurate reading since it reads a positive and negative signal from the wideband sensor, and the data log output will be accurate, but the signal output to the ecu is wrong. My autronic reading is always +/- 1 on the air/fuel gauge depending on whether or not I have the headlights on. Also, since i'm running individual coils on my engine, they will pull more electricity at higher rpms, further affecting my air/fuel ratio by changing the overall voltage. It is irritating that the AEM wideband controller is made so crappily. It seems that the signal output is only a selling point and not really a fully functional unit. Again it works great when not feeding my autronic, but sucks on a car that requires accuracy.

I would imagine that the boost gauge is made with the same "love and care" and has flaws of its own.

Sounds like you just didn't read the instructions!

the instructions sucked lol.

for future reference, almost all digital/electrical gauges need to be on a constant 12V source. something that does not get turned off when you turn the key to start.

i know. i powered it to to radio fuse... didn't work, so i went off of the ignition.

Hello friends...Hey any1 can help me on an st205 stock engine...Where should i connect my boost gauge vaccum line on the inlet manifold?????, i'm not using charcoal canister ..any1 plz? send me some pics or explain briefly plz

This post has been edited by chrismru: Apr 16, 2013 - 1:23 AM