[cbatters]

Couple thoughts...

1. Sorry for being ambiguous about one of the cases that I need you to measure. Please advise logger reading with ignition on and logger on but with engine not running. (Cannot be -14 PSI)

2. Motorolla 4250 sensor is a 2.5 BAR MAP sensor that can measure up to 36.2 PSI absolute pressure = 21.75 PSI of boost. A reading of 23.2 PSI implies a max voltage of 5.00V with scaling set for the 2.5 BAR sensor. However, the MAP sensor is not supposed to put out more than ~4.8v

3. Please review wiring at beginning of post. (Not sure what you are referring to as EGRT "gage" connections in Chiltons.) Good starting point would be to check voltage on pins 1,2,3 with ignition on but engine not running you should see ~1.9V output. (assuming you are somewhere near sea level.)

No need to check for boost if you don't see a pressure of zero before you start the engine and -10.5 PSI at idle.

4. Pin 1 has a bump on the lead.



Clint

Originally Posted by QuasiMondo

With the engine off, it reads -14 psi. At idle it reads -7.9 psi. I did some 3rd and 4th gear runs, going to full boost, but when I looked at my logger, it showed a peak reading of 23.2 psi. I logged the 0-5V for the sensor, and anything past 10 psi on my boost gauge maxed out my logger.

There's only three things I can think of:

1. Bad sensor. Or at least I wired it in wrong. I checked my chilton's manual, to make sure I have it wired up to the egrt gauge properly, but I wonder if I have the sensor wired correctly. The instructions show pins 1, 2, and 3 as the ones used by the sensor, but when I looked back at the picture Samco took of his setup, it looked like pins 4, 5, and 6 were the ones he used. Different chips, or was the picture taken with the sensor flipped upside down?

2. Bad gauge. Or at least bad tubing. I have an autometer gauge and I used the nylon tubing the gauge came with. I'm going to eliminate that possiblity by replacing it with a 1/8" rubber hose.

3. Wrong sensor? I checked the receipt, and it's supposed to be good up to 36 psi. But if it is and I'm maxing this thing out, that would mean that I'm pushing over 36 pounds of boost! I have my doubts about this theory since my engine is still in one piece, though I did log 19 counts of knock.

Any ideas? I'll let you know what happens when I replace the hoses for my boost gauge.