1G Electronic Boost Data Logging

[BLACK94TT]

Originally Posted by cbatters

The ground lead of A22 is ECU Signal Ground. You don't want to tie Chassis ground to Signal ground at the MAP sensor because it would create a ground loop. (Chassis ground and Signal ground should only be tied at one point which in this case is at the ECU.)

Low power instrumentation like A/F and Boost meters should be connected to signal ground. Incorrect ground reference of an A/F meter for example, could cause your A/F to change everytime you step on the brakes or turn on your blinkers.



Clint

That's good stuff. Sounds like you do this for a living. I just PM'd you with my results from hooking up the Autometer boost gauge MAP sensor to A-22. Also included is the info you were asking for.

[cbatters]

Originally Posted by BLACK94TT

That's good stuff. Sounds like you do this for a living. I just PM'd you with my results from hooking up the Autometer boost gauge MAP sensor to A-22. Also included is the info you were asking for.

You are right - I have been involved in instrumentation for many years. Automobile just happens to be a particularly harsh/hostile/noisy environment for making analog measurments. Compounded by the fact that all of the inputs to the ECU are single ended which simply means that measurements are made with respect to ECU ground so where you "ground" sensors / gages is critical.

Next time you are crawling around under your dash, you should connect all of your gage ground connections to the ECU signal ground.



Clint

[QuasiMondo]

I hate to bring up an old thread like this, but for the folks using the DigiKey chips, how has that chip worked out for you? I installed it for my DSM, and I haven't been able log anything higher than 15.9 psi. I was just wondering if I had hit the limits of my chip, or if it's an issue related to the MMCD software.

[skunkworks]

I have been using the digikey 2.5 bar sensor. I am stock so I don't boost anything over 14-15 on purpose. I have seen spikes to 18 when I had some problems with my mbc. It should go to 21 or so psi no problem.

I would make sure you have mmcd set up to read a 2.5 bar sensor - mmcd defaults to a 3 bar sensor.
sam

Originally Posted by QuasiMondo

I hate to bring up an old thread like this, but for the folks using the DigiKey chips, how has that chip worked out for you? I installed it for my DSM, and I haven't been able log anything higher than 15.9 psi. I was just wondering if I had hit the limits of my chip, or if it's an issue related to the MMCD software.

[cbatters]

Good input from Samco, one of the "Early Adopters" of boost logging (although I did the math and am not sure that you can explain a reading of 15.9 PSI based on selected the 3.0 bar scaling. 15.9 PSI on 3.0 bar scaling = ~10.8 PSI on 2.5 BAR scaling)

Please confirm that you have selected the 2.5 BAR from the configuration menu. (There is also an option for displaying the EGRT signal as 0-5V that would eliminate any confusion.)

Another quick test is to advise what pressure you are seeing with engine off and and warm idle.


Clint

[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.

[skunkworks]

My picture is correct. pin 1 is the right most pin looking at the front of the sensor. It is the pin with the notch in it. That is probably your problem. It is kind of odd because I am used to pin 1 being the left most pin on most IC packages. With the engine off and key on it should measure 0 psi. and remeber that the 36.3 psi rating is absolute pressure - you need to subtract 14.4 to convert it to guage which gives you around -14 to 21psi range. Idle should be around -13 to -14 or so.


cbatters - I agree with your assesment. Just didn't want to post it because I wasn't sure if I would be talking out of my ass.


sam

[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.

[cbatters]

Originally Posted by samco

cbatters - I agree with your assesment. Just didn't want to post it because I wasn't sure if I would be talking out of my ass.

sam

Sorry for the duplicate post... Samco was typing faster than I was. Further, I have never seen Samco talking out of his ass...

Like Sam the man said, probably a wiring error...



Clint

[rdmelton]

I have read about boost logging for a while, and now that my engine is back together, I am about to attempt it. I purchased the MSD 3 bar MAP sensor from summitracing.com (under $60 shipped), but it's on backorder until 8/4. so anyway, I decided to go ahead and look at the wiring for it in the mean time. It appears that the wire colors aren't the same on my car (93 Stealth TT), but that's not surprising, because I've found many differences in wiring colors between different years/models. So being not electrically inclined, I wanted to confirm the wiring so that I hopefully won't screw anything up.
I believe that the 5V signal is pretty straightforward: it is PIN #1 as identified in the 3/S repair manual, correct? (the uppermost wire when it is connected to the TPS) FYI: I checked this in the manual to make sure, and on my car the color is green/yellow, not green/white as you stated.
For the EGRT signal and ground, the wire colors on mine are white/black and black. I believe that the white/black is PIN #1 as identified in the manual, and the black is PIN #2 as identified in the manual. So I'm assuming that PIN #2 is the wire that needs to be connected to ground on the MAP sensor, and that PIN #1 is the signal from the MAP sensor?
Is that right?