1G Electronic Boost Data Logging

[cbatters]

Originally Posted by 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?

Logic / reasoning sounds good. However, I am troubled by the differences in the colors. The color coding I posted was straight out of the manual and I don't recall any differences when I went to hook it up.

UPDATE: Went back and checked notes / schematic and you are right about TPS, it is Green/Yellow, not Green/White. Manual says EGRT sig is LightGreen/Black but I will check this tomorrow to make sure.

I would suggest you confirm all voltages with a meter before connecting to the MAP sensor.

+5 signal from TPS sensor should +5V +/- 5% with respect to chassis/EGRT ground
EGRT Ground should be very close to chassis ground
EGRT signal should measure ~ +4.5V with respect to ground



Clint

[QuasiMondo]

When I said EGRT, I meant the connector plug for that probe. I couldn't use your color codes because they're different for DSM's. But I did check against my Chilton's manual, and performed a voltage check beforehand. As for the MAP sensor, I got that 36psi figure from what the Digi-Key receipt. Sorry for the confusion

But after looking at the instructions again, I did have the sensor wired wrong. I'm going to rewire it tomorrow and let you know how it goes.

[cbatters]

Originally Posted by QuasiMondo

When I said EGRT, I meant the connector plug for that probe. I don't know about 3SI's but for non-California DSM's they don't install that sensor, but the plug for it is there and taped off to the harness. I couldn't use your color codes because they're different for DSM's. Sorry for the confusion. As for the MAP sensor, I got that 36psi figure from what the Digi-Key receipt.

But after looking at the PDF, I do have the sensor wired wrong. I'm going to rewire it tomorrow and let you know how it goes.

1. Advise DSM colors and I will update the post to include correct wiring colors for DSM

2. 36 PSI is correct - you just need to subtract 14.5 PSI so it agrees with what most people refer to as "boost"

3. Good luck on rewiring the sensor. Not sure if hooking it up wrong will cause any damage. Quick check is to hook up +5 / Ground and look for ~1.9V out.



Clint

[QuasiMondo]

For 1G DSM's:

SIG is blue/yellow
GND is green/black
+5V on the TPS is green/red.

The plug for the EGRT probe is not connected to anything. It should be taped up to the wiring harness beaneath the intake manifold.

The 5v line is the important one. I had it tapped into the green/white wire and it caused horrible random misfires. For DSM's that green/white wire is the TPS signal wire.

I'm not worried about damaging this sensor. I planned for something to go wrong and ordered two just in case.

[cbatters]

Originally Posted by QuasiMondo

For 1G DSM's:

SIG is blue/yellow
GND is green/black
+5V on the TPS is green/red.

The plug for the EGRT probe is not connected to anything. It should be taped up to the wiring harness beaneath the intake manifold.

The 5v line is the important one. I had it tapped into the green/white wire and it caused horrible random misfires. For DSM's that green/white wire is the TPS signal wire.

I'm not worried about damaging this sensor. I planned for something to go wrong and ordered two just in case.

Appreciate your input... I will add info for DSM's and also suggest that all voltages be verified with a DVM before hooking up the MAP sensor.


Thanks,

Clint

[QuasiMondo]

No problem. I'll confirm everything when I re-wire the sensor.

[rdmelton]

Originally Posted by cbatters

EGRT Ground should be very close to chassis ground
EGRT signal should measure ~ +4.5V with respect to ground

Ok, this is right out of the manual, correct? (pg 13A-135 and 13A-136)
That means that EGRT Ground is called pin #1; EGRT signal is called pin #2

I know this will sound dumb, but do I connect the EGRT ground to the MAP sensor ground, and the EGRT signal to the MAP sensor signal? The ground to ground sounds right, but it sounds odd that you would send a signal from the MAP sensor to something that already has a voltage output (i.e. pin #2 which is already reading ~4.5V). It seems like that wouldn't work. If I hook it up the other way, then the EGRT signal goes to ground on the MAP sensor, and the MAP sensor signal gets sent to ground, or is that the place where the ECU is looking for the modified EGRT signal?

[cbatters]

Originally Posted by rdmelton

Ok, this is right out of the manual, correct? (pg 13A-135 and 13A-136)
That means that EGRT Ground is called pin #1; EGRT signal is called pin #2

I know this will sound dumb, but do I connect the EGRT ground to the MAP sensor ground, and the EGRT signal to the MAP sensor signal? The ground to ground sounds right, but it sounds odd that you would send a signal from the MAP sensor to something that already has a voltage output (i.e. pin #2 which is already reading ~4.5V). It seems like that wouldn't work. If I hook it up the other way, then the EGRT signal goes to ground on the MAP sensor, and the MAP sensor signal gets sent to ground, or is that the place where the ECU is looking for the modified EGRT signal?

No such thing as a dumb question when it comes to hooking up wiring correctly. (And thanks again for the heads up on my wiring color error.)

EGRT input has 10K ohm resistor to +4.5V to provide excitation for the EGRT sensor. This is why the logger will show the count at ~229 counts or 90% of full scale before you conect anything to it. (If your connect the EGRT signal to EGRT ground it will go to zero.)

The MAP sensor has sufficiently low output impedance (referred to as sink current) that the 10K pullup on the EGRT input introduces less than 1/4 LSB (near zero) error. (If you were a zealot you could open up the ECU and attempt to find the pullup resistor but it would be a waste of time and you would never see the difference on the logger - and you might screw up your ECU!)

I'll add this info to the FAQ.

Make sure to post when you "Got Boost!" (Boost logging is pretty slick - even better after I added Peak/Hold to MMCd.)


Clint

[tfw a-ok]

I use the sensor for boost measurement in a custom LED instrument cluster display. I works great and should measure all the way up to about 20-21 psi.

Ceck out my Custom LED Boost Gauge

[cbatters]

Updated the info at start of thread. Let me know if there are any errors or if you have any installation pics you think would be useful to include.


Clint