1G Electronic Boost Data Logging

[Roybatty]

Originally Posted by DoctorDex

I never ended up trying it. I found a GM sensor for a good price, so I just used it instead. However, I am looking at revisiting this idea no that the GM sensor has crapped out on me.

Badass' post #102 is pretty clear - but thought you would have tried it by now - and gotten past all the mistakes I am about to make Also could not find data identifying bar range of DSBC. Surprised you didn't do it - seems going with the GM sensor while already having an EBC is being a glutton for extra work.

I will attempt it within the week and let you know how it works out.

[Roybatty]

This didn't work out for me yet - I need to check on my wiring. I attached the EGR light green input wire to the white wire between the solenoid and blitz control. Set the scanmaster expanded mode to allow EGR input retrieve boost data and data subsititution egr to boost, and the scanmaster only shows 23.2 the entire time its on- no matter what boost the blitz shows.

[bjmsam]

Originally Posted by Roybatty

the scanmaster only shows 23.2 the entire time its on- no matter what boost the blitz shows.

That's about what my MirageCorp Hybrid logger reports when the EGR temperature probe is connected to the EGRT port. You did disconnect it, right?


My first-gen AVC-R (installed in 1997!) uses a Denso 3 bar MAP sensor with 5 VDC output (DPS-310-2000A 949940 6270 5V, blue wire is signal), but it apparently represents vacuum and pressure at voltages slightly higher than the sensor(s) for which the MirageCorp Hybrid logger is calibrated. For example (voltmeter = AVC-R display = datalogger display):

Ignition on, engine off
2.08 VDC = 0.00 kg/cm^2 = +4.86 psi

Warm idle
1.10 VDC = -485 mmHg (-9.36 psi) = -3.7 psi

AVC-R limiting boost
0.8 kg/cm^2 (11.38 psi) = 15.4 psi
0.9 kg/cm^2 (12.80 psi) = 16.6 psi
1.0 kg/cm^2 (14.22 psi) = 17.8 psi
1.1 kg/cm^2 (15.65 psi) = 19.0 psi

Here is a chart representing all of the data I collected:



So this Denso sensor's range for positive boost is 2.079 - 5.0 VDC while the hybrid logger software seems to expect more like 1.52 - 5.0 VDC.

z = voltage logger expects at zero boost
s = scaling factor

At zero pressure, my sensor outputs 2.08 VDC and the logger displays 4.86 psi.
(2.08 - z) * s = 4.86
s = 4.86 / (2.08 - z)

Under warm idle vacuum, my sensor outputs 1.10 VDC and the logger displays -3.7 psi.
(1.10 - z) * s = -3.7
s = -3.7 / (1.10 - z)

4.86 / (2.08 - z) = -3.7 / (1.10 - z)
4.86 * (1.10 - z) = -3.7 * (2.08 - z)
5.346 - 4.86z = -7.696 + 3.7z
8.56z = 13.042
z = 1.52


Anyway, unless someone has a better idea, I'm adjusting offset and scale (translating 4.8 - 19 to 0 - 15.65) as follows:
(logged boost - 4.86) * (15.65 / (19 - 4.86))
(logged boost - 4.86) * 1.1068


BTW, one side of a slightly collapsed female crimp connector slips snugly over the pin:

[itismike]

Hi Jim,

I may have missed something, but what are you calibrating the logger against?

I see the 'Engine off' state, and I suppose you could note the barometric pressure in your driveway at the same moment to get one datapoint, but where's your second 'known value' in the scale?

Seems like you'd need a stable (non-fluctuating) vacuum source with an external vacuum gauge to provide the next datapoint.

-Mike

[bjmsam]

Hey Mike,

I've been wondering about the influence of barometric pressure as well. The gauge on my boost controller does not always read 0.00 with the engine off, but it did both yesterday and today. My weather station currently reads 1036 hPa, which is 15.02591 - 14.50377 = 0.52214 psi high. I can't calibrate the boost controller or the logger; all I've done is compare the pressure displayed on the boost controller to the pressure displayed on the logger and come up with a translation function to apply when I get home.

[itismike]

Hi Jim,

That's interesting too, but that's not what I mean. It seems like you are trying to come up with a formula to apply to the voltage readouts on your logger that will translate into accurate pressure/vacuum numbers. It also seems that the sensor you're grabbing the data from is providing data at a different scale from the sensor you were using previously.

What I'm suggesting is to calibrate your scale (using math - I understand the gauge isn't adjustable.) You know the voltage readout at atmospheric pressure (1036 hPa a few minutes ago), but I don't see where you're checking the gauge against a second datapoint (preferably at the other extreme - near full vacuum.)

This would give you a volts/hPa scale for the new sensor, completely bypassing any error introduced by previous sources.

Just my .02,
-Mike

[bjmsam]

I am able to measure voltage only while the car is at rest, but I tried to record enough samples (plotted in blue) to verify that they are interpreted as expected (the ECU converts the sensor output to an 8 bit number (0-255) which the logger looks up in a linear table to report pressure). All of the pressure datapoints I collected are plotted in yellow and range from full vacuum (where I could glance at the gauge and logger and jot down the values) to full boost (where I could set the limit and know the gauge reading for later comparison with the logs). None of the data is adjusted to account for baro since I don't know whether the readings are absolute or relative.

[netmechanic]

Anybody know an updated source for this?

http://rdmelton.autoeducation.com/ca.../boostlog.html

[bjmsam]

I found it here via this archive service.

[netmechanic]

Thanks!