2011 Nissan Xterra

[AndreyB]

MAF wire reports 0.4v engine off, 1.4v on high idle

1.4v is 25 kg/hours how is that for a 4L engine?

Internet says "Idling uses up to ½ gallon of fuel per hour" so a bit over a kilo of gas so 25kg of air is possible?

[mck1117]

25kg/h is 7g/s, which is very reasonable for high idle.

You can read airflow over OBD2, right?

[AndreyB]

You can read airflow over OBD2, right?

I've played with torque via BT and it was refreshing like only once per 30 seconds and showing two very different MAF values in two different MAF gauges. But yes "7" was one of the values displayed, the other one was 500 I think

Do not have any good PC software for my OBDLink SX USB cable.

[AndreyB]

I need to start eating my dog food right?

Tune with MAF calibration from internet https://rusefi.com/online/view.php?msq=1288
Repetitive cranking log just for history attached since https://github.com/rusefi/web_backend/issues/190

[AndreyB]

Wow! No wideband ever, with that random MAF calibration and no tune it revs pretty nicely! I would appreciate any guess for acceleration enrichment calibration.

[AndreyB]

This 2011 vehicle uses a 2003 model year ECU does it? With only 20ish unique CAN IDs on the CAN bus it looks like TCU integration is extremely basic. I've just driven three feet and it's just OK, not like on the 2006 Passat which seem to insist on torque model.

[AndreyB]

Reinventing the bicycle of CAN decoding, some basic automation at https://github.com/rusefi/can-log-tools

Step one: took five PCAN traces with different scenarios https://github.com/rusefi/rusefi_documentation/tree/master/OEM-Docs/Nissan/2011_Xterra/CAN-Nov-2022

Tool counts number of unique values at each SID each offset, tool compares such report between each pair of files in specified folder.

So for instance different in unique values count between "engine off" and "let me play with pedal while TPS is unhooked"

Comparing ignition-on-engine-off-new-pcan.trc and ignition-on-engine-off-with-pps-removed-tps-pcan.trc
573/0x23d_byte_1_bit_8: 1 vs 227
561/0x231_byte_2_bit_16: 1 vs 185
561/0x231_byte_4_bit_32: 1 vs 25
2/0x2_byte_4_bit_32: 31 vs 26
670/0x29e_byte_7_bit_56: 4 vs 9
721/0x2d1_byte_5_bit_40: 9 vs 4
640/0x280_byte_6_bit_48: 7 vs 2
573/0x23d_byte_0_bit_0: 4 vs 8

Next tool creates an MegaLogViewer log of each byte individually, let's look at these top three bytes.

Nice

0x23D byte 1 is PPS 0 to 255
0x231 byte 2 is same PPS 0 to 200

What is that white line 0x231@4 which goes down once I release pedal? Need to try a different pedal action pattern.

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[AndreyB]

Now with TPS connected

Comparing ignition-on-engine-off-pps-tps-pcan.trc and ignition-on-engine-off-with-pps-removed-tps-pcan.trc
574/0x23e_byte_2_bit_16: 253 vs 3
574/0x23e_byte_6_bit_48: 253 vs 3
573/0x23d_byte_2_bit_16: 140 vs 2
573/0x23d_byte_1_bit_8: 255 vs 227
670/0x29e_byte_0_bit_0: 24 vs 2
561/0x231_byte_0_bit_0: 24 vs 2

0x23e_byte_6 TPS
0x23e_byte_2 inverted TPS
0x23d_byte_2 TPS capped at 50%?

I like my little toy tool.

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[AndreyB]

Let's compare idle with MAF sensor with idling without MAF sensor

Comparing unique value count per byte idling-pcan.trc (duration=39secs) and idling-without-maf-pcan.trc (duration=18secs)
573/0x23d_byte_5_bit_40: 230 vs 63
574/0x23e_byte_3_bit_24: 230 vs 63
563/0x233_byte_1_bit_8: 174 vs 29
595/0x253_byte_6_bit_48: 211 vs 73
505/0x1f9_byte_3_bit_24: 124 vs 37
573/0x23d_byte_3_bit_24: 124 vs 37
563/0x233_byte_4_bit_32: 124 vs 37

Does not look like either of those is raw MAF, those look like different RPM values. Also looks like I should make all log files more or less same length or maybe programmatically compare same duration.

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[AndreyB]

I am too old to scan for counters with my naked eye so https://github.com/rusefi/can-log-tools/commit/75b130547601d6dcbc4cda2b919a7c3f3fa53b21

Found Counter{start at {2/0x2, byteIndex 4, bitIndex 0}, totalNumberOfBits 4}
Found Counter{start at {573/0x23d, byteIndex 0, bitIndex 5}, totalNumberOfBits 2}
Found Counter{start at {593/0x251, byteIndex 5, bitIndex 6}, totalNumberOfBits 2}
Found Counter{start at {595/0x253, byteIndex 0, bitIndex 0}, totalNumberOfBits 2}
Found Counter{start at {644/0x284, byteIndex 7, bitIndex 0}, totalNumberOfBits 8}
Found Counter{start at {645/0x285, byteIndex 7, bitIndex 0}, totalNumberOfBits 8}
Found Counter{start at {721/0x2d1, byteIndex 3, bitIndex 0}, totalNumberOfBits 2}
Found Counter{start at {1783/0x6f7, byteIndex 7, bitIndex 0}, totalNumberOfBits 2}

[AndreyB]

Let's glance at SID 0x23D

White line on top is known to be RPM. Yellow and red are interesting more multiple reasons:
* those jumps from 0 to 255 tell us that it's a two byte field, the behavior of the red line clearly confirms that. I can automate filtering of such cross-overs
* those small jumps on the yellow line, what do these tell us? does this smell like computed, not measure value? as in commanded fuel or torque approximation?

How wild should I go with charts? An individual chart for every bit? Definitely a chart of each two consecutive bytes together.

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[AndreyB]

0x23D bytes 3 and 4 being RPM is common knowledge. https://www.drive2.ru/l/558846302222287264/ suggest wheel speeds at 0x284

Cute fact: order of bytes in these two packets is different?! Well, I guess I should not be surprised considering packet 0х233 has two bytes of RPM as bytes 4 and 7. Yes, a two byte value with two bytes of random shit between bytes.

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[AndreyB]

Acceleration and driving at 20mph with gear selector in "1"

top line RPM, bottom line is wheel speed or output shaft speed

Question: does middle line look like torque?
Vehicle is 4200 lbs/1900 kg, speed is 20mph/32kph white line says 300ish

engine RPM is 3000

Google points me at "When traveling on level roads at constant speed, most passenger cars need only about 20 hp or so to overcome rolling friction and air drag

Reference: https://www.physicsforums.com/threads/how-much-power-does-my-car-actually-need-to-maintain-speed.803219/"

HP = Torque x RPM ÷ 5252

20 = Torque x 3000 / 5252


So when traveling on level roads at constant speed I need 35nM of torque? is that 300ish scaled at 0.1 giving me 30nM to roll at 20mph in a large tall square truck-based compact SUV? LOL *compact*.

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[AndreyB]

Fun fact: Marussia is a vehicle with FWD VG35 and Aisin automatic transmission!

Renault Vel Satis Aisin aw55-50sn

[AndreyB]

Yep.