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Barometric Compensation Reading....WHEN?

Started by freudie1, October 15, 2019, 04:54:53 PM

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freudie1

Hello all,

I'm trying to discern the facts in regards to the Delphi ECU on a Vrod (the more modern of the two that incorporates O2 sensors that is) and barometric pressure sensing.  Hear me out:

I know that these bikes have a single pressure sensor (the MAP sensor) and that it's a 1 bar map sensor.

With that being said, it appears the ECU will read the MAP sensor at key on/engine off to sample the ambient/barometric pressure.  This of course is a variable used in the AFR equation to determine how much to command (IPW) from the injectors.

So...........THE QUESTION:

Does anyone know FOR SURE (as in has seen a document stating as such, has internal knowledge, was part of the Delphi dev team....) WHEN the ECU uses the MAP sensor output voltage as a barometric pressure reading?

Case in point, I have "heard" the following:

"All the time!".

"Only at key on/engine off"

"Key on/engine off, low load, and WOT"

Which is it!?  I can prove that it's key on/engine off with a multimeter in seconds, however the other conditions?  I'm about to take a bike to the base of a mountain pass (I have such access being a north westerner), turn off the bike, turn it on, get a reading, then ride to the top of the mountain pass.  IF (big IF) the ECU ONLY reads at key on/engine off I would expect my overall AFR reading from my widebands (I use the PowerVision with the TargetTune module so I can see and log actual AFR readings) to get richer as I go up the pass (read:  less air, but the ECU would not know it in this scenario assuming it only samples baro pressure at engine off condition).  Conversely IF this is the only case then I could do the same at the top of the pass (turn engine off/on) and expect the mixture to go leaner as I go down the pass.

MUCH appreciated any facts that can be shared/discerned here as I'm trying to finalize this puzzle (think replacing a 1 bar with a 2 bar sensor and scaling tables....and YES I know about the voltage differences between 1 bar and 2 bar at ambient...).




Pirsch Fire Wagon

Short Answer is ALL THE TIME. BUT, both are used.

----------------------------------------------------------------

FYI ......

KOEO: it compares stored data to current environmental data (real time) and selects either Stored Data or Default DELTA based on the difference between the two to begin the monitoring process.

KOER: it continually monitors and adjusts based on Environmental Conditions but begins the process based on the above.

----------------------------------------------------------------

IF YOU'RE BOARD.....

All Speed Density work the same. Delphi is a Speed Density System Harley-Davidson has had two. The recent  is used on all vehicle since 2005 (IIRC) when Oxygen Sensors were used (Closed Loop)

The Delphi is a "Speed Density System". MAP sensor data is converted to "air mass data by using a second variable coming from an IAT Sensor." Engine speed (RPM) is also used to determine where on a look up table to determine fueling Hence, the "speed-density method."

The MAP Control (Three Wires 12v Power, Ground, and 5vRef). The 5vR changes based on Altitude, IAT, and RPM. Basically, it requires 0.20 -  0.30 to change the "Fuel Table Look Up" based on Elevation.

Fuel Table Look Up  = DELTA +/- Altitude +/- IAT + (RMP)

Fuel Table Selection = DELTA +/- Altitude +/- IAT + (RMP) +/- O2

Using a DVOM, Scantool or similar will display a Voltage. This is useful but a poor way to monitor the MAP as changes may be minimal i.e. .01 - The easiest, most effective way to monitor is using Bar Measurement; connecting a Pressure Inducer to a Gauge. One BAR = 100 kilopascals. As a unit of measurement it changes when the MAP changes its Signal and is much easier to determine differences based on altitude. If your logging data for review, the Voltage will provide a more usable Graphing.

IF YOU'RE REALLY BOARD.....

The Oxygen Sensors,  use the MAP Data (sort of).

These sensors use Temperature to determine Fuel Mixture, subsequently, the Reference Voltage determines the Fuel Table Look Up. Based on the MAP, and the +/- of the Oxygen Sensor (usually "5" is the DELTA (-5 to +5)) on Narrow Band) the ECU determines the final Fuel Table to be used. This is Short Term Fuel Trim, as it gathers data it stores (ECM) based on pre-determined history – Long Term Fuel Trim – this is what is used every time the Engine is Started based on the last stored data to begin with. If it's out of range because of a failure the ECM uses a default Fuel Table in lieu  of the data.

Harley-Davidson has used two of the three types of Oxygen Sensors since the introduction of the Ca compliance.

This gets a little complicated because in actuality, they're all "Narrow Band" even though one is referred to a Wideband.

Those are: zirconia O2 sensors, Titania O2 the narrowband lambda sensor (or O2 sensor) can only determine three types of mixtures in the exhaust gases.

If you have Wide Band O2 sensors 'narrowband' lambda sensor is generally 'wideband' lambda sensor.

Harley-Davidson has used two of the three: Zirconia type of air fuel ratio sensor. It comes in two types - Heated and unheated (Closed Loop). This is where you will see the First Gen has only two wires and the later has Four Wires. The non-heated (Bar Type) are poor at measuring at idle or high heat. Therefore, being replaced with the Heated to compensate and improve readings at idle and extended hot periods.

My Head Hurts.


Tom

freudie1

Quote from: PIRSCH FIRE WAGON on October 16, 2019, 05:08:52 AM
Short Answer is ALL THE TIME. BUT, both are used.

----------------------------------------------------------------

FYI ......

KOEO: it compares stored data to current environmental data (real time) and selects either Stored Data or Default DELTA based on the difference between the two to begin the monitoring process.

KOER: it continually monitors and adjusts based on Environmental Conditions but begins the process based on the above.

----------------------------------------------------------------

IF YOU'RE BOARD.....

All Speed Density work the same. Delphi is a Speed Density System Harley-Davidson has had two. The recent  is used on all vehicle since 2005 (IIRC) when Oxygen Sensors were used (Closed Loop)

The Delphi is a "Speed Density System". MAP sensor data is converted to "air mass data by using a second variable coming from an IAT Sensor." Engine speed (RPM) is also used to determine where on a look up table to determine fueling Hence, the "speed-density method."

The MAP Control (Three Wires 12v Power, Ground, and 5vRef). The 5vR changes based on Altitude, IAT, and RPM. Basically, it requires 0.20 -  0.30 to change the "Fuel Table Look Up" based on Elevation.

Fuel Table Look Up  = DELTA +/- Altitude +/- IAT + (RMP)

Fuel Table Selection = DELTA +/- Altitude +/- IAT + (RMP) +/- O2



First, did you quote that from somewhere or did you type that from scratch (thank you either way!).

Second,

The "Altitude" variable is the real question.  No offense implied, but I fail to believe that the ECU uses the MAP sensor "all the time" to determine this (however I do know and agree that it uses the MAP sensor all the time to read pressure in the manifold to input for purposes of determining the actual load/air entering the engine).

Hear me out:

IF the ECU was to use the MAP sensor output (as you stated "5vR"/5 volt reference) for ALTITUDE (i.e. barometric pressure) "all the time" the why would there be a need to read the baro pressure (the 5vR value) at KOEO)?  There wouldn't be.  The reason the ECU (at a minimum) reads and stores that value as "altitude" is that is one of the few times you can use the MAP sensor (once again we do NOT have a dedicated pressure sensor for determining the ambient pressure, rather we have the share the MAP sensor) for reading ambient air pressure. 

Other places I am aware that you COULD potentially read the MAP sensor to determine ambient air pressure:

Idle:  My airflow formulas show you can assume idle MAP readings are about 1/3 of actual ambient pressure.

WOT:  In a naturally aspirated engine at WOT theoretically you would be measuring atmospheric pressure (can't really exceed that in NA of course).

So, once again...are you SURE it really uses the MAP sensor 5vR for determining the "altitude" variable in the above equation "all the time"?  I'm not convinced, but admittedly I'm looking for information and logic behind this (which was the point of my original post).

Thank you VERY much for the time you spent replying!

freudie1

Can't edit.

One more data point.  The ECU (at least on the Vrod) is a hybrid system.  For VE it measures tps vs rpm (alpha-n) and for AFR and Spark it uses pressure vs rpm (speed density as it uses a MAP sensor to determine pressure).

So with that being said, indeed I need to know for certain what events will result in the ECU using the 5vR value from the MAP sensor as the "altitude"/barometric pressure value. 

More thoughts....if it really uses that value all the time to continually (realtime) update the altitude variable I can't wrap my head around how that value would be of any validity beyond the three conditions I mentioned above.  Case in point, the 5vR value at mid load range would be complete garbage (unless there is an interesting formula to offset the value back to ambient values) for purposes of baro reading.  NOW....knowing that indeed the ECU knows what RPM we are at, what would make more sense to me is that it uses the RPM value to determine WHERE in the scenarios book (if you will) we are at.....i.e.  RPM < 1000?  Engine off, key on!  Read.  As for WOT...well we have TPS, so perhaps TPS = 100%?  Read!

Hope I'm making sense, but something smells rotten in Denmark and I just need to get my head around this.