GPEC2A - Sensed MAP vs. Calc MAP

[Stoopalini]

2023 Dodge Durango R/T with TnG Package
Gen 5 Whipple 3.0L
MAP sensor part number: 53010887AA

As far as I can tell, this Mopar MAP sensor is the OEM 3bar TMAP sensor included in 2021+ Hellcats. I believe the profiling data is:

• Slope: 61.05
• kPa offset: 7.00
• Voltage offset: 0.1001v

At least this is what I see in a stock 2021 Hellcat Durango tune file and is what Whipple's canned tune had.

I have found conflicting information showing the following though:

• Slope: 61.85
• kPa offset: 6.80
• Voltage offset: 0.1001v

I have tried both, as well as a variety of mixing the slope and kPa offset values from each, and nothing I do will make the Sensed MAP and Calculated MAP be equal with KOEO. Everytime I try different values, both the Sensed and Calc MAP values move in the same direction, around the same amount, always having a delta around 12 kPa.

Shouldn't these two channels read the same value (and match barometric) with key on engine off? Another strange observation is the sensed MAP reads higher during the real-time scanning than it shows in the data after collection.

In the attached KOEO log, if you zoom way in and look at the sensed MAP for the 1st millisecond, it's reading 121 kPa. This is what was showing on the screen the entire time the scanner was polling. The log shows Sensed MAP as 109 for the rest of the KOEO log even though in real-time the screen showed 121 while scanning. The calculated MAP reads 97 kPa throughout the log.

MOD94_KOEO_Log.hpl

The tune for that log had:

• Slope: 61.05
• kPa offset: 6.80
• Voltage offset: 0.1001v

Here is the tune file: MOD94.hpt


The barometric pressure where I live is 101 kPa, or 14.6 psi. The MAP sensor registers a voltage of 1.58v with KOEO.

So using y = mx + b ... where y is the map value, m is the slope, x is the voltage, and b is the offset...

• y = (61.05 * 1.58) + 6.80
• y = 103.259

This doesn't match up to my local barometric, nor the sensed MAP value, nor the calculated MAP value though. So it makes me question the profile data. Even if I use 7 kPa as the offset, I still get a result of 103.46.

So then I tried accounting for the voltage offset to see if it would match, but I'm not sure if the voltage offset would be a positive or a negative modifier. So I tried both:

Positive Modifier:

• y = (61.05 * (1.58 + 0.1001)) + 6.80
• Y = 109.37

Negative Modifier:

• y = (61.05 * (1.58 - 0.1001)) + 6.80
• Y = 97.14

It appears if I apply the voltage offset as a positive modifier, the result matches the Sensed MAP.
But if I apply the voltage offset as a negative modifier, the result matches the Calculated MAP.

I'm currently on Beta version 5.1.3003. Am I doing something wrong here in the math, or am I seeing an issue VCM has with the way it is deriving the Sensed or Calculated MAP values? Maybe there's a bug where one of the MAP calculations are using the reverse sign for voltage offset?

Any help or input in why my Sensed and Calc MAP values are not matching with KOEO would be greatly appreciated.

Maybe I have a bad MAP sensor? It was included in the Whipple kit, which is only a few months old ... but maybe it was DOA?

[N2speed]

Try logging with PID MAP Hi-Res

[Stoopalini]

Try logging with PID MAP Hi-Res

It's in there ... it tracks the calculated MAP value

[Stoopalini]

I guess I could try zero'ing out the voltage offset and testing with KOEO, to see if the Sensed and Calc MAP readings line up. If they do, then it would appear VCM has a bug in one of the calculations

[Stoopalini]

So with zero offset, Sensed MAP and Calc MAP both increased

Zero_v_offset.JPG

Have I by chance selected the wrong Parameter in the chart to represent Sensed MAP?

Sensed_MAP_Channel.JPG

[LilSick]

Have I by chance selected the wrong Parameter in the chart to represent Sensed MAP?

I do not believe you have

native values are measured in kpa

map NATIVE VALUES.PNG

[LilSick]

granted, i am running a different os than you supercharged guys are

but still, we are both gpec2

map.PNG
map 1.PNG
map 2.PNG
map 3.PNG

[Stoopalini]

Thanks, that's helpful. So it looks like the "Manifold Absolute Pressure (sensor)" channel is reading higher on yours (~108 kPa ) as well; so maybe this is normal.

It seems the characteristics I'm using for this sensor are probably not correct, or ... it has failed; hence the Baro and KOEO MAP readings are not showing accurate barometric pressure.

I wish I could find a datasheet on this sensor, or at least some accurate characteristic data. For good measure, I went ahead and ordered part number 68207074AB, which is the 2015 - 2017 Hellcat 2.25 bar TMAP. This version seems to have more proven characteristic data available, and I'm only going to be running 8psi max for now. I might go up to 10 - 12 psi in the future, along with a forged lower end. Even then, 2.25 bar should be fine as I'll never get close to the sensor limit; especially considering the OS I have limits MAP to 195 kPa anyway (which would be 13.87 psi of boost).

[LilSick]

yer welcome

[Stoopalini]

Just to followup on this ... It seems I was looking at the wrong parameter for sensed MAP, as there is a specific "Sensed MAP" parameter. I added this and started tracking it instead of the "Manifold Absolute Pressure (sensor)" parameter

Sensed_MAP.JPG


Then I adjusted the MAP characteristics, leaving the offsets alone, and tweaking the slope until both Sensed and Calculated values matched my current atmospheric barometric pressure reading (29.9 inHG)

MAP_Characteristics.JPG


So now with KOEO, both Sensed and Calculated MAP values are matching atmospheric baro

MAP-to-Baro.JPG


The "Manifold Absolute Pressure (Sensor)" parameter still reads higher than the others, maybe it's due to the TMAP Multiplier table (44395)? When I check, the math seems to track.

TMAP_Multiplier.JPG

[Stoopalini]

Still chasing this down ...

Apparently, the 53010887AA 3-Bar MAP sensor does not have a linear response. When used in an OEM supercharged application, there are parameters which are considered for taking the sensor output and converting to an accurate measurement .. ie: To account for the transfer function in relation to the sensor's response function.

So in a Hellcat, with a factory supercharger, these parameters are exposed in the Engine -> Supercharger tab.

Supercharger_Tab.JPG

But for these parameters to be considered by the PCM, the "Equipped" drop down needs to be set to "Yes". Doing that in a non-Hellcat vehicle produces errors though, due to the missing electronic bypass controller as well as the additional TMAP sensors found in a Hellcat not found in an R/T or SRT.

So it seems this 3-bar MAP sensor is not ideal for adding forced induction to a non-Hellcat vehicle due to the non-linear response of it, and there's no way to account for the non-linear curve in the operating system without flipping this "equipped" flag. I'm surprised Whipple provides this sensor in their kits ...

2+ weeks ago, I ordered the Mopar 2.25 bar MAP sensor 68207074AB, which I believe has a linear response. Although it's on back order and still waiting for it to ship.

Curious how others are using this 3-bar Hellcat sensor effectively in a non-Hellcat vehicle?

[smokeshow]

The sensed map and calculated MAP (both calculations) are online estimators that work in tandem. The calculation requires that the engine be running in order to arrive at the pressure estimates. So don't fixate on the KOEO values. The solution is fixing those models to represent the engine mods, namely the supercharger. Sensed and calculated pressure will never match so long as you haven't configured for the additional pressure drop behind the throttle. The error will be buried in sensed map error as well as learning into the throttle flow correction.... You really need to set it up with the proper sensors and cal configuration. Otherwise you can plan on chasing your tail on it forever.

[HaasExp]

Sensed and calculated pressure will never match so long as you haven't configured for the additional pressure drop behind the throttle. The error will be buried in sensed map error as well as learning into the throttle flow correction.... You really need to set it up with the proper sensors and cal configuration. Otherwise you can plan on chasing your tail on it forever.

This has plagued the FCA tuning community forever, especially for the earlier GPEC2 PCM's
There still seems to be a stack of missing tables and parameters that have not yet been defined to model the airflow beyond atmospheric conditions properly.
Typically, the calculated MAP will closely follow the sensed MAP until the manifold pressure reaches near atmospheric. Once that happens, the calculated MAP stayed pinned, and the sensed MAP seems to follow the rise in the actual manifold pressure.

[smokeshow]

This has plagued the FCA tuning community forever, especially for the earlier GPEC2 PCM's
There still seems to be a stack of missing tables and parameters that have not yet been defined to model the airflow beyond atmospheric conditions properly.
Typically, the calculated MAP will closely follow the sensed MAP until the manifold pressure reaches near atmospheric. Once that happens, the calculated MAP stayed pinned, and the sensed MAP seems to follow the rise in the actual manifold pressure.

I always say just follow the physics. It usually leads you to the calibrations you need to adjust. When it doesn't...good chance the ECM's software can't support what you want to do and you need to use some workaround. His file looks to have everything necessary to support the addition of the Whipple though.

[Stoopalini]

When I turn the key on, but don't start the engine .. barometric pressure seems to be set based on the sensed MAP. This value is not matching to my area's atmospheric pressure though, even when I use the MAP characteristic data appropriate for this sensor.

It does seem like calculated MAP stops tracking once it reaches whatever was stored for baro during key on. But with Sensed MAP enabled, the PR Threshold should drive the change over to the Sensed MAP signal instead.

It's just not clear what each of the MAP channels represent. I sent HP Tuners support a request, asking for clarification ... but they were no help. They basically said I should go to this forum and look for answers ...

As an example, here are 6 different MAP channels, showing key on engine off values.

MAP_Values.JPG

So I have:

1. Calculated MAP
2. MAP (SAE)
3. Sensed MAP
4. MAP (HiRes)
5. MAP
6. MAP (Sensor)

Then I also have MAP Sensor Voltage, as well as a stored Baro value (since Baro learning is disabled).

I realize I don't need all of these to understand the tune and what's going on .. but it's not clear what each of them is representing. The 1st four track each other fairly closely, except Calculated stops tracking when PRatio rises above 1.0 PRatio.

The other two - MAP and MAP (Sensor), always read higher than the others ... and I'm not sure why, or if it matters.