When and Why your C-Max Grille Shutters Move

[plus 3 golfer]

The purpose of this thread is to document how the grille shutters operate under a variety of different on road conditions on my 2013 C-Max SEL with CSP 13B07 programming / calibration done in June 2013.  I have the ForScan App and an OBDLink MX Bluetooth Scan Tool to record real-time data as I drive.  I will upload the recorded data and attach a graph of the pertinent data for discussion, analysis, and comparison.  I have grille covers but rarely use them in Phoenix.

 

I will primarily record the listed PIDs below but can always add more.  I believe these are the significant “drivers” that the shutter control algorithm uses to command the shutters.  I not sure what the Grill_A_INF PID is used for.   It may be a calculated value from many sources of vehicle data to “infer” what the shutter position actually is, perhaps the position feedback from the shutter control module, or something else.  According to the Service Manual, upon every startup, the grille shutters are calibrated by operating the shutters from one full position to the other full position (one can hear / see them operate). 

• AAT = Ambient Air Temperature (*F)
• ECT = Engine Coolant Temperature (*F)
• VSS = Vehicle Speed Sensor (mph)
• GRILL_A_CMD = Commanded Grille Shutter A Position (%)
• GRILL_A_INF = Inferred Grille Shutter A Position (%)
• ACP = Air Compressor Pressure (psi)

GS1 Data Graph (attached) - 10/25/18  around 6 am, clear, no wind, sunrise 6:39 am. Initial ECT = 81F in garage.

1. From the left Time Stamp (TS), the shutters upon startup, close as AC is off (yellow line) showing low equalized refrigerant psi.
2. I pushed the AC button and the AC pressure increases to over 150 psi and grille shutters immediately open TS 0.67.
3. I cycled the AC button off and back on between TS 0.67 and just after TS 1.00.  ACP drops when AC off and shutters cycle full closed to full open.
4. AC is left on for about 4.2 minutes until TS 5:17.  Note that as ACP falls grille opening decreases but also appears to react to (+ and -) once ACP reaches an oscillating state (about 115 psi to 100 psi) as AC cabin set point temp of 74F was being reached.  At TS 4:05 there is an abrupt closing of the shutters from about 67% to near 30%. This appears at a speed of around 50 mph.  I have seen this many times and believe that is the point where Ford believes the aerodynamic benefits become more important than compressor load reduction benefits and decrease the shutter opening.
5. At TS 4:59 I got on I10 accelerating to 84 mph to merge.  I set the eco-cruise to around 75- 76 mph (speed limit is 75mph) with slight accelerations / decelerations when passing.  ECT continues to climb and reaches a plateau of 180F at around TS 450.   The cooling thermostat begins to open at 180F and is fully open, IIRC, at 202F per spec.
6. At about TS 6.92, ECT begins to climb again up to about 192F and then grille shutters begin to open.  I have also seen this many time between around 192 – 197F.
7. ETC continues to climb to 206 – 207 F where this recording ends with no further opening of shutters.  I still had several miles at these speeds.  When I got to about 10 miles from the airport where I started to experience congestion.  Fortunately, I could use the car pool lane. The next graph will pick up about 10 miles from the airport.

Summary GS1

I have highlighted in red what I believe are two important points in the control algorithm.  We will watch these as I add more graphs.  I also believe that adding grille would help FE because ECT would rise faster and likely slightly higher plus  there’s a lot more  driving at speeds of greater than 50 mph where the aero benefits of covers will be better than closed grille covers (how much is the question).  The downside would likely be slightly increased ACP load up to 50 mph.  But at AAT of 61F or so, it would be minimal.

 

[plus 3 golfer]

Here's another graph.  I want to note that I only ran th AC for this test as at these ambient temps and speeds, I would normally just crack the front window and back window slightly.  But at higher speeds like in GS1, it's way to noisy to open the windows at higher speeds or in heavy traffic.  

 

GS3 Graph: 10/25/18 8:30 am, ambient upper 60s-70F.   

• AAT = Ambient Air Temperature (*F)
• ECT = Engine Coolant Temperature (*F)
• VSS = Vehicle Speed Sensor (mph)
• GRILL_A_CMD = Commanded Grille Shutter A Position (%)
• GRILL_A_INF = Inferred Grille Shutter A Position (%)
• ACP = Air Compressor Pressure (psi)
• IAT =  Intake Air Temperature (*F)

I replaced AAT with IAT in my recording of data. I have noted several interesting observations.

1. AC is ON initially, turned off at 7:53, and back ON at 14:43.
2. Speed passes through 50 mph four times with AC on.  Note grilling opening decreases  when speed goes above about 50 mph and increases when speed falls below 50 mph.
3. At about 10:25 I accelerate about 2 mph and back off pedal to allow EV to kick in since I noted the HVB had plenty of charge to run in EV for some time (about 48 seconds).  IAT increases because ICE is off and no air is entering intake. ECT falls because ICE is off, and shutters close when ECT falls to about 192F.  
4. ECT begins to rise again as EV ends and ICE starts.  At 12:33 ECT climbs above 192F and shutters open to about 14% at ECT of 201F. 
5. Near the end of the graph, ACP rises substantially even though shutters are virtually wide open to allow to allow more air to the condenser.  I will begin monitoring cooling fan operation and other AC data as I want to get a handle on AC load.  I do watch “Climate Control Load” in the left dash display in My View.  I know that after cabin reaches conditioned steady state, AC load is rather small even at high ambient temps (100F+).  At start of conditioning cabin, climate load can be around 4 to 5 kW as AC.  Once SS is reached, climate load seems to be between 250 - 500 Watts.

 

[ptjones]

Just got this XGauge PID from Linear-Logic for shutters: 

Grill Shutter Position Commanded (%)

TXD: 07E0220707
RXF: 046205070607
RXD: 3008
MTH: 006400FF0000
NAME: GRL

 

It looks like it works. :) 

 

Paul

Edited November 26, 2018 by ptjones

[ptjones]

It works now by removing the first zero in MATH. Now with the shutters closed it reads 0%.

 

Paul

Edited November 26, 2018 by ptjones