Hybrids: 2005 Diet Ford Escape FWD, 2000 Honda Insight
Posts: 2,562
Why an EV button will be difficult
I just read that the FEH computer ( ECU? ) checks to make sure the CHT and HO2S warm up in a predictable manner based on intake air temperature, and engine load conditions.
If any value falls outside of an expected range, a MIL may be triggered, and the car may enter limp home mode.
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What this also tells me is... since the computer uses several analog sensors used together, there is nearly an infinite set of conditions that will trigger the OK to enter EV... or not. It's really not a specific list of parameters.
You can make some general assumptions though... if intake air is mild ( 70'S) and battery temp is mild ( 70's ) and CHT is mild ( 230'F ) and engine load is medium ( 50% ) and CAT is hot ( 1300'F ) you're probably going to get EV at your next stop. ( or next under 40 MPH ). But this is still not a gurantee. There are also TIME requirements. The above needs to occur for at least 330 seconds for example to get a good HO2S reading.
But if you push a button in your garage to "spoof" all those readings, the car will not believe it, and you will get a MIL since those "hot" numbers did not occur over an expected period of time. The car thinks a sensor has malfunctioned.
So an EV button will need a serious hack, or software re-write. I'm very good with hardware items... but software is beyond my means.
I am going to try an "EV extender" button. So that after the car heats up on its own, and decides to go to EV on its own, I can trick it into staying "hot" longer... so like that Highlander commercial, you can pull into the garage on your way home with guranteed EV every time. This way, only the Battery SOC will be the limiting factor.
I am going to try an "EV extender" button. So that after the car heats up on its own, and decides to go to EV on its own, I can trick it into staying "hot" longer... so like that Highlander commercial, you can pull into the garage on your way home with guranteed EV every time. This way, only the Battery SOC will be the limiting factor..
Yes Sir, that's what I'm looking for. Extending EV a smidge to get that last block into the driveway/parking place/garage would be GREAT.
What the PCM is looking for is closed loop operation and a cat that has lit off. This is a Gordian knot as you suspected. Most strategies look at engine temp, O2 sensor operation and to a lesser degree intake air temp and load. The FEH also uses the O2 in the center of the cat to determine cat light off. I also suspect they want the cat at full operating temp which is a little past light off. This is so it wont cool when in EV mode to much and drop below light of temp. This is all as a result of the way the EPA tests emissions. If they would make a special case for full HEVs we could have a cold EV and start the engine later in the process.
Ducit Amour Hybridae
Mark Smith
Master Certifited Technician
Tempus non reparabilis fugit
"It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it."
Best Tank 35.0 MPG
And many thanks to all you seasoned hybrid owners for all your info and great tips. Sincerely, I mean it.
As another poster said, If you could just start out EV until SoC dropped to ~40%, then the engine start and begin the normal warm up cycle, the enviromental impact would not be compromised. Or like on a warm day, you stop and run into the store for a bottle of pop, only gone 1 minute, and the blasted ICE has to start immediately. Or just to move the car out into the driveway (50 feet, to wash it), then drive it back.
I have been gathering information for a possible EV button. I present the following which may not be 100% correct and has been edited for my own needs.
The energy management & control section of the PCM probably controls the EV mode using the inputs from the SOC, CHT and CAT. Those inputs and possibly more, probably send digital control data to the TCM. The BECM and the BSCM may also be involved.
Altering inputs to effect EV:
The HO2S sensors are the heart of the Fuel and Catalyst monitors.
The CAT which is inferred, is developed in the PCM from the two HO2S outputs and probably other data. The HO2S’s produce a voltage between 0.1 and 0.9 volts depending on the amount of Hot Oxygen to which it is exposed in the exhaust stream. In Lean conditions (High in Oxygen, low fuel level) the sensor returns a low voltage because there is less differential between the oxygen in atmosphere, while in Rich conditions, (Low Oxygen, high fuel) it reads high because there is a large differential between the level of oxygen in the exhaust stream and atmosphere. The change between the two readings occurs suddenly in what is known as a 'switch', but this term does not have any electrical connotation, although it occurs at about .5 volts. These voltages go into the PCM (pins 30 & 42 of C175E) where they are probably combined with other information and are used to develop the inferred CAT and are probably used in other control circuitry.
The front sensor is tested continuously for switching during Closed Loop operation provided the Conditions are met. Excessive time between switches, or no switches, indicates a malfunction. Since the lack of switching could be caused by fuel trim shifts as well as a sensor malfunction a stored DTC indicates whether the sensor was always indicating lean or rich when it stopped and if the Fuel Trim was at max.
NOTE In extreme cases where the Front sensor(s) is not switching the Closed Loop operation is never achieved the system stays on Open Loop fuelling.
The rear (downstream) HO2S sensors are treated rather differently. The peak and low voltages are also continuously monitored, but if the monitor has not detected a peak or low voltage beyond threshold, then the fuel/air mixture is forced high or low in order to get the sensors to start switching. If this sequence does not 'shock' the rear sensor(s) into switching, then a DTC is recorded.
All in all it looks like the HO2S’s are very complicated in their operation and would be very difficult to spoof their operation.
The CHT sensor measures cylinder head metal temperature as opposed to engine coolant temperature. The analog signal has malfunction thresholds of < 0.244 volts or voltage > 4.96 volts. The voltage enters the PCM on pin 33 of C175E. The PCM software calculates both CHT and ECT values for use by the PCM control and OBD systems. It will be necessary to keep the CHT voltage within the required parameters.
Optional control might be out of the PCM going into the TCM. The TCM is located inside the transmission and that could make it difficult to get information about the TCM.
Reference:
2005 MY OBD System Operation
2008 wiring diagrams
Ford Scorpio site
Obviously it would be easy for Ford to include the EV button, but I think there are a few "real world" tweaks Ford could have programmed that could add additional fuel economy...albeit small.
I would have liked to see Ford include some real-world common sense programming into the logic. For example, if you are sitting at a red light or running into the store....clearly the ICE doesn't need to come on. As the driver, we have the option to shift to neutral to 'lock' it in EV mode, but why do we have to do that. Ford has set parameters that keep the battery charge above 40% and the temps above X degrees.....but why not throw a little If/then into the equation while they are at it? How about "if the charge drops below 40% and the vehicle MPH is 0, then DO NOT restart ICE for 3 minutes or until charge = 35%. Why force a restart before it is really necessary when, in 99% of situations, you could simply have a restart 60seconds later when the light turns green and the vehicle moves?
-Tim
2006 Mercury Mariner Hybrid AWD
Black with Pebble interior
Premium Package with Nav & Moonroof
Current ODO: 26,152 Typical Drive: 20 min crosstown in heavy traffic (3.5mi there and back twice a day)
532 Gallons of gas saved
That's 10,642 lbs less CO2 emitted
Obviously it would be easy for Ford to include the EV button, but I think there are a few "real world" tweaks Ford could have programmed that could add additional fuel economy...albeit small.
I would have liked to see Ford include some real-world common sense programming into the logic. For example, if you are sitting at a red light or running into the store....clearly the ICE doesn't need to come on. As the driver, we have the option to shift to neutral to 'lock' it in EV mode, but why do we have to do that. Ford has set parameters that keep the battery charge above 40% and the temps above X degrees.....but why not throw a little If/then into the equation while they are at it? How about "if the charge drops below 40% and the vehicle miles per hour is 0, then DO NOT restart ICE for 3 minutes or until charge = 35%. Why force a restart before it is really necessary when, in 99% of situations, you could simply have a restart 60seconds later when the light turns green and the vehicle moves?
The two reasons I've seen cited are:
1) Because during EPA testing the vehicles CAT temp would drop below the level where it does its job and thus would exceed EPA emission limits while the car "rewarmed" the CAT
2) Because it allows the engine and the oil to cool more (and for more of the oil to drip back down into the oilpan?) than Ford Engineers liked... therefore the restarts would be harder and would perhaps cause more wear in the engine.
I can't say if either of those is actually correct. I'm merely repeating them because I'd like to hear them discussed to see if either of them has any truth or if they are just "urban FEH legends"
Hybrids: 2005 Diet Ford Escape FWD, 2000 Honda Insight
Posts: 2,562
Re: Why an EV button will be difficult
CAT temp is almost never the cause. Min Temp to be effective is about 750 degrees, and the CAT gets to 1400-1500 degrees quickly, and cools about 1 degree per second. Thus, if CAT temp were making the decision, you would have about 10-12 minutes of EV after each 2 minutes of ICE.
CHT temp cools more quickly, and where the CAT has 750 degrees of range to play with, the CHT only has a range of about 25 degrees to play with. CHT looks like the #1 PID to watch, but is not the only one to watch.
CHT has at least 3 stages or ranges that I have found *(so far) based on weather. I have found a warm range, and cool range, and a darn right bitter cold range.
The following are 'estimates' with a small sample size:
1 car, and only a few day worth of data:
In sunny, warm, Los Angeles ( 72-80 degrees while on December vacation ) I could have EV with CHT above 160.
In mild ( cool ) Colorado, ( 32-60 degrees ) I can have EV with CHT above 188.
In bitter cold ( -10 to 20 degrees ) I can only have EV with CHT above 200 degrees.
It normally takes 16 to 20 degrees above these minimums to trigger EV.
Thus, an initial warm up will require 216 to 220 to enable EV for the first time if you start a drive at zero degrees. Then you can drive EV down to about 200. That's not much range ( or time ) when it is cold out.
On a warm CA day... your CHT will probably still be at 220 quickly... but you are #1 allowed to keep EV down to 160 and #2 it takes a long time to get to 160 when it is 80 degrees ambient.
This probably has to do with the computer model that predicts how fast the rest of the car ( CAT, Water, etc. ) cools under these conditions.
Why an EV button will be difficult
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