No engine start in neutral? - GreenHybrid

stevedebi · #1 (**permalink**) 05-30-2008, 11:35 AM

On my morning commute there is a long stoplight that I always hit. I end up sitting for over a minute. Since it is fairly close to home I'm invariably still using the ICE to warm the engine. So I stop the engine with the key, then restart it just before the traffic moves on the green light.

No problem, except I have found that the FEH has to be in "P" in order to start the engine. If I shut down the engine in "N" it will not start unless I move it to "P".

Anybody have a logical reason why Ford doesn't allow the key to start the engine in neutral? I mean, I could understand if they didn't want the engine stopped in neutral (people would try and shut it down to coast), but why prevent engine start?

DesertDog · #2 (**permalink**) 05-30-2008, 01:40 PM

Quote:

Originally Posted by stevedebi

On my morning commute there is a long stoplight that I always hit. I end up sitting for over a minute. Since it is fairly close to home I'm invariably still using the ICE to warm the engine. So I stop the engine with the key, then restart it just before the traffic moves on the green light.

No problem, except I have found that the FEH has to be in "P" in order to start the engine. If I shut down the engine in "N" it will not start unless I move it to "P".

Anybody have a logical reason why Ford doesn't allow the key to start the engine in neutral? I mean, I could understand if they didn't want the engine stopped in neutral (people would try and shut it down to coast), but why prevent engine start?

The ICE can be started in N at speeds above about 6 MPH. When starting, there will be a slight lurch forward, which is not noticeable at higher speeds. At low speeds people would not be expecting the car to move forward when in N, even slightly. You have to put in P so the vehicle won't move when starting the ICE.

Tim K · #3 (**permalink**) 05-31-2008, 07:13 AM

I believe it is a physical limitation of the way the ICE is actually started. The electric motor actually spins up the ICE when starting it. If the vehicle is in neutral and stopped and the motor tries to spin the ICE, it won't turn. Think of it like standing on an ice rink and trying to push something heavier than you. You have no traction and will slide backwards. If someone nailed a board into the ice behind your feet you could push off (putting the vehicle in park inserts the parking pawl thereby allowing the motor some "traction"). Once the vehicle is already moving forward at 6mph, the forward momentum of the vehicle and the spinning of the motors provides enough "traction" for it to spin up the ICE even in neutral.

I hope this makes sense.

Billyk · #4 (**permalink**) 05-31-2008, 09:02 AM

Just a reminder, GaryG use to do the Forced Auto Stop (FAS) routine as part of his hypermiling techniques. This involves shutting off the engine and quickly turning the key to "on" but not to "start" as a means to boost fuel mileage while keeping the auto electronics and control on. He no longer does this and was convinced his nearly $1200(?) repair bill

earlier this year was partially due to FAS. One can do a search and read his report.

gpsman1 · #5 (**permalink**) 05-31-2008, 11:03 PM

Tim- Very good explanation of something few owners understand!

You've got it!

This car has a 3-way transmission.
If you spin the starter (generator) it can spin the engine and/or the wheels at the same time. In Park, the wheels are locked, and the wheels can't spin, so the engine must spin.
The tendancy is to spin the wheels in reverse.
Thus, if you are traveling forward the wheels cannot spin in reverse.
Thus the engine much start.
Thus, you can start the engine in "Neutral" if the car is rolling ( over 6 MPH ).

Oh yeah... there is no physical disconnect in "Neutral".
Your transmission still spins, but the motors don't get any power or load ( regen ).

DesertDog · #6 (**permalink**) 06-01-2008, 11:55 AM

Quote:

Originally Posted by Tim K

I believe it is a physical limitation of the way the ICE is actually started. The electric motor actually spins up the ICE when starting it. If the vehicle is in neutral and stopped and the motor tries to spin the ICE, it won't turn. Think of it like standing on an ice rink and trying to push something heavier than you. You have no traction and will slide backwards. If someone nailed a board into the ice behind your feet you could push off (putting the vehicle in park inserts the parking pawl thereby allowing the motor some "traction"). Once the vehicle is already moving forward at 6mph, the forward momentum of the vehicle and the spinning of the motors provides enough "traction" for it to spin up the ICE even in neutral.

I hope this makes sense.

Yes, I guess my explanation was a little fuzzy. The forward lurch at speeds less than 6 miles per hour would occur once the ICE starts turning. With the ICE stopped, starting the ICE requires that the generator spin in a direction that would cause the vehicle to move backwards, or slowdown when moving forward. However, even at speeds less than 6 MPH there is enough forward energy to spin the ICE. This is again an NVH issue. You can see this by starting the ICE in N while going 6 or 7 MPH. Slowdown, lurch. There is no practical reason why you can't start the ICE in N when stopped with your foot on the brakes, but that is what Ford chose to do.

stevedebi · #7 (**permalink**) 06-02-2008, 08:23 AM

Thanks for all your replies. This is an interesting note as to the way the ecvt / motor interact.

KenE · #8 (**permalink**) 06-02-2008, 12:20 PM

I believe this no start in Neutral can be advantageous. Say you are tooling along at 25mph in EV mode, about 1/4 mile to your destination, and you have to stop for a 90 second traffic light, and your SOC is 42% and falling quickly. With the selector in ‘D’, the ICE must start in about 15 seconds, which forces you to sit there with the engine running going zero MPH just to build the SOC. Ugly! But if you shift into ‘N’, the SOC can continue to drop for the entire 90 second traffic light, even below the magical 40% level, then when the light turns Green, you shift into ‘D’ or ‘L’, ICE spins up, and you drive the last 1/4 mile to your destination.

In this situation, you may have prevented ~75 seconds of ICE on time getting 0 MPG by shifting to Neutral.

stevedebi · #9 (**permalink**) 06-02-2008, 12:24 PM

Quote:

Originally Posted by KenE

I believe this no start in Neutral can be advantageous. Say you are tooling along at 25mph in EV mode, about 1/4 mile to your destination, and you have to stop for a 90 second traffic light, and your SOC is 42% and falling quickly. With the selector in ‘D’, the ICE must start in about 15 seconds, which forces you to sit there with the engine running going zero miles per hour just to build the SOC. Ugly! But if you shift into ‘N’, the SOC can continue to drop for the entire 90 second traffic light, even below the magical 40% level, then when the light turns Green, you shift into ‘D’ or ‘L’, ICE spins up, and you drive the last 1/4 mile to your destination.

In this situation, you may have prevented ~75 seconds of ICE on time getting 0 MPG by shifting to Neutral.

Maybe I haven't learned to drain my SOC, but I've never had the ICE come on at a traffic signal. It has come on after about 5-10 minutes when I stayed with the vehicle while my wife went in to shop, and shop...

But if I get to this situation I'll give it a try.

econoline · #10 (**permalink**) 06-02-2008, 12:34 PM

Quote:

Originally Posted by KenE

I believe this no start in Neutral can be advantageous. Say you are tooling along at 25mph in EV mode, about 1/4 mile to your destination, and you have to stop for a 90 second traffic light, and your SOC is 42% and falling quickly. With the selector in ‘D’, the ICE must start in about 15 seconds, which forces you to sit there with the engine running going zero miles per hour just to build the SOC. Ugly! But if you shift into ‘N’, the SOC can continue to drop for the entire 90 second traffic light, even below the magical 40% level, then when the light turns Green, you shift into ‘D’ or ‘L’, ICE spins up, and you drive the last 1/4 mile to your destination.

In this situation, you may have prevented ~75 seconds of ICE on time getting 0 MPG by shifting to Neutral.

Good idea, but I wondering how to do it. You need to shift into neutral before the ICE starts and below 6mph? IIRC, once the ICE is runnng, shifting into neutral at a stop will have no effect, the ICE continues to run until a SoC is reached that allows shutdown. I'll have to experiment with this. Thanks.