REMOVE SPEED LIMITER

[lotusman]

Anybody offering a solution for this? The car seems to have the power to go past the 85 mark, 100 would be a lot more usable.

People routinely drive 80-85 on the highway, and it is a safety issue not being able to pass anyone.

Any ECU tuners out there have a solution?

 

[paw160]

Electric motors experience a severe drop in torque near 100% speed. I would assume that Ford arranged the 1 speed gearbox so that the motor stays within the nice portion of the motors torque curve.

I would assume that if you want to go faster than 85 you would need to modify the gearbox. There are ways to have the motor controller spin the motor past 100% rated speed but you will lose torque which you want for passing.

How about not driving so fast? Not sure where you are but around here 75-80mph puts you faster than most people on the road.

 

[Astrand1]

This topic seems to creep up every now and again. I for one used to be a heavy foot fast lane driver going 80-85 all the time. Of course out here in LA everybody goes 80 if there is not a traffic jam. But now that I am electric I have calmed down and I find just staying to the right lanes I have no problem. There are a few times when I get up near the speed limiter when I need to make a move but there is such a range hit that I do my best not too. My 2 cents is that I'm fine with it the way it is.

 

[michael]

I'm also thinking that the limit may relate to maximum allowable speeds for the motor or other components. I don't know what speed the motor is spinning at 84 MPH in the FFE, but I'm told the Tesla motor runs up to 16,000 RPM. I'd be concerned with overstressing components and impairing their life.

Ford could have used a different drive ratio and allowed higher speed, but at the cost of reduced low-end acceleration.

And bear in mind also the greatly reduced range at higher speeds.

I'm with Astrand1....I'm also in LA and I used to drive my BMW like a low-flying jet. Now I find it more fun to tuck in behind a truck going 60 and try to achieve lower energy consumption.

 

[jeffand]

This causes more stress on the battery when driving at high speeds. Increasing your speed from 60 mph to 80 mph will about double the current draw on the battery. The only reason a Tesla can go so fast is because its battery is more than 3 times the size of the Focus battery. This is one of the reasons the Tesla also has a speed limiter on it. A sustained high load on the battery can damage it by over taxing the cooling system.

 

[rabar10]

Jack it up and put bigger tires on it :lol:

 

[EVA]

The range hit at 84 MPH is horrible, almost worse than running the heater. I think Jeffand has the right idea, the limit has more to do with battery stress.

You know there could also be a safety issue with the suspension. We've discussed towing the car on this forum. The owner's manual says to never tow the car with the rear wheels on the ground. The most logical conclusion I saw from that discussion was the increased weight of the battery (or whole car) and the weight shifted to the rear suspension not being safe. There may be some kind of limit that the car can't hit that high speed.

 

[v_traveller]

The only reason a Tesla can go so fast is because its battery is more than 3 times the size of the Focus battery.

I'm thinking that another reason is that the Tesla has a motor that is three times as powerful as the FFE motor. If it had the same or similar motor as the FFE, it would probably be programmed with a lower top speed, closer to the FFE... Perhaps its top speed would be even lower than the FFE, since the Model S is even more of a pig than the FFE - almost 5000 pounds!

In my opinion, the absurdly low limit on the FFE's top speed is probably very conservative - I'm guessing that the drive system is capable of more, at least 100mph. Here's why:

1) The Leaf, with a programmed max of 92-93 mph, has a similarly-sized battery (24kWh) and similarly-capable motor (Leaf is 80kW, FFE is 100kW... the Tesla, 310 kW!) This is about 8mph more than the FFE, and the Leaf doesn't even have a thermal management system for its battery. So I'm guessing that the FFE, with its thermal management, should be able to overcome any heat issues at a sustained speed of 93mph or higher.

2) The Volt has a top speed of 101mph, and there's a youtube of a guy doing it in Needles, CA in pure electric mode. The Volt also has a similarly capable motor (111kW), but has a much smaller, thermally managed 16kWh battery. I would think based on jeffand's theory of bigger battery means higher top speed, that the FFE should then be capable of over 101mph if not for its annoying speed limiter.

So maybe that low limit might be related more to what paw160 mentioned - that perhaps the way the FFE is geared, at 85mph the motor is near where the torque really starts dropping off. But then I've hit that 85mph numerous times just to merge into the HOV lane, and it sure doesn't feel like the torque is ready to drop off... the FFE pulls and pulls right up to its limit.

Wish there was more info out there. Without published documentation from the manufacturer it's all just conjecture by a bunch of hacks like me.

 

[jmueller065]

Also note that the motor is liquid cooled as well. In the cutaway pictures of the motor you can see a water jacket, and if you remove the big piece of foam from under the hood you can see where the coolant hoses go in/out.
Sure EVs don't generate as much heat as an ICE but there is heat there.

 

[WattsUp]

Also note that the motor is liquid cooled as well. In the cutaway pictures of the motor you can see a water jacket, and if you remove the big piece of foam from under the hood you can see where the coolant hoses go in/out.
Sure EVs don't generate as much heat as an ICE but there is heat there.

I hope they at least cycle the heat from the motor to heat the battery (when needed). It would be cool if they could use any excess heat to warm the cabin too.

 

[ayedurand]

Tons of reasons why NOT to do it.

Don't care. My car, my problem.

Anyone here actually done it? Doesn't seem like it.

OP- if you figure it out before I do, let me know. I'm also interested in having the same accelerator tip-in for forward that exists in reverse.

 

[Anti_Climax]

If you're going to try, my guess is that it will require modifications to the firmware of the TCM rather than just being a setting through CANBus.

I know it's WAY late, but for anyone that cares, the car will cycle coolant from the motor into the battery loop when it would otherwise need to run the battery heater (~40F I believe).

 

[calvinhc]

Long before we routinely had electric cars, the railway industry started using motors to move trains in diesel-electric locomotives. They used a diesel prime mover to generate electricity used to operate the traction motors. It was found that motors have speed range that they can safely operate at.

Minimum speed was determined by heating effects of high currents with little airflow and maximum speed was determined by how fast the motor's rotating components could spin without flying apart. Minimum speed was specified as a minimum for sustained operation. Lower speeds could be tolerated, but only for a limited amount of time.

A gearbox was used to transmit the motors' rotation to the wheels and differed by type of locomotive. For instance, freight locomotives were typically geared to have a top speed of 65 mph which allowed a lower minimum speed for continuous operation. Passenger locomotives would be geared for a higher top speed as they didn't need to sustain the same minimum speed.

Minimum motor speeds were a greater concern for DC motors, as rotor and/or stator coil burn-outs at low speeds could occur easily. AC motors don't eliminate this, but they are better capable of sustained low speed operations.

Getting back to motors in EVs, the issue of a maximum top speed remains, but issues of stress on the battery are an added concern. In other words, the maximum speed is set for a very good reason. Having said that, I should also add that the maximum speed is not set to a value that, if exceeded by 1 mph, would result in the motor exploding. As is usual engineering practice, a wide margin of error is used.

Consider the last elevator ride you took. That elevator had some maximum load, say 2000 lbs. The elevator will not break off its cable and fall if it is loaded to 2001 lbs (for the example, I'm ignoring the fact that it would not fall if the cable actually broke!). That cable was tested to find that it breaks at something significantly over the 2000 lb rating, possible as much as double. That rating is there to say that if maintained properly, it will continue to carry the stated weight for its expected lifetime. Exceeding the rating by enough will result in immediate failure, but exceeding it by smaller increments will translate in reducing its expected lifetime.

Another example of exceeding ratings is the incandescent light bulb. A bulb may be rated for 120 volts, but if you exceed this, its life will be shortened. If you apply 240 volts to it, it will instantly fail as it does its impression of a photo flash (I've seen this happen). But it will not instantly fail if it were to be powered by 125 volts. In the case of incandescent bulbs, life expectancy reduces by approximately 50% for every 10% the rated voltage is exceeded.

In conclusion, there is a good reason for a limit to the top speed of the motor. Increasing it will reduce life expectancy, but by how much will be something to be determined. Venture at your own risk.

 

[Anti_Climax]

In regards to the light bulb example, it's considered "normal" for input voltage to vary by up to 10% from spec, so most 120V incandescent bulbs are tested for their light output around 132V but their lifetime is tested around 108V for those very reasons.

I'm still hoping to edit the SOBDM code to bump the current draw to 32A. It's still strange to me that it pulls 29A and not 30A like every other 6.6kW car.

 

[Heima]

Thanks Calvinhc! I have wondered about that and learned something new today!

 

[calvinhc]

Glad it helped with understanding.

I never thought the train geek side of me would translate to an EV issue.