Why does the Tribute/Escape Hybrid only capable of 25mph in EV mode ?

I noticed that the porsche cayenne hybrid can go 75 miles per hour in EV mode.

So I looked at the stats and the Ford has more EV power


TributeSUV
330-volt 70-kw
25mph in EV


Cayenne SUV
288 Volts 38 kW
75 miles per hour in EV


So, almost twice as much more in the tribute 70kw versus 38kw so
I would think the tribute should go twice as fast as the porsche, not
the other way around ?

Is the Escape overly limited or capped too early in EV mode ?
Could someone tweak the electronics to lift this cap ?

 

Has it been validated that the Cayene can actually do that? Also, I think it has been noted by others that speeds of up to 40 mph can be achieved if properly operating your vehicle and the driving conditions are appropriate. Maybe this is the case of Ford undercommitting and outperforming their literature and Porsche doing overcommitting and underperforming theirs.

Would be nice to see some real comparisons. Also, how does the Cayene compare to the Ford pricewise?

 

If I were to take a guess at it I think it has to do with the battery management model. Ford works the batteries VERY conservatively. Mostly due to the warranty imposed by the feds and state of Calif where applicable.

The batteries only hold so much and if one were to floor it and accelerate it would drain them faster than Ford allows which would or could cause the batteries to wear out sooner. While the electric motor is used in a pulsed fashion while driving down the freeway to help bleed charge off of the battery pack and maintain a constant state of charge, to drive in EV only at higher rates of speed above 30 mph is far too taxing on the small battery pack and thus not allowed.

We are still in a learning/ Beta testing mode. Ford will know more as time goes on and there may indeed be the capability to extend the SOC and use of the battery pack to a lower SOC before mandating and ICE recharge. But for now we have to drive/play by Fords rules/programing.

 

The drivetrain needs lubrication which is one of the reasons I've heard that Ford (and Toyota) cuts EV at 40mph.

Realistically though, this should be filed in the "who cares" department. In order for the FEH to be able to cruise on batteries at 75mph for any distance, the whole back of the car would be consumed by batteries. I would like it if the engine could power down on downhills at higher speeds for drag-free coasting, but electric motivation at those speeds is of no interest unless you are driving a big battery with a big plug on it...

 

So it sounds like it is a function of the programming of the electronics for various reasons.

Before you dismiss this into the who cares file kristian, I am not done yet. I just wanted to know first what the basis was and here is why.

If one were to convert to phev which would change the factors that went into ford deciding on the cap, then I would think the phev conversion should also include an update to this limitation. I asked hybrids plus and they dont change it, I think this is a serious oversight. Considering the price you pay for a conversion and the techs they have working at hybrids plus, you would think that they would modify the conservatively low cap.

 

The reason the Prius was limited was to prevent overspeeding the generator. The FEH generator can handle much higher speeds. The self-imposed limit on the FEH is in all likelyhood due to the amount of torque required to spin the ICE with the generator while also driving the traction motor. Tough to do smoothly and without an enormous drop in SoC at high speed. The FEH can be towed all wheels down at 75 miles per hour. This spins the generator and traction motor just the same as EV, so there is no mechanical reason for the 40 miles per hour EV limit.

 

DesertDog, does that mean that a tow job will charge the FEH?

 

Cut and pasted from a test site.
Our driver told us that a fully charged battery can propel the Cayenne in electric mode up to about 30-35 mph. Indeed our ride stayed all-electric as we wound our way through the Weissach campus at low speed. When coasting, the ICE can remain off at speeds up to 75 mph.

 

Sounds like the Cayenne can go ICE off at up to 75MPH, but the motors cannot actually propel the vehicle while at those speeds. Similar to how the FEH will go ice off if you coast under 40mph. Seems like it is just a programming limit and is probably not actually important for fuel use. If I am not mistaken, several users have theorized (possibly proven) that in the FEH when coasting at high speed, the engine will remain "on" but there will not actually be fuel delivered or burned. (fuel cut)