On the energy flow screen, at what vehicle speed does the electric motor generally stop providing power to the wheels?

I know it's already been shown that for highway speeds you take a mileage hit above 55, but I have a road trip coming up for Easter weekend that's going to put me on some 70mph limit highways. If someone is able to tell me that for example the electric motor doesn't help above 60, then I'll try not to exceed that threshhold.

 

My '08 assists even when traveling 65 to 70 mph. I'm also driving up and down hills/mountains on the interstate so I'm not sure if that is playing a factor or not. You'll take a hit in fuel mileage but you'll still do better than if you were driving a non-hybrid Escape.

 

That's true, I recently drove from Upstate NY to Cleveland OH at around 75 mph the whole way(I was in a big hurry to get there by a certain time). I forget exactly what my mpg was, but it was FAR better than a V6 Escape would have been(I was quite surprised at how good it was actually).

~John

 

I think there is a tendency to believe that the reason the FEH gets good mileage is ONLY because it has EV mode and the electric motors to assist. The energy to the electric motor when you are *cruising* still esentially all comes from the ICE, not the battery (sure energy will flow into the battery for a bit on downhills for example, and out again on uphills--but its too small to provide a constant source of power). Its a matter of balancing the RPM of the ICE with the speed of the vechicle, and the amount of torque required. When you are cruising and the motor is on the ICE will be putting some of its torque into the generator to make electricity for the electric motor.

So during that cruise its a matter of the FEH deciding what the most efficient way to turn the tires at the desired speed is... at certain times the most efficient way will be by sending the power straight to the wheels and bypassing the motor completely.... You'll still save gas in such situations over a 6-cylinder because you are using a smaller engine to do the cruising. A 6cylinder isn't necesary to cruise.... its needed to provide extra torque to accelerate and the extra weight and fuel for 6cylinders is wasted while cruising.... here we get that extra torque from the electric motor.

Its a misnomer to feel that once the electric shuts off you are in some sort of efficiency vaccum and the vehicle stops being efficient....

 

I have never seen the electrics "cut out" as it were at any speed, nor have I read about it. As others have mentioned, hybrid mode is a good thing, not just electric.

 

Thanks guys. Last time I took this trip I got around 29mpg, which of course is still good for an SUV at highway speeds, but definitely pulls down my average.

Rich I'm headed up to the Port Huron area from Chicago- how is I-94 through Detroit these days? Last time I went that way it was pretty decent, but I've also seen a lot of major construction through there from time to time.

 

Brady, the most important thing about highway driving IMO is to keep RPM's under 2,000. If you can, accelerate slowly on the on ramps up to speed. Assist from the electric motors has a big payback at speeds of 70mph as far as MPG.

It is not true that EV is the only way to get very good mileage in the FEH/MMH. Since the highway doesn't have the stop and go in the city, you can take advantage of the benefits of highway driving. Forget about motor assist and concentrate on holding a steady gas pedal and back off it to lower RPM's while maintaining speeds. You can do this in any vehicle you drive with great results. You don't have to draft either.

The longer the trip, the better chance you can bring up your mileage on the highway. I went to miami and my mileage average kept getting better the further I went. It was still climbing after 100 miles at 45mpg, so I know longer trips will do me even better. Forget about the EPA ratings and go for it. Keep your mind on the gas pedal and RPM's, because that's where it's at for great mileage.

GaryG

 

Another great tip is take cues from Truckers. Contrary to popular belief, most average 18 wheelers have the power to climb hills at the speed limit. They choose not to to save fuel. ( hey, when you're getting 8 MPG, saving one MPG is like a 12% bonus )

Slow down 5 or 10 on the uphill side of hills, and speed up 5 or 10 on the downhill side. You'll get much better MPG ( 10%? 20%? ) and not really loose time.

I've driven off battery power only at speeds of 75 MPH.
What I mean is, the engine is spinning to moderate RPM, but you can get some, or ALL of your torque from the battery at any speed. At any speed, the motors can assist to reduce the demand on the gas engine. But this power is limited to 1 or 2 minutes at a time.

-John

 

29 is right around what I get on most freeway trips without trying. From what I've been told by a friend who owns one--the v6 4WD gets 17 on the freeway if you are lucky.

It has less to do with the inefficiency of the vehicle at a particular speed than the fact that you are trying to push a huge BRICK through the air. Pull up to a fairly safe distance behind a truck (give yourself decent stopping distance) and you'll find your MPG will climb over the same speed out in the open. I find you can actually stay pretty decently far back and still get some effect of the draft. However in the 4WD.... 29 isn't that bad.

 

Hey, let's not forget the efficiency bonus of the atkinson engine. Its not just the motor assist that is responsible for the fuel economy. In my AWD Mariner Hybrid I get great mileage cruising at 65mpg. I would estimate in the 33+ range. At 70-75mph I think it drops to about 30-31mpg.

As others have said, its not about the speed as much as it is how you drive. Slow and steady acceleration and maintaining RPMs seems to be the key to me. I never try to maintain speed on big inclines...eats too much gas. Rather, I sacrifice 5-10mph on the way up and pick up speed on the way down. Also, keep an eye on the RPMs while you drive especially after a bit of acceleration. It sometimes creeps up and needs to be nudged back down. Take your foot of the gas for a half second and let the CVT settle in at a lower RPM. (I believe you will see this referred to as a 'fake shift')

Also, following a big rig can offer tremendous benefits. I chose the word "following" not drafting. Even 4-5 car lengths behind a trailer will give you a significant boost. There is also an area about 1-2 car lengths behind the trailer but in the adjacent driving lane that also experiences the benefits.