C-Max EV Torque

[nsteblay]

One observation I have after driving my C-Max these past 4 years ... it has great torque from 0 to 30 MPH.  I drive in some aggressive commuter traffic where quick acceleration at slow speeds is useful. When driving other cars, even with bigger engines, I find myself feeling that they are sluggish at slower speeds. It's not unusual for me to "burn rubber" when accelerating from a stop in my C-Max.  My understanding is EV's have maximum torque at zero RPMs. I'm thinking that the EV assists initial acceleration.  Am I living in a delusion or do others observe something similar?  BTW - Lifetime 42 MPG in cold Minnesota and I don't try to get good mileage.    

[plus 3 golfer]

I'm guessing the power control algorithm for the traction motor will provide a straight line maximum torque from zero up to several 1000 rpm of the traction motor (motor rpm is around 9500 - 10,000 rpm at IIRC around 75 mph).  Whether that's up to 30 mph or something lower or higher I don't know.  With ForScan one should be able to record data on full throttle acceleration from stop and observe what happens.  But I'm fairly sure that after that speed is reached, the motor torque will not be maximum but decline with speed.  I believe the HP may be held constant after that point and thus torque will be reduced.  It may be to prevent damage to the motor or gears / bearings at high rpm, high power or perhaps simply because it will discharge the HVB very quickly.  

 

At higher speeds when cruising in EV, ICE can be virtually instantaneously fueled to it's maximum torque under full throttle acceleration since a holding torque can be applied to the generator very quickly ramping up ICE.  When I watch ForScan data, the transferring of load from the traction motor to ICE by stopping the generator / motor from spinning happens in milliseconds.  EV assist can supply additional torque. I have continually searched for a torque curve for the C-Max traction motor vs speed and but have yet to find one.

 

You're seeing how I believe the torque control operates in the C-Max powersplit system.

 

Do you use grille blocks?  I find that grille blocks really help FE in the winter to warm up the engine and to keep it at a higher operating temperature.  So, once ICE is up to operating temp, FE isn't that bad for longer trips except for the density of air being higher when colder than warmer and thus increasing aero drag.

Edited August 21, 2016 by Plus 3 Golfer

[jackalopetx]

Yes you're right, I've posted about that too. The C-Max is great for city driving because you can accelerate quickly from a stop. Before I had a Volvo V70 turbo and before that a 2006 Mustang GT. The Volvo had turbo lag so accelerating from a stop was terrible. Once the engine had some revs it was fast. The Mustang I had to drop the clutch. The C-Max is better at lower speeds. It's also not bad at merging, IE accelerating from 40-60

 

The weird thing is they don't market the drivetrain as anything other than efficient

Edited August 22, 2016 by jackalopetx

[ptjones]

I agree too, 0-60 mph times are quick around 7 sec. range IIRC.  If battery is charged the FWY acceleration is good too. :) 

 

Paul 

[plus 3 golfer]

I agree too, 0-60 mph times are quick around 7 sec. range IIRC.  If battery is charged the FWY acceleration is good too. :)

 

Paul

Let's just say it's quicker than a Prius! :)  My 2009 TDI Jetta and 2008 Nissan Rogue are virtually the same as the C-Max.  Seven seconds is pretty quick.  The C-Max is likely quicker up to 30 mph or so than a lot of cars with the same or better 0-60 times but after that it's okay but not a rocket ship.

 

Here's a link for 0-60 times.

 

Energi Plug-In Hybrid Wagon

7.9 sec

16.1 sec @ 88 mph

Car and Driver

 

Energi Plug-In Hybrid Wagon (Electric Only)

16.1 sec

20.2 sec @ 65 mph

Car and Driver

 

Energi Plug-In Hybrid Wagon

8.5 sec

16.7 sec @ 87 mph

Motor Week

 

Hybrid SEL Wagon

8.8 sec

16.7 sec @ 86 mph

Car and Driver

 

Hybrid SEL Wagon

8.1 sec

16.2 sec @ 86.8 mph

Motor Trend

 

Hybrid SEL Wagon

8.1 sec

16.2 sec @ 88.3 mph

Motor Trend

Edited August 22, 2016 by Plus 3 Golfer

[ptjones]

I think mine is quicker. LOL :)  Actually I would think the SOC would have a significant effect in acceleration numbers.  I noticed I need +50% SOC to get EV assist  to work good.

 

Paul

[fbov]

.... I have continually searched for a torque curve for the C-Max traction motor vs speed and but have yet to find one....

 

Here's a nice tutorial on DC electrical motor characteristics; the last figure summarizes basic characteristics nicely.  

http://lancet.mit.edu/motors/motors3.html

 

And one explaining a lot of Prius details. (Keep an eye on the axes; power, energy and RPM characteristics are shown repeatedly, along with everyone's favorite, "output.") Note that the torque curve flat spots at low RPM are due to current limits. 

http://www.roperld.com/science/Prius/PriusPhysics.htm

 

So, yes, at 0 RPM (rest), the traction motor has all the torque it'll ever have. This is why modern locomotives are diesel-electric, and before that, steam. They share this characteristic. Makes for great pull off the line, but part of the tire noise is due to the tires' focus on economy and life, not traction. 

 

HAve fun,

Frank