What exactly does SPORT MODE do?

[MIN FUEL]

OK so I have been reading like crazy to find out exactly what sport mode does. It is all very confusing. I know when I use sport mode the acceleration is much quicker, but why? I have read that above 70 MPH that both electric motors are enganged by the system (is that true?), and if it is, is that what sport mode does? I originally thought that the second motor was really just a generator. Also what are the HP or both motors?

[DonC]

It simply remaps the accelerator so less pressure gives you the same speed. It works at all speeds. The two motors do work together under hard accelerations or above 70 MPH. This is really done for efficiency reasons since the larger traction motor would have to run at inefficiently high RPMs. The best explanation can probably be found here: http://vxlive.feedroom.com/feedroom/...by/default.htm

[mfennell]

Under hard acceleration, it reverts to one motor mode because that's faster due to the gearing advantage. If you've ever floored it at highway speeds, you've experienced a downshift-like delay before strong acceleration. That's the time taken for MG1 to slow to a stop and disconnect.

Another forum member posted the sequence captured with his scan tool.

[rubley]

I thought sport mode enabled the full 150 HP, and normal limited it to 120 HP ?

[saghost]

OK so I have been reading like crazy to find out exactly what sport mode does. It is all very confusing. I know when I use sport mode the acceleration is much quicker, but why?

As mentioned by another poster, sport mode remaps the accelerator - you can get the same response by seriously stomping on the pedal in normal mode. (originally, they said it was going to allow the system to give you another 10 or 20 kW, but that didn't make it to our cars - possibly a future model or update will work that way, though I wouldn't count on it. Power limits are usually more about the power electronics or the battery than the motor...)

I have read that above 70 MPH that both electric motors are enganged by the system (is that true?), and if it is, is that what sport mode does? I originally thought that the second motor was really just a generator. Also what are the HP or both motors?

The main traction motor is rated for 110 kW (149 HP). I belive the motor generator is rated for 50 kW (65 HP), but I'm not 100% positive. According to the papers presented at SAE, the Volt can choose to engage a mode that uses the second motor at any speed above 70 kph or so, if the load is low enough (not sure where the 70 MPH comes from - it's quoted all over, but GM sources have said it isn't a hard number repeatedly.) There's a chart in the engineering and design forums here I've seen several times which shows this - I don't have a link handy.

The second motor isn't capable of delivering the torque levels of the main motor, and since it's tied in a torque split (like a prius) when in two motor mode, the lower capacity of the second motor limits the maximum axle torque - which is why the Volt will switch back to single motor at any speed at WOT - that lets it put more power to the ground, even though it's less efficient.

Incidentally, being in two motor mode while running the engine in Charge Sustaining mode is how the gasoline generator can power the wheel mechanically, which created a lot of commotion in the media when it came out a year ago, even if I'm not sure why.

[stephent]

If you floor it you are going to get max power in both modes, and the same acceleration.

Sport just remaps the input to make it more sensitive to position changes when you have the pedal partially depressed. See
http://gm-volt.com/forum/showthread....l-mode.-Really
particularly resident technical expert WopOntour's explanation
http://gm-volt.com/forum/showthread....7766#post47766