Originally Posted by MyColorIsGreen
Originally Posted by SoCalGuy
noise, vibration and harshness. this really is in the context of the range extender - the noise, shuddering etc. you feel when it kicks in and when you accelerate for example in Sport mode. The Volt does this with amazingly low levels of NVH - kudos for GM on perfecting it.
I agree the volt makes little noise and has little vibration.... but think about it.. the Volt is weak..
so what car has more NVH?... a Mercedes C300 that puts out 228hp or a Mercedes C63 that puts out 451hp? (twice the power) although the Karma has more than 3 times the power vs the volt.
111 kW MAX output on traction motor
54 kW MAX output on generator
80 hp Internal Combustion Motor
250 kW MAX output on traction motor
175 kW MAX output on generator
260-hp Internal Combustion Motor
I'll take the shake, rattle and roll with more ponies any day.
Well remember that pretty much all the NVH in the Karma (and Volt for that matter) come from the ICE/gen combo and not the two electric motors. Also, the ICE never operates beyond 170hp (3500 rpm); it never gets to the 260hp 6,000 rpm peak that the Ecotec is capable of. The Karma's NVH signature is mostly notable at two specific and discrete points:
1. High power applications like acceleration
2. Start up/shut down of the ICE (you can feel the car 'wobble' at long stoplights when the ICE shuts down)
(1.) might eventually be improved with a redesigned (4.0) muffler that Karma 1.0 owners can retrofit onto our cars. Alternatively, a software upgrade could do the trick by running the ICE at lower RPM levels longer - in other words, rather than having it run at full 170hp throttle during acceleration, it could provide say 120hp at 2500 rpm and borrow more energy from the A123 battery (which as we all know, is capable of burst discharge of up to 50C or roughly 1,300hp). The ICE could then 'pay back' the borrowed energy by running at the lower hp level for longer, say a couple of minutes. It's a choice between a shout for a few seconds or a moderate whisper for a couple minutes. I'd prefer the latter!
(2.) Might be accomplished with a software upgrade that winds down the ICE more slowly so the wobble effect is less noticeable. I don't think the Ecotec was designed for start/stop like the new Ford and Chevy hybrid ICEs, so Fisker probably had to modify it for this application.