woody todd:   (Quote)

JonP.: Statik& Sherman @ 8“Er…I’m sorry…may I just say WTF? The engine will be used to drive the car? When the hell did this happen? I thought the idea of not having the engine linked to the drive train was what made the Volt so much different from a hybrid. Is this really true?”Me too, i was under the impression from the very start that the generator would never be used to propel the elctric motor. What happened to eliminating the “human factor”. Just a few weeks ago they were saying that once the battery reached it’s “depletion point” the generator would run to “maintain” the battery at a 30% SOC to power the car.When did this change, or is this just another douche bag reporter that can’t change a flat?  (Quote)

After reading many comments my understanding is that the ICE/dc generator which is rated at 53 kW will ONLY be used to supply power to a controller which converted to 3 ph PWM variable frequency feeds a 120 kW induction motor, speed reducing differential and the front wheels. This generator only comes on after the battery charge is depleted to around 25 – 30% (4 – 5 kwH remaining)
If there is then a heavy demand exceeding 53 kW, the battery kicks in to supply juice for a very limited time,(I figure about 5 – 8 minutes)
During deceleration/braking the car’s kinetic energy regenerates the battery, the wheels supply mechanical energy to the induction motor now running as a generator above synchronous speed, back to the 3 phase controller which is rectified to the 120 V DC of the battery
During this time the dc generator PRESUMABLY is disconnected from the controller???
Also when the ICE is operating the design is such that the battery cannot receive current from it so it also must be disconnected from the dc bus of the power controller??

Power/energy flows
Drive mode
ICE/dc generator-A (after40 mi)–> dcbus controller–>diffl–>wheels
battery@30%cap(load >53kW)B–>dcbus controller–>diffl.->wheels

Regeneration deceleration/braking intermittently
ICE/dc generator..A
battery<-@ 30 – 80%capB<–dcbus controller<–diffl<–wheels
QUESTION:

What method is used to prevent the generator in drive mode from directly feeding the battery if both are connected to a dc bus, allowing the battery to supply power when needed? and in the regeneration mode disconnect the dc generator from the bus while allowing power to flow back into the battery? some type of switching is required.at A and B?

Or, even better……..dual-fuel CNG/GAS.

See ya later OPEC ! ! !

“This also aligns with the fact that most other hybrids use Atkinson cycle.”

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Dave,

The Volt is *not* a hybrid, it is an RE EV. The differences are not trivial. One of the problems with Atkinson engines is that they can only be used in RARE circumstances. In the case of the Prius, the Atkinson engine can always be assisted by an electric motor that has 300 ft/lbs from 0 to 4k rpm. Most V-8s don’t even develop 300 lb/ft and certainly not sub 3k rpm. This is the reason they chose to use this engine.

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So I’m assuming that GM knows what they are doing will opt for maximum efficiency by using an Atkinson type camshaft tuning. The 53kW, 75hp, and other numbers we have seen all seem to very this.

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The Volt’s ICE will never see NORTH of 3000 rpm and therefore will never EVER produce more than 75 HP at best. THIS is the reason for the stated HP rating, not an assumption that it is an Atkinson cycle engine. GM has already stated that it is a family Zero engine off the shelf and we know that the previously planned 1.0 Turbo as *not* an Atkinson engine. An Atkinson engine would never be able to deliver the output at a modest 1800 rpm that is required. Too many assume that the Volt’s ICE is in a free spin turning the genset.
It is NOT. Have you ever ran a generator and plugged in a refrigerator or portable air conditioner and listened to the sound of the engine under duty? An Atkinson engine is not only not possible, it’s not optimal. Maximum efficiency is not always the smallest or “meekest’, it depends on the application. In this case it mandates maximum ft/lbs at minimum rpm and that is not an application for a Atkinson engine.

This also aligns with the fact that most other hybrids use Atkinson cycle.

As far as the 3 very narrow RPM ranges, we still have not heard anything about what these actual engine speeds will be. In fact, GM just said “a few” – we don’t even know if its 3 constant RPMs. So it’s very possible one of these RPMs will set fairly high to get maximum power output from this engine design. Nobody is going to expect 50MPG at 100MPH.

But as always, we never know for sure until they tell us.

“GM has stated that the 1.4L gas engine will only deliver 75 max horsepower. That has to be an Atkinson cycle engine. There is no other explanation I know of. A 1.4L Otto Cycle would have way more power than that. Besides, an Otto Cycle would never deliver 50MPG.”

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You cannot determine what type of engine is being used by the relative/stated power output or EPA figures. This depends on so many factors not the least of which is the specific application thereof. In the case of the ICE in the Volt, it will operate over 3 very narrow RPM ranges, none of which are close to what would maximize HP in an engine this size. Therefore it’s nominal HP will be much less than if this same non turbo engine were used in a conventional vehicle like the Cruze to power the wheels. The only way we’ll know is when GM tells us what they’re using. Quite frankly with the duty the genset will demand from this engine at modest RPM I don’t think an atkinson engine would be optimal.

GM has stated that the 1.4L gas engine will only deliver 75 max horsepower. That has to be an Atkinson cycle engine. There is no other explanation I know of. A 1.4L Otto Cycle would have way more power than that. Besides, an Otto Cycle would never deliver 50MPG.
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As for cycles and power and all the good stuff, GM released…well, all kinds of information on the new 4 banger today:

“The 1.4L engine will initially be available in two flavors here in North America. As we learned back in July from Larry Nitz, a normally aspirated version will be used as the range extender for Volt. That variant will have an output of about 100 hp. The Cruze gets the turbo for an estimated 140 hp and 148 lb-ft of torque. ”

http://www.autobloggreen.com/2008/09/26/tech-analysis-of-gms-new-1-4l-four-cylinder-engine/