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Regenerative braking, significantly simpler drivetrain, pure electric for the cities. Only problem I have is they use normal car engines as range extenders. Co

by byw 8y ago

Regenerative braking, significantly simpler drivetrain, pure electric for the cities. Only problem I have is they use normal car engines as range extenders. Could've gone with a simpler/cheaper wankel or microturbine optimized for high RPM, but I guess it's quicker to slap on an engine you already have.

Laforet 8y ago
Recently there is some buzz that Mazda might bring back their rotary engine in a hybrid, which actually might be a good way to go about the power/weight problem.
- newnewpdro 8y ago
  There is absolutely zero reason to mass produce a Wankel ever again.
darkpuma 8y ago
A microturbine would be interesting, but does GM currently have an design experience with wankel engines? It's my impression that making a low emission wankel takes some clever engineering, you'd want a team with experience before investing in such a design. And has the apex seal problem ever been solved? Taking such a risk on that component of the car could be very risky.
ThenAsNow 8y ago
> Could've gone with a simpler/cheaper wankel or microturbine optimized for high RPM, but I guess it's quicker to slap on an engine you already have. In these size classes, it's pretty hard to beat Otto or Miller cycle efficiencies, especially with a Wankel configuration or a small Brayton cycle ("microturbine"). You can get much higher power-to-mass with Wankels or gas turbines, but their thermal efficiencies (again, in these kinds of size classes) will be lower with today's technology. And since the overall fuel economy is less sensitive to mass than engine thermal efficiency, these avenues wouldn't make much sense. I do think there are ways to potentially meet or exceed Otto/Miller cycle efficiencies with a gas turbine, but it would require significant dedicated engineering. Not something that would make sense for GM to pursue when they can seek greater payoffs from lean combustion technologies, etc. To put it another way, as far as the Volt combustion engine is concerned, GM made a sound engineering decision.

by byw 8y ago

Laforet 8y ago

Recently there is some buzz that Mazda might bring back their rotary engine in a hybrid, which actually might be a good way to go about the power/weight problem.

newnewpdro 8y ago
There is absolutely zero reason to mass produce a Wankel ever again.

darkpuma 8y ago

A microturbine would be interesting, but does GM currently have an design experience with wankel engines? It's my impression that making a low emission wankel takes some clever engineering, you'd want a team with experience before investing in such a design. And has the apex seal problem ever been solved? Taking such a risk on that component of the car could be very risky.

ThenAsNow 8y ago

> Could've gone with a simpler/cheaper wankel or microturbine optimized for high RPM, but I guess it's quicker to slap on an engine you already have. In these size classes, it's pretty hard to beat Otto or Miller cycle efficiencies, especially with a Wankel configuration or a small Brayton cycle ("microturbine"). You can get much higher power-to-mass with Wankels or gas turbines, but their thermal efficiencies (again, in these kinds of size classes) will be lower with today's technology. And since the overall fuel economy is less sensitive to mass than engine thermal efficiency, these avenues wouldn't make much sense. I do think there are ways to potentially meet or exceed Otto/Miller cycle efficiencies with a gas turbine, but it would require significant dedicated engineering. Not something that would make sense for GM to pursue when they can seek greater payoffs from lean combustion technologies, etc. To put it another way, as far as the Volt combustion engine is concerned, GM made a sound engineering decision.