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^^^ A Vette size car will need to achieve the currently mandated Corporate goal of 56 mpg in 2025 (perhaps it will reduce to ~50 mpg is my guess.) Big pushrod V8's can't get there! IMO a smaller lighter ME with a small cid turbo engine is essential. Other things like Start/Stop and probably a light weight F1 type KERS system to reduce energy use while accelerating from a stop and recovering some of the 1/3 wasted energy braking etc. Hopefully that combo versus all electric, or a large battery hybrid. There will be plenty of those in grocery getters. GM has no time to mess with an interim FE sports car!
To get to 56 mpg (believe that gas been reduced to 46) without a major technological breakthrough would require something like a ME Miata with a 1.5 liter engine. I cannot see any way for a V8 unless it is primary electric driven.
Yep, I agree a pushrod V8 could never get there but also don't think by 2025 a 1.5 Liter engine will be needed!
First you can use some of that 33% of the energy in gasoline going out the exhaust to power a turbine so a smaller, lower friction cid engine can be used. (By the way there was a WWII airplane engine that used an exhaust turbine to directly assist in powering the prop. Can be done with lots of gears!)
Then use Start/Stop to recue some of the energy waste when idling. (Forget the hollering - what about on the highway etc, below is based on EPA AVERAGES.) By the way harder to do with a standard shift but the C8 DCT will handle it!
Then although I don't have hard numbers, a lot of energy is wasted accelerating, even modestly from a stop light. So a simple, under 100 lb F1 KERS could be used to keep that Start/Stop engine off until the desired steady state speed was reached. By 2025 the technology should be available that gives F1 cars 160 hp for 10/20 seconds and weighs ~60 lbs with it's battery. All you'd need is perhaps 50 hp for perhaps 30 seconds. KERS also stores energy back into the small battery when braking.
Note on average only 13% of the energy in gasoline gets to the rear wheels! Of that "On Average" 42% converts to heat while braking! KERS won't capture it all- BUT enough perhaps to meet the goal.
Yep things will change in 7 years for cars a bit like it does in electronics! Hold on!
Weight will be more important than engine. That ME Miata will have to be under 2,000 to even think about coming anywhere near 50 mpg. Think old school Lotus.
Weight will be more important than engine. That ME Miata will have to be under 2,000 to even think about coming anywhere near 50 mpg. Think old school Lotus.
Low weight helps, mostly in less energy needed to accelerate and wasting less energy when braking. But just need to get ~20% of the energy in gasoline to power the rear wheels and recover some of that ~20% that is wasted when braking to double mpg!
11-18-2018, 12:23 PM
A Vette size car will need to achieve the currently mandated Corporate goal of 56 mpg in 2025 (perhaps it will reduce to ~50 mpg is my guess.) Big pushrod V8's can't get there! IMO a smaller lighter ME with a small cid turbo engine is essential. Other things like Start/Stop and probably a light weight F1 type KERS system to reduce energy use while accelerating from a stop and recovering some of the 1/3 wasted energy braking etc. Hopefully that combo versus all electric, or a large battery hybrid. There will be plenty of those in grocery getters. GM has no time to mess with an interim FE sports car!
Low weight helps, mostly in less energy needed to accelerate and wasting less energy when braking. But just need to get ~20% of the energy in gasoline to power the rear wheels and recover some of that ~20% that is wasted when braking to double mpg! 
