Vehicle efficiency and design wrt fuel costs.

[dootdootdoot]

From what I've gathered, even in the 1NZ-FXE engine, pumping losses reduce engine efficiency by a significant amount. For example, this is supposedly a model based on dyno data

http://www-personal.engin.umd.umich.edu/~chrismi/downloads/HEVModel/FC_PRIUS_JPN.m

and according to this the approximate power needed to move the Prius on level ground, at ~21.5m/s, with no wind, and ideal surfaces...
Well, anyhow, I figure the Prius needs ~10-15hp to move at that speed, ~1/7-1/5 of the engine's available power. Or, the corresponding amount of the engine's torque at the appropriate rpm... So, this seems to indicate that the engine efficiency at ~21.5mph is only ~20-25%, compared to ~36% peak efficiency. Now, as speed decreases, so does the force needed to overcome fluid friction which is good for vehicle efficiency, but the load drops, which is bad for engine efficiency. To take advantage of the apparent ability of the Prius to coast with the engine off during some low speed range (~15-20m/s, or whatever it is), some drivers are accelerating (loading the engine and I would think increasing efficiency) up to a certain speed, and coasting back down to another speed. With the result being much better efficiency (i.e. mileage) versus cruising at the same average speed.

Now my question is, aside from "is the above supposition correct?", why don't manufacturers just put bigger plug-in battery "buffers" in, coupled with smaller gasoline generators and electric motors? Peak efficiency could very good, acceleration brisk provided the electric motor was suitable, fuel supply diversified, and fuel costs greatly reduced.

My answer to this (my own question is that gas has always been so cheap that the additional cost of the system wouldn't be worthwhile over the lifetime of the vehicle. Now that gasoline prices have risen, the use of more efficient/more costly parallel hybrids is cost effective. And if gas prices rise again, the use of serial hybrids with even greater efficiencies available to the average driver would be practical.

Also, other factors such as patents (supposedly toyota gets all of their batteries from cobasys, and as such must pay a relatively high premium), demand destruction (don't want to cut consumption too much or price drops), manufacturer supply chains (3-7 years turn-around, maybe more?), potential reliability issues, both from unproven technology (more expensive for the manufacturer), and modular vehicle design (possibly cheaper for the consumer in the long run) could significantly influence the makeup of a modern vehicle.

So... yeah, talk about OT. Anyway, does anyone have any opinions about where the current auto is headed?

 

[dootdootdoot]

should be in auto ot too, tried flaggin it, hopefully it'll be moved soon. ^^

 

[dgallup]

All the high milage competitions run WOT up to a certain (fairly low) speed and then coast down with the engine off. No electric motors or batteries, they just add weight, don't contribute any net energy. Of course, these are not practical vehicals or driving practices for real world driving situations.

The cost of hybrid powertrains with the current battery/motor/engine sizing are not cost effective yet, even with government tax breaks so either the technology has to get a lot cheaper or energy costs have to go higher

 

[dootdootdoot]

With government tax brakes similar cars, like the base Prius and base Corolla, have the same price at ~200k miles with gas at $2.50 a gallon. As gas prices increase the overlap point naturally drops, and both of these aren't nearly as economical as a 3L Lupo, which we unfortunately can't get here in the states, but I'm wondering how much the additional cost of hybrids will drop with greater volume and fewer licensing costs wrt battery tech. For example, if Toyota uses an li-ion pack in it's next gen Prius, would that be cheaper per mile compared to NiMH? Something else to consider is the disparity vehicle features, a comparably equiped Corolla would drop the price equilibruim point down to ~120-140k miles iirc.