[Vwdiesel] something worth trading the A4 in for

[Patrick Dolan]

The electric car promoters (and don't doubt it, the vast majority of these scheisters are nothing BUT promoters) like to imply that electric motors are somehow "better" for the purpose, because they produce max torque at zero RPM.  However, you can't RUN them at that speed, and they have a torque CURVE, and unless run in the fat part, they aren't particularly good at power density or efficiency.  The implication that you can go from zero to 130 mph with no gears is pretty unlikely in reality - unless you had a REALLY inefficient setup in normal driving range.

Plug ins will come, and they will improve rapidly (since there is already a very mature industry for them to draw technology from), but it is indeed the batteries that we need.  The latest go-around of LiPos are where the promise lies, but as you can clearly see in the marketplace, there are as yet no serious series producers (that's a sparky joke).  When they are there, the prices will come down, the power density will go up and reliability will start to approach automotive industry standards (which are by some experiences, quite variable from maker to maker).

----- Original Message -----
From: Val Christian <val at mongo.mongobird.com>
Date: Friday, July 4, 2008 10:17 pm
Subject: Re: [Vwdiesel] something worth trading the A4 in for

> > 
> > "Power robbing transmission" my boot! Typical manual 
> transmission is 95% 
> > efficient, and improves prime mover efficiency by allowing it to 
> operate 
> > within its peak efficiency and power bands more of the time.
> > 
> > You could drive a normal car without a transmission, but you'd 
> need a 
> > single step-down (or really tiny wheels) and some way to 
> decouple the 
> > engine from the wheels while stopped. These two alone would 
> introduce 
> > the same level of power loss as a gear-gear 
> transmission/differential 
> > and dry clutch. Electric motors, granted, get around the 
> decoupling 
> > necessity.
> > 
> > Oh, and your engine would need to be able to produce 100% of the 
> hp 
> > necessary to begin accelerating the vehicle's mass at low RPM 
> points, as 
> 
> 	Not hp, rather torque.  A gas turbine is an example of 
> 	an engine which has high torque at low output shart RPMs.
> 	Diesels are not as good, but they do have more torque at 
> 	lower RPMs, favorably impacting drivability.
> 
> 	However gas turbines near output shaft stall, are not 
> 	as efficient as diesel engines.  
> 
> > opposed to being able to wind it out to its peak HP point to do 
> your 
> > standing acceleration.
> > 
> > In other words, you'd need a V8 to move a Rabbit around.
> > 
> 
> 	No, you simply need a configuration where suitable torque is
> 	available at low wheel RPMs.
> 
> 	HP is needed for acceleration, but it's also needed for 
> 	max cruise (drag) and hill climb (lift).  
> 
> 	A 48 hp Rabbit, heading into a 50 knot wind, is speed limited
> 	due to increased aerodynamic drag on the Rabbit.  With a 
> 	50 knot headwind, don't expect a road speed much over 60 mph.
> 
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