[Vwdiesel] something worth trading the A4 in for

[Terry Briggs]

to use an old racers saying, HP doesn't win races, torque wins races. 
Torque gets you moving, hp allows you to maintain speed once the torque 
drops off. The curve of which determines how fast the end result is.
On Jul 5, 2008, at 1:25 AM, Kurt Nolte wrote:

> Val Christian wrote:
>>> 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.
>>
>
> As you yourself will later say, you use hp to accelerate. Torque pulls,
> horsepower accelerates. So yes, you would need something that would
> produce the -horsepower- necessary to -accelerate- the car at
> near-wheel-speed RPM... unless you want to utilize a device that
> modifies the speed the wheels see, that is, a transmission...
>
> The gear reduction on the output shaft of a gas turbine is a
> "transmission" too. Fixed speed for the most part, but it's a
> transmission nonetheless. It involves the use of gears of varying sizes
> to accomplish the purpose of modifying a prime mover's input
> characteristics to better accomplish a desired output characteristic
> set. In this case, the high-RPM, (relatively) low torque output of the
> gas turbines themselves into the lower RPM, much higher torque output
> shaft characteristics.
>
>> 	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.
>>
>
> And thus, a transmission. Or an engine that produces all your hp needs
> (torque @ RPM) down at the bottom end, while still having breathing 
> room
> left up top for cruising. Bigger engines produce more low-end torque
> (and thus hp) as a byproduct of their larger displacements and/or 
> longer
> strokes.
>
> Without a transmission, your wheel RPM = engine RPM, remember.
>> 	HP is needed for acceleration, but it's also needed for
>> 	max cruise (drag) and hill climb (lift).
>>
>
> Here, by the way, is the aforementioned instance of HP being necessary
> to accelerate.
>> 	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.
>>
>
> Your landspeed would only be 60mph, but your effective windspeed most
> certainly isn't 60mph at that point. The commentary about 23hp being
> sufficient is assuming no headwind, but simply what is necessary to 
> move
> a vehicle through calm air at a given speed on flat ground. Lots of
> similar assumptions are made by these hawkers, why can't I make a
> (common) assumption of my own?
>
> The claim is that electric cars don't "need" a transmission. Why would
> they, peak torque output at 0RPM, you've got lots of power down low!
>
> And sure, you can brute force muscle your way into motion like that,
> using an oversized, higher torque motor than you need, but it would be
> -like powering a Rabbit with a V8, just to avoid using a transmission.-
> Going to a bigger, torquier mover just so you don't have to involve
> gears between the mover and the wheels.
>
> -Kurt
>
>
>
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