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4K vs. 2Y, not much difference?



On Nov 2, 2006, at 2:37 PM, Allyn wrote:

>> (hey, the same is true in reverse with regards to brakes, I
>> love shooting at that one too :-) )
>
> Surely you're not talking about the MK2 beastie GRM car... I was  
> half tempted to start sucking on the vacuum line myself as those
> autocross cones came closer and closer :)

No no, that's the "bigger brakes always work better" lunacy - anybody  
wanna throw down? :-)

>
>> Keeping 1-5th gears the same, attached to same engine, a 3.94
>> R&P makes more torque at the tires then a 3.67 - everywhere.
>> The multiplier is higher numerically, lower in ratio.  (this
>> is for those in the crowd that might not be following along,
>> Dan already knows all this obviously).
>
> Careful here.  I've run sims on this, and for some 'styles' of  
> torque curves, the wider ratio wins in the 1/4 - because of the 1-2
> wshift occuring later (earlier acceleration = better), and because  
> of there being one less necessary gear change.

So have I (and by reading the next paragraph below, you see that I  
say the exact same thing).  Except that
I spelled vehicle wrong, yep.

>
>> Ah, but does the lower maximum speed in a particular gear
>> (due to redline restrictions) and higher RPMs bother the
>> driver, and does the increased acceleration due to the higher
>> torque output offset the lower overall speed when measuring
>> the time it took to reach that speed?  And that's what I
>> wanted to work out again using a vehical dynamics calculator tool.
>>
>> We kind of got off on a tangent when I tried to express
>> optimal shift points using far too simplistic language that
>> is *not* related expressly to engine torque,
>> but rather torque through the driveline to the edge of the wheel.
>> This translates
>> to the maximum *power* that the car makes as measured at the
>> tires in any given gear.
>>
>> As Dan said, power is a term expressly used to denote the
>> effect of the driveline and is more accurate but it's
>> connotation is not commonly understood.  Torque is more
>> understood, but it takes qualifications to say where it's
>> being measured at.
>
> Torque and Power are both as interchangable at the flywheel as they  
> are at the wheels.  Driveline losses can be reverse-translated
> into a decrease in torque (vs. power) at the wheels.  Granted there  
> are slight differences from gear-to-gear due to transmission
> design (this delta is typically negilgable compared to the overall  
> losses), but those differences cause a difference in both torque
> and power.
>
> ...or am I off-base here?

That's exactly the statement I just made.  The "problem" is that  
there's almost no way to make a "statement" without being
dinged in some way - so any statement of "fact" or observation must  
be surrounded with the proper qualifications and
circumstances in which that "fact" can be examined.

Dan used the proper term (naturally) to describe the force ultimately  
accelerating the car as measured at the outer part
of the tire, power.

I threw around the term "torque" way too loosely and got called  
out. :-)  That's what technical discussions are about, eh?

==Brett



>
> Al
>