4K vs. 2Y, not much difference?

[brett at ataxxia.com (Brett Van Sprewenburg)]

No biggie Dan, I fell into a thinking trap as I was typing it  
out...hence
my immediate conversational responses to myself saying, "wait, no,  
that's not quite
correct either."

The reality is I previously stated, you have know what the torque  
value as obviously
measured through the transmission at the rubber / road surface in  
order to
know if shifting up at a particular RPM is advantagous or not.   As  
you say, maximize
the power of your engine, what's your favorite unit of measure here?

I thought torque would be more appropriate to the transmission  
discussion because
the HP output of the engine is always the same, but the torque at the  
tire / road
changes from gear to gear at different RPMs (with final drive being  
quite pivotal
to the discussion formerly at hand)

And this is (no longer?) relevant to the discussion because the  
orginal question
pertained to what transmission is "better".  More torque is better to  
the point of
tire slippage.  "Torque wins races" is not just a fun addage.  (hey,  
the same is
true in reverse with regards to brakes, I love shooting at that one  
too :-) )

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).

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.

The question here is, given that 1-5 gear set and one of those final  
drives, is the
engine happy (and in turn, does this make the driver happy)?  You cannot
compute acceration over time in any gear unless you know the torque  
input at
those RPMs (and weight of the car) - again, engine torque is one  
input to
figuring out if the driver is going to be happy with their choice of  
final drive
(trying to get back at the original question a bit).

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.

==Brett


On Nov 2, 2006, at 12:17 PM, Dan Bubb wrote:

> I read all your messages.
> I'm only disagreeing with shifting right beyond the torque peak.  
> For max acceleration you should shift beyond the POWER peak.
> Dan
>
> From: "Brett Van Sprewenburg" <brett@ataxxia.com>
> Sent: Thursday, November 02, 2006 12:09 PM
> Subject: Re: 4K vs. 2Y, not much difference?
>
>
>>
>> I think that if you had waited until you had read my next message,
>> you wouldn't have pulled
>> the trigger so fast Dan. :)
>>
>> (My next message talked about torque peak at the wheels, because we
>> are here discussing
>> the variabilites of a transmission and it's effects).
>>
>> Here's a nice article detailing pretty much what my second message
>> said, and what you just
>> restated:
>>
>> http://www.allpar.com/eek/hp-vs-torque.html
>>
>>
>> ==Brett
>>
>>
>>
>> On Nov 2, 2006, at 11:39 AM, Dan Bubb wrote:
>>
>>> No, no, no!!
>>> You should shift after the power peak, not the torque peak.
>>> You can plot torque at the wheels through the gears or power at the
>>> wheels through the gears and they will give you the same results as
>>> far as shift points. Where the torque available at the wheels in
>>> one gear drops below the torque in the next gear will be the shift
>>> point although you'd probably want to shift a couple hundred revs
>>> higher to accommodate the slight drop in speed during shifting.
>>> It's worth noting that the shift RPM will vary depending on the
>>> gear spacing. Typically you want to shift at higher RPM in the
>>> lower gears.
>>> Grant did a study of this a year or so ago.
>>> If I had time at work I'd take the time to demonstrate. It'll have
>>> to wait till later.
>>> Dan
>>>
>>> From: "Brett Van Sprewenburg" <brett@ataxxia.com>
>>> Sent: Thursday, November 02, 2006 9:43 AM
>>> Subject: Re: 4K vs. 2Y, not much difference?
>>>
>