Fwd: Throttle-by-Wire

[Asylist]

> Why?.
> how many stock engined cars are going to spin the tires during accleration
> at 70?.
<snipped>
> Yep.
> Again is wheeelspin thru accleration with a stock engine an issue at?.

In a less than optimal traction situation, its entirely possible.  Hell, my
Grand Am routinely breaks traction on the freeway in the rain.  Granted, the
turbo kicks in a little harshly, and the tires could stand to be replaced,
but nonetheless, the tires do break traction.  Besides that, its not just
acceleration we are concerned with.  Imagine this situation-you are cruising
thru the rain, somewhere around 70.  Altho the highway is wet, the car is
stable, and hooking up just fine.  You come to a small valley in the road,
with about 3 inches of standing water.  Its too much for the tires to
handle, and they break traction.  It doesn't take much for the rear end to
start coming around at this point, and with the drive tires spinning at a
good rate faster than ground speed, its quite easy to continue the spin.  An
inexperienced driver could panic at this point, slam on the brakes, and make
a slightly bad situation very bad, very quick.  On the other hand, a
properly functioning TC system will prevent the wheels from spinning.  When
you exit the standing water, even if the car is off axis, it will quickly
return to straight.  This would all happen so quickly, the driver would
barely even notice it.  Of course this is in a RWD vehicle.  FWD vehicles
exhibit different behaviors, but could still benefit from TC.  With the
front wheels then breaking traction, its the front we then have to worry
about.  Torque steer becomes an issue, as does the results of the tires
coming back into the contact with pavement, and the increased traction.
Altho the wheels continue to spin faster than ground speed, the torque can
still be an issue, pulling the front end off axis.  Altho a spin is unlikely
at this point, it can still be unsettling to the driver, again causing an
overapplication of the brakes, therby sending the vehicle out of control.


>
> In the total lack of traction, no traction control unit will work anyway.


But it can.  See above about the rain, and hydroplaning.  Even on ice,
keeping the wheel speed equal to ground speed can go a long way towards
maintaining control.


> Explain how.
> Are you now switching tpoics to race cars?.

Do I have to go back to previous posts, where my first points were TC on the
track?  The key is in maintaining momentum, and speed thru a corner.  You
are coming to a corner on a roadcourse, going 60mph.  In order to maintain
100% traction, you might have to slow to 30mph.  However, while you may not
have total traction in a power slide, you may be able to maintain 50mph
ground speed in doing so.  Of course, you do have options.  Such as
modifying the suspension, and installing race tires in order to maintain
that traction at higher speeds.  But, we are talking about stock cars here,
not modified ones.  An easy way to prove this is to watch any race held on a
dirt track, be it desert trucks, rally cars, or sprint cars on a circle
track.  An extreme example, but the physics don't change whether you are on
dirt or pavement.


> I'mjust trying to get to the actual *truths* in what you are saying.
> Having missed the 40 MPH shut off, is missing a rather inportant
> part of the
> overall strategy.  Worring about traction in a none traction event is
> meaningless in my opinion


There is no surface on which our cars are driven that we truly have zero
traction.  There is traction on ice, low traction, but traction nonetheless.



Eric Klos, Chesterfield Twp, MI   www.geocities.com/asylist
1989 Saab 900, project car-goal 200HP naturally aspirated (in storage, bad
trans) "Saab-They're not for everyone"
1989 Pontiac Grand Am SE 2L Turbo (daily driver)
1986 Dodge Daytona Turbo Z with an NA motor :( parts car
as listed in my Livejournal interests-"beating up on V8s with my turbo 4
cylinder", :)

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