TT crashes may be caused by Haldex..... Newspaper Article
02-17-2000, 03:00 PM
#1
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TT crashes may be caused by Haldex..... Newspaper Article
<ul><li><a href="http://www.drive.com.au/news/default.asp?section=news&page=http://drive.fairfax.com.au/content/20000218/news/news3.html">http://www.drive.com.au/news/default.asp?section=news&page=http://drive.fairfax.com.au/content/20000218/news/new
02-17-2000, 03:13 PM
#2
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If he's an automotive engineer he must be misquoted.
The quote was "However, when the driver lifts off the accelerator, drive to the rear wheels is abruptly disconnected. It's this sudden 'torque unloading' of the rear axle allied with weight transfer to the front end under braking that unbalances the car."
This doesn't make sense to me. In fact, such "torque unloading of the rear axle" would be a measure to prevent rear unstability, and I think the Haldex is programmed to do this to increase stability.
This doesn't make sense to me. In fact, such "torque unloading of the rear axle" would be a measure to prevent rear unstability, and I think the Haldex is programmed to do this to increase stability.
02-17-2000, 05:20 PM
#3
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Depends on what he means by 'unbalances'... (more)
The condition described in the quote would tend to create an understeering or 'plowing' condition. The car would be somewhat unresponsive to the steering wheel.
If that's what the author means by 'unbalances', then sure, it's a correct statement.
The condition, however, DOES tend to increase the stability of the car. It would have less of a tendency to swing its back end forward in turns if you take your foot off the accelerator, the rear wheels are no longer driven, and the weight shifts to the front when braking.
The quoted person might be commenting on the tendency of the car to plow, or he may just be clueless. I've been amazed at how many automotive professionals really have no grasp of the understeer/oversteer concept, and how even fewer understand the difference between true oversteer and power-induced oversteer. I once had a mechanic tell me that a Dodge Ram is an oversteering vehicle because it's RWD!!!
If that's what the author means by 'unbalances', then sure, it's a correct statement.
The condition, however, DOES tend to increase the stability of the car. It would have less of a tendency to swing its back end forward in turns if you take your foot off the accelerator, the rear wheels are no longer driven, and the weight shifts to the front when braking.
The quoted person might be commenting on the tendency of the car to plow, or he may just be clueless. I've been amazed at how many automotive professionals really have no grasp of the understeer/oversteer concept, and how even fewer understand the difference between true oversteer and power-induced oversteer. I once had a mechanic tell me that a Dodge Ram is an oversteering vehicle because it's RWD!!!
02-18-2000, 05:26 AM
#7
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Sounds ridiculous ! (more)
This theory is completely ridiculous. If you cut off the power on a powertrain you INCREASE the grip on this train, since you reduce the constraints on this train.
If the downforce (weight + dynamics (susp.) + aerodynamics)remains constant, the grip should even be better when you cut off the power!
First : the Haldex is defined to transfer engine brake to the rear as well (it shares the torque between front and rear electronically in all conditions). Of course problems with electronics may happen.
And : the problem, (supposing there is really one)comes from the suspension and the aerodynamics : when you cut off the power or apply brakes, you remove downforce on the rear and reduce the grip.
The only solution is to apply aerodynamic downforce thanks to the spoiler and to reduce the mass transfer from the rear to the front by modifying the suspension (more rigid).
If you want to be convinced, just try the early built roadsters : with a much softer suspension, the problem of stability was increased.
And don't forget the "stability problem" of the TT was just a problem of feeling of the car limits
that's all.
That's why professional drivers (that perfectly feel the limits of a car) found the TT's handling very good at the beginning.
Only regular drivers driving very fast, maybe for the first time experience problems.
My advice : when you drive fast, drive smooth : no violence with the wheel.
Sorry for the length of my "speech" and drive happy !
If the downforce (weight + dynamics (susp.) + aerodynamics)remains constant, the grip should even be better when you cut off the power!
First : the Haldex is defined to transfer engine brake to the rear as well (it shares the torque between front and rear electronically in all conditions). Of course problems with electronics may happen.
And : the problem, (supposing there is really one)comes from the suspension and the aerodynamics : when you cut off the power or apply brakes, you remove downforce on the rear and reduce the grip.
The only solution is to apply aerodynamic downforce thanks to the spoiler and to reduce the mass transfer from the rear to the front by modifying the suspension (more rigid).
If you want to be convinced, just try the early built roadsters : with a much softer suspension, the problem of stability was increased.
And don't forget the "stability problem" of the TT was just a problem of feeling of the car limits
that's all.
That's why professional drivers (that perfectly feel the limits of a car) found the TT's handling very good at the beginning.
Only regular drivers driving very fast, maybe for the first time experience problems.
My advice : when you drive fast, drive smooth : no violence with the wheel.
Sorry for the length of my "speech" and drive happy !
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02-18-2000, 06:12 AM
#10
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Another viewpoint
The car is taking a fast turn. If the rear wheels are suddenly left idle, all you have left is centrifugal force. If you suddenly release the throttle and brake, the rear swings out even
more. Now you have a split second to realign. You don't do it right, or you do it too late
and it's a sure spin. With enough wind up-lift or just a bump on the road, you have a spin
and a flip.
more. Now you have a split second to realign. You don't do it right, or you do it too late
and it's a sure spin. With enough wind up-lift or just a bump on the road, you have a spin
and a flip.