Just bought an '07 ZX4 ST. Wondering how the traction control drops the rpm? If I really put my foot into it, with traction control on, it feels like the engine is bogging down. I know that some cars drop cylinders, to achieve the drop in power(rpm), and I'm wondering whether this is the case with the Focus? Or is some other method being used to achieve the drop in rpm?
Yes, you are correct, however, in addition to the use of the brakes, when there is excessive acceleration (tire spin) when traction control is engaged, something else occurs which reduces the rpm (likely as mentioned above, that the fuel is reduced). This is similar to when you reach the speed at which the governor is set, for maximum speed.
Most traction control systems start out by taking out ignition timing which would definately give you the sense of the engine bogging down. This would be the the first line of defense so to speak. Thats all well and good but the engine computer is typically slow to restore that timing. It doesnt know if you're spinning just because you are in a puddle of water or on a ice covered road so it works on the 'abundance of caution' principle.
In addition to that, depending on the set up, the ABS may be engaged as well to reduce the the spin of the wheel that doesnt have traction (if it happens to be just one and this also requires a 4-channel ABS system).
Those are the primary methods. Depending on the sophistication of the engine management and the cost of the vehicle, and if it has an automatic or tiptronic style tranny then it may employ an upshift scheme whereby the transmission is shifted into the next higher gear to reduce torque. GM used to install on their performance cars a feature called 2ng Gear Start where you could push a button and force the transmission to start from second gear. I havent seen it used in the last few years probably due to the improved traction control systems.
On my GTP's traction control it uses timing reduction and the 4-channel ABS (I dont think there are many 2-channel ABS systems out there anymore but I could be wrong about that I just havent seen them). However, I can completely disable it at the push of a button.
I know, for instance, on the Dodge Charger you can turn it off but after a certain speed the computer will override that and on the Focus it used to be there was no way to disable the traction control system alone. You could pull the fuse but I believe you disabled ABS as well. On my GTP I can turn off the traction control but still have ABS (I did, ummmmm, an experiment, just to be sure of that).
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
Oh, I thought I would add, I personally dont know of any traction control systems that cut fuel in an attempt to restore traction. If you think about it, that is a very risky way to do so. If it is not done correctly then you risk stalling the car. If you were trying to avoid a collision with a car ahead of you and the motor stalled the ABS is probably not going to function and you will lock up the brakes and in addition to that with the motor not running you wont have any or extremely limited steering because the power steering pump wont be working. Even if the ABS were to continue functioning, without the motor running you would bleed off brake pressure and make matters even worse.
If there is a vehicle out there that uses that kind of system for traction control I would be extremely hesitant to own such a vehicle. Even if the computer were to just reduce fuel pressure (for what reason such a method would be used is beyond me) you would run the risk of damage to the motor due to a sudden lean condition.
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
Nahh, TCS is a good system. What makes it bad is not being able to disable it, at least from a performance perspective, such as track days and so forth. Furthermore the manufacturers are making the TCS more and more aggressive and sensative but its a good system overall.
There is a technology out there, that has actually been around for quite some time, but is just now being implemented where the car is equipped with a system that is very similar to the collision avoidance systems on airplanes. The car actually detects how close you are to vehicles ahead of you and if the closure rate is too fast it automatically applies the brakes.
I dont recall which vehicle it is but there is one out there that is using this system now. All in all, you can equip a vehicle with the most technologically advanced protection systems and the driver will still be the wild card. All those systems can only do so much. Like the Allstate commercial goes "They have made everything safer about the automobile except the driver". ProjectFocusFast wrote: All I can say is, TCS is FTL. Too bad it's mandated by 2012.
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
Thanks for the very informative response. Ignition timing makes complete sense. On my ST, I do have the option of disabling the Traction Control (I tested it, and could rev as high as I wanted with spinning tires), and plan on doing just that, in the spring/summer months. Unfortunately, I have been driving on ice for the past month, and expect to for the majority of the next 4 or 5 months. I look forward to the summer, and being able to put my foot into it, to see what the ST performance is really like.
I agree, TCS is good (and I'm not generally a fan of technology), but it is definitely good to be able to turn it off (for performance driving). The Infinity G35 Coupe uses the sensing technology. When placed in cruise control, it senses if you are coming up to quickly on another vehicle, and adjusts speed to match the vehicle that you are following. It will apply brakes, up to 25%. I just had this conversation with my buddy, who own's the Coupe, yesterday.
