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V6-I4 differences Posted by Ari [Email] ![]() ![]() In Reply to: Re: Not all TCS created equally, James, Mon, 27 Sep 2004 13:24:57 Members do not see ads below this line. - Help Keep This Site Online - Signup |
On the 4-cylinder, on Manual tranny cars, the TCS controls the position of the throttle butterfly at all road speeds, and at low road speed, applies the brakes to the slipping wheel. On Autotranny cars, only the throttle butterfly is controlled, autotranny TCS does not apply the brakes. However, the autotranny TCS can also activate the kick-down cable. There is only one throttle butterfly, and that is controlled by a motor; if the TCS has a sensor or other problem, it severely limits the throttle butterfly position - 'limp-home.'
From what I've gathered on the V6 TCS, it actually has two throttle butterflies. The main one is conventional, fully controlled by the gas pedal position. This allows full control of the throttle by the driver. The second butterfly is controlled by the TCS, and it can effectively close the throttle - so you can open the first butterfly all you want; if the TCS thinks there is slip, it closes the second one. However, that second one is spring-loaded, and the default is wide open, so if the V6 TCS detects a problem, it just defaults to the wide open position, and the driver had full control - no 'limp-home' mode. You'll still get a TCS light indicating a problem.
It is possible that the V6 TCS can also control the brakes, but I doubt it. I don't have facts either way, but I can speculate. Saab's approach on the autotranny 4-cylinder cars was NOT to apply the brakes. Since in the US, the V6 cars came only with autotrannies, I assume that they used the same approach.
As to starting up in a higher gear, I'm pretty sure that's the Winter mode. However, the ZF tranny in the 9000 is non-electronic; forcing it to start in a higher gear would require a mechanical servo. I haven't found evidence of one. On the 9-3 and 9-5 with electronically-controlled transmissions, it would be a different story.
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