Idle control

[markocosic]

Does anybody know how the 3.5.4.2/"no drive by wire" rule applies to an idle-speed control?

Assuming you have an ordinary cable actuated throttle body, can you add an electrically actuated 'bypass valve' for idle-speed control provided that (by virtue of the size/airflow capability of the thing) its clearly just for manipulating idle-speed electrically and not "driving" by wire?

[markocosic]

Does anybody know how the 3.5.4.2/"no drive by wire" rule applies to an idle-speed control?

Assuming you have an ordinary cable actuated throttle body, can you add an electrically actuated 'bypass valve' for idle-speed control provided that (by virtue of the size/airflow capability of the thing) its clearly just for manipulating idle-speed electrically and not "driving" by wire?

[Rob Battiston]

Marko, most non-'drive-by-wire' systems are fail-safe, meaning that if a cable snaps, the intake valve shuts and the car goes to idle(hence, two retaining springs on butterfly valves...).

I can imagine that your idle speed controller should have a fail-safe position whereby the valve goes to idle mechanically should you lose power to it or the control signal fails. If it doesn't, you'd have a hard time convincing the tech boys that it's okay. They'd want to see that if something f'd up, that it wouldn't jam open the throttle somehow.

[Patrick W. Crane]

I disagree. most of the cars i've looked at have their idle screw on the butterfly and if the cable were to snap - it would only close to idle speed. I don't have the rules in front of me, but i imagine that as long as you can prove you can't control your engine beyond idle with it, i can't see why not. but be ready to prove it.

[Sam Zimmerman]

I would email the rules committee on this. I can't see where there would be a problem, but you should get email confirmation from SAE. Can I ask what your motivation is for doing this, design points or a better idle?