Disabling drive-by-wire by pulling a fuse? (x-post from B6 forum)
12-08-2004, 03:31 PM
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Alittle about the DBW smoothing function that the ECU applies to the accel pedal...
Here is what I have found...
The ECU definitely enables a smoothing function on the accel pedal. This means that all input is both delayed and averaged, reducing spikes and surges, creating less jerky ride, especially on bumpy pavement.
HOWEVER - if this smoothing was enabled with the clutch engaged, it would make pulling out very difficult. SO, the ECU removes all smoothing when the clutch is depressed... But only for 15 seconds I believe. Then it re-enables it. I believe it also disables it when the car is at rest (0 mph).
Try this. Coast in neutral. Hold the accel at 2000 and blip the throttle. Do it a few times and notice the engine response. Now coast and hold in the clutch and do the same. You'll notice it revs much higher, and quicker. Hold the clutch in for 15 seconds and you'll be back to a "smoothed response".
You could build a circuit to hold the clutch signal "on", and pulse it every 10 seconds or so - removing all smoothing. BUT....
I think the clutch switch does more. At idle, stopped, the idle changes when pushing it. I think it may do something with timing to make pulling out easier. It's something I never logged or checked, but it's something you might want to investigate should you decide to try to remove the ECU's smoothing through the clutch signal.
BTW - This smoothing is standard in the industry, but only recently is it implementable in production cars (with DBW). I've written several car-control programs on high effeciency concept vehicles (HEV's). On the dyno, and more so on the road, we could obtain almost 15% better energy ecomony from smoothing the accel pedal. You can't imagine how much your foot bounces around on bumps, which results in quick bursts of wasted energy (fuel) being absorbed by shocks/motor mounts, motor response time and such. You can also imagine the decrease in emissions (accel pump function...)
Enjoy
--Dan
The ECU definitely enables a smoothing function on the accel pedal. This means that all input is both delayed and averaged, reducing spikes and surges, creating less jerky ride, especially on bumpy pavement.
HOWEVER - if this smoothing was enabled with the clutch engaged, it would make pulling out very difficult. SO, the ECU removes all smoothing when the clutch is depressed... But only for 15 seconds I believe. Then it re-enables it. I believe it also disables it when the car is at rest (0 mph).
Try this. Coast in neutral. Hold the accel at 2000 and blip the throttle. Do it a few times and notice the engine response. Now coast and hold in the clutch and do the same. You'll notice it revs much higher, and quicker. Hold the clutch in for 15 seconds and you'll be back to a "smoothed response".
You could build a circuit to hold the clutch signal "on", and pulse it every 10 seconds or so - removing all smoothing. BUT....
I think the clutch switch does more. At idle, stopped, the idle changes when pushing it. I think it may do something with timing to make pulling out easier. It's something I never logged or checked, but it's something you might want to investigate should you decide to try to remove the ECU's smoothing through the clutch signal.
BTW - This smoothing is standard in the industry, but only recently is it implementable in production cars (with DBW). I've written several car-control programs on high effeciency concept vehicles (HEV's). On the dyno, and more so on the road, we could obtain almost 15% better energy ecomony from smoothing the accel pedal. You can't imagine how much your foot bounces around on bumps, which results in quick bursts of wasted energy (fuel) being absorbed by shocks/motor mounts, motor response time and such. You can also imagine the decrease in emissions (accel pump function...)
Enjoy
--Dan
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