I see what you mean now. Thanks for clearing that up.

 

My main concern, is won't the brushes end up wearing out faster, due to the additional pressure being applied by moving the cover forward

 

That's a good question. I'm sure Ford designed the carbon traces to withstand years of use/wear but I am not sure that it will self-calibrate for the WOT position. There were some S197 GT owners that datalogged TPS and found they couldn't get more than 85% throttle. The PCM can self-calibrate for closed throttle/idle because that is the zero position. However, a potentiometer would essentially have to sweep to a certain position on the carbon trace to send out the "WOT" signal due to the change in resistance on that trace.

 

Well, there are only two possibilities after the mod. The brushes could sweep past the end of the carbon track, which will give a fixed value that the CPU always reads as WOT. Or, they sweep to a new position further along the track and give the CPU a max value higher than anything it's ever seen before, and that maximum becomes the new WOT value.

I think the data logging you're referring to wasn't exactly relevant to this. In the past, people have found a mismatch between pedal position and throttle position. If the computer is reading pedal position correctly at 100% but not opening the throttle all the way, then there is probably engine management stuff going on that you have no control over by messing with your throttle assembly. The best you can do is give the computer 100% pedal position; it might still decide that you really don't want your neck snapped back by a hard shift and only open the throttle 85%. A tune will do something about that.

 

I have one other concern: what is the risk factor of the brushes breaking, once the cover is pushed forward. In other words, will the additional pressure cause damage to the brushes, from the cover bending them further onto the carbon trace.

 

There is no additional pressure, and they aren't being bent more. To get more pressure or increase the bend you'd have to somehow screw the case together tighter.

 

Thanks once again for your expertise, and positive feedback SStang.

 

No it doesn't. I have a $300 joystick that self calibrates BOTH ends of all axes every time it fires up. It then fine tunes the calibration as I use the stick in a game.

If a $300 joystick can properly implement a functioning self calibration routine, don't tell me a $30,000 car CAN'T do it.

Any time you use a pot in critical applications, you have to spend a bit or resources to make SURE the signal you are getting back is the correct signal. That means calibration. That means having multiple traces so you can compare the results. That means having VERY effective routines to identify any kind of fault and fail safe.

As for those with 85% throttle, are you sure that is calibrated in throttle OPENING (aka: 0% is fully closed an 100% is throttle plate at 90 degrees), or is it simply calibrated in percent of full scale voltage (VERY common in electronics)?? I don't know how it is calibrated, but I wouldn't get too worried about 85% until I KNEW how it was.

 

The $20,000 car uses a $44 part. I wouldn't put it past Ford to use some cheap potentiometer design instead of something that BMW, Mercedes, Infiniti, or Lexus would use.

 

Thats drawn on the conclusion that merc, bmw, infinity are superior? Really? Last I check they have less on wards 10 combined than ford alone in the last 10 years.

As for the pot being at fault. It does recalibrate. There is a routine to recalibrate throttle position. It looks like it needs some tweaking in some cars. Not so much in others.

 

Ok. So you think the pots (multiple, five actually) in the $300 joystick are better than the the pot that is used in the drive by wire pedal assembly??? Considering I can buy replacement pots for less than $6 from the joystick manufacturer or less than $2 from Digikey, I REALLY don't think the joystick is using better hardware!

Actually, I KNOW they aren't. I've taken the joystick pots apart before and comparing the guts of these pots to the pictures posted above of the insides of the TPS, well, there IS no comparison! The TPS is built WAY better and WAY more reliable.

 

http://www.crownvic.net/ubbthreads/u...gonew=1#UNREAD

There are also other cases of DBW systems exhibiting unusual behavior and not just in Fords. I wish they had stuck with the cable throttle.

 

I somewhat agree with you. But it wasn't really their choice. Blame fuel economy and emission requirements for the death of the throttle cable.

 

I can appreciate the simplicity of DBW and the reduction in NVH from not having a cable. However, the GM rental cars I drove (G6 GT and Impala) had severe throttle lag. I'm grateful that my Mustang does not have throttle lag because the lag is a much bigger problem than dead-play.