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Offline andrew

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Pedal Potentiometer
« on: December 02, 2015, 03:56:28 pm »
I pulled the pedal cluster from my donor car today. After spending a some time under the dash of a B4 Passat learning which muscles I haven't used in a while, I am not terribly excited about repeating a similar feat in the van. I've been looking at different ways that people have done the pedal potentiometer, and I'm offering up an idea for criticism.

Because the spring is inside the potentiometer assembly, it will operate the pedal properly independent of where it is installed. There's a bracket that the coolant reservoir mounts to directly adjacent to the exit point of the gasser throttle cable exit point on the firewall. Can anyone think of downsides to mounting the potentiometer there, cutting the throttle cable and looping it back on itself to make a loop?

I was thinking that I could bolt the cable to itself using very small U-shaped clamps, which would have the added benefit of pedal position adjustment.

There is the engine heat to consider, as well as the potential for some bonehead to spill water out when filling up the coolant. I think a suitable debris shield would probably be very easy to make for that location, though.



Thoughts?
« Last Edit: December 02, 2015, 04:02:56 pm by andrew »

Re: Pedal Potentiometer
« Reply #1 on: December 02, 2015, 11:35:42 pm »
Interesting idea but if the pedal pot goes there where will your coolant reservoir go?  IIRC on B4 Passats the pedal pot is located in the engine bay, near the battery and connected to the pedal via a short run of cable.  If you take out the instrument cluster and all the lower steering column trim and knee bumper the access to the "normal" pot location isn't as bad as on a Mk3 Jetta.  You can access it from above and below with the cluster removed.

Justin
Justin
2000 EVW 1.9l TDI 5spd Syncro

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Offline andrew

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Re: Pedal Potentiometer
« Reply #2 on: December 03, 2015, 03:18:39 pm »
I went ahead and pulled the dash on the T4 for wiring and to fix the blend door flaps. I am still having mixed thoughts on how to place the potentiometer. JoshWa sent me a picture of the under-dash mounting position and there's plenty of room, but it would require some modification either way.

Very interesting to know that VW has placed the pot in the engine bay. My donor car is a B4 and it was under the dash, but I imagine there's a lot more variety in Europe.

Justin, do you basically just bend the top of the accelerator pedal back (i.e. toward the driver) and make a custom linkage?

Re: Pedal Potentiometer
« Reply #3 on: December 03, 2015, 04:05:05 pm »
Ok maybe it's in the eng compartment on an AHU Jetta then, not a B4 Passat I know I've removed it from that location here in the US.  What I've found to be the best solution is to remove the T4 pedal and cut it and then weld on the business end of the Mk3/B4 pedal.  Then you have the correct length and stock pedal action and just need to mount the pot to the pedal cluster.  There are lots of options here, even some convenient holes/studs that can be utilized, but it's a custom job every time.  When setting up just make sure you get 0% throttle position at rest and 100% at fully depressed (measured with VCDS, measuring blocks group 2 IIRC).

Justin
2000 EVW 1.9l TDI 5spd Syncro

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Offline andrew

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Re: Pedal Potentiometer
« Reply #4 on: December 03, 2015, 10:31:27 pm »
Sounds good. Just waiting on my welder to arrive, then. At least I finally fixed the blend door issue, so the dash wasn't pulled in vain. My neighbours have to be at least a little curious at this point, though   :o


Re: Pedal Potentiometer
« Reply #5 on: December 04, 2015, 10:16:39 pm »
Scroll down about 2/3rds on this post on my blog and you will find more info on the pedal mods (T4/A3 hybrid pedal, etc) I spoke about above:
http://greaseworks.blogspot.com/search?updated-min=2012-01-01T00:00:00-08:00&updated-max=2013-01-01T00:00:00-08:00&max-results=22

I know I've posted other pedal pot installs on my blog over the years so if you want to spend some time going through the archives I'm sure you'll find some helpful info.

Viel spaß!
Justin
2000 EVW 1.9l TDI 5spd Syncro

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Offline JoshWa

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Re: Pedal Potentiometer
« Reply #6 on: December 10, 2015, 09:25:47 am »
Here's my setup for reference.  Stock style pot bracket made by noiseybugger on the T4 forum and welded the top part of the my jetta donor pedal to the bottom half of my stock pedal.  The pedal picture is prewelded, using hose clamps to get the right height alignment.  Works good.





Here's the alternative picture on using the donor cars bracket to mount the pot.

« Last Edit: December 10, 2015, 09:39:03 am by JoshWa »

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Offline andrew

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Re: Pedal Potentiometer
« Reply #7 on: December 18, 2015, 09:38:54 pm »
I tackled this yesterday and today. The Passat potentiometer bracket holds the potentiometer at about 45° to the steering wheel piece that it mounts to, as opposed to the bracket shown above that looks to be pretty close to 0°. This means that the end wants to pull the cable down (a direction perpendicular to the tangent of the potentiometer channel) unless the pedal is bent nearly 90°.  However, even if it were bent 90° the end's distance from the fulcrum would be far too short to pull all the way from 0% to 100%.

So I ended up cutting potentiometer circle part of the bracket off the mount/bend part, rotating it up and welding it back on.
I then welded the very end of the Passat pedal to the cut-off Eurovan pedal. It's not fun holding 4 different parts in place and varying numerous degrees of freedom trying to get everything tacked up, but the end result is that it works very well.

I don't have a steering wheel in yet because the column is unbolted, so it's tough to tell how "normal" it feels, but placement seems right. I'll try to put up pictures on my website pretty quick here.

Now how do I remove the old throttle cable? Can I just pull really hard?

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Offline JoshWa

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Re: Pedal Potentiometer
« Reply #8 on: December 18, 2015, 11:02:22 pm »
Yeah. You can see in my pictures that I've just got it dangling. I'm assuming it just needs to be cut to be pulled out.  My is still just looped up and tucked out of the way.  Post a picture up here too and we'll a good example thread of pot setups.  I'd like to see some pics of how some have set theirs up in the engine bays.

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Offline andrew

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Re: Pedal Potentiometer
« Reply #9 on: December 24, 2015, 09:42:52 pm »
Yes, you can simply pull hard on the accelerator cable.

Finally got pics posted. I should have the clutch hydraulics connected up tomorrow and then I'll have all three pedals back!

Click to embiggen




http://andrewclink.com/projects/thebus/pedals