As set out in this thread
https://www.jaguarforums.com/forum/x...engine-268012/
I and a few others have despaired of the low quality and frequent re-setting requirements of the aftemarket TPSs now available. As a consequence I sourced and fitted a Hall effect TPS, which relies on a magnetic, non-touching system to give a variable voltage signal to the ECU (which tells the ECU how far open the throttles are. This modification has and continues to work wonderfully. I souced the TPS from Variohm, who are really helpful and will make a TPS to the exact requirements of the client. In a 5.3 litre HE engine's case, a 90° clockwise turn from closed throttle 0.32v to WOT 4.9v.
However, contrary to what I wrote in the above thread, the TPS does not power up the first time used, regardless of position, to 032v. You still have to set the TPS up to start at 0.32v at the closed throttle position, just like the OEM type has to be. To this end, slots are provided in the TPS:

Although adjustment "wings" are provided on the TPS, you still have to get the fixing points in the correct voltage region before drilling and tapping the fixing holes.

TPS here with fixing holes tapped, tiny bolts fitted and then voltage adjusted.

Furthmore, Jaguar maintenance procedures state that the TPS closed voltage should be checked, and the TPS if needed adjusted, every 20,000 miles; which of course, nobody does because it is a royal pain to do. Involving removing the capstan and needing two people, one to adjust and one to handle the multimeter. Now, in the case of the Hall effect TPS, it should not, once set, go out of adjustment; but even so, it would obviously be MILES better if one could adjust, the TPS without having to remove the capstan and undo the TPS. It would also greatly ease the initial fitment, if you could just mount the TPS and adjust it from above.

So I got to thinking, and with the help of Ben Kenobi's 3D printer and Lousi the Lathe King, this is the GiF solution:

The OEM throttle capstan spindle has a fixed welded-on disc, attached to the capstan by two screws. As the capstan turns, the disc/spindle turns and this turns the TPS. This is the OEM spindle:


OEM spindle in position


OEM spindle on its own

Now, if the spindle could be turned independently of the disc it is welded to, then in principal the TPS could be adjusted by turning the spindle only. Here are the parts Louis Roi de Tours (Louis the Lathe King) made for me over the summer:


From left to right: shouldered spindle with 5mm threaded top, disc, locknut to lock disc to spindle shoulder, wingnut to be attached to threaded part with permanent Loctite 270 to act as adjuster and counter-torque when doing up the locknut.


Picasso's recently discovered diagram of dimensions (only accurate for the spindle length for using a Variohm TPS). Note that actually the OEM spindle diameter is just under 8mm at 7.85mm and 8mm will not fit! A fact I found out this morning involving a pleasant 30 minutes with 400 grit and the spindle in a drill!


Disc on spindle shoulder


Closeup of spindle shoulder/5mm threaded part


Locknut in place, locking the disc to the spindle


Wingnut in place


Spindle lower end perfect length for the Variohm Halll effect TPS. NOTE: the bottom of the capstan is not flat, there is a protrusion round the centre. Ben Kenobi kindly ran up a spacer (in brown) on his 3D printer to level out the surface


The wingnut has been fixed in place with Loctite 270, this requires 400°C to loosen, so the wingnut will work both to hold the spindle in position both to loosen and tighten the locknut, as well as with the locknut loosened, to turn the spindle independently of the disc and thus to adjust the TPS position.


TPS in place. All that is now needed is two tapped fixing holes, all adjustment being from the top. Note the spacer hole slightly out of position. This is not Ben's fault; rather a tribute to the variability of Jaguar's throttle capstan machining! It fitted his capstan holes perfectly!

 

Bloody Brilliant.

I aviioed that adjustment.check like the plague, and had to really be in the mood to do it, that is so simple, and there is NO excuse for not checking the OE or the Hall Sensor at any time.

 

Excellent innovative work, Greg! Well done!

Paul

 

Nice job, I reached out to them to see if they could come up with something for the 4.0L

 

Absolutely outstanding, Greg!!

 

I have just got round to actually fitting the modified spindle, and adjusting the TPS on the capstan, capstan on the car.

I proceded as follows:

• remove the OEM capstan spindle/disc assembly. This can be done by just undoing the two disc securing screws and with a small pick easing it upwards and off
• push in the new spindle, looking down the hole to align the drive with the TPS and be certain it is engaged with the TPS drive. My advice if you decide to create one of these, is to remove the old spindle, give it to your machining guy, and ask him to create the new one to the same spindle dimensions and drive system (D, prong, or slot).
• drop the disc onto the spindle, and align it with the screw holes in the capstan. You may have to push it into place a bit against the capstan return spring
• screw the disc in place. It uses 8mm headed setscrews
• screw the locknut onto the spindle but do not lock it, my spindle has 5mm metric threads which use 8mm nuts,
• screw on the top fixed nut and Loctite it with 638. This is the nut that you use to turn the spindle to make the TPS adjustments
• wait for a couple of hours for the loctite to go off sufficiently, or use two nuts as the fixed nut and lock them together
• holding the fixed nut, tighten the locknut so the spindle can JUST be turned with the fixed nut. This means any adjustment you do will not spring back.

Now the metering:

• get a narrow crocodile clip, eg
  Amazon
  Amazon
  and attach it to your meter's positive lead
• pull out the loom to TPS rubber plug about 1/4 inch; this will reveal enough of the plug metal male terminal to attach the crocodile positive meter lead to, while still leaving the plug in electrical contact with the loom. The crocodile must be attached to the signal feed, see the attached pdf for wire colours and positioning of the signal feed on the loom and TPS plugs.
• Attach the negative meter lead to an earth (ground) point on the engine
• Switch on the ignition and the meter, and ensuring the locknut is only loose enough to be able to JUST turn it, use the fixed spindle nut to adjust the TPS voltage to 0.32v (+/- 0.02v).
• with the adjustment spanner on the top fixed nut, and another on the locknut (which is already pretty tight remember), carefully tighten the locknut using the spanner on the top nut to torque in the opposite direction, so as to ensure the adjustment does not go out of spec when you tighten the locknut. This may take a couple of goes; but you soon get the hang of doing it without spoiling the adjustment.

Some photos: Note that my first idea of using a wingnut as the fixed adjusting nut was not a good plan, as it can interfere with the throttle rods. Note also the attachment which gives OEM wire colours and plug positioning of the 5v TPS feed, the earth and the signal.







TPS to loom plug slightly pulled apart, so the meter can contact the metal male while the connection to the loom is still good. In this shot the signal wire connection is top left, the earth top right, the 5v feed bottom right. The TPS plug is black and the loom plug is white.


Loom plug in its normal connected position