Soooooo… Anyway… Cars!
I am digging your water rail! I’ve looked into having one fabbed up in stainless and good lord you’d think I wanted a rocket ship! I should learn to weld.
But you’ve solved that part here with only solder and some brazed joints! This could be reproduced by most anyone. Can you tell me a bit about it? Are those brass washer flanges?
Folks…take it off-list.
By the looks of the bare interior, it appears you’ve made essentially a “track car:” any further fotos of the interior?
Any suspension mods?
Thanks! And to get them all aligned and spaced properly, I’m assuming you assembled the pre-built ports all on the engine then soldered the rail connections?
Thanks JW, your comments and likes are very much appreciated.
I actually really like the look of the gauges and switches. Spartan for sure but with some door cards and if the wires and things we can see behind are not exposed normally or a plate could be fashioned it would in no way seem stripped out like a real track car. It still has a great visual appeal to me at least.
It’s been said a few times, but is worth repeating…
You WILL crack something in your piping there between radiator and engine.
I can say that with 100% certainly, that it will happen.
A flexible hose is required between the radiator and the engine. Please do it - let’s not make believe physics and science doesn’t exist. 
It’s about 30 minutes of work and some hose clamps to avoid this.
I’m finding 3/4 by 1-1/2” copper tees. Anyone know the ID of the rad hoses?
1-1/2” copper water rail would look nice and ( if correctly sized ) could take standard water hoses.
Longer 3/4” 45 deg streets are avail too. I’m liking this idea more and more.
HOME DEPOT is doing well at least!
i say give it some time , and shake out the bugs!
Seems to me that there is a rubber hose that connects the rad to the copper piping. Why wont that suffice to provide give with engine movement.
Well It’s a very short hose, and it’s at the end of a long arm, so just one degree of deflection in the engine will result in a fair bit of movement. I could do the math, but its clear from eyeballing it that this is not enough, and the flex is in the wrong plane too. There should be much more hose to allow for engine twisting and so there is no force applied to rigid things like pipes which will best case, fatigue over time, or worse.
EDIT:
I did the math.
If the engine twists just ONE degree (which it most certainly will), that is a tenth of an inch of deflection, and it’s not in the plane that the hose is going to “give” much.
I like that Frank, eternal optimism.
A pessimist would say the those Best British Rubber engine mounts are now hard as a rock, so no chance the engine will bounce around any more.
Whatever, if it works it works and nothing like trying a new approach to keep an old XJ-S on the road.
I still have the ECU harness running from back to front in my coupe, although it is no longer used since fitting an aftermarket EFI system which is now in front of the radiator.
I have diced into a couple of the old harness wires when needing a wire from cabin to engine bay.
I would expect a hall effect TPS to have 3 wires. My hall efect TPS has 3 wires.
Should be a ground, a +5V ( or a +ve of some type ) and a signal wire.
That is the one I used and with a bit of fiddling it will fit into the existing capstan arrangement…but…mine is “talking” to a Megasquirt…and I remember thinking that I would have had trouble getting it to “talk” to the original ECU…have you checked this aspect of the swap?
The standard Jag position sensor is a resistor that changes as it rotates. It fits in a circuit that has to be designed to measure the changing resistance by some means.
I don’t know how it is configured but I think the Hall Effect sensor just outputs voltage depending on position…no resistance change…and I don’t know if the Jag circuit can cope with this.
That’s what I was thinking earlier…so safer to find a potentiometer with the same resistances at 0 and 90 degrees as the original Jag .
I’m pretty sure the CPS is just many turns of fine wire on a magnetic armature. Some residual magnetism gives the signal. Copper expands so the wire breaks.
Jim XJSC 3.6 MANUAL 1984
Why not send the HRS100 back for replacement if it was DOA ?
Trouble is you do need a gadget that gives 0 - 5V out for 90deg.
Regular potentiometers that were made by the billion ( once upon a time ) were 270deg.
They are probably made by the thousand now since digital pots are all the go in just about anyhting.
A 90deg job is a very specla one.
You could cheat a bit. Take a regular 270deg pot, maybe 5k as a guess.
At one end put the battery voltage which can be about 14V when running.
That can give you pretty close to 0V - 5V over 90deg.
Play safe with a low current fuse in series with the 14V.
The TPS signal is not so critical.
At 0V it tells the ECU the throttle is closed.
If you stamp on the gas the rapid voltage increase from the TPS tells the ECU to deliver more fuel.
Under steady state driving the fuel delivery depends on the vacuum and speed signals to the ECU and the TPS signal is probably ignored.
If you go down this road best to use a wire wound pot, not a regular carbon one.
Should last much longer.
Matt,
I suspect there is no issue with using a hall effect sensor. Since the signal is a variable voltage…the change in voltage is a direct action of change is resistance. The ECU doesn’t particularly care what the resistance is…it only wants a particular voltage (ie at idle).
Cheers
Gary
You are correct any car using a pot for throttle position sensing is probably a 90deg one.
However, not easy to find and might be even more expensive than a genuine Jag OEM one.
That one you had ( 0.5V to 3.5V ) sounds a little odd, but maybe the car that used it needed that voltage range.
As you say, any source of 12V on the car is suitable.
I would avoid taking that 12V from anywhere near the ignition system, could be noisy.
270deg pots are easy to find. You could even temporarily wire one up and hold it in your hand while driving.
Then simulate best you can how it would move in sympathy with the throttle.
Easier if you have a trained passenger to do that.
I reckon the only really important thing is to make sure you get 0V at throttle closed, and a rapidly increasing voltage if you tramp the pedal.
True, the voltage will fluctuate but once the engine fires up it will be close to 14V nearly all the time.
I doubt it will cause you any trouble.
This is for pre-HE, for HE throttle pot you’ll need to hook your voltmeter up to the red and yellow wires connected to the TPS without disconnecting the harness. Turn ignition on, and set voltage between 0.32 and 0.36VDC at closed throttle. Check if the voltage changes consistently from closed to wide open throttle. Should be ~ 4.5VDC at WOT
