Anyone tried this ? Move the B bank EFI sensor and wire to the A bank, and moving the cold start thermo sensor and wire on to the A bank ? Essentially swapping sides of sensors and wires ?
1977 xj12

 

Nope.

I have heard the suggestion a loooong time ago, but never had anyone do it, and see no reason why.

 

It’s recommended in the Kirby Palm book as the B bank runs hotter than the A bank. Placing the EFI sensor on the Cooler A bank will make sure the mixture of the B bank will be on the richer side. But only if the two thermostats outlets are plumbed independently (original set up). If they are connected to a shared manifold before entering the radiator inlet ports the temp on both banks should be equal. Rendering the EFI move obsolete

 

Heard that, dont see it, unless the system is ill maintained.

AND


Jaguar Guru's spent thousands of hours developing this system, and the sensors, to run the system, and did it that way.

The CTS is not an exact science, its wiithin parameters, and the ECU is within its parameters, and the thing works, and works well.

Again, mine were/are Daily Drivers, and in our Summers of 42C+, withthe single Efan (A/C activated), the Thermo Efan NEVER comes on, so I dont see any issues that need re-inventing.

 

Kirby also has some very strongly held opinions, I wouldn't necessary treat them all as the absolute and undisputed truth.

Regarding sensor input, don't forget that there is a difference between what the calculated fueling and actual fueling is. The code in the ECU determines a pulse width to open the injector based on an assumed flow rate through the injector. 45 years on, who knows if that assumed flowrate is anything close to actual? There will be variances due to fuel pressure and the flow through each injector. I expect that the errors over 12 injectors somewhat average out to a reasonably well running engine. With the addition of ethanol to fuel now, the fuel is not the same as the system was designed for in the 70's. The Oxygen sensor is there is compensate for the errors and to trim things a bit closer to ideal.

The other thing you need to consider is are the thermostats opening at exactly the same temperature? Is the foot on each closing off the bypass exactly equally? It's doubtful, as they are inexpensive mass produced items.

A long winded way of saying that you probably will see absolutely no difference by swapping the sensor from one side to the other. In general I have found that Jaguars from that time may have been let down by build quality, but the Engineers knew what they were doing when they designed things. As a Mechanical Engineer myself, I'm often impressed by what they did with so few resources.

 

I agree with that.

I have maintained over far too many years and Jaguars.
.
Get the car you have saved to the Original Specification first and foremost.
They are 30 40 50 years old and have worked very well all that time.
Lack of care, became the "spare car" long ago. Parked outside and forgotten, mostly.

Once you have sorted all the rubbish, and returned to Original, AND, you are not happy with something, go for it, modify the hell out of it.

NOT my road at all.

Our S2 XJ12, Fuel Infected, just topped 800K kms, same engine as Coventry fitted. Efans in 1994, THAT'S IT. On its 3rd trans (BW12), 4th alternator, 3rd fuel pump, A/C is a compact Sanden (1994), thats about it. OK it leaks oil, tappet blocks a a mongrel, BUT, its all part of the Jaguar "Anti Rust System", so why mess with that.

The XJ40 3.6, just over 600K kms, and still as made.
The S2 XJ6, God knows, Odometer stopped working in 1995, care factor, ZERO.

BUT

Its your car, and that is the most important thing in the world.

 

100% right! Totally agree.

 

I am installing new thermostats Tridon tt 228-180 I’ll test them before install.
will probably run a small crossfeed between the 2 coolant lines to the radiator to average out the back pressure and see how it will affect block temperature evenness. Running it on 110 Leaded fuel, and it does really well on that ! I don’t intend to modify things. I maintain, preserve and restore.

 

Would you please explain this idea in more detail? I am not sure having exactly the same pressure in the radiator top hoses (if that is what you mean) would result in exactly the same amount of flow from each head through the radiator, as A bank has an easier path than B bank into the bottom section of the cross flow.

 

Thanks for the input. I posted it on the other thread. But this is the idea. Red line is a 1/2in or 5/8 hose. Between the B bank thermostat outlet and A bank thermostat outlet.

 

You have that already with that steel tuube, with a suction value to the water pump.

As I have also said many times, that stat disc is NOT a 100% seal with teh alloy face, so there is bleed from there to the pipe at all times.

I dont understand what is supposed to be achieved with the Re line, the thing works well as is, until lack of maintenance kicks in.

The B Bank hose will need more oomph than the A side. Otherwise the A Side liquid will flow to the B side. Again, its a balance thing, and works well as designed.

 

Yes, I forgot about the thermostat not 100% but open. Car is fine as is. I’ll leave it alone.
I’ll swap out the cross pipe with a stainless xjs pipe and angle the car to get rid of all the air.
I’ll monitor the temp differential and go from there.

 

I call Beer O'Clock.

I was at the point of changing my HE to a PreHE steel header tank, when it just got too hard.

The PreHE header has a spigot in the bottom, that joins to a "T" in the heater return pipe, going to the Bottom Hose. This is the BEST way to fill any system. The air is "pushed" out as you SLOWLY fill it, sweet.

My PreHE's never had filling/air issues, that was allocated to the HE things.

BUT

Fill it slowly. I use a 1 ltr bottle, the 20ltr container is on the bench, some 20 steps away, and at 10 steps is the Beer Fridge, DUH, who the silly one now.

Even the silly X Type gets filled that way, and they git more, and sillier hoses, than a V12.