First post of this thread: I have a 1974 XJ12 with a carbed 5.3 and original speed tranny converted to 2004R 4 speed overdrive. And next phase is a 6.0 liter V12 with 4l80e trans.

 

This will be Such fun to watch!
(';')

 

Andy, I love that Fern Grey colour!

 

This WILL be fun to watch. I have thought to myself the "perfect" car would be an early XJC with a modern XJS 6.0. Stock auto transmission or manual depending on your driving preferences. I would probably keep the 6.0 auto trans for simplicity's sake. Or is one of the reasons for the 4l80e swap because of clearance issues if using the stock 6.0 transmission?

I will be especially interested to see how all of the electronics get wired.

 

Assuming that he has the engine and transmission ECU / Trans TCM plus harnesses, it would be a simple operation.


Larry Louton

 

I have the original '95 XJ12 and thought to use the stock ECU and TCU but discovered that the ABS and gauge cluster are intermingled with those electronics and so I abandoned using stock ECU's. Researching Megasquirt and Haltech stand alone ECU.

 

You can use the stock ECU, you don't need to worry about ABS, and you can apply either voltage or ground ( I don't remember which) to one pin on the ECU to have it default to traction control off.
I've done Megasquirt on a 1966 S Type and getting the tune right is a very labour intensive process. I still do not have the factory levels of refinement after years of tuning.

 

Hi
have a look at this they can tune your car by remote management
read real time date and adjust on the fly
how clever is that

 

Hello, If you are near Atlanta, I have a friend that first put his 6.0 V-12 with 4L80E in a 1966 Jaguar Mk 10 with Megasquirt engine and trans ECU's. He then moved .the engine to a 1985 Jaguar XJS but changed up to a 5 speed
manual trans with stock 2.88 gears. Claims 24 MPG and 140 top speed in Rally trim. He has a winning combination. Your going to need help, He has made all the mistakes all ready and has Megasqurt on speed dial.

Larry Louton

 

Those insights about the stock ECU and the mega squirt insights both seem promising. I am especially intrigued by the idea of using stock ECU…

I started to pull the stock ‘74 engine today and got stopped by the stock down pipes. With all of the nuts removed and flanges separated, I couldn’t get the Down pipe off the exhaust manifold—even after pounding on it with a sledge.

So, new technique tomorrow unless y’all have some insights…

 

Bullittandy,

Just did this recently on Series 2 V12. Lots 'n' lots of Blaster. Should eventually soak into gaskets. Try tapping it side-to-side & front-to-back, back-to-front.

For all the jokes about parts falling off British cars while they roll down the road...NOTHING wants to 'fall off' a V12 you're trying to disassemble.

Be careful taking that apart...I may need that block!

 

Well, the entire engine is on eBay currently...so snap it up!

 

That would be great to get in touch with him. Before i go too deep into Megasquirt, give me some more insight about using stock ECU. I have the entire donor car.

 

Give me some more insight about using stock ECU. I've read that the it was all integrated but if its possible to reuse stock engine wiring and ECU that would be great. I'm scared of Megasquirt

 

Do you have the electrical guide? It is here: http://www.jagrepair.com/images/Auto.../jagxj1995.pdf The engine ECU is section 4.4 and 4.5 or 4.8 and 4.9, depending on your VIN.. Transmission is 5.4

I am doing the conversion with an XJR engine, but it uses the same transmission. Larry Louton has done the conversion using the XJR as well.

You will need both constant and ignition switched power to the ECU, and fuel pump relays. The XJ12 and the XJR have 2 fuel pumps, the second turns on over 3500 rpm. The pumps are rated at 90 Litres/ min ( I think - look for posts by XJR Engineer on the X300 forum). I was planning to use a larger single pump and eliminate the need for the second pump. You're fortunate that you have a Canadian/US market car, as these don't have the immobilizer that the rest of the world does, so you can use your existing ignition switch. You will need the shifter from the 95, as it has the linear switch for telling the ECU what gear the transmission is in, and activates the reverse lights. For the instruments, you can reuse the Series 2 things, like the fuel gauge. There is a fuel level input to the ECU, but I think you can safely ignore that, or just put a resistor in to give it a full reading and be done with it. For the speedometer, I would use the output shaft speed sensor on the transmission and then a Dakota Digital box to reduce the signal. Series 2 is a mechanical speedometer, you might want to the switch the guts to an electronic speedometer from a Series 3. You could probably simply switch the faces to keep the Series 2 look. The output shaft does 128,000 pulses per mile and the speedometer ( and later Series 3 cruise control box) want to see 8000. The Dakota Digital box can reduce the 128,000 to 8,000. Things like traction control can be faked to "off" simply by applying voltage or ground. The guide tells what is the off condition for each circuit.

Fortunately, the diagrams are well laid out, and there is key on the page before the diagram that says what the signal is in each wire. Most are simply voltages, there is no encoded data.

What I did was go through each of the outputs and inputs on the ECUs for fuel and transmission and made a list of what was external to the engine and transmission itself. All the sensors on the engine will come with it, so those you don't need to bother with. It's things like power, ground and crank that you need to work on.

 

Excellent, gonna have to read through this a couple of times but it sounds like you’ve figured out the fundamentals. That part about the shifter is an excellent insight.

 

The car's main harness can be trimmed considerably. I'm assuming you are keeping the Series 2 climate control, so you can ignore the parts that go to the climate ECU. You will also want to look at the cooling section, as I am assuming that you'll transfer over the electric radiator fans, and probably the radiator too. The kickdown switch under the gas pedal should be transferred over too.

I've spent quite a bit of quality time studying all the circuit diagrams. I'm intending to have a check engine light, so am keeping the OBDII port, but reducing the components on the network to just the engine and transmission.

 

What you said about "years of tuning" on the Megasquirt is definitely what I want to avoid and since I have the entire car there isn't a reason to not give the stock ECU a shot (especially since you've done a lot of work for me! ).

How much are transmission and engine integrated? Would it be easier to use an aftermarket stand alone TCU?

 

And one more quick question (s). Do I need to keep the air injection and O2 sensors? meaning, if they're missing, will ECU go into a limp mode?

 

You can probably eliminate air injection, it is to get the catalyst lit off after startup. Not having it will turn on the check engine light, if you're planning to keep that. I was simply as a diagnostic tool.

Not sure about O2 sensors. For sure it would default to the programmed in table values, with no correction for if the engine is actually rich or lean. I would keep them, as the car will run better with them. Similarly, I am keeping the downpipe catalyists on my car, as I hate the stink of non emission controlled engines. I had a 92 V12 and I removed the cats and from the drivers seat there was no difference in performance or fuel economy - all it did was make the exhaust smell, so I think there is no downside to keeping the cats. Especially as you already have them.

I think the engine and trans ECU's are integrated, they certainly communicate back and forth; for example there is an engine torque reduction during shifting. It also won't allow you to over rev the engine during manual shifting. I can't really see any advantage of an aftermarket trans controller.