New Project: Jaguar 420 (4.2L, I6, XK) manual

[schilpr]

A quick introduction of my latest project.

Although I haven't posted on the forum before, I do have some car, engine and tuning experience.

Looking for any help you can provide with this project, feedback on my plans and so on.

The car:

• 1968 Jaguar 420, with a 4.2 liter, straight 6, XK engine, with dual carburator setup (3rd "carb" for startup enrichment) and a manual transmission. Car is currently my daily driver and performs well but starting to have carburator issues.

Planned setup:
First step:

• Megasquirt v3.0
• custom intake manifold
• 6 2007 Suzuki Hayabusa 1300 throttle bodies (3 double ones), spacing is almost exact the same as jaguar cylinder spacing
• 6 42lbs injectors (1 per intake port) and yes I know these are big
• Original air cleaner (modified receiver dish)
• Single fuel pump feeding from 1 tank (the car has 2 30l fuel tanks)
• Distributor point trigger for ignition
• Megasquirt to control the coil firing

Second step:

• Replace coil for coil pack, going to wasted spark, spark control from Megasquirt (yes I have the right hardware to do this and modded my board)

Third step:

• Convert input signal to EDIS trigger

I have a full machine shop to make parts, from earlier projects I also have the Megasquirt test board.

The intake is mostly complete, I need to finish the mounting of the intake runners into the coolant passages. The attached pictures are from the intake being machined, I started with a standard intake which I modified and added new straight through runners onto.

I've got all the parts already purchased or at least identified (fuel safe 50mm hose is last item to be purchased).

I have a full "mule" engine sitting in the shop to test my setup on, I can do all the sensors, wiring and test fitting on this engine before final mounting in the car. This test engine can not be run in the current setup.

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[Matt Cramer]

You'll want to switch steps 2 and 3. You can do a distributor plus 36-1 crank trigger, but coil packs won't work with a distributor trigger.

Looks like a cool project.

[trakkies]

My initial reaction is I'm surprised you're going to the bother of making all those parts as the Series 111 XJ6 with the same XK engine had Lucas EFI. So basically, all the hard work is done for you - just change the Lucas ECU for MegaSquirt. This is what I've done on my Rover V-8, which has similar Lucas injection. And generally, a plenum system with port injection will give better results for a road car over throttle bodies. Throttle bodies are really best for ultra high RPM - not the 6000 or so limit of the XK engine.

And as Matt said, ditch the dizzy and go for a crank trigger wheel and say EDIS. The more accurate control of the spark timing will give benefits - as will dispensing with the dizzy cap and rotor arm. But you might also be able to use COP on this engine. For fully sequential you could keep a modified dizzy to provide just the cam signal - that doesn't need to be that accurate.

All IMHO, of course.

[schilpr]

Thanks for the responses guys.. making progress on the project, I've got the Megasquirt hw finished and the software configured, I made the last pieces for my throttle bodies and found the 50mm id fuel safe hose to make my connections, next step is to get the throttle linkages completed and get the car in the shop to start fitting the parts.

You'll want to switch steps 2 and 3. You can do a distributor plus 36-1 crank trigger, but coil packs won't work with a distributor trigger.

Looks like a cool project.

Thanks for that knowledge, that will definatly change the plans.

My initial reaction is I'm surprised you're going to the bother of making all those parts as the Series 111 XJ6 with the same XK engine had Lucas EFI. So basically, all the hard work is done for you - just change the Lucas ECU for MegaSquirt. This is what I've done on my Rover V-8, which has similar Lucas injection. And generally, a plenum system with port injection will give better results for a road car over throttle bodies. Throttle bodies are really best for ultra high RPM - not the 6000 or so limit of the XK engine.

And as Matt said, ditch the dizzy and go for a crank trigger wheel and say EDIS. The more accurate control of the spark timing will give benefits - as will dispensing with the dizzy cap and rotor arm. But you might also be able to use COP on this engine. For fully sequential you could keep a modified dizzy to provide just the cam signal - that doesn't need to be that accurate.

All IMHO, of course.

I've got the lucas EFI parts from a Series III XJ6, they are a terribly inefficient setup and not just because of the lucas electronics. My experience is that well tuned throtle bodies provide a much more direct reponse when driving even at lower speeds. But you are also right that if tuned to RPM's they can shine in that area as well.

I've done the crankwheel before, this is not a simple change on the XK engine while fitted in the car, so I've decided to make it drive first with the existing ignition setup with Megasquirt controlling the timing. If quality of the drive if not good enough I'll speed up the ignition step, if it does drive acceptable (can't be much worse then the current worn out carbs) I'll drive it for a while with the dizzy.

[trakkies]

I've got the lucas EFI parts from a Series III XJ6, they are a terribly inefficient setup and not just because of the lucas electronics. My experience is that well tuned throtle bodies provide a much more direct reponse when driving even at lower speeds. But you are also right that if tuned to RPM's they can shine in that area as well.

The whole XK engine is terribly inefficient by today's standards. Not surprising given its age.

But a plenum system has a lot going for it and is still used on many modern cars. And not just down to costs. Different matter for a high revving 'race' engine, where ITBs are the norm.
Accurate mapping of the ignition curve for today's fuels is likely to have very real benefits too.