Project: 1968 Jaguar 420 (4.2L, I6, XK) manual, ITB

[schilpr]

A quick introduction of my latest project.

Although I haven't posted on the forum before, I do have some (ok, a lot of) 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 60lbs 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:

• Convert input signal to EDIS trigger
• 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)

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.

I do have a full (minus computer) EFI setup from a Jaguar XJ6 series III which has the "same" engine as my car but with an awful early '80s EFI system, I decided that making a throtlle body setup was more fun and would result in a better performing EFI system, if that is true I'll find out soon enough.

The size of the throttle bodies is by far good enough, the airflow calculation I use for situations like this is displacement times redline rpm for each engine, the numbers should be close. In this case. I have 1.5 throttle bodies (6 tb's from a 4 cylinder) for a 1,300cc engine doing 15,000rpm redline going into a 4,200cc engine with a 6,000rpm redline.
Resulting calculations is 1.5 * 1.3 * 15 = 29.25 (Hayabusa throtlle bodies) and the XK 4.2 liter 4.2 x 6 = 25.2 or in other words if anything the throttle bodies are slightly big.

The injectors at 60lbs are big, possibly overkill, but I had them left over from a blown v12 469cu project that I sold before the EFI was installed, in simulation with EFI analytics I can stress them to 55% duty cycle, I think that will be fine.

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[billr]

" (fuel safe 50mm hose is last item to be purchased)."

Yeah, 50mm should be big enough for even those "oversize" injectors! Seriously, though, I suggest you don't fuss with the EDIS, just use the same 36-1 (or a 60-2) crank wheel and let MS handle all of the ignition chores. In the time I have been on this forum I have heard of no advantages to using EDIS, only problems. At one time, using the EDIS driver/coil module was probably convenient, but now there are a lot of simpler options.

[schilpr]

" (fuel safe 50mm hose is last item to be purchased)."

Yeah, 50mm should be big enough for even those "oversize" injectors! Seriously, though, I suggest you don't fuss with the EDIS, just use the same 36-1 (or a 60-2) crank wheel and let MS handle all of the ignition chores. In the time I have been on this forum I have heard of no advantages to using EDIS, only problems. At one time, using the EDIS driver/coil module was probably convenient, but now there are a lot of simpler options.

The 50mm fuel hose is to connect the throttle bodies to the intake, but I guess it would flow enough for this engine if I decide to make an airplane out of it.

Skipping the EDIS would be great, last time I did a project like this that was the go-to option in situations like this, good to hear I can now do this directly in Megasquirt.

[DaveEFI]

Interesting you've decided on throttle bodies. Jaguar did fuel inject the XK engine, but used a more usual plenum with twin throttle bodies and port injection. I'd say that approach gives better results on a road car, since the XK engine has quite a low rev limit.

Dunno why some think EDIS unreliable. It's probably one of the most reliable ignition systems ever made. And will still spark even when MS ain't working. Not saying it is better than doing wasted spark via MS - just easier.

[js1tr3]

We'll have to share some engine maps.
I'm working on a 68 XKE with my dad. Its been a 5 year project as I only get to help over the holidays when I am back home.
we got the car started this past holiday, its running LC-1 wideband O2 with Megasqurit 2 extra.

I also went with motorcycle ITBs form a gs600, had to do a little bit of re-spacing and make a custom manifold.


you can find some more details here.

http://megaxke.blogspot.com/

[schilpr]

Very nice, exchanging tips and experience sounds like a great idea.

As you can see from my original post I'm also making my own intake manifold.

Where are you located? I'm in the Netherlands.

[luxmoggy]

Hello
I am mega squirting an XJ6 4.2i engine which I am fitting to a kit car. I am using the injectors and manifold from jag. I would like to exchange ideas.
At the moment I am working on the brakes. The next item is to fit the engine.
I am based in Germany.

[bradyzq]

Regarding your throttle body sizing guesstimates, you could also estimate that, stock, each throttle body is good for a bit more than 40hp worth of airflow, plus whatever headroom Suzuki built in. This is based on 160-170hp being the stock output of a Busa 1300 or 1340.

[bradyzq]

Maximum airlfow should occur at peak HP RPM, which in the case of a stock Hayabusa, is around 10000RPM, not 15000RPM. Of course the stock throttles are not maxxed out at stock power levels, but still, it might throw off your calculations.

[schilpr]

Regarding your throttle body sizing guesstimates, you could also estimate that, stock, each throttle body is good for a bit more than 40hp worth of airflow, plus whatever headroom Suzuki built in. This is based on 160-170hp being the stock output of a Busa 1300 or 1340.

That would fit beautifully then.. as I'm using one and a half Hayabusa injection setup.. for a total of 6 * 40hp = 240hp.. for an engine that should handle around 225hp.

Maximum airlfow should occur at peak HP RPM, which in the case of a stock Hayabusa, is around 10000RPM, not 15000RPM. Of course the stock throttles are not maxxed out at stock power levels, but still, it might throw off your calculations.

Even then the calculation is still close enough to make me think this will work.

Wondering if the TB's from the 600cc bike will flow enough.. but even there I think you should be ok