Hello all,

I have been slowly restoring/building a 75 XJC and just came across a 96 xjs which I may buy to swap all the electrics, suspension and drivetrain in. It has a 175k mile 4.0 in it. (I had intended to put a 6.0 v12 in the coupe - I bought a 96 xj12 but wound up going through it and bringing it back as a driver instead.)

Question: I sometimes see xjr's in the local wrecking yards, what would I need to pull to run the supercharger on the regular 4.0 motor? If there's a thread on this somewhere. can you post the link so I don't start another one. Cheers

 

it would probably be easier to transplant the entire driveline - SC engine has lower compression, so you would need to change pistons, cam timing, change the ECU, add the dual fuel pump gas tank from the XJR and change the gearbox, driveshaft, LSD, charge cooler, ETC.

 

In theory it can be done but would be far less then optimum without the added components to be at the factory performance level of 1995

JREngineer would be best to answer as he was on the engine design team at Jaguar at the time and is more up to speed of current activity with the AJ16 engine tweaking today by individuals.

 

Thanks for responses, i can see it's not viable having also looked at the shop manuals etc. I might just swap the 4.0 and drivetrain in for now and figure out a stick shift, then if i find a complete donor xj6r somewhere in the future I can swap the relevant model specific components . The problem with the wrecking yards is that it's really hard to get all the components off, someone has usually taken a couple of them already. I also have a wishful thinking problem.

 

The hard part I think is a different crankshaft for shorted strokes for a less compression SC engine

The different crankshaft may be stronger metallurgy

The valves are different as well as higher flow rate fuel injectors but will probably compensate for that until higher engine ranges where the injector flow rate would be limiting

Over time your SC components will be even harder to find vs. a normal aspirated that is more common

 

As I have had the same thought and actually have a complete 4.0 spare engine

top of my head

• Compression, this is achieved by different pistons. Flat vs dished.
• crank and rods are the same forged steel
• Valves are with different part numbers, seemingly identical with weight and dimensions, might have different material used
• cams are same; profile and lift. Difference is between timing mark /notch that the timing tool locks into --> different timing
• 4.0 block does not have the SC mount fixing holes machined, bosses in the casting exist. Anyways block casting seems to be the same between the version (which would make sense in manufacturing point of view) and the difference is what mounting /fixings have been machined in to the block casting.
• SC belt tightener mounting holes / bosses I did not check this in the 4.0 block
• intake and intake trackt is different of course due SC intercooler and routing
• injectors difference
• MAF different
• motor harness difference? just because sensors are in different place?

Might be more differencies that people with more info will share

the 10:1 compression of 4.0 might or might not be issue, depends on tuning, actual shape /geometry of the combustion chamber / piston, fuel used, intake air temp controls and other normal things to be taken in account

 

AnttiM,
This is a really good list, and demonstrates why I would never recommend trying to build an supercharged AJ16 engine from a naturally aspirated engine. The unique block machining is the most difficult difference to overcome.

 

In addition to AnttiM's list, the external coolant hard line from front to back is notched on the XJR, to fit around the throttle position sensor.

Honestly if I started with an N/A I'd be more keen to make my own setup, starting with an M112 instead of the M90, but obviously that's going to be incredibly difficult and time consuming. The stock setup is very hard to service because everything is underneath the intercooler.

 

Yeah, I missed that and I have always wondered if the whole SC exercise has been a bit of an afterthought. The notched coolant pipe notch, the ribbed rubber piping with aluminum metal pipe insert to align the elbow from intercooler to throttlebody all seem bit of a bodge job to be honest.

And I whole heartedly agree with the sentiment that servicing tb and nearby located components is difficult...

 

The supercharged AJ16 engine had to be designed to have the body drop over it, on the production line, as a complete assembly. This resulted in the requirement to keep the engine intake system compact and led to the compromised throttle body location and water rail. I have since designed an Eaton M112 supercharger installation, without a cut out in the water rail and with a larger throttle body co-axial with the supercharger. However, I had to complete re-engineering the whole intake system. It certainly won't "body drop", but that is not a requirement for a DIY installation.


Eaton M112 installation on Jaguar AJ16 engine

 

Here is my new water rail, which includes an additional feed into the back of the cylinder head to improve head cooling.


Additional rear coolant entry to cylinder head (only 2 fixings installed for purposes of photo)

Increased flow rate water rail

 

Impressive @XJRengineer! Wondering if adding a turbo to a standard 4.0 is feasible? I have no plans to do it, just curious...

 

It’s been done but the engine died
https://www.jaguarforums.com/forum/x...l-done-238278/

 

A twin turbo engine would work much better than a single turbo engine. The 2 groups of front and rear cylinders would have 240crank degree intervals between firing pulses, which would match the 242crank degree period of the exhaust cams. This avoids any "stuffing effects" between the exhaust pulses on the turbo. 3 cylinders connected to 1 turbocharger is the optimum turbo installation; so 2 turbos for 6 cylinders. This also allows for the use of smaller turbos to reduce turbo lag. In the early 90's Jaguar designed and built a twin turbo version of the AJ6 engine for XJ41, but it never went into production. Even with early 90's turbocharger technology, that engine could produce 600Nm (440lb.ft) of torque and 300kW (400bhp).

 

This is very interesting, thanks Andy.
It's always seemed odd to me that after the huge performance industry around the XK engine (and even the V12) that the subsequent AJ 4.0 series engines had such a poor performance culture around them. Someone I know who raced XK 4.2 engines told me they were hand grenades above certain levels whereas the AJ 4.0 engine is pretty burst proof, at least in stock form.
My other concern is if I put a supercharged AJ16 in the coupe I'm building what happens when I can't get parts for what is quite a rare engine. I'd much rather have a plentiful supply of XK parts than having to buy dubious quality XJR bits off ebay.
AJ's are still plentiful, a twin turbo setup could be put on a 'new' wrecking yard motor if the old one expired. Presumably there's not enough demand to justify an aftermarket kit...