I bought a 97 xj6 a few months back, and after a little while of looking for a supercharger kit, was wondering if anyone had done a conversion from an xj6 to an xjr and how they did it

 

Different Engine, different transmission, different ECU, different fuel tank, and I haven't even started on the suspension yet.

Although increasingly rare, if you want an XJR, best to buy an XJR.

 

wonder what’s the bare minimum to hack an AJ16S into running. the NA ECU will run an XJR (barely) and as far as I remember the XJR has absolutely no additional sensors in its wiring loom. the ZF isn’t particularly weak either

 

The engine and fuel management would be a major challenge. XJR has two in-tank pumps. Apart from hardware you would need to remap the ECU. A more feasible alteration to get more out of the same engine is to convert the auto transmission into manual, and fit a 3.58 differential instead.

 

I think mine already has a 3.55 diff, would a conversion to a 3.58 make a big difference? And if so where do I find a new differential

 

No it would not. And anyways if your having 4.0 car with automatic that should be already 3.58:1

I always thought the ratios are as below

• XJR auto (and manual?) 3.27:1
• 4.0 auto 3.58:1
• 3.2 auto 3.77:1
• 3.2 manual 4.09:1 ? (last one I am not sure )

but Jaguar tech doc "XJ6 and XJ12 range 1995 model year technical introduction" list the ratios as follows



but anyways 3.54 , 3,55 3,58 should not make anykind of a differense in my opinion.

Are you thinking of adding supercharger to the naturally aspirated engine or changing to XJR engine?

 

my original plan was to just add the supercharger

 

This question arises from time to time in our model forums with both the 6 cylinder and 8 cylinder variants. Appealing though it is, the majority soon conclude that a trade-in against the S/C equivalent is by far the most cost effective solution.

Graham

 

The engines are significantly different, the most important being that the compression ratio is MUCH lower on the SC car. NOT sensibility it put SC on a high compression engine line the NA one.

 

Just get the full engine, I know of a couple Rs getting parted.

Doing the swap the right way would be expensive but what would stop you from running a full SC engine + ECU + MAF + injectors and keeping everything stock NA car from the bellhousing back? Both the GM and the ZF TCU receive pretty much the same signals from what I remember.


@XJRengineer

 

Would the reason be risk of detonation (or the need to run lower than desired "boost levels" to keep detonation at bay) or increased cylinder pressure ?

I am asking as the 10:1 is not that high compression level to be used with boosted or supercharged application in theory (and even Jaguar is using 9,5:1 in 5.0 SC versions iirc, and usually factory configurations/setups tend to be on the conservative side if anything) One just needs to manage "boost", intake air temperatures, timing and fueling more carefully against detonation and/ or pick more detonation resistant fuel.

Adding SC to AJ16 NA; If wanting to use purely Jaguar components the easiest (least things to think or modify) ways would be

1. Buy XJR
2. Install whole XJR running gear (with electronics) in to the XJ
3. Installing XJR engine (basically what Xalty was proposing, I think you would need to transfer the transmission adapter and flexplate from NA to SC block also)

for 2 and 3 the MAF sourcing (if one can not find complete engine) could be biggest obstacle anyways

you could also add XJR auxilaries/components to NA engine; improve the intercooling (bosch pump and maybe intercooler radiator fan) And trust that the knock sensors would be up to task.. the block would need the SC fixings to be tapped and threaded, in my understanding the block casting are the same across the range (3,2, 4,0 4,0SC) but I might be wrong here so if someone knows better it would be good to know. Btw Aj16 service manual list only one ring gap spec so that should be ok as is




Transmission (ZF) might live (and work ) or grenade itself who knows before trying...

Anyways first the target should be picked and then evaluated against the combination of available skill, money and motivation

 

Yes, detention is the problem. The new engine would have been designed from the off for supercharger.

The main thing is, Andy who designed the thing to begin with doesn’t recommend doing it lol
https://www.jaguarforums.com/forum/x...j6-xjr-214589/

 

I would tend to agree that using M90 (H)eaton running at the same ratio (2,5:1) and same intercooling / cooling system as in XJR and with normal pump gas (95E5 in Finland) might not be the optimal (and not necessary safe in all loading conditions) solution.

But I would argue that either reducing the running speed of the M90 (and thus reducing both pressure and heat generation to intake) and/or improving intercooling and / or going with E85 (ethanol has better compression ignition resistance and when evaporating cools intake air more and yes then the fueling and timing need to be addressed as the fuel system hardware). Again I am not saying this is the optimal solution for problem (but like alcohol is) it is a solution. (again more on that can/how it could be done than does it make any sense to do )


on the more modern designs
It would interesting to see/hear what is the individual contribution of improvements of combustion chamber design (flame propagation, hot spot reduction etc), better intercooling and using TVS1900 (quite lot more efficient = less heat than to older generation eatons) in using 9,5:1 compression in the 5.0 SC.

anyways it boils down to the target/(money+skill+motivation) ratio what one _likes_ to do (as most of things automotivehobby related are wants / likes not need or rational things)

 

It seems to me that the only sensible approach would be to swap engine, gearbox, associated electronics, diff and fuel tank. You could probably drive around quite happily and reliably at that point, although you would likely be wondering how much better it would be with XJR steering and suspension. Swap those too, and job done: you have an XJR. Except the logbook doesnt say that, so it would be less valuable than an XJR. And depending on which N/A car you started with, it has all that chrome around the windows, and doesnt have sports seats....
Depending on which part of the world you live in, rust could be an issue. If you could find an XJR which has a rust compromised body, and have an XJ6 which has a solid body, you could have a basis for a sensible project. When I say sensible, only in terms of performing a public service by preventing a shrinkage in the number of extant XJRs! The financial cost and physical effort involved would be unlikely to be recouped anytime soon given the values these cars attract these days, sadly.
Buying an XJR is by far the simplest and most satisfactory way ahead, as has already been pointed out. Ultimately though, if effort and cost are not considerations, then yes, you can convert an XJ6 to an XJR, in basically the same way as Jaguar did, but bolting on a shedload of different parts.

 

If the 4-24 in the Jag is built like the one in the BMWs it should be able to take the heat. I know of a couple 850i TTs pushing 400+ at the wheels, only thing they (Dinan) did was add a high stall converter to take advantage of the powerband. Level 10 sells the latter and an upgraded “bulletproof” valve body.