It is certainly perfectly feasible and I have discussed this with the amazing Lawson Smith at Powerhouse Automotive. Lawson sells and installs the Wizards of NOS kits with the Number 8 kit being suitable for our V8 models both in supercharged and non-supercharged form. Costs are around £1500 for a suitable kit. Details on the Powerhouse site.
The one issue is that the supercharger would have to come off yet AGAIN! No way, Sunshine. I`m not going though all that again!! With the charger removed, all you have to do is drill and tap eight holes into the cylinder head intake ports to take the NOS injectors. This needs a 90 degree drill, a steady hand and much patience. Otherwise, you take the heads off and do the job on the bench. Another nice easy job. Not so me thinks. The distribution unit has around twenty small bore pipes attached to it and is mounted atop the block valley as in this image. Note also shown very clearly on this image is the notorious valley pipe. This is the best picture I have found of it to date. It usually disintegrates at the front end which is on the right in this shot. The pipe is 2W93-9F814-BC. Yip, I would love to do it but I think one could expect to see the 4.2R unit beginning to get close to the upper limits of dependability. Tom Lenthall told me up to 630hp is possible but after that the engine can explode!
Once the big pump and inter-cooler rad are in place, then that will be it as far as I`m concerned. Pushing an engine to the max is probably a very bad move. I have achieved enough and got the drivability result that I was looking for.
Out and about in the car at the peak of the temperature, I gave the car a couple of quick bursts and noted a slightly flat response. The temperature of the day at that point was at its peak and probably around 10 degrees up from when I last used the car. Increased IAT temperatures at the inlet have a knock on effect at the output manifold and that heat which could easily be up at 180 degrees takes some getting shot of and keeping under control. Detected by the Power Control Module, the usual response is for ignition timing to be retarded and extra fuel to be added to ensure the engine does not become damaged or detonation occur. The net result is a drop in power. There is only so much heat that can be exchanged given the actual size of the inter-cooler bricks, the volume of coolant, the capacity of the inter-cooler radiator and the flow rate of the auxiliary supercharger pump. This is common supercharger theory and the biggest challenge any supercharger owner will face is that of temperature control. Add to that extra performance bolt on goodies and even more heat may be generated. At that point the OE cooling system becomes inadequate for the given local ambient temperature conditions and power demanded from the engine. Drivability issues then become evident. Yesterday I reached that point during that heat spell. OK, now I know the limit for the system and when I can expect it to go flat.
Non of the above is unexpected. In my case I predicted the occurrence at some point and ages ago made contingency plans for the eventuality. A very large capacity aluminum inter-cooler radiator and a high flow inter-cooler pump were bought earlier this year but have yet to be fitted. The cooler was £165 and the Bosch pump £135, both sourced via ebay. The cooler rad is specifically designed for X308R and XKR 4.2 models so I know it will handle the demands of my X350R. Minor mounting bracket modifications are needed and perhaps some slight angular coolant pipe adjustments.
Viper Performance have supplied weld on ali hose tail tubes to take care of any coolant hose discrepancies. The cooler rad is 30mm thicker than a standard cooler but has 50mm less height and width. Wide width weld on ali brackets will have be made to handle the difference in size. Improved access to the auxilliar supercharger pump also looks a distict possibility. The cross brace behind the radiator grill will need to be unbolted and packed forward slightly to make room for the increased tank cross sectional area. Old compression tubes removed from dead wishbone bushes would make ideal selective sized packers. Longer bolts may be needed. The tubular power steering "fin rad" cooler will also have to be moved forward by 50mm or so. Hopefully the feed and return pipes will be long enough to allow the move. I have found a co-operative local ali welder only a couple of miles away who appears happy to help with modifications at a reasonable price. In fact, the fellow makes our replacement steel Marina pontoon structures so that augers well.
Once again I have to find the time and physical strength to tackle this job. As usual my sciatic condition limits me greatly so I`m looking around for some willing character here to give me a hand. It will all come together, I`m sure. Off to Halfords to get some more antifreeze although I am considering Evans Waterless Coolant. About £120 needed if I go in that direction....perhaps not.
A bit of feedback now as to how the car is performing with the ported charger. I had to belt up to Caterham early yesterday morning as my dear old Parkinsons ridden Father had a bad turn and was rushed into East Surrey Hospital. Mother was in a state so I was up there in double quick time. Glad to say I had towed my Father back home in the supercharged recovery truck by lunchtime. A good rest last night and today is back at his desk building model aircraft again. Both now look about fifty years younger. Phew, that was a close one! If ever I needed a car to do that run again, the XJR performed like the Energiser Bunny and is the car to have. No fuss, no scares, just pure mile munching magnificence.
I continue to be enjoying a hugely improved car with no issues at all. Even having opened up the charger internals and making use of the power, fuel consumption is little affected. The car returned 28mpg and that was with me in a hell of a rush and enduring the heavy traffic northwards through Guildford at 07.30 yesterday morning. The figure also includes country lane driving from Nutfield to Redhill return. The remainder was A22/M25/A3 and M27. There is no doubt that the mods to date have given the car a much larger spread of torque across the rev band. The "all or nothing" original effect of the charger is reduced and the grunt is vastly more useful generally. Before the mods, little would happen until the pedal was well depressed and the box had changed down a couple of gears. That made for quite a brutal drive. Now things can happen more progressively which makes for a much smoother, refined and less stressful driving experience.
My Father was hugely relieved to be extracted from the hospital. "Go like hell" he said as soon as we moved off. I took my time getting him home. He enjoyed the drive back hugely. So did I. I was quite amused to learn that he calls his Blue Badge Disabled Parking cards, his "Trade Plates". You can park on double yellow lines with those. Most useful!
I took my time covering the seventy two miles traveling between 55 mph and 70mph in my best economy mode driving style and making constant use of the cruise control. Despite a bit of traffic from Kingston north towards Putney and several waits at traffic lights, the XJR managed a very creditable indicated 33.1mpg. Even allowing for a 10% error, 30mpg is quite acceptable for a car that is now producing at least 500bhp. That is an improvement of 4mpg when compared to my old five speed auto 4 litre S-type with just 289 verified bhp recorded at Paramount. How technology moved on at Jaguar in just three or four years.
I put this improvement in fuel consumption primarily down to the newly fitted sports cats. Porting out the charger may well have also helped inlet breathing whilst not spoiling fuel consumption in any way. Thrashing the car will of course produce a totally different scenario.
The mods continue to make an impression. Around the houses, the first to second change and the second to third gear change appear to occur sooner. That is quite nice. In fact the whole experience is very nice with the car being much more laid back in power delivery than before the mods. Traffic trickling is just as pleasurable as the occasional full throttle blast.
The more I drive this car, the more I enjoy it. Eventual replacement of this car is going to be quite a challenge.
At 83k miles, with all the new parts fitted, new cats and EGR valve, one would think that good enough. Just to finish the work on the induction and exhaust system off, I reasoned that an internal fuel and combustion clean out would be no bad thing.
All done and dusted by the local franchise holder down here in Hampshire, I can`t fault the service, knowledge, technical explanation or the end result although any emissions improvement has yet to be ascertained. The proof of the pud is often in the way a car drives at the end of some maintenance. What I can say is that pick up from a standing start is more positive with the most noticeable feature being a quicker gear change into second on pull away. Over run with a closed throttle is smoother and going back on the throttle appears very subtle. There seems to be an improvement in fluidity at slower speeds. That was just what I was aiming for. Above 1800 rpm, the car drives as previously.
The results are not Earth shattering and I never expected that to be the case. However I now have the knowledge that the XJR has had its vital organs given a flush out and that the engine is as clean internally as it will ever be barring a complete mechanical strip down.
I see the procedure as preventative maintenance and that alone justifies the expense.
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