A guide to tuning the Jaguar 4.2 V8R and other V8 motors.

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A guide to tuning the Jaguar 4.2 V8R and other V8 motors.

Postby J44EAG » Sat Sep 17, 2016 7:44 pm

This is a locked thread and intended to be a reference article rather than one for discussion.

If you wish to discuss any items within this thread please start a new thread of your own or drop me an email.

This thread will have more images and text added over time. My aim is to build a definitive thread document here covering my recent journey through the extensive rework and servicing of my XJR. In other words, I`ll pull together everything I`ve learned about maintaining, servicing, modifying and up-rating the 4.2 V8 so that it is all here in one comprehensive thread. To my knowledge, nothing like it exists elsewhere on the internet. If it does, then I have not found it!
X350 sidelights. MaF, temp sensor 002.jpg
After nearly a year of 4.2R X350 ownership and having posted several threads on different aspects of power tuning the superb V8R motor, I thought it would be an idea to bring the various aspects together under one heading. Although I shall predominantly be detailing the 4.2R unit as fitted to X350R, S-type R, the XKR and 4.2 XFR, my discussion will equally well apply to earlier four litre V8R and indeed six cylinder X300R models, all of which are fitted with an Eaton supercharger. The principles I have applied to my 350R are just as relevant to all of these Jaguar models. Owners of naturally aspirated V8, V6 or straight six powered cars need not feel left out. There is plenty of useful material in this thread for them also.
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It would perhaps be a good start to explain the reasons why I embarked upon over a year of servicing and tuning modifications to my XJR. I am an ex-aircraft engineer and have a passion for extracting the best from any car that I own. My ownership of the Jaguar marque goes back some eleven years and in that period have never been without one. I started with ownership with a V6 S-type, progressed to a 4 litre model and in the intervening period owned a V12 XJS and a four litre X308R. My current car is an MY04 X350R which has been extensively and sympathetically up-rated. This car has been the subject of a rolling campaign to bring it to a level that exceeds its original factory performance and has brought it to a higher level as the more friendly and usable car I thought that I would be buying. Whilst the car was a reasonably capable machine in standard build, I soon found that I was becoming frustrated with sluggish and poor progression at slow speeds but also with limited useful and progressive access to the supercharger unless at full throttle. This resulted in an "all or nothing" effect and a consequential rather brutal driving experience that was not smooth, linear or in keeping as a comfortable, fast upper case executive class car. My aim was to adjust power delivery and make the car easier to drive and enjoy in everyday use.
Although the standard car possessed huge torque and power, there was little to be had at slow speed and what torque was available towards wide open throttle was generally somewhat lacking at mid range. For a road car, I opinion that insufficient development work was carried out by Jaguar to ensure that the motor developed sensible and usable power and torque towards the lower end of the power band and that what was available towards the top end was inaccessibly placed for normal sensible everyday road going use. With perhaps too little cash available whilst in Ford ownership, Jaguar simply plonked an Eaton supercharger on the top of the engine and sent its flagship XJR and Super V8 models out onto the market in the hope that they would make worthy contenders for the Merc CLS55 and the BMW M5. A classic case of anything being better than nothing. Please don`t mis-understand these words. It isn`t that the car is dreadful; far from it. It is just that it could have been a little better and more driver friendly. See this video to watch it battle things out with the equivalent Mercedes of the period.
Some might see me as being overly critical of the standard 4.2R. That is as may be, but I also had a rather lower specified car with which to compare it. That came in the form of a simple base model Paramount Performance re-flashed, naturally aspirated, V8 four litre S-type fitted with a big bore exhaust and a fast flowing K&N air-filter. Other than that, the S-type had nothing else modified on the engine. This car was raw as it could get but as an everyday fast road car in general use, it ran rings around my newly acquired X350R.
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The reason it performed so well was that it lacked a supercharger, its internal parasitic air flow drag and the physical restrictive obstructions that clogged up the inlet and exhaust sides of the 4.2 V8R. The S-type Miltek exhaust system was also less restrictive which helped exhaust gas flow on the outlet side of the engine. The S-type was faster off the line, being generally more responsive, had no initial throttle pedal lag and could rocket up a dual carriage way like a rat up a drain pipe. The X350R by comparison took ages to get going, was rather disappointing with low speed power delivery but once up to motorway speeds rapidly stole the thunder from the S-type.

Before beginning to tackle the issues mentioned above, I spent long evenings trawling the internet for information and performance parts suppliers. Powerhouse Automotive immediately shone out as masters of supercharger reworks and Tom Lenthall gave me valuable insight into what de-restriction was required to make the XJR more tractable, quicker and more economical. One would think those ideas would not mix well together or would results meld into reality. My own hands on practical experience has proved that such things are obtainable possibilities and that there is everything to gain by undertaking the work and making a good car become an even greater one. There have been absolutely no negative effects from modifying the car in any shape or form as I detail it here. This then is how I improved my XJR and not all of what I carried out cost enormous sums of money to achieve. The X350R, S-type R, XKR and 4.2 XFR all share the same power plant so anything you read here can also be incorporated into any of those models. Similar methodology can also be applied to X308R and X300R models.

This PDF link should be very useful to anyone reading this thread. Some excellent drawings of the supercharger layout and component parts feature. These together with some of my own images will help to make this article a little more graphic. Knowing what you are dealing with before tearing out components is half the battle.http://api.viglink.com/api/click?format ... mp%3BI.pdf

I`ll start with the basics and then move onto the modifications describing the work required, effects and costs involved. I shall use the edit facility available to be to add, subtract and alter content over time. What you read tonight might be changed tomorrow!

I began to improve the XJR by giving it a complete service and replace other important parts as described later within this posting. This involved an oil change together with buying and installing a K&N manufactured HP 1014 oil filter featuring high quality filtration media together with an anti drain valve to ensure oil remained in the filter ready for the next cold start. The HP 1014 is suitable for all 4.2 V8 models. Four litre owners should check for suitability before buying. The part number may be different.
A new set of spark plugs were also fitted.
Two cans of Cataclean fluid added to half a tank of fuel. The product does everything it says on the tin and helps clean out carbonized deposits within the catalytic converters. It also helps the Lambda sensors stay clean and fulfill their function. After only fifteen minutes driving with Cataclean being fired through the injectors, more torque began to be developed which was easily noticed as quicker gear changes and a more solid feel upon acceleration. For any car equipped with converters, this product comes highly recommended and is probably best used shortly before the annual MOT test. The product assists with keeping emissions to sensible and acceptable levels and in practice I saw my S-type HC output fall from 80ppm to zero between two consecutive MOT tests. These actions ensured I was starting with a car in good solid healthy condition which set the base line datum for improvements as they occurred.

One year on after buying this car, I now slightly regret not going one stage further with my initial servicing regime. Hind sight is a wonderful thing. I should have had this car given the Terraclean treatment immediately I had completed the servicing listed above. This would have given an even better starting point on which to base my tuning modifications. I have listed a separate section below regarding Terraclean. The chemical cleaning process worked wonders as regards low speed response and indeed general driving. After 83k miles of use, my XJR benefited hugely from deep cleaning applied to the fuel system injectors and combustion chambers and it is a process which I would seriously encourage others to use. For around £150 it is worth every penny. The results totally exceeded my expectations.
Terraclean 006.jpg
A washable, high flow oiled cotton K&N air filter under part number 33-2273 replaced the standard restrictive Jaguar paper filter.
A similar filter fitted to my S-type unlocked four flywheel bhp when tested some years ago on the Paramount Performance rolling road. Two restrictive plastic baffles were cut out from the lower filter air-box to help a more flow of incoming charge air distribute across the entire air filter surface rather than be drawn through unevenly. I noted a black stain on the old filter element through which air had previously been drawn and also cleaner areas with almost no staining. That said, this is the filter that I removed at 78k miles and I suspect that it was the original filter fitted at the factory some eleven years earlier!
The baffle modification on the bottom of the airbox is carried out with a hacksaw blade and a pair of pliers and takes just a couple of minutes to perform. That modification can be done on both supercharged and naturally aspirated model lower air boxes. At this stage, what we are looking to achieve is a gradual increase in power and torque. Some modifications might add just a couple of horse power. Others might add up to forty. When large and small gains are added together, the total gain becomes the eventual prize. Bit by bit, the gains can become quite impressive.

One often comes across cone air filters which are generally used with faster cold air intake systems. Modifications for cone provision often require the removal of the complete OE air box component. This type of modification is deemed by Powerhouse Automotive as un-necessary for a road going application even with engine tuning taken to high levels. The K&N oiled panel filter is more than capable of flowing in excess of 600lpm and that figure is more than adequate for supplying even the most highly tuned Eaton supercharger supplied tuning modifications we are likely to construct. Cold air continues to be supplied via the existing below air box snorkel intake and avoids having to construct a baffle arrangement to stop hot engine compartment air being drawn in by an otherwise un-sealed cone filter type arrangement. Cold air intake system design and fitting will be discussed later within this post.

My next move was to spray clean the Mass Air Flow sensor.
This is a hot wire and bulb arrangement which tends to get very dirty in service. Using spray carburetor cleaner, the build up of black oil dirt is quickly removed. I carry out this action every 10k miles to ensure the sensor stays squeaky clean. This sensor cleaning action is not within Jaguar service schedules and that surprises me somewhat.
Dirty or time expired MAF sensors cause poor running, fault code issues and can damage fuel economy. On the V8R there also exists the Inlet Air Temperature sensor. This is located at the rear of the throttle body elbow below the throttle body itself. Unfortunately it becomes covered in crank case breather residue. It sits in a channel within the elbow and can frequently become drowned in a hardened puddle of tar like substance. Fortunately, just one small Torx screw holds it to the elbow and it is a simple pull out extraction for cleaning. Again use spray carb cleaner. These two important sensors should be kept as clean as possible to ensure their correct signals transmit to the engine ECU. Their condition greatly affects engine power delivery and performance. Naturally aspirated cars also need this level of cleanliness applied.

From experience, I know that Cylinder Head Temperature sensors can break down from around 80k miles. This has occurred on two separate occasions on the V8 models I have owned.
This important sensor not only transmits to the dash temperature gauge but also to the engine ECU. Its condition also affects cold engine starts which can become difficult if the sensor begins to fail. I`d advise changing this sensor every 80k miles in the light of my own experiences. Note when total failure occurs a full overheat condition ie needle into the red sector of the dash gauge with no apparent engine overheat is a typical sign that the sensor has gone duff. Again, this sensor condition is vital to good running characteristics of an engine. I changed this sensor soon after buying my car and the effect was immediately noticeable. A new sensor will improve reliability and drivability.

The thermostat condition is just as important as the CHT sensor. These can become unreliable with age and mileage and can become sluggish in operation which has a surprisingly detrimental effect on the way in which the 4.2 V8 runs. I suggest V8 thermostats that have seen 80k miles of service be replaced. Note that there are two or may be even three thermostats available for the V8R 4.2 unit. Which one has been fitted will be Vin Number dependent so always have a note of your Vin Number when ordering new parts. Only the last six alpha numeric digits are required ie G33207.

Engine speed and idle quality are controlled by the throttle body which may be drive by wire or cable controlled dependent on model. All 4.2 V8 cars, whether supercharged or naturally aspirated are of the drive by wire type. Opening the throttle will move the throttle plate and it is quite usual to find a heavy ring of crank case breather sludge accumulated around the throttle plate to throat inlet duct.
This build up of crud will affect idle stability and throttle pick up. Soft cloth, spray carb cleaner and ten minutes work will make a car run better at slow speeds. If build up is heavy, it is a simple matter to remove four long Torx screws securing the throttle to the elbow and take the throttle to the bench for complete cleaning. An enormous amount of crud can accumulate beneath the throttle plate and it is best removed. Obtain a new crush gasket before removing the throttle body. The cost is about £6.
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The throttle body gasket is to the top left of the picture.

It is also important to check that the part load breather pipe which links the near side cam cover outlet to the inlet trunking is also clear of sludge and that the o-rings within the fittings at either end of the pipe are soft, lubricated with Vasaline and are able to seal correctly and tightly.

Let us now define what we are attempting to achieve. The common definition is to increase volumetric efficiency within engine cylinders. Essentially, an engine can have modifications applied to help make it "breath deeper". Simplistically when modifying, we are seeking to fill engine cylinders with air to the maximum capacity and perhaps more during the inlet stroke. A naturally aspirated engine can only ever achieve that goal at no more than the local atmospheric pressure present at the time the engine is running. At the other end of the scale, engines equipped with superchargers or exhaust driven turbo chargers or perhaps both, may "force feed" an engine with an increased volume of charge air. If more air is present in an engine cylinder, then an additional amount of fuel may also be added. Extra air and fuel in chemically correct proportions of fourteen parts of air to one part of fuel will produce more power. Force feeding an engine has been very common practice and the method has been used for many years. The first superchargers appeared at the turn of the last century and have been on the motoring and aviation scene ever since. I need to avoid a long history lesson here and short cut back to our Jaguar models.

We have established a reason and purpose for supercharging. That is to greatly increase the volumetric efficiency of an engine set as a direct comparison to a similar engine that is devoid of supercharging or turbo charging equipment. Our bench marks are that a naturally aspirated Jaguar 4.2 V8 found in cars manufactured from around mid 2002, will produce some 300 flywheel bhp. V8R specified cars include the supercharger modification and churn out some 400 flywheel bhp. But much more is still safely available.....What Jaguar produced is just the tip of the iceberg. The fat end is there to be expanded by the enthusiastic owner and there people there who can make it easy for us to obtain a further slice of the potential action.

Back on Earth, now we need to define the terms of power and torque. Torque is a factor of force times distance. Ten tons placed on the end of a ten metre lever arm will have less torque applied to it than a lever arm which has twenty tons applied to it. If the lever arm is pivoted at one end and a calibrated brake unit is linked to it to measure force, it is possible to calculate that the ten ton weight at a set distance is likely to have less turning force than the twenty ton weight. Torque is what causes a mass to accelerate. More torque in a vehicle application means quicker acceleration. The more torque available, the quicker acceleration becomes.

I always find power more difficult to define. Having accelerated a mass, it is power that maintains the speed. The power of four hundred horses is greater than just three hundred. Higher speeds can therefore be obtained and held at a required level but only if the power is available to do so.

What "we" are trying to do is to modify a car to have more power and torque. Not only that though, because we are trying to improve both power and torque delivery in a fashion that makes ones chariot smoother, more drivable, pleasant and perhaps quicker than a standard factory product. The aim is to "fill in the holes" that may be present in a vehicles inbuilt DNA and create something that is irritant free and a total silky and effortless pleasure to drive. Subtle, seamless and sublime are just a few words that describe what I have attempted to achieve with my XJR. My hope is that some people will emulate some of the work I have done and also enjoy the pleasure of success each and every time they undertake even a small modification for which there is a noticeable and seriously positive effect. Every little helps as they say at Tescos, Powerhouse Automotive, Tom Lenthall Jaguar, Viezu Berkshire and EAG Marine in Fareham!

There are three generations of Eaton charger to be found on our 4.0 and 4.2 litre supercharged cars. The Generation Six TVS units as fitted to 5.0 litre XFR and XKR models are not covered in this posting.

The four litre X300R is fitted with a Generation Three, M90 unit which produces 90cfm of air flow.

The Generation Four M112 unit is fitted to four litre X308R and XKR and produces 112cfm of airflow.

The Generation Five M112 is an up-rated Generation Four unit with larger inlet tracts and a somewhat smaller throttle body elbow than Generation Four units. The upper pressure manifold has also been completely redesigned, to improve air flow and delivery characteristics. This version will be found on 4.2 models which include the S-type R, the X350R, the XKR and the early 4.2 XFR.
Once basic servicing has been completed, the car is ready for modifications. Below, I`ve listed various modification headings in broad terms as a suggested order of progression using the experience gained modifying my own X350R fitted with the Generation Five, M112 Eaton charger. Modifications, however can be "pick and mixed" as time, enthusiasm and expenditure allow. In practice, there really is no set installation order but I can almost guarantee that for each modification carried out, there will be a noticeable positive effect with some modifications having a larger effect than others.

Inlet Topics covered below.

Lower air filter box baffle removal.
Replacement of standard paper filter with K&N or similar oiled cotton performance part.
Removal of plastic flash ring on MAF sensor housing.
Standard inlet feed pipe modification from MAF sensor housing to aluminum plenum above throttle body.
Replacement performance inlet pipe, MAF to aluminum plenum inlet.
Porting and polishing the aluminum inlet plenum.
Throttle body cleaning and polishing.
Modification, porting and polishing of the "cowhorn" pressure plenum above the supercharger.
Inspection and replacement of the rubber by-pass actuator pressure pipe.
The importance of oil changing on an Eaton supercharger every 60k miles.
Replacement of the supercharger drive coupling.
Installation of smaller supercharger over-drive pulleys.
Major performance modifications to the supercharger and throttle body elbow.
The important replacement of the valley coolant pipe whilst the supercharger is off the car.
The Terraclean process and effects. Money well spent. De-carbonising combustion chambers and fuel injectors.

Lower air filter box baffle removal.
Two small vertical plastic baffle plates are to be found at the base of the lower air cleaner box. They obstruct air flow immediately after incoming charge air exits from the inlet snorkel. As discussed earlier in this thread, their presence disrupts airflow within the lower part of the air box and tends to lead to air being pulled through the panel air filter in an uneven fashion. The baffles are easy to remove with a hacksaw by cutting down the sides and then snapping them off with a pair of pliers. The resultant cleaner air flow is then better distributed across the underside of the air filter and if nothing else will avoid heavy dirt deposits building up in one localised area. Although the effect of baffle removal will be negligible at lower throttle openings, wide open throttle conditions will draw a large amount of air through the filter and anything that can be done to reduce turbulence within the lower air filter box, cannot be a bad thing. Turbulence costs performance.

Replacement of standard paper air filter with a washable, re-usable, high flow oiled cotton K&N type filter. This is a well known, tried and trusted after-market fitment. A K&N panel filter will increase available air flow into an engine with a slight increase in power being made available. My K&N equipped 4 litre S-type gained another 4hp when tested on the Paramount performance rolling road.

Removal of a small plastic mounding flash ring on the top air filter air box lid as the outflow pipe exits the lid.
This small but slightly intrusive flash is easily removed with a sharp Stanley knife. It can be further smoothed away with abrasive paper. Small though the flash may be, it is never the less an turbulence maker which does not need to be present.

Standard inlet feed pipe modification.
Modifications to this standard fit high turbulence component are difficult. This right angled pipe joins to the MAF sensor housing with a turbulence making convoluted rubber joiner section. This is not good as it severely robs an engine of power. In addition, six hollow closed ended noise attenuation pipes bristle out of this induction pipe to help control noise generation when the supercharger is at full chat. A large "bump" also internally protrudes into the induction pipe in the worst possible place... right on the bend of the induction pipe. This bump was molded into the pipe in order to ensure it did not touch the header tank! In practice, the bend, even if Jaguar hadn`t molded the bump in it would have cleared the header tank by around 4mm. A miss is as good as a mile! As an experiment, I blocked up the noise attenuaters with builders foam and profile trimmed it to the profile of the manifold once cured. The experiment was a success in as much as it gave the car more torque at slow speeds and proved that the standard inlet pipe impacted negatively upon potential performance.
Replacement performance inlet feed pipe.
Having proved that the standard OE inlet pipe stole performance from the car, I went on to install a Mina Gallery cold air pipe sourced from the USA. This is a simple 75mm OD aluminum pipe with a 90 degree bend in it. The interior has a smooth finish, is devoid of the "bump" as found in the OE pipe, does not have noise attenuation pipes, or a convoluted joiner.
It is supplied with two rubber joining collars and a stub inlet for the part load breather. This pipe makes the car a little more responsive at slower speeds and rather quicker when the throttle is opened up. It is definitely worth fitting, but for XJR model use I had to buy an extended collar from Viper Performance as the item supplied by Mina was too short. The S-type R/XFR being perhaps narrower at the point that this pipe is fitted, would probably not have this issue.

I also had a problem joining the part load breather to the induction pipe and ended up having to make my own local modification to get around the issue. Mina told me they would supply the correct parts but they never arrived which was disappointing given the relatively high cost of the component. Delivery from the States took a month which was also not pleasing. For those considering this type of modification, I would suggest you could have one easily made up by a local aluminum fabricator for rather less than the £175 I forked out to Mina for mine. This pipe has however come into its own with the introduction of other performance parts which were added after this aluminum inlet pipe was fitted.

The cold air pipe together with the airflow meter housing, air-filter box and were also wrapped with high insulation, self adhesive aluminum backed fibre-glass tape. Temperatures within the engine bay can become very high and lead to heat soak on many components. Wrapping the inlet pipe components helps stop ambient engine bay temperatures from heating the cold charge air pipe and the air passing through it. After wrapping the cold air pipe with the insulation tape, temperatures recorded with an infra red heat gun by dropped 3 degrees internally thus slightly increasing air density and oxygen content. These two factors are important especially to owners of super charged cars where every possible opportunity to decrease air temperature adds towards increased power and torque. Once again, every little gain helps the overall result.
Porting and polishing the aluminum inlet plenum.
This component links the induction pipe to the throttle body. It is a cast unit with an oval shaped inlet mouth at one end and has a circular exit at the other. The oval mouth has a blunt profile which is easily re-profiled to a bell mouth profile to reduce air turbulence caused by its stepped entry.
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At the outlet, the circular mouth has a smaller internal diameter than the throttle body to which it adjoins. This circular exit can be opened out to the diameter of the throttle body throat which de-restricts airflow at that point.
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In addition the plenum is flattened above the circular outlet which further constricts and restricts the volume and flow of incoming charger air. Using either an air of electric powered die grinder fitted with tungsten cutting burrs, both the oval neck, circular exit and the constricted flattened roof of the plenum can be opened out by cutting away constrictive material. Further use of small garnet sanding barrels of P60, P120 and P600 grade abrasive material is undertaken to further smooth the surfaces before buffing with cutting and polishing compounds to leave a smooth highly polished finish. Re-profiling and internally polishing this component greatly eases charge air flow into the engine and costs little more than an hours labour and a bit of effort. This modification will have a meritorious effect even on a standard motor and lead to a more fluid throttle response.

Throttle body cleaning and polishing.
Removal of the throttle body is recommended in order to thoroughly clean this component. The throat and throttle plate can become choked with a large build up of oily black hardened crank case breather residue which can lead to a poor idle and sluggish throttle response. Four long Torx bolts secure the throttle body to the supercharger elbow on R models or to the plain inlet manifold on naturally aspirated models. A crush gasket below the throttle ensures an air seal. A new gasket should be sourced before undertaking removal and cleaning of the throttle body. Spray carburetor cleaner and a soft rag is used to remove deposits and a piece of fine Scotchbright pad used to smooth top and bottom throats followed by buffing to a high lustra. This will again improve airflow through the throttle and the induction system. extreme care should be used to ensure the slippery PTFE coating around the throttle throat in the area of the throttle plate should not be damaged or abraded. Note that the supercharger elbow or plain inlet manifold mounting for the throttle body will probably again have a constricting ridge showing which again will cause turbulence and restriction if not removed. Sadly this ridge remains due to poor machining detail when originally produced at the factory. I will detail removal of this ridge and other de-restriction removal operations later in this thread.

Modification, porting and polishing of the "cowhorn" pressure manifold above the supercharger.
This modification may be undertaken without removal of the supercharger from the car and has highly productive results. Remove the aluminum inlet plenum from the throttle body to access the cowhorn pressure manifold from the top of the supercharger. Four bolts secure the manifold to the charger together with one spring hose clip around the by-pass neck. Once the bolts and clip have been removed, the manifold can be lifted away. The re-useable thick rubber and steel composite gasket may be re-used after cleaning and application of a little Loctite Si 5980 sealer which is available from Halfords or similar outlets.

Using a die grinder, cutting burrs, sanding barrels and polishing mops, this pressure manifold can be reworked in three or four hours. This is a modification which can be applied to both standard vehicles and more highly tuned versions. It works well. Particular attention should be paid to the circular by-pass throat which is rather small in size and as supplied by the factory has a massive excess of metal left in place due to poor machining detail. This can be quickly removed with a tungsten burr before being fined down and polished. Cleaning out this constriction has a huge effect on throttle response and general low speed running. Further cutting away of material is also recommended around the by-pass neck within the roof of this manifold together with general smoothing and high level polishing of all internal surfaces. Excess material around the gasket land surfaces is recommended with cut back dimensions being taken from the outlet of the supercharger outlet casing. The charger casing and pressure manifold can be "port matched" to ensure the two mating surface dimensions are identical and are matched to ensure there are as few turbulence inducing steps as possible. This attention to detail is what makes for a powerful and smooth running engine. This type of work is known as "Blueprinting". Re-working this pressure manifold in conjunction with opening out induction components discussed above, makes for a very nice user friendly Stage One modification which can be left at that, or taken further as described below.

Inspection and replacement of the small rubber by-pass actuator pipe.
This 3.3mm/ 1/8" small bore rubber pipe can cause massive issues if not replaced. With age, this £7 pipe can simply disintegrate and even fall off the end of the stub pipe to which it adjoins the cowhorn manifold.
Be warned. If the pipe is rotten at one end, it will also be rotten at the other! This little pipe runs from a prominent stub pipe on the near side of the cowhorn, under the throttle body elbow to emerge on the offside where it rises to a connection on the by-pass actuator. For some reason the pipe is cut in half at mid point and a white straight connector is inserted. This is prone to leakage, is un-necessary and is a confounded nuisance. I suggest a replacement pipe be installed as one complete length and is lead over the top of the throttle body elbow rather than below it.
There is plenty of space available to do this. Re-routing this pipe will make it more accessible and easier to keep an eye on in the future. For information, a spilt or rotted pipe will generate "Lean banks A&B" fault codes as P0171 and P0174. Replacement of this pipe and cancellation of fault codes with a suitable diagnostic tool will cure this irritating issue.

The importance of oil changing on an Eaton supercharger every 60k miles.
Maintenance is all and a stitch in time saves nine. This applies significantly to the Eaton supercharger to which the manufacturers service recommendation is an oil change every sixty thousand miles. The fact that oil when sampled at higher mileages may look clean and "OK" is not sufficient an argument to avoid oil changing. A sample of oil on a white cloth does not prove its continued use as being of sufficiently good enough chemical composition to afford continued reliable service as a lubricant. Synthetic oil has a finite life after which it decays rapidly and its lubrication qualities plummet like a stone. If you disbelieve this, ask any aircraft gas turbine engineer to tell you what occurs to components which run in time expired lubricant! It is only when old used oil is extracted from a charger and is placed in volume in a container, that you will see just how degraded the lubricant has become at an over extended mileage. Mine was black at 78k miles and typically had developed an appallingly foul smell. When eventually changed some eighteen thousand miles late, this was the result and I think I only just caught the issue in time.

Supercharger rotors, the tip speeds which may reach 1600mph, run in heavy duty sealed ball bearing units. It is the oil that affords the sole and essential lubrication. As oil reaches the end of its finite life, its lubrication properties diminish rapidly which will cause the bearing units to fail completely if oil changing is ignored. Rumbling charger bearings indicates a big and expensive problem ahead. Charger bearings are swaged permanently into the centre bearing plate after installation and are not replaceable. Without exception all companies dealing with charger overhaul state that they are unable to develop a reconditioning regime to replace these bearings. If they are worn, then the only alternative solution IS TO BUY A COMPLETE NEW SUPERCHARGER at a cost of around £1400 plus VAT. New rotor packs alone are not supplied by Eaton as each rotor pack is matched to a rotor casing at original manufacture. Powerhouse Automotive will corroborate my statement here. I would suggest few Main Dealers change supercharger oil at the important sixty thousand mile manufacturers recommendation. In the case of my own car which had a Main Dealer service history, I know from extracting used charger oil eighteen thousand miles after the Dealer stamped sixty thousand mile service, that this had NOT been carried out. An image of what I recovered will be posted here shortly!

Charger oil changing is not difficult although space is limited in front of the screw out plug on the front of the charger sump case. A 3/16 Allen key is essential for the job. Powerhouse Automotive are able to supply the correct volume and type of oil required. It is to Aeroshell 100 specification and is the only suitable oil for lubrication. Do not use any other substitute. The cost is around £25 which includes oil, a syringe and a flexible small sized extraction tube. Oil changing should only take around ten minutes to achieve and is easier if the oil has reached operating temperature. This image depicts a bottle of new supercharger oil, rear rotor needle roller grease and an up-rated supercharger coupling, all supplied by Lawson Smith.
Replacement of the supercharger drive coupling.
This coupling wears with age and mileage. A rattling noise becomes evident from the front of the charger if the coupling is worn. Excessive wear may become evident from around 150k miles. The coupling acts as a shock cushion between the belt driven input shaft and the driven rotor gear peg drive. Its concept is similar to the function of the springs found on a typical clutch plate although its method of operation is different. The supercharger needs to come off the car for this work. Details on charger removal are covered below in the relevant section.

Six Torx head bolts secure the drive shaft shout unit to the charger. Extract the old charger oil using a syringe and tube. Remove the six bolts and pull the snout unit away from the charger case. Whether you fit an OE Eaton genuine part or uprate to a rather more robust aftermarket coupling as supplied by Powerhouse Automotive, the procedure is the same. Pull off the old coupling and examine. The drive spring may be broken or weak and drive peg holes may be worn. Fit the OE or up-rated coupling and refit the bolts. Torque evenly to manufacturers specification. Fill with fresh oil via the screw in bung. A 3/16" Imperial Allen key or hex drive socket is needed. The screw in bung can tightly fitted some considerable torque may be needed to remove it. It can let go rapidly as torque is applied. Watch your knuckles! Note that an up-rated coupling can be a little noisier at idle than the OE part. Backlash in the drive gear set becomes more pronounced with an up-rate coupling fitted.

Installation of smaller over-drive supercharger pulleys.
These aftermarket components may be sourced on the internet or via Lawson Smith at Powerhouse Automotive. Lawson markets 6% and 10% power increasing pulleys for DIY or professional fitting. He also offers a full or part reconditioning supercharger service with a fast turn around. See the Powerhouse Automotive site for details. These stainless steel pulleys spin the supercharger faster than the larger OE pulley fitted at the factory. This produces a noticeable 6% or 10% increase in power and torque and are particularly useful in as much as the supercharger produces boost lower down the RPM rev range.This makes for a more tractable and user friendly car. There are no negative aspects from fitting one of Lawsons` up-rate pulleys.

Fitting a 6%/25hp pulley is quite straight forward. Having removed the supercharger drive belt, cover up the engine with a thick sheet. Use an angle grinder to grind down through the original pulley "along the drive shaft axis" to break the hoop tension between the shaft and the old pulley. Stop immediately you see a black line appear as you grind along the old pulley and down to the supercharger drive shaft. Tap the remains off the drive shaft with a light hammer. Heat a new small stainless steel 6% pulley with a gas blow torch until it goes to a straw colour.
Remove the heat and quickly slide the hot pulley onto the shaft. Lightly spray with water until cool, paying particular attention to keeping the oil seal and drive shaft as cool as possible during the period the pulley is still hot.
Fitting a 10%/35hp pulley is more complected as a procedure. The 10% pulley is approximately 4mm smaller in inside and outside diameter and it is necessary to remove aluminum from around the outside diameter of the supercharger snout component to allow fitting of this 10% smaller pulley. Whilst with the use of a power file, assorted hand files, vernier measuring equipment, and other cutting and abrasive tools, it is possible to machine down the charger snout with the supercharger still bolted to the engine. Ideally though, the snout should be removed, placed in a four jaw lathe chuck and carefully controlled amounts of metal removed. With either method being considered, the work should only be attempted by skilled people who have a a high level of competence and skill.

Considerably more belt drive grip is required for the 10% set up and this should not be fitted unless a genuine Jaguar up-rated tensioner kit which includes a double sided ribbed belt, a modified idler bracket and a shouldered and ribbed idler pulley are fitted.
Displacement of the drive belt is usual unless this additional pack of parts are fitted.
Please do not ignore this up-rate if fitting a super small 10% pulley.
Note well. The tensioner units can seize to the mounting bracket due to corrosion. Two pegs on the tensioner engage with the mounting plate. Seizure can be so bad as to cause a breakage upon removing an old tensioner. Repair is by removing the bracket to the bench to drill out the remains of the peg, or if you are lucky and possess a 9o degree drill, the job can be done on the car. It will however be a right cuss! Here we see a new shouldered pulley fitted to prevent belt flinging.
The 6% pulley will generate a noticeable power increase from around 2500rpm. The 10% has a rather larger effect from 1800rpm. Both pulley conversions work well as stand alone installations but a bigger effect is obtained through having the Power Train Control Module reflashed at a reputable establishment. Viezu are a well known, tired and trusted tuning establishment and I have used their up-rate services on two occasions now. The installation of alternative pulleys then really comes into play.

Major modifications to the supercharger and throttle body elbow.
Once again a high level of knowledge and mechanical competence is needed to understand and complete this type of work. The biggest issue is that of supercharger removal from the car. The first half of the work is easily achieved using basic hand tools. The problems of removal of a charger from the car centre around the difficulties of removal of the EGR valve. The valve must be removed to allow access to two obscurely placed bolts which secure the throttle body elbow to a bracket which is affixed to the top of the engine valley. It is only then possible to remove the elbow once those two badly placed bolts have been removed. That action alone forced me to send my XJR to my local Jaguar independent garage in order to have those two bolts removed and allow the elbow to be removed. I have a sciatic condition which limited me removing those bolts due to inaccessibility. I know that I am not the only person to have been stumped by EGR valve removal so please be warned that supercharger removal is NOT an easy job. Once the elbow has been removed, one last bolt at the rear of the charger allows the charger to be removed.

A good tip here is to remove the across car thermostat housing and manifold. Removal is simple enough with only a few bolts to remove. Salvage the manifold seals between the manifold and the cylinder heads. It will take only a few minutes to remove the manifold and that in turn will free up space towards the front of the engine and make charger removal easier and faster than if the manifold had been left in place.

Once removed, the charger should have all openings taped up to prevent foreign objects and washing liquids entering the charger. The charger should be washed with engine cleaner before being dismantled. This link to another of my threads describes servicing, porting and polishing of the Eaton M112.http://www.jec.org.uk/forums/viewtopic. ... 81&t=10231

The important replacement of the valley coolant pipe when the supercharger is off the car.
The condition of this pipe is vital to the reliability of supercharged 4.2 models. This pipe is only inspectable and replaceable with the supercharger removed from the car. There are no short cuts to removal and the bullet must be bitten. These two threads provide an in depth guide to replacing this hose. Ignore at your own peril! http://www.jec.org.uk/forums/viewtopic. ... 82&t=10706
http://www.jec.org.uk/forums/viewtopic. ... 81&t=10701
The Terraclean process and effects. Money well spent.
Believe me, this cleaning process works! Despite modifications, my car was still sluggish around town. Something had to be done so I called the Terraclean man in! How I wish I had done this sooner. 83k miles and twelve years on the road had clogged up fuel injectors, coked combustion chambers and sapped my XJR of power. The two stage process transformed my car back to its original ex-factory youthfulness in less than an hour. The process cost just £150 and was possibly the finest gift I could ever bestow on the car. I`ve just one further Five Star recommendation...Do it yourself today and restore what the years have taken away!
Terraclean 009.jpg

Sports catalytic converters.
Standard 600 cell catalytic converter cores are fitted by Jaguar at the factory. Coils of Fecla metal fill the internal converter cases to form a chamber that processes noxious exhaust gas and expels "cleaned up" gas that is less harmful to the environment when compared to an exhaust system that is devoid of converter material. A standard exhaust has converter cores which cover something like 55% of its internal cross sectional area. Only 45% of the original exhaust pipe size remains to flow exhaust gas. This is highly restrictive and costs a vehicle operator in terms of increased fuel consumption and lost performance.
The most restrictive part of the complete Jaguar V8R induction, combustion and exhaust system are the catalytic converter cores. Performance "sports" converters offer a highly effective solution towards nullifying the power and economy sapping effects of a standard exhaust system. The cores are lined with high flow 200 cell media and are a quick and easy solution to unblocking an exhaust. Taken to a performance exhaust fitting business such as the National franchise chain of Longlife Exhausts, standard converters can be cut open and filled with the less dense 200 cell material. Such modifications offer significant performance and economy gains and I can only but heartily recommend this type of modification. My XJR V8 has been fitted with 200 cell cores and the effects have surprised and delighted me. The car accelerates faster, is more responsive and driven at reasonable speeds on the motorway regularly exhibits a fuel saving of up to three miles per gallon. Emissions readings remain unchanged from the standard cell results obtained at the last MOT. Excellent results can be obtained by fitting sports cats in conjunction with a 6% or 10% overdrive supercharger pulley, a K&N air filter and an ECU software re-flash. Power output will be very near to 500 flywheel bhp with that combination of parts fitted....ie a 25% power increase when compared to a standard factory issued car.

X-pipe replacements.
Fitting an X-pipe in place of the standard H-pipe arrangement greatly improves cylinder scavenging and speeds up exhaust gas evacuation from the engine. The X-pipe fitted to my car at the same time as the 200 cell catalysts, has added to general engine de-restriction and further increases power, drive-ability and economy.
Other exhaust modifications.
It is a "pick and mix" choice to your own design really. The over riding factor for most people will be a major decision about exhaust noise levels. The modified cats and x-pipe fitted to my own car bears that out. I wanted a performance system but without the loud exhaust note that I had previously lived with for eight years on my V8 S-type. That car featured a loud, straight through Miltec system which whilst sounding fantastic to by-standers, but could become extremely wearing to the ear if traveling several hundred miles in a day. On some occasions when using this car, I would stuff cotton wool in my ears just to get some relief from the racket! A loud exhaust can give you a grin factor initially but it can soon fade. With that experience behind me, my brief to Longlife Exhausts was to build me a quiet system that would not be intrusive within the car. The advice then is to choose your noise levels carefully and discuss your project with your exhaust builder.


Fitting a Bosch high flow inter-cooler pump.
The standard fitted pump is manufactured by Hella. In service it is a reasonably reliable unit with a usual life expectancy of around 130k miles. Replacement cost is around £173 plus VAT.
Bosch XJR supercharger intercooler pump. 001.jpg
On the X350R it is located just inboard of the off side main beam headlight behind the front bumper cover. To access, the bumper cover must be removed. This pump provides pressure and flow to circulate coolant around the supercharger inter-cooler bricks and the inter-cooler radiator which is located immediately in front of the main engine coolant radiator. Fusing is in the front engine compartment fuse box, fuse F27. The pump runs when the ignition key is turned to the first position and at all times whilst the engine is running. When the pump is operating, listening with your ear adjacent to the off side front main beam headlight unit will confirm the pump is functional. Pulling fuse F27 also aids diagnosis that the power circuit is functioning.

Should a Hella pump cease functioning, the supercharger cooling system will show signs of an over-heat condition. By somewhat strange design, the cooling system shares the same header tank as the engine coolant although a division within the header tank will be found. Note the air-bleed screw on the header tank used to evacuate air from the top of the inter-cooler radiator circuit. This should be opened when filling the inter-cooler circuit with coolant after pump or perhaps radiator replacement. Owners facing the need to replace the Hella pump should consider buying a Bosch high flow alternative that is available from Advanced Vehicle Tuning via ebay. This pump is currently available for around £135 including VAT. It is a little larger than the OE Hella unit and is much loved by the racing and drag racing community due to its high flow rate and exceptional reliability. A small modification to its mounting is usually required which is simple to action. Its high flow rate help to lower inter-cooler system temperatures and prevent power drops often experienced in hot weather.

Fitting an up-rated inter-cooler radiator.
The standard inter-cooler radiator is a reliable unit which gives few problems in service. However, it does not have much reserve cooling dispersal ability where higher engine power outputs from tuned units are concerned. Heat is work and work is heat. Higher tuned engines produce more heat which is particularly noticeable during hot climatic spells or in countries with much elevated general ambient temperatures. In addition prolonged use of an engine at high power settings in hot climates can cause the standard inter-cooler circuit to become over-heated due to the heat generating effects of the supercharger and the cooler circuit becomes incapable of dispersing excessive heat via the standard inter-cooler radiator.

It is an easy matter to fit a higher flow pump as detailed above. In addition it is again easy to find a purpose built higher capacity radiator on ebay specifically designed for the XK8R and the X308R. They are one and the same unit. The cost for an up-rated radiator with a stated 33% up-rated heat dispersal core is around £165 and is a direct fit to either car. It is suitable for both 4 litre and 4.2 litre cars.
Sadly, no one has designed or marketed an up-rate for the 4.2 X350R or the XFR. Perhaps there is little demand for it. All is not however lost. As a project, I have obtained one of the XKR radiators but not yet fitted it. Space is tight in the X350R but early indications and measurements lead me to believe that the XKR unit with some small bracket and outlet pipe modifications could make fitting to the XJR a possibility. More on this as and when I get around to the job.

This is a "plug and play" after-market units which plugs into the accelerator pedal and allows the driver to modify throttle response. Details of the unit may be found in these links and BB threads.
http://www.jec.org.uk/forums/viewtopic. ... 96&t=10708
http://www.jec.org.uk/forums/viewtopic. ... 96&t=10898

A cost effective way to increase torque and power on V8R models. I have a Devilsown system installed on my own XJR. You can also expect cooler inter-cooler system temperatures especially in the summer and a much cleaner internal engine as a result of using one of these kits. It is totally non destructive in use and adds greatly to the fun and performance to be potentially available from a modified V8R. Highly recommended. Details in this link.http://www.jec.org.uk/forums/viewtopic. ... 81&t=10887

Nitrous oxide is a well known method of increasing the power of an engine. Bottled nitrous can be fed to an engine but installation may be quite time consuming and complex. Wizards of Nos market various kits with Lawson Smith at Powerhouse Automotive in Sheffield being an excellent agent and installer of the product range. The No 8 kit is for V8 models with the No 6 kit being designed for V6 models. DIY fitting is a possibility for both naturally aspirated and supercharged Jaguar models. Note that a supercharger would need to be removed to allow installation. Please see my comments on supercharger removal before you contemplate this modification. Removal is not an easy job.

The above notes describe fitting of various modification parts which can be mixed and matched according to budget and preference. None of the modifications discussed or indeed fitted to my own 4.2 XJR have done anything other than significantly improve the car. Drivability both in town and out on the open road improves greatly each time a modification has been installed. Fitting sports catalytic converters has seen a significant improvement in fuel consumption. Prior to fitting of the new cats, I struggled to obtain more than 28 mpg. With new sports cats fitted, the mpg rose to 33. Without doubt, it is possible to greatly modify the 4.2R engine to higher power levels without destroying fuel consumption in general use or ending up with a hard nosed bullish driving car. In all respects, I have found the 4.2R engine to be easily capable of absorbing power increasing components without incurring difficulties of fitting or ending up with disappointing results. Modify and enjoy without fear is what I say.

This post might never be complete. There will always be something that can be added as further modifications occur or more information comes to hand.

Mike K
X350 Co-ordinator

2004 XJR

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Re: A guide to tuning the Jaguar 4.2 V8R and other V8 motors

Postby J44EAG » Sun Dec 18, 2016 10:45 am


This locked thread, as at 18/12/2016, is probably as complete now as it will ever be. I`ve added in my latest modifications, namely in regard to the Sprint Booster unit and also Water/Methanol injection with those subjects being covered by links posted as separate threads.

There is little more I can do to my own car now. It has reached a high level of tune utilising the common up-grade parts available for the model. Perhaps the only item not fitting is the Quafe LSD available from Tom Lenthal. That is not a cheap item at around £2,200 fitted and for a road car, I think it rather an "over-kill" item. It is unlikely that one will ever be installed on my car. A good pair of premium grade tyres on the rear end of the car provides more than enough grip which I consider to be good enough for the purpose. Cheap tyres previously caused issues with minimal grip being afforded.... my best advice is not to skimp on tyre quality. Fit good tyres and you won`t go far wrong.

X350 Co-ordinator

2004 XJR

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