Our core business is bike tuning, but we also have an interest in Jaguar cars
and can offer some very popular and good value Jaguar upgrades:

Supercharger upper pulley 4.0 & 4.2

Supercharger upper pulley 5.0 £186.00

Supercharger upper pulley 3.0
- coming soon

Supercharger lower pulley 4.0 XJR-6

Supercharger lower pulley kit 4.0 XJR/XKR V8 £325.00

Upgraded intercooler radiators £575.00

XKR X100 & XJR X308 uprated rear anti-roll bars £145.00

XKR X100 uprated front anti-roll bars £349.00

Lowered Springs Set from £285.00

Selectable Power Steering Weight £125.00

Trade Enquiries Welcome

Supercharger Pulley Upgrades

Jaguar XKR & XJR, & Range Rover Sport

Unlike other marques or engine types, there are very few cost effective bolt-on performance upgrades available for the AJ27 and AJ34 engines found in Jaguar XKR, XJR and Range Rover Sport engines. Fortunately though, we do have a couple of very simple upgrades which not only give extra power and torque you really can feel, but offer seriously good cost effectiveness in terms of £ per bhp, especially compared to exhaust changes or remapping.

There is a choice of upper or lower pulley change on these cars, offering driven speed increase of the supercharger which can be increased by anything from 10% to 17%. The upper pulleys are 10% smaller than the standard item, and it is generally accepted that a 10% blower speed increase on these cars gives 2.5-3psi boost pressure rise and 35-40bhp (with 40ftlb) improvement. While that sort of figure is realistic for the midrange, actual peak power rise may be more like 15bhp, because the Eaton M112 becomes less efficient at the high end of its operating range. Dyno graphs for M112-equipped cars tend to show boost dropping off towards redline, but that doesn't prevent the trusty Eaton from responding beautifully across most of the rev range, giving the feel of a larger motor as well as more instant response.

The lower pulleys are more than 16% larger than standard 4.0 items, with gains of 4-4.5psi and 45-50bhp/ft lbs on a 4.0 engine. On the 4.2, which comes from the factory with a larger lower pulley as standard, the lower only offers an 8% driven speed increase. For this reason the upper pulley should be first choice for 4.2 litre cars.

Pulley Options – which to go for?

In terms of performance, both options offer the same gain to a 4.0 engine, but it is generally accepted tat the lower pulley gives more surface area for belt grip..

Both options can be fitted with relative ease by the competent home mechanic or any garage, and should take 2-3 hours. The upper pulley requires minor modification to the supercharger snout casing, and acetylene gear to heat the new pulley which is an interference fit on the pulley shaft. The lower pulley requires special tools to remove the existing crankshaft pulley, and access underneath the car (we can loan the required tools for a small fee).

Upper pulley


  • Half the price of the lower pulley kit.
  • Longevity of a stainless steel pulley – other suppliers use cheap mild steel or aluminium.
  • No need to access under the car, or for special tool to remove the crank pulley.
  • Best option on 4.2l applications which already have larger lower pulleys.


  • Acetylene gear required to heat the pulley on fitment.
  • Modification/material removal from supercharger snout required.
  • Less outright grip available to the belt.*

*Some other pulleys are made in aluminium which gives grip problems when hot – our steel pulleys do not.

Lower pulley


  • No modification required to the supercharger.
  • No fitting cost if done at the same time as camchain tensioner replacement.
  • Increased belt grip area.
  • Easily transferred to another car.
  • Best option on 4.0l applications.


  • Twice the price of the upper pulley.
  • Requires return of your existing crank pulley.
  • Only adds 5% to 4.2l cars.
  • Need to access under the car to lock the gearbox and a special tool to remove crank pulley.

Upper pulley for XKR, XJR, Range Rover Sport   £120.00

Purchase includes stainless upper pulley, fitting instructions and loan of fitting template.

Fitting available at our premises for £175.

Lower pulley kit for XKR, XJR, Range Rover Sport   £295.00

Kit includes a modified Jaguar lower crank pulley, fitted with an aluminium lower supercharger pulley, replacement supercharger drive belt, replacement original Jaguar pulley bolt, and instructions.

There is a £95 surcharge refunded on receipt of your old crank lower pulley.

Fitting available at our premises for £140.

Can I Upgrade Both?

Yes you can! The peak power increase at high rpm may be no greater than with one pulley, but the midrange increase will be doubled, and for acceleration that's what counts. There is a downside to changing both pulleys, which is heat build-up in the intercooler circuit. The standard Jaguar intercooler radiator and charge coolers don't have much reserve capacity, and cannot deal with sustained high power use with both pulleys upgraded. That is easily cured however, by installing an upgraded pre-cooler radiator and intercooler circuit water pump (see below).

Uprated Intercooler Radiator Jaguar XKR 1996-2005

Unfortunately, Jaguar didn't design much reserve into the intercooler circuit. If coolant and inlet air temperatures rise too much, the ECU detects the changes and retards ignition accordingly to protect the engine – this will even happen on a standard car in hot conditions, though it is rarely noticeable to the driver.

Unless intended for track or very hard road use, the cooling system can cope comfortably with a single pulley upgrade. Driven hard however, standard and single pulley upgraded engines will benefit from cooler inlet air temperatures, and that means more power. Engines with both pulleys upgraded don't just benefit from uprated intercooling – they need it. We have invested in the manufacture of drop-in replacement intercooler radiators to fit the XKR and offer them at far more affordable prices than the £650-£800 typical from other sellers.

Uprated intercooler radiator   £550.00

Direct bolt-in replacement for the standard pre-cooler radiator.

Uprated intercooler water pump   £175.00

Direct plug-in replacement for the standard intercooler water pump.

Trade Enquiries Welcome

We also manufacture small batches of radiators for other applications – please enquire.

Jaguar Performance Upgrades at the Powerhouse

Air filtration

By very careful of cones filters! It is possible to fit effective enclosed cone systems with air supplies from outside the engine bay, but open cones will feed the engine with hot air from inside the engine compartment – a very hot place on an XKR or XJR – and that may even lose power compared to a standard filter in the stock airbox.

We therefore recommend the 'drop-in' K&N replacement for the factory air filter, which we know has been proved effective on XKRs running over 600bhp.

We can also supply K&N filters for other applications – please enquire.

Jaguar Performance Upgrades at the Powerhouse

Sports Catalysts  Jaguar XKR & XK8 1996-2005

When cats need replacing, it's bad, bad news! The cost of standard units is horrific, even from well-reputed non-dealer suppliers the price is about £550 per side. Some specialists offer sports replacement units but these tend only to fit a particular brand of exhaust, and will be anything from £1000 to £1700 for a pair!

Well, we weren't happy with that, so we have built jigs to manufacture high quality stainless catalyst downpipes with laser cut flanges and stainless steel monolith catalyst inserts made by the UK's leading catalyst cell manufacturer. Usually, fitting an aftermarket 'cat-back' exhaust gives a nice V8 burble but the potential performance gains are strangled by the factory cats. With our sports cats you can now get the most from your sports exhaust, or just free up power from the standard Jaguar pipework.

Catalyst Elements

Different grades of catalyst element are available to order. Standard factory cats have at least 400 cells per inch, while our sports cats have much more free-flowing 200 cells per inch (we can also on request fit cats with 100 cells per inch for competition use but these would not pass MOT emissions standards).

Sports cats to fit 4.0 (2-Lamda)   £720.00

Price per pair, direct bolt-in replacement for the standard units.

Sports cats to fit 4.0/4.2 (4-Lambda)   £750.00

Price per pair, direct bolt-in replacement for the standard units.

Sports Catalysts Refurbishment Service  All models

If you already have a set of aftermarket stainless cat downpipes, any make, but your catalysts need changing, we can help! Instead of replacing your units for over £1000, send them to us and we will rebuild them with new catalyst elements, using the same high standard cat inserts as our complete downpipes.

Sports cats element replacement   £525.00

Price per pair, fitting catalyst elements with cell density to your requirement.

Catalyst Type Approval

Please be aware that under the latest Type Approval legislation for automotive catalytic converters, we are not permitted to sell these catalysts for road use on vehicles registered after 1st January 2001. They would fit, perform exactly the same and do the job of controlling emissions on later vehicles, but the law now requires cats supplied to vehicles made after that date to have gone through a more expensive approval and control process. However, if your 2001-on car is for track or other non-highway use, we can still supply you.

Jaguar Performance Upgrades at the Powerhouse

Poly Bush Kits  Jaguar XKR & XK8 1996-2005

The X100 series cars are no longer young, and most now have tired suspension bushes – even low mileage cars. Rubber not only gets battered by road wear but oxidises and perishes with age. The whole driving experience can be improved up by replacing old bushes with new standard items, or sharpened further by fitting polyurethane bushes. Better still, poly bushes offer the huge advantage that they are not subject to ageing like rubber so will virtually last forever.

If you enjoy driving your XK, and want handling precision and feedback without sacrificing ride comfort, poly bushing the car needs to be high on your modification wish list.

Powerflex Jaguar Upgrades at Powerhouse Automotive

Powerflex Poly Bush Kit  £375.00  (rrp £430)

Full car set, can be purchased as front/rear sets or separately.

Fitting service available.

Lowering Springs  Jaguar XKR & XK8 1996-2005

The lines of these cars are wonderful but can be significantly improved with lowered springs, offering improved road handling as well as a stance which really does justice to the lines of the XK.

Our springs our made by one of the UK's leading aftermarket road spring specialists and will lower an XK8 by 25-30mm, or an XKR by 10-20mm. It does vary from car to car because depending on the age and production batch of your original springs, your car's starting height may vary. While the ride is firmer they do not give the harsh and unpleasant ride that is sometimes associated with aftermarket lowered springs. The cars remain able to manage speed bumps and sacrifice little of that Jaguar refinement and comfort.

Lowered Spring Set  £265.00

Price per set of 4, fitting service available. Suitable for both CATS and non-CATS cars

Please specify coupe or cabriolet.

We can supply springs for most Jaguars and other marques of performance car.

Jaguar Performance Upgrades at the Powerhouse

Switchable Power Steering Weight  Jaguar XKR & XK8

The XK and XKR come from Jaguar with variable rate power steering assistance, but the pump pressure is not reduced until the car is travelling at, or close to, motorway speed. Unfortunately, that means the steering is still too light to give feedback when you're making your way through twisting B-roads, and one of the few criticisms of these cars by many owners is that the steering is too light. However, there is a simple and well-proven solution, which is to fit an electrical bypass to the steering control module, allowing the driver to switch between full and partial steering pump assistance. This can be performed in a morning or afternoon and we believe is a 'must have' for the XK - most users only use the light mode for parking.

Selectable Steering Weight  £125.00

Allows the driver to switch between normal and enhanced steering weight and feel.

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