Description: Leask Adjustable WUR

If you drive a Porsche 930 or 964 Turbo, you are probably well aware of the shortcomings of the Bosch K-Jetronic CIS fuel injection system.  While in its day it may have been a relatively simple and robust fuel system, it has become quite antiquated by today's standards.  In the quest for better drive-ability and more horsepower, many owners have upgraded their cars by adding aftermarket headers, larger turbochargers, more efficient intercoolers, increased boost, higher lift cams, ported intake manifolds, modified fuel distributors, and many more specialized pieces.  But, without installing a stand-alone EFI system you are still stuck with the tune-ability issues of the CIS system.

An often overlooked component in the equation is the Warm Up Regulator (WUR).  It is actually more appropriate to think of the WUR as a Control Pressure Regulator due to its never-ending role in the fuel delivery process.  It does more than just regulate the warm-up stage, as it affects fuel delivery based upon manifold pressure (boost) as well.  Most Turbos can benefit greatly from tuning the WUR to match the engine's modifications.  This will allow the engine to achieve the performance and Air/Fuel Ratios (AFRs) desired.

The Leask Adjustable WUR allows all aspects of the WUR to be adjusted externally, without taking the unit apart.  There are 4 basic adjustments offered by these modifications.  They are:

All of the adjustment features are manufactured from high quality stainless steel for longevity and resistance to corrosion.  You will not find modified WURs of this quality available anywhere else, as I have spent many hours researching and developing the custom machined pieces that are the key to these modifications.



A new development has been made in extending the life of a WUR used on a highly boosted Turbo.  Quite often the fuel metering diaphragm will fail, especially on cars running 1.0+ bar of boost.  If you track your car, the constant on/off boost transitions are what tends to break the factory piece.  When this happens, it allows raw fuel to dump out of the vent tube on the top of the WUR.  Not only can this leave you stranded on a rural highway or ruin a DE track-day, it can potentially cause a major engine fire if the fuel ignites on the hot exhaust system.

I have researched and developed a heavy-duty replacement diaphragm that is 50% stronger than the original piece.  Having this diaphragm installed will give you the ability to run high boost with confidence.  The additional strength of the replacement diaphragm will keep it from failing even under the most strenuous conditions.


RPM control of the enrichment circuit has been developed in an effort to eliminate the absurdly rich mid-range condition exhibited by modified CIS Turbos.  This condition is particularly noticeable on cars that are running a modified fuel distributor, aftermarket turbocharger, short-tube headers, 0.9+ bar of boost, and the Adjustable WUR.  In order to have enough fuel for a proper 12.0 AFR at high RPM, the mid-range will typically be incredibly rich at the onset of boost.  This is because the WUR enriches based upon boost pressure alone, regardless of engine speed.

The RPM Controlled Solenoid Valve (CSV) remedies this problem by allowing you to select when the enrichment circuit is enabled.  This is achieved by swapping "chips" on the RPM controller.  By controlling when the WUR receives its boost signal from the intake manifold, a much flatter Air/Fuel Ratio (AFR) curve can be achieved.  This results in improved throttle response and more mid-range torque and horsepower.  A side benefit is improved gas mileage and extended engine oil life, as the oil is no longer diluted with any fuel laden blow-by at the onset of boost.

The dyno chart below shows typical gains at only 0.9 bar of boost.  The blue curve represents a dyno run with a precisely tuned Adjustable WUR.  The red curve has the enrichment delayed until 4200 RPM.  These runs were made back-to-back with no other changes between runs.  You might be wondering what happened to DYNORUN_006.  DYNORUN_006 was made with a 4400 RPM module installed which caused the AFR to peak at nearly 13.0 just before the enrichment was enabled.  This was deemed to be too lean.  A 4200 RPM module was installed and the car was re-run yielding the following results:

Description: C:\Users\Brian\Desktop\full_dyno_chart1.jpg

Here is another dyno chart of a completely different car at 1.0 bar of boost.  Note the substantial gains in torque and horsepower between 2600 and 4400 RPM.  The blue curve shows the dyno run made with a tuned Adjustable WUR.  The red curve shows the RPM CSV being triggered at 4400 RPM:


The RPM CSV kits contain all the components you need to install it on the car, minus the tools required.  In depth, 20 page color documentation provides a walk-thru of the installation process, complete with pictures.  The complete kits are now available for purchase.  Please refer to the contact information below.


The Adjustable WUR modifications are available for different makes and models of automobiles which use the Bosch CIS injection system.  I have made Adjustable WURs for Audis, Mercedes, Saabs, Volvos and other turbocharged and normally aspirated vehicles.  I have also made Adjustable WURs for Porsche 924 Turbos and 911 SCs with great success.

If you would like an Adjustable WUR for your particular vehicle, the procedure involves shipping me your existing WUR (or a spare if you have one) for modification and rebuild.  This process normally takes about 1 to 2 weeks from the time I receive the unit.  If you can provide me a detailed list of engine modifications including the intended boost level for turbocharged cars, I can preset the Adjustable WUR to get you close to the optimal mixture settings for your engine.  This will minimize the amount of fine tuning required.


$349.00:  Adjustable Porsche Turbo WUR

$379.00:  Adjustable Porsche Turbo WUR with heavy-duty diaphragm upgrade

$289.00:  RPM CSV kit

$319.00:  RPM CSV kit (for distributor-less ignitions)

Bundle price:  Purchase an Adjustable WUR and RPM CSV kit together and you can subtract $69.00 from total.

Porsche Turbo WURs are classified as Bosch P/Ns = 0 438 140 054, 112, 153, 160 or 164

Note:  In order to make the 964 Turbo WURs (0 438 140 160 and 0 438 140 164) fully adjustable, the altitude compensation mechanism must be permanently removed from the WUR.  This makes it function exactly as a 930 WUR does.  Removing the altitude compensation feature usually goes unnoticed for most 964 Turbo owners, unless frequently traveling to regions with greatly differing altitudes (delta > 5000 ft.).

For any other Adjustable WURs, please contact Brian for pricing details.

Prices listed do not include California state taxes (if applicable), shipping costs, and/or PayPal fees.

Please contact Brian Leask at for more information.

Website last updated on March 16, 2019