Porsche Special Tools P 228 b and P228 c Throttle Correlation Protractors
On cars with mechanical fuel injection, there is a requirement that the movement of the regulator control arm on the injection pump moves in correlation with the opening of the throttle body valves. This correlation is determined by the length of the link rods connecting the throttle bodies to the cross shaft. By shortening or lengthening the links the amount of movement at the throttle body can be adjusted. Once set up the volume of fuel delivered by the pump is then directly correlated to the volume of air being drawn through the induction stacks. It is essential that all the throttles come off their stops at the same time and that the opening angle of the throttles on the left bank are matched with those of the right and with the pump.
To determine this Porsche designed a set of protractors to be fitted to the pump and throttle bodies during tuning. These Protractors were sold to Porsche dealers, and were available as a spare part service tool to owners and independent garages.
Now after years of being unobtainable, I have had the Porsche Special Tools P228B and P228C remanufactured. These protractors are an exact replica of the original Porsche Special Tools except they are be fitted with much stronger Neodymium magnets in place of the original Ferrite magnets. The degree scales have been accurately calibrated to each protractor individually in 1-degree intervals as the originals and accurately printed Black on Silver foil vinyl.
The set contains all five protractors, a set of five brass pointers, preformed to fit and requiring only minimal adjustment to zero during use. The protractors are supplied in a plastic storage case with fitted foam insert and come with Fitting and Operating Instructions including calibration data.
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Full set of Special Tool Protractors P228B to fit all 2.0lt and 2.2lt 911 cars and P228C Protractors to fit 2.4lt and later cars.
Set of five brass pointers. Preformed in 2mm brass to fit both the P228B and P228C sets.
Storage case. (10" x 8") Durable plastic case with fitted foam insert to take the protractors and pointers.
Fitting and Operating instructions. 18 pages with clear photos and correlation data. Wire spiral bound with laminated card front and rear covers.
My new protractors seen on the left , original Porsche protractors on the right for comparison
If you would like a FREE A2 PDF poster of the fabrication drawing, please click on the image below to download the PDF file.
Mercedes Throttle Correlation Protractors
Detailed below are the protractors used to set up the PES pumps and induction system on Mercedes. If you have a set of these or any information, photos etc, please contact the author as there are a number of readers seeking them or asking about remanufacturing.