2 — Temperature switch
3 — Fuel distributor
4 — Control pressure regulator
To have sufficient charging voltage at low engine speed, the pulley ratio has been changed from 1.909 to 2.065 by installing a smaller alternator pulley.
The drive belt is new (toothed version), but has the same length as the old belt.
Pulley dia.: 61 mm (formerly 66 mm) Toothed drive belt size: 888 x 9.5 mm
The fuel and ignition systems of cars for North America have different modifications as listed below.
Survey o Mixture control unit o Warm-up control o Oxygen control o Distributor o Electronic idle stabilizer o Tank vent with carbon canister
— only in USA with CO antitamper lock
— with temperature switch (USA/Canada)
— with acceleration enrichment (USA/Canada)
— with Hall sensor transisterized ignition (USA/Canada)
— with temperature switch (USA, Canada)
Mixture Control Unit (only USA)
The mixture control units have an anti-tamper plug for the CO level adjustment. US legislation requires that a certain minimum amount of time be necessary to unplug the hole in the air sensor housing for access to the CO adjustment. This legislation aims at preventing unauthorized tampering with the CO level setting.
Consequently the bore providing access to the CO level adjustment in USA air sensor housings is plugged with a 6 mm dia. steel ball. The ball is pressed in the housing against a stop.
Should it become necessary to adjust the engine idle speed/CO level, which is only very seldom the case for engines with oxygen sensor, the mixture control unit must be removed so that the steel ball can be pushed out from underneath.
After completion of adjustments the bore must again be plugged with a steel ball.
Control Pressure Regulator with Temperature Switch (USA, Canada)
The new control pressure regulator has a flatter control curve at ambient temperatures below + 15 °C to provide better running and transition behavior during warm-up.
The control pressure regulator with temperature switch has two heating elements Rv1 and RV2 as well as the temperature switch, which switches the heating element Rv1 on or off depending on the operating temperature.
With the engine running, the heating element RV2 receives power. At temperatures below + 15 °C temperature switch (t) will be open so that heating element Rvi can't be heated. Due to the limited amount of heat developed by only one heating element the control pressure will increase slowly.
If the temperature rises above + 15 °C, either because of higher ambient temperature or heat from heating element Rv2, the temperature switch will close and connect both heating elements Rvi and Rv2. In this manner more heat can be developed and the control pressure increases rapidly.
Was this article helpful?
The History of Porsche Cars through its generational changes. A must have ebook for any Porsche fanatic, this ebook is a reference book for Porsche enthusiasts. Discover all there is to know about the greatest Porsches ever made. All models are fully described and illustrated providing a definitive production history plus an accurate guide to original specs and equipment.