The throttle slide limits the flow of air to the engine. Its degree of opening is determined by turning the throttle grip. The further it is opened the more air can flow in. Some throttle slides have air pockets on the top side and cut sections (so-called 'cutaways') on the underside. These add additional air to the petrol mix and make it leaner as a result. The slides with the flat underside do not add any additional air and are therefore ideal for compensating a leaner middle range. To be able to comply with the required emissions values for the new PX, the SI carburettors that are currently available are fitted with a throttle slide with 2 additional air pockets. This attenuates the mix such that partial load pinking and piston jams can occur on tuned engines. The solution to this problem is to replace the throttle slide that is fitted with a thicker throttle valve without any air pockets (e.g. throttle slide SIP 04, part no 84920400). As of now, the SIP throttle slides are also available in the versions 4.1 (opening 50% of original size, slightlly richer in medium/low range) and 4.2 (no opening, richer in medium/low range).
Fazit: Gasschieber werden bei der Vergaserabstimmung häufig übersehen und sind das I-Tüpfelchen im SI Tuning.
Conclusion: Throttle valves are often overlooked during carburettor tuning and are the icing on the cake in SI tuning.
SIP-TIP: Order the carburettor gasket (e.g. part no 9206000) at the same time.
SIP community user 'sTEFANO64' on part no 68230100: "Finally found! Hard to find, but SIP has it!!!"