3.6 MFI Injector Blocks

$ 510

[ application – 3.6-based MFI engines ]

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Although the mounting bosses for the injection pump console are present on every Porsche case since the MFI era, only the earlier MFI-equipped engines had a provision in the cylinder head for the injector – an important feature that changed with the introduction of the CIS engines – and although those cylinder heads retained enough material in the casting of the intake boss to accommodate the machining of injector ports if desired, this is not so for the 3.2 or 3.6.

The primary challenge in adapting MFI throttles to a newer engine is keeping any increase in height of the mounting plane of the throttle bodies to a minimum, so as not to create geometry issues with linkage between the pump and throttles. The ratio of fuel delivery to air delivery between the pump and throttles is affected by the calibration of the linkages; the length of the linkage rods and the arcs of the pump and throttle levers, and the respective positioning of the pivots of each. Changes in mounting planes of pump or throttles will affect the correlation between the two over the range of throttle travel and consequently need to minimized.

Fortunately, Porsche reduced the height of the intake bosses on the cylinder heads with the release of the 3.2L engine. This is particularly beneficial as the MFI injector port was mounted in the material that is absent on the 3.2/3.6 intake boss, and now needs to be mounted in the adapter. The injector in turn needs to be aimed properly for fuel delivery, and its physical dimensions and installation angle ultimately dictate the height of the injector block. The delta between the height of the intake of the MFI and later cylinder head reduces the effective height of the adapter – which is great, since there is a lot to package in a fairly small vertical space 😉

Another primary concern for us was the appearance of the injector block. We’ve been concerning ourselves with the finer points of backdating 911s for some time, and while we love an engine swap as much as the next red-blooded American, we simply don’t want to open the decklid on a long-hood 911 and see an engine that looks out of place. Our injector block allows the use of the early shroud and keeps the overall increase in throttle body mounting height down to 12mm. Best of all, it is more or less hidden once assembled.

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