Porsche Enthusiasts Club Forum

A little knowledge is a dangerous thing!

I have embraced this because it ties in with my experience in the past, where DME and AFM didn't work as well as DME, AFM and injectors. There was no science behind it though.

Roughly calculating a corrected flow figure for the injectors based on the FRWilk test pressures versus actual, albeit static pressures I get the following...

Early injectors (pre 86) flow 20.45 Lbs/hr
Late injectors (86 - 88) flow 21.8 lbs/hr

This of course does not take into account any possible alterations to flow characteristics versus pressure that either of the injectors might suffer that stop a simple scaling up of flow from being totally realistic, however it should be reasonable.

So from this, with some assumptions, the late injectors will flow 5.12% more fuel than the early ones which would not be a great deal once you boil it down to air fuel ratios in real terms.

I would be tempted to say the change in injectors from the factories viewpoint is probably down to testing or recommendations from Bosch that the later injector would provide lower emissions due to a slightly different spray pattern, as back then, as now, Porsche were under a lot of pressure from the California emissions authorities and California was an important market for them.