Quote:
Originally Posted by berty987
I personally believe the 987 OEM filter has one big advantage in that the larger filter area over the 986 (14.5 sqft vs 6.1sqft) not only gives a lower pressure drop but also a significant longevity to the element. In other words the element maintains the benefits of the lower pressure drop for a sustained period as it takes longer for the element to be come contaminated and restrictive. This type of cone filter is normally used in race applications where the filter is either replaced or cleaned and re oiled after a relatively short period (ie one race).
Providing the cone filter can be located somewhere accessible and the owner is happy to clean the element frequently , the next issue is contamination of the MAF from oil carry over. An air box and indirect route to the MAF should reduce some of the risk of oil contamination as the oil will drop out of suspension in the air at lower velocities where the diameter of the air tract increases and velocities reduce. A silicone hose direct from the inlet cone filter doesn't allow the velocities to drop so the MAF is more at risk from contamination. I believe there were revisions on the MAF design on both the 986 and between 986 and 987 whereby additional screens were placed in front of the element on the 987 to protect it.
Of the cone element installs I've seen , they all seem to rely on removing the baffle plate in front of the air box to give better flow. Whilst this does indeed work it also increases the risk of water droplets getting onto the MAF or in extreme cases making
the filter wet and losing capacity.
I think that to make a satisfactory street version of an intake system all these elements need to be considered. If the aim is purely to make a track orientated modification then a cone filter and silicone tube will give the best results for minimum outlay.
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Yes the 987 filter is massive; the biggest I have seen. I think if you were to adapt a smaller MAF housing to it, the cumlative losses would still be a lot less. I believe that large volume airbox designs are considered to be the most efficient perhaps because they have a huge volume of high static pressure air to draw on right before the filter. I am not sure high velocity all the way is the best thing. It is just that this 987 air box set up has a MAF housing dia that my DME may not be expecting.
I am not sure I understand what you term the baffle plate....the air box wall at the end of the scoop air duct?? I personally would not put an unprotected cone in the air duct for the reasons you outlined. I had envisioned a snorkle or duct sealed in scoop air duct via a "baffle" plate or heat shield. There would be no air injestion from the engine bay. There would be a 90 degree bend to knock out water leading, uphill to a sealed BMC oval trumpet or CDA airbox. The MAF housing could be placed behind another 90 to further protect the sensor. The filter would be accessible in the engine bay. I have yet to hear anything substancially negative about the BMC air box set up be it maintenance or performance. I imagine the filtering would not be as good as paper elements.
Yes I believe there have been revisions the sensor but you need the DME update from Porshe to run them. They may ruin you custom flash if they hook there diag. tools.....I am not sure of the cost of this update. So I guess you need to be working with a stock flash to get the updated more robust sensors.......