987 v 986 Air box

[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.

[jaykay]

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.

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.......

[Marchie]

Hi,
Just to clear something up for me, if I put the 987 airbox on my 986 2.7 , I can still use my existing maf sensor on the new larger maf housing with no problems ?
My plan would be to do the airbox, ipd plenum and larger 74 mm throttle body. Can anybody see any issues here and would I have to do any exhaust mods to compliment this. Mine is stock apart from a sport muffler( silencer) . In Australia we don't have the pre cats either just the rear ones. I would appreciate any opinions , within reason, lol.
Thanks.

[berty987]

To be honest I would fit the 996 3.6 inlet tee rather than the IPD plenum to mount the 74mm throttle body and then fabricate my own hose to connect to the airbox via the MAF. The IPD plenum is an unearthly cost and gives very little benefit in its own right. Ideally i'd suggest the MAF should be the later type in the larger housing , but this requires reconfiguring in the DME I believe. With the original MAF and housing you risk the MAF becoming a restriction and ofsetting any gains from fitting the larger throttle body and plenum. The MAF will have a set range its allowed to accept in the DME, force too much air through it and the DME can throw a fault ,though i've only ever experienced it on a tubo car. good luck with hte mods , it would be interesting to see the result you come up with.

[onaFLYer]

Originally Posted by berty987

Ideally i'd suggest the MAF should be the later type in the larger housing , but this requires reconfiguring in the DME I believe. The MAF will have a set range its allowed to accept in the DME, force too much air through it and the DME can throw a fault ,though i've only ever experienced it on a tubo car.

This seems to be the very problem I am having with my 987 box in my 986.

The MAF has the proper voltage, but I keep getting a CEL for MAF. And I cant get it smogged as a result. I started another thread trying to explore all of this.

[Marchie]

Hi Once,
What about trying your old Maf sensor from the 986 airbox. I thought I saw Brad say you should use it and that it fits. Just a thought. Brad has been quiet on here of late, I hope he's ok.

[onaFLYer]

Originally Posted by Marchie

Hi Once,
What about trying your old Maf sensor from the 986 airbox. I thought I saw Brad say you should use it and that it fits. Just a thought. Brad has been quiet on here of late, I hope he's ok.

I did try that, it fits the same yes. Turns out the tube is too big for the DME to compensate for it, so I stuck some foam in there to reduce the size a little. Seems to be working so far, no CEL.

[Marchie]

Hi Ona,
I'm glad it's at least working even though it's probably not exactly as planned.

[onaFLYer]

Originally Posted by Marchie

Hi Ona,
I'm glad it's at least working even though it's probably not exactly as planned.

Passed the smog test, removed the large foam and replaced it with a much smaller one. All good now.

[JAAY]

I just got my 987 airbox in the mail the other day. I am waiting to take my hardtop off to tackle trying this box out. I think it will be a good addition to the 3.4 in there now. I will take photos and keep people up date if anyone would like.

[Paul]

Wear gloves, this job will slice up the backs of your hands!

[JAAY]

Thanks for the thought of my hands. I am going to pull the intake manifold on that side and then there should be no worries of the hand mashing.

[Brad Roberts]

Just finished modding two boxes. One is going in the 3.2 I mentioned early. I'll go to dyno this week with the car.

I found something else interesting during all this that I'll share this week also.

The MAF you want to run is the .125.01

[Marchie]

Yeah, I"m interested keep us updated. It's all interesting JAAY & Brad

[onaFLYer]

Originally Posted by Brad Roberts

Just finished modding two boxes. One is going in the 3.2 I mentioned early. I'll go to dyno this week with the car.

I found something else interesting during all this that I'll share this week also.

The MAF you want to run is the .125.01

Thats the one I used also. Works great.

The one from the 987, not so much.

[JAAY]

Brad. Why the .125.01? I mean what is saying to you better or not? Better afrs?

[Brad Roberts]

The 125.01 is the updated MAF that we all run in all of our FBW cars. It appears to be a more robust MAF, that is less prone to failure than the 125.00

I have been told numerous times that it needs "programming" to work, but I haven't seen a need in the last 4 years we have been selling them.

The engine is going in the -S today. We finished the engine build on Sat.



B

[Brad Roberts]

Command decision made:

If we are going to install a 987 air box.. why not switch it over to the larger CaymanS 3.4 throttle body



B

[Brad Roberts]

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[Brad Roberts]

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