987 v 986 Air box

[Frank A]

I have been following this post for a while now and it is a very tempting mod. I have a 2000 boxster S 6 speed and was hoping to get some direction from those of you who have done this. I recently acquired a 2007 cayman S diverter T and throttle body and would like to build from there. I have a few questions perhaps some of you could shed lite on.

1- What do I use for a vacuum signal for the flap in the T
2- do I continue sourcing the rest of the 2007 cayman S intake, MAF, and air box
3-From what I gather from the post, I use the maf sensor from my old setup installed in the cayman s MAF tube and my DME will adapt, if not will the X-51 flash help.

Thanks for your knowlege and advice
Frank

[The Radium King]

1. i *think* you should be able to take the vacuum signal that drives the resonance flap on your intake and use it. if you look at your intake there are two tubes that join the two sides together - the diverter 't' and the resonance tube. on the resonance tube there is a vacuum-driven flapper valve. 't' off this vacuum signal to drive the flapper on your diverter.

2. personally, i would just connect the new diverter/throttle body to your existing airbox/maf housing to start. this way your car can work with it's original tune and you can see if you get any performance improvements, if the flapper in your diverter is working, etc.

3. if you do go to the cayman airbox, you can saw-off the maf housing on your original airbox and plumb it into the system, or you can use the cayman maf housing and see if your ecu will adapt, or you can push a 996 tune onto your car (designed for the larger maf housing). only the first is certain to work; i've not heard with any certainty that the other two will work.

[berty987]

The 987 and 986 have different ECU programmes (and ECU's) , even though they share the same heads and much of the internal engine parts. If you fit a 987 inlet plenum T its supposed to modulate independently from the cross flap that is in the other link tube between the inlet manifolds. Unless you get a custom ECU I cant see how you could get the plenum T to modulate correctly , so it may be better to simply fit the T without any control. I also suspect that the variocam on the inlet also adjusts based on the plenum T as would possibly ignition and fuelling. Assuming you are fitting the airbox as a performance modification, it may also be better to fit a cayman / post 2006 boxster plenum T rather than the earlier 987 boxster 3.2 model. The later model plenum used on the M97 engine uses the same airbox but has a larger throttle body ( 76mm rather than 68mm diameter). I would still sugest this is fitted without the vacuum control or if possible with a 996 3.6 manifold T which doesnt have the internal flap control. If you fit either the M97 76mm plenum or the 996 3.6 item you need to also fit silicone reducers to mate the T to the inlet manifold on each side as the diameters are about 10mm different. There is a write up on planet 9 under the articles section and a few posts on 996 plenum tees into 986 boxsters under the tuning part of the forum. Hope this helps.

[jaykay]

I would also be concerned as to where the flap is flapping without controls attached to it.