This article will describe the installation process for the IPD Competition Plenum and GT3 throttle body, and contrast those parts with the stock and standard IPD plenums and throttle bodies.

The stock Porsche plenum bifurcates the flow just behind the 75mm throttle body, and uses a flapper valve to adjust intake manifold resonances to improve low-rpm power. Some high-rpm power is sacrificed by the restriction to the flow imposed by the flapper valve, but Porsche was evidently willing to accept that loss in order to improve low-rpm power.

The IPD plenums eliminate the flapper valve, and the restriction to the flow that the flapper valve provides at high-rpm's. Also, the IPD plenums utilize a "Y" design to smoothly split the flow towards the left and right cylinder banks. This patented design feature is intended to provide better flow than the factory "T" design. The improved engine power than can be obtained with the IPD plenums has been documented by several independent dyno tests.

An extensive, and often lively, discussion of the original IPD plenum is here New IPD Plenum for CS, and some dyno test results are here Dyno'd my Cayman S before and after an IPD plenum install and here Dyno run with and without plenum.

IPD has recently developed a new "Competition" plenum that is designed to work with a GT3 throttle body Cayman S Competition Plenum and GT3 throttle body. The GT3 throttle body is 82mm in diameter, instead of 75mm for the factory throttle body. The increased diameter of the GT3 throttle body, and the matching plenum, are intended to provide increased performance for cars that have better overall engine breathing from a free-flow exhaust and other engine mods such as the EVOMS intake (see EVO V-Flow Air Intake Installation).

A comparison of the the standard factory throttle body (on the left) with the GT3 throttle body (on the right) that is supplied with the IPD Competition plenum is shown below:



This photo compares the base IPD plenum (on the left) with the new Competition plenum (on the right)



The installation of the Competition plenum is very straightforward, and is in all respects identical to the installation procedure for the base plenum. Excellent installation instructions are available here http://sb4.shread.net/cayman/IPD%20C...structions.pdf. I do have a few suggested improvements to these instructions:

First of all, DISCONNECT YOUR BATTERY! If the IPD plenum accidently touches your starter then the car will crank, and this will probably NOT be A Good Thing.

0. In the list of tools, it is better to use the correct E10 external Torx socket than the ill-fitting 8mm socket cited in the instructions. See External Torx socket set.

1. Do not use a screwdriver to pry up the carpet on top of the engine cover as described in the instructions. Instead, use the interior trim tools described here Interior Trim Removal Tools.

2. On the 4th page there is a photo of the factory plenum. Underneath the picture is a caption that says "For reference, the plenum, removed, is pictured top-down above." The "top-down" comment makes no sense to me at all. The photo shows the factory plenum in the same orientation that it is installed on the engine.

9. In step 9 the instructions say that the vacuum hose that is attached to the flapper valve actuator should be pulled off. This can be very difficult or impossible. It is better to simply cut this hose. The hose can be easily spliced back together if there is ever a need to return the car to stock. There is a good chance that something will get damaged from the excessive force required to try and pull the hose off the actuator as called-for in the instructions.

12. Use the E10 external Torx socket here instead of the ill-fitting 8mm socket.

20. The discussion about the "elbow grease" needed for the hose connection is obsolete. The new IPD hoses fits PERFECTLY, and you'll have no trouble with it at all.

That's it. Other than these comments the downloadable instructions provide an excellent step-by-step procedure. I had no difficulty with the installation at all.

Here is a photo of the new Competition plenum installed:



Note that there is an improved "MotorSports" vapor-oil separator installed on my engine (Installation of Improved Vapor Oil Separator), and so the connection of the hose from the VOS to the plenum is slightly different than normal.

I don't trust my butt-dyno, and so I'll defer to the previously-cited dyno results as indicators of the performance gains provided by the new Competition plenum. The car certainly runs very strong!