Project 987.2 Cayman S: Getting More Out of the Engine to Chase the GT4 Part 3

Now it’s time to remove the intake runners.

The bolts holding the wire harness to the runners are removed.

You can see the Dundon manifold runners are shorter and bigger diameter.  This changes the tuning to resonate at higher rpm as well as improves the flow.

You can see that the plenum extension for the Dundon intake runners is deeper and bigger in volume. What is interesting is that functionality of the dimples in the IPD plenum was a controversial subject among our readers yet here they are in the OEM plenum from Porsche!

The IPD plenum has more internal volume and a more aerodynamic internal shape than the OEM plenum on the right.  The plenum entrance to the throttle body is a lot bigger too.

A look at the inside of the plenum shows the dimples and just how much larger the plenum is internally.


  1. If the dimples in the IPD work, great, but I doubt they make a big enough difference to justify the added costs of adding them. I’d much rather them make the plenum out of a heat resistant plastic.

  2. I’m pretty sure that the dimples work, as it is well known for golf balls. My argument was about the fact that the golf ball is rotating. I guess that you could argue that in this case the dimples are located in turns and transitions (from what I can see), so the flow is rotating. I suppose at maximum intake velocity the dimples are going to have some effects. I know that they can help with fuel atomization near the injector, if you have port injection.

  3. Really looking forward to seeing how the finished project performs on track- the articles and the video released thus far for this project have been some of the most interesting at MotoIQ (all of the articles here are informative and interesting though!).

    Also, thank you Mike and the MotoIQ staff/contributors for the knowledge and information that you share here. I am a long term reader, first time poster, but I’ve read your technical articles since the days of SCC Magazine in the 90’s. I don’t keep up to date with the automotive industry as much these days, but I frequently check this site for interesting tech articles, and the stories your share. Truly appreciate the effort and dedication of all the staff/contributors at MotoIQ.

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