You may remember I was one of the few doubters about this product when the debate was raging 12 months ago. I'd bought a plenum for my '05 997S and found it made the car subjectively slower, something I reported on here at the time.

I did however, have a problem with the plenum in that it didn't seem to fit properly. By the time the whole plenum debate was in full-flight, I'd taken the IPD piece off my car and it's sat on my shelf ever since.

As we had a rare dry and sunny week in the UK last week, I decided to give the plenum another go and see if I could 1) get to the bottom of the fitment issues and 2) find the performance that seems to make so many other people here like the thing!

Anyway - off came the Porsche stock plenum. 1st job, compare it to the IPD one. Well, I've no wonder it won't fit - it's a different size. Given it doesn't even fit the car properly, I'm not surprised it doesn't work! As I found last year, the IPD 996/997 plenum is longer front to back than the Porsche one by a good half inch. This means the intake tract length past the throttle body has been altered and also the support bracket doesn't fit.

Below are some photographs to incontrovertibly prove the unit is a different (wrong) size.

The problem with this is that anyone who got the plenum to line up with the support bracket has got it way out of line with the intake runners. Not good for performance in any way whatsoever.

How can IPD/RSS possibly have released a product that doesn't even fit properly? Certainly explains why the results can be odd.

 

At the time of thr great debate it was clear that something was amiss with your installation as I recall. Glad you found it. More recently weren't you going to do some dyno testing? I have not seen a follow up to your post of several weeks back.....

 

I was going to do some dyno testing, yes. However I discovered a problem with the ECU on my car that was stopping it adapting properly. Thankfully this has now been resolved. I've also decided that as the lease on the car is up at the end of the year, I can't really justify spending any more on modifications that I'll only get to use for a few weeks. Reluctantly therefore, I've cancelled the custom mapping session - the money's better put towards mods for the 997TT I'm hoping to get (money permitting) once the 7S has gone.

 

Ian did you get the plenum to finally fit?

 

Unfortunately not. As it's a different size to the original Porsche plenum, it can never fit properly. IPD have simply made the part the wrong size.

I'm guessing that's why it loses, rather than gains, power - as my photographs prove, it's the wrong shape for the car!

 

I don't understand why the IPD being 1/4 inch longer front to back is preventing you from installing it. That 1/4 inch hasn't prevented me or countless others from a successful installation. It may require a bit of jiggering for you, but on my car, with a hose pick, it was a breeze.

I remain surprised by your experience- and sorry to hear about it, what a headache it's been for you!

If I ever get back across the pond I'd love to buy you a pint and come take a look for myself.
CATTMAN

 

Hi and thanks for the reply.

There's no problem putting the part on the car - with a big enough hammer, everything fits!!! In fact I have the IPD plenum installed at the moment (together with some appropriate changes to the support bracket). It had always been my intention to give the plenum another try to see if I could find the gains I'd paid for. At the moment there doesn't seem to be any change in performance except for the same slight reduction in mid-range I'd experienced last time I used the part. What I intend to do this time is leave it in there for a couple of weeks and see if the ECU adapts over time.

I'm still seriously concerned though that the plenum doesn't fit properly. It's hardly a confidence-builder when the manufacturer of a frankly very expensive part, can't even make it the correct size! Changing the length of the inlet tract will also change its characteristics (resonance frequency) too. Whether this is relevant to the rest of the intake system I don't know, but the whole thing does seem to make big use of resonance to fatten-out the torque curve.

To be really honest, I've completely lost interest in the whole thing now. - I think the plenum will just end up staying on the car as I can't summon up the enthusiasm to change it again!!

 

As mentioned by Cattman, I don't understand why this has not been an issue for so many others that have installed the plenum successfully. Did they send you the wrong one?

 

The first picture shows that it is the 996/997 plenum. I think that it is a minimal design flaw but wonder if this is really the source of the problem.

 

I'm wondering if the stock plenum is different on Euro spec cars or maybe on 2004/5 engines. Weren't there some changes to the engine spec in 2006?

I can't believe that all the plenums supplied are the wrong size either but the one I have is definitely different to the stock one on my car

 

IanUK1,

As the worldwide distributor and manufacturer of the IPD Intake Plenum, RSS has always stood by our products and our customers. With nearly 2000 IPD Plenums sold, “you” seem to have experienced a unique issue. Please feel free to contact me directly by phone, email, or PM, so I can offer you further assistance and customer support.

Best Regards,

RSSmike

 

Mike - thanks for the reply. You have PM