IPD Plenum on an M150 Car

Hello all I've trawled through a few threads yet, whilst there is some good info, I'm unable to find anything that relates to my situation. I have a '97 built Carrera with cable throttle, to which I have fitted Fabspeed Maxflo mufflers. My car has option M150, which means it has no cats from the factory. I'm wondering if an IPD Plenum might match up well to the extra flow. The 3.4 engine may or may not benefit from the IPD, from what I have read here, but with the mods and options on my 996, maybe it coudl benefit. I'd appreciate any advice.

You asked a controversial question. Some say the plenum adds nothing other than moving the powerband up a little on the rev range. Others say its the bigger throttle body that makes the difference. What I have heard many times is that you need headwork done as well as a better flowing set of equal length headers in combination with the plenum and larger throttle body to get more power out of using the plenum/throttle body combo. I do have a 3.6 with the IPD Competition plenum with the GT3 Throttle body in combo with FVDs 200 cell cats and Revo software. My indy used my car as a test case to see what the dyno said on their dime. They spent all day tuning and did not get any extra power out of the IPD/GT3 TB combo. What the plenum/throttle body combo did do was move the powerband up the rev range, eliminating some of the lower midrange delivery of the 3.6. But it does have a glorious sucking sound. I still have my old factory plenum and throttle body on the shelf and in spite of no additional performance, I kept the IPD/GT3 TB on the car. I figured one of these days I will have the engine rebuilt into something bigger and better with appropriate headwork and equal length ported headers and will be able to get something out of the combo. Hope this helps to start the discussion.

I don't think its worth the cost to be up font. I fitted one on mine and with headers, 200cell cats etc it made 338hp on the dyno but the guy doing the mapping said it would likely have made more without it from other he's done and would of liked to be able to put the stock stuff back on. something to do with the air wave resonance between cylinders. It would be better without the wedge in it. its more suited to forced induction apparently

That exactly. Brandon from Slakker talked about this in several videos and explained the importance of the intake resonances and the flap in the second cross-over piper on the intake manifold. For that reason, they use a larger plenum without the wedge when adding a bigger throttle body on their engines.

It sounds like, with the effort required, along with the risk of breaking parts during the installation, and theminimal improvement (at best), that I'll leave it stock.Thanks all.

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Its refreshing to hear of honest shops that tell it like it is. Many shops you see advertising 'their upgrade parts' will bend and twist the dyno results to show improvement. Or outright lie. They commonly go under the curve to claim more HP/Torque even though a thousand rpm later/before in the power band there is loss of power. And peak HP is almost always down or a minuscule increase... This just proves how good the Porsche engineers design/tune their engines. Very rarely will the massive Porsche R&D department leave easy obtained HP on the NA engines table.

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A good indy makes all our lives easier. The entire cost for the IPD Plenum, GT3 Throttle body and dyno was theirs. They just wanted to test it out and see if there was any improvement. I said go for it because I was interested. I already had the Revo stage 2 software which was the tuneable version on the car. This was 15 years ago. Interestingly, the car lost quite a bit of HP and torque from baseline when the plenum/throttle body was added. So they had to do alot of tuning to get it back. I ended up keeping them because I loved the giant sucking sound that they produced. But no performance enhancement one bit. It was a bummer.