IPD Competition Plenum and 82mm throtle body

Hi all, I’ve read conflicting information on the IPD composition plenum and 82mm throttle body. I’ve had one sat in the garage for months now, should I fit it? Do they make any difference? Or is it just a scam? Im looking for insights from those who know the truth Thanks!

Oh boy, a chance to get up on my soapbox. For any engine, improving the air flow generally is something you do to gain slight improvements in your peak horsepower. If you are racing in a spec class, this can be the difference between winning and losing. But it is also generally understood that if you mess with high rpm airflow you may adversely affect mid-range performance. Also, to obtain the best gains of this type of hardware change, you would want to couple it with cylinder head modification (also for improved air flow and cylinder filling) and a performance exhaust . And then you would want to change the fuel map in the ECU . And you've just spent a lot of money for performance in a very specific area of operation that you probably don't use in street driving. It is very rare that you can tackle one part of the overall system and see appreciable improvement. So, unless you are indeed racing, I would leave it on the shelf.

I want to second exactly what Harvey said. I have not installed one myself, but I know a very knowledgeable PCA instructor who has tried it and removed it because it didn’t improve his performance. As Harvey said, more intake only helps when other components like exhaust and ECU tune are done concurrently. And even then it’s not a huge gain for our cars. Definitely not worth it on a street car and would come after other upgrades such as suspension and brakes and exhaust on a track car.

Great responses, guys. I had thought about doing it at some point in my 987.2 (especially with my Fabspeed exhaust going on this fall), but I had heard that it really makes minimal difference so I'm skipping it. I'm not tracking the 987.2 ; it's my daily. Your explanations here are excellent. I'm pretty sure that my 981 Outlaw 3.8L has it (plus a Cargraphics exhaust ), and that was ECU mapped; the car was built as a track weapon @ 400 hp. But now I'm curious to find out if any cylinder head modification mods were done. Again, great job!

Foodbiker, I'd suggest you reread harvyf's and porschegreg's comments. What they're saying is that by itself, the IPD+TB isn't much help. That you'll need to do more. I completely agree with that. (I did IPD, TB, Fabspeed street headers , and pro tune to my 2010 BS pretty much all at once. It's now a seriously screaming machine.) If you're planning to add a set of headers in the next several months then the value of the IPD+TB will be there. Especially if you throw in a tune. This is definitly a situation where "the total is greater than the sum of the parts." Think of an engine as an air pump which generates power. If you open the constraint on the input or the output side, you don't get much improvement in the power. Open up both sides and you do. Good luck. Joe Henley

If you want to see an example of what an integrated approach can get you, go look at what they are doing at Slakker Racing Development. Most of the extra grunt comes from the displacement increase but they do pay attention to the entire assembly, so that you get the best results possible. Not cheap, I'm sure, but better than experimenting with a variety of ad-hoc changes.

I think I have mentioned this before. Many decades ago I raced sailboats. Hold on, there is a similarity. Sail construction, went from cotton to dacron to mylar to kevlar to carbon fiber (I think). I bought into several of these progressions looking for more speed. I finally learned, one bad tack (aka turn) or wind change missed call and your $1000 investment, was down the drain.

@ JoeHenley - Oh, I totally agree with you! I apologize as my post likely wasn't clear. You explained it really well. Putting my former science hat on, if one looks at combustion as a chemical equation, sometimes the mods we do have the potential to further shift the equation to the right. To achieve this, one needs to eliminate bottlenecks along the way to make that happen (ie, an improved plenum/throttle body will be helped along with a more free-flowing exhaust at the end, etc.). Once I eventually get that Fabspeed on there, just don't tempt me to modify my 2.9L more! Your 987.2 BS sounds amazing, Joe. Cheers.

I drive a 987.1 BS 3.2 6 speed. I think it's important to think about how you drive your car as in if you shift at 3500 I would agree you will probably not notice a difference in any engine mods. 3 years ago I did a Pedro's 4" under drive pulley and I felt like it did make an improvement in response and it felt quicker at all engine speeds, so that worked out great. 2 years ago I added the Pure Performance UK/ Soul USA valved cat back exhaust which is a total hoot and again I felt a pretty good improvement especially above 4000. An additional improvement was the engine was now loud enough for much better heel toe and blip throttle down shifts ... ok another winner. A couple months later I did the IPD Plenum and Bosch 74.5mm throttle body and did a custom lip hone inside (the 82mm is right for your 3.4) and this combined with the cat back made a "substantial" improvement. The manufacturer's dyno results indicate + 5-7 hp for the under drive pulley, the exhaust 8 hp and the plenum and throttle body +14 hp and 12 lbft at 5600 ya at 5600 and probably a very small portion of that at 3500. So my opinion is if you are trolling around you won't feel much But if you are shifting at 6500 you will notice a "good" improvement. I guesstimate I'm getting 305 hp and have nocked a few tenths off my quarter mile time and 1/10th equals a car length at 100 mph so when I'm on the straight away at Laguna Seca it means the difference of passing or not passing. Note: the exhaust was -10 lbs. and the Interstate MT-MX-5 370 CCA Miata battery with custom aluminum retainer saves me -28.9 lbs. over the Odyssey 850 CCA

Thanks for the insights everyone. I do have a carnewal exhaust . Which I believe is ‘decatted’ and better flowing. Would you suggest with this already on the car, the IPD makes more sense to install too?

I would say yes, especially if it's just collecting dust Image after custom hone