Is a 24HP gain possible just by changing the plenum? IPD and LN say it is...

LN Engineering and IPD claim that with a 40th anniversary edition 911 with existing X51PU, you can gain an additional 24HP/22Torque just by changing the plenum to an IPD plenum. Here's the info they provide: 996 X51 IPD Plenum: HP Gains 24 / Torque 22 - For 74mm TB $795.00In stockSKU: 96174-X 996 X51 IPD Plenum: HP Gains 24 / Torque 22 - For 74mm TB The 996 3.6L X51 package was typically found on the "40th Anniversary" limited edition cars (MY 2004) but could also be special ordered by performance minded customers. The X51 engine package increased horsepower from the standard 316 up to 345. The X5 lnengineering.com I'd love to realize those gains on my 40th but I'm getting mixed input from others. What's the reality here? Does anyone have the real Dyno info on this or personal experience behind the wheel? Is IPD BS-ing us to sell $795 plenums? Dying to know, cause I would love to get my 40th up from 345 to 370HP which is GT3 territory.

Placebo

340hp is plenty. Asking an old engine to produce more power than it did 20yrs ago is asking for trouble and lots of $$$ Swap it for a Turbo if you "need" more power

Quotes source post: 2703974

They first claim that their plenum produces a bit more to the extra bhp that the X51 pack already gives compared to standard cars. The later mention of 24 seems a tad ambitious.

That plus the throttle body, plus a remap to align to the changes bhp changes are quicker to attain, torque is another matter

Quotes source post: 2704028

In other words, you're saying you can't add 24HP by just changing the plenum and retuning? I don't disagree with you, but I think it's risky for IPD and LN to make a 24HP gain that can't come close to being realized, and I wonder why these two reputable firms are doing it. So as you see it, their claim - a 24hp gain by changing the plenum- isn't credible. I would agree with that but I wonder why two reputable firms would make that claim in the first place and ask their customers to pay $750 for something that won't deliver against the promise. It's easily disproven with a dyno test. I'd love to gain 24 more hp with my 40th by simply changing the plenum. Then it's in GT3 territory.

Quotes source post: 2704013

Thanks, Uncle, but you can ask any old engine to produce more power. And my 40th has 15k miles on it and is ripe for the right upgrades. It's not a Chevy, it's a Porsche.

You could always give it a go and do their test yourself, independent testing if you will! A friend has a rolling road but id not currently be willing to spend £700 doing it myself.

Quotes source post: 2704091

Do you think the claim of a 24hp gain is credible or even possible by just changing the plenum?

Quotes source post: 2704092

Not personally, no. I built an old BMW and had it mapped by Wayne Schofield, who does lots of Porsche mapping (I believe he does all the Hartec cars that require it too) and he's dispelled the IPD plenum myths on his rollers albeit I've not heard specifically about the X51 application. My car has the X51 engine as well so id certainly like it to be true haha

No replacement for displacement as they say. Manufacturers are good at inventing figures, just look at hybrids - claims they do 80mpg yet only return 28mpg.......and that's coming from the big boys, not some small 'mod' manufacturer.

Quotes source post: 2704090

I've run the full set up with GT3 throttle body, IPD plenum and IPD competition y pipe on a 997 turbo over 35,000 miles. I lost torque in mid range. May have gained some bhp at top of the rev range. Fine on track and if the car lives in high RPM range but for me I prefer the stock set up with better mid range torque for 99% road use. I'm surpised you feel the X51 engine lacking in power. I've only driven the stock 996 C2 and always felt it fantastic for road. Much more characterful than the stock set up in both 996 and 997.1 turbo. If you want more power I'd swap out to a 997 C2S or GTS. They feel much quicker than 996 C2 especially from 4500rpm. Having said that I love the 40th Anni. Sub zero cool 996

Quotes source post: 2704102

I love my 40th from the standpoint of quickness, handling, response, etc. It's fast and fast enough. We boys are always looking for even more performance. But i get what you're saying and I think you've satisfied my question very well. I might see some minor gains in the high RPM range, but I'll likely sacrifice the mid-range, and overall, the cost won't justify any small gains in performance and changing the stock set-up. IPD should clarify the claim. Right? Thanks very much for finally giving me the answer I needed.

Glad you got the answer you were looking for and good luck with the "next level sex"

...